ICSE 10

2024-25

SAVIOUR OF
BIOLOGY

A Complete Saviour of ICSE Class 10 Biology. It Includes -:

High Graphic Theory Notes

Chapter wise Multiple Choice Questions
Boards Centric Short Answer Questions
 Contents
CLASS 10TH BIOLOGY THEORY
NOTES
Comprehensive Coverage: Provides detailed
explanations of all ICSE Class 10 Chemistry topics
According to the latest ICSE Boards Syllabus
Structured Learning: Organized in a systematic
manner for easy understanding and quick revision.
Clarity and Conciseness: Presents complex concepts
in a clear and concise manner, aiding retention.
Illustrative Examples: Includes relevant examples to
reinforce theoretical concepts.

MCQS
Chapter wise Mcqs : Mcqs after Each
Chapter for quick revision and to grasp
the concepts
Based On Latest Techniques : Mcqs
Based on Latest Techniques Released By
the ICSE

SHORT ANSWER QUESTIONS

Chapter wise Short Answer Questions : 20

Short Answer Questions at the end of each
Chapter to Retain all the concepts.
Boards Centric : Based On Latest Techniques
Of ICSE and According to the Questions
Asked in ICSE Examination
 Cell Cycle and Cell Division
The cell cycle is the series of events that a cell
undergoes as it grows, replicates its DNA, and
divides to form two daughter cells. It is divided into
two main phases:
Interphase (Preparation Phase)
The phase between two successive cell divisions.
Often called the "resting phase," but it is highly
active metabolically.
Divided into three sub-phases:
Significance of the Cell Cycle:
a. G1 Phase (Gap 1) Ensures growth and development
Cell grows in size. of organisms.
Synthesis of proteins and organelles. Maintains genetic continuity.
Facilitates repair and
Prepares for DNA replication.
replacement of cells.

b. S Phase (Synthesis Phase)

DNA replication occurs.
Each chromosome duplicates to form two identical
sister chromatids.

c. G2 Phase (Gap 2)
Further growth of the cell.
Synthesis of proteins required for mitosis.
Cell checks for errors in DNA replication and
prepares for division.
Mitotic Phase (M Phase) : The phase of actual cell division.
Divided into two processes:
a. Karyokinesis (Nuclear Division):
Division of the nucleus into two.
Stages: Prophase, Metaphase, Anaphase, and Telophase.

b. Cytokinesis (Cytoplasmic Division): Division of the cytoplasm to form two daughter

cells.

CELL DIVISION : Cell division is a process by which a mature cell

divides and forms daughter cells which resemble the parent cell in
several characteristics.
Cell Division
Mitosis : Mitosis is the division of somatic cells in which two
identical daughter cells are produced by the division of one
parent cell. Mitosis is also known as equational division or
somatic cell division because during the process daughter cells
receive an equal number of chromosomes and the division Mitosis Meiosis
occurs in the body cells or somatic cells
 THE FOUR STAGES OF KARYOKINESIS

1. Prophase :
During prophase, chromatin fibres condense and thick
chromosomes are visible.
The nucleolus and nuclear membrane disappear. 
A pair of centrioles duplicates. 
Spindle apparatus starts forming.

2. Metaphase :
Chromosomes are arranged on the metaphase plate or
equatorial plane.

3.Anaphase : 
The centromere divides, and the sister chromatids separate from
each other. 
Spindle fibres contract and pull chromatids towards opposite poles.

4. Telophase 
Spindle apparatus disappears. 
Chromosomes become thin and turn into chromatin fibres. 
Nuclear membranes and nucleoli reappear.

Significance of Mitosis 
Meiosis : A reduction division resulting in four
daughter cells, each with half the number of
chromosomes (haploid).
It is important for the growth of
Occurs in germ cells to produce gametes.
organisms. 
Repair of damaged and wounded Involves two successive divisions (Meiosis I
tissues occurs through mitosis. and Meiosis II).
Old or worn out cells are replaced
during normal body functioning.

Homologous Chromosomes and Significance of Cell Division:

Crossing Over: Mitosis: Ensures growth, repair, and asexual
Homologous chromosomes pair reproduction; maintains genetic stability.
during Meiosis I. Meiosis: Produces gametes for sexual
Crossing over occurs, where genetic reproduction; increases genetic diversity.
material is exchanged between
homologous chromosomes.
Leads to genetic variation.
 Major Differences Between Mitosis and
Meiosis:

Mitosis Meiosis:

Occurs in reproductive cells only.

Occurs in somatic cells.
Cells divide twice in two
Cells divide only once at a time.
successive divisions, i.e. meiosis I
It is also called equational
and meiosis II.
division, because the daughter
It is also called reductional
cells have identical genetic
division, because the daughter
material as the parent cell.
cells have half the number of
Two diploid daughter cells are
chromosomes as the parent cell.
formed.
Four haploid daughter cells are
formed.

Multiple Choice Questions

Recall
Q: Which phase of the cell cycle is also known as the "resting phase"?
a) G1 Phase
b) G2 Phase
c) Interphase
d) Mitotic Phase
Answer: c) Interphase
Explanation: Interphase is metabolically active but does not involve actual cell division.

Understanding
Q: What is the primary event in the S-phase of interphase?
a) Growth of the cell
b) Replication of DNA
c) Synthesis of organelles
d) Division of cytoplasm
Answer: b) Replication of DNA
Explanation: The S-phase is responsible for synthesizing a duplicate copy of DNA.

Application
Q: A cell has completed G2 phase. What process will it undergo next?
a) DNA replication
b) Mitosis
c) Cytokinesis
d) Protein synthesis
Answer: b) Mitosis
Explanation: After G2 phase, the cell enters the mitotic phase for division.
Analysis
Q: If DNA replication does not occur during the S-phase, which of the following consequences is likely?
a) Cells with uneven distribution of DNA
b) Normal division of cells
c) Reduced organelle synthesis
d) Formation of abnormal proteins
Answer: a) Cells with uneven distribution of DNA
Explanation: DNA replication ensures equal genetic material in daughter cells.

Recall and Understanding

Q: What happens during prophase of mitosis?
a) Chromosomes align at the equator.
b) Spindle fibers disappear.
c) Nuclear membrane dissolves.
d) Chromatids are pulled apart.
Answer: c) Nuclear membrane dissolves.
Explanation: During prophase, chromosomes condense, and the nuclear envelope disintegrate

Understanding and Application

Q: A scientist observes that chromosomes are aligned at the equatorial plane of a dividing cell. What phase
is the cell in?
a) Prophase
b) Metaphase
c) Anaphase
d) Telophase
Answer: b) Metaphase
Explanation: In metaphase, chromosomes align at the cell's equator.

Recall
Q: What is the end result of mitosis?
a) Four daughter cells
b) Two genetically identical cells
c) Haploid gametes
d) Two genetically diverse cells
Answer: b) Two genetically identical cells
Explanation: Mitosis produces two identical daughter cells with the same number of chromosomes.

Application and Analysis

Q: During cell division, a cell fails to complete cytokinesis. What will likely result?
a) A cell with no nucleus
b) Two identical cells
c) A multinucleated cell
d) An incomplete nuclear division
Answer: c) A multinucleated cell
Explanation: Without cytokinesis, the cell does not split its cytoplasm.
Recall
Q: Which type of cell division leads to genetic diversity?
a) Binary fission
b) Mitosis
c) Meiosis
d) Budding
Answer: c) Meiosis
Explanation: Meiosis includes crossing over and produces genetically varied gametes.

Understanding
Q: Why is meiosis referred to as "reduction division"?
a) It reduces cell size.
b) It reduces chromosome number by half.
c) It reduces protein synthesis.
d) It reduces organelle number.
Answer: b) It reduces chromosome number by half.
Explanation: Meiosis produces haploid cells.

Recall
Q: What is the first phase of mitosis?
a) Telophase
b) Metaphase
c) Prophase
d) Anaphase
Answer: c) Prophase
Explanation: Prophase is the first stage of mitosis where chromosomes condense, and spindle fibers begin to
form.

Understanding
Q: Why is crossing over important in meiosis?
a) It ensures equal division of cytoplasm.
b) It produces two identical daughter cells.
c) It introduces genetic variation in gametes.
d) It replicates DNA.
Answer: c) It introduces genetic variation in gametes.
Explanation: Crossing over during meiosis creates new combinations of genetic material.

Application
Q: If a somatic cell has 46 chromosomes, how many chromosomes will each daughter cell have after
mitosis?
a) 23
b) 46
c) 69
d) 92
Answer: b) 46
Explanation: Mitosis produces daughter cells that are genetically identical to the parent cell, maintaining the
chromosome number.
Analysis
if meiosis fails to occur properly in a germ cell, what is the likely consequence?
a) A multinucleated cell
b) Abnormal chromosome numbers in gametes
c) Cells with no DNA
d) Identical daughter cells
Answer: b) Abnormal chromosome numbers in gametes
Explanation: Errors in meiosis can lead to aneuploidy, where gametes have extra or missing
chromosomes.

Recall and Understanding

Q: What ensures sister chromatids separate during anaphase?
a) The nuclear membrane reforms.
b) The spindle fibers pull them apart.
c) Chromosomes align at the equator.
d) Crossing over occurs.
Answer: b) The spindle fibers pull them apart.
Explanation: During anaphase, spindle fibers contract to separate sister chromatids to opposite poles.

Application
Q: Why can homologous chromosomes be considered "matching pairs"?
a) They are identical copies of each other.
b) They contain genes for the same traits in the same order.
c) They have the same centromere location.
d) They divide at the same rate.
Answer: b) They contain genes for the same traits in the same order.
Explanation: Homologous chromosomes carry genes for the same traits but may have different alleles.

Recall
Q: What process forms a tetrad during meiosis?
a) Prophase
b) Synapsis
c) Cytokinesis
d) Telophase
Answer: b) Synapsis
Explanation: During synapsis, homologous chromosomes pair up to form a tetrad in meiosis I.

Understanding
Q: What distinguishes mitosis from meiosis?
a) Mitosis occurs in germ cells, while meiosis occurs in body cells.
b) Mitosis reduces chromosome number, while meiosis maintains it.
c) Mitosis produces identical cells, while meiosis increases genetic diversity.
d) Mitosis involves two divisions, while meiosis involves one.
Answer: c) Mitosis produces identical cells, while meiosis increases genetic diversity.
Explanation: Mitosis is for growth and repair, while meiosis creates genetically diverse gametes.
Recall
Q: What structure attaches spindle fibers to chromosomes?
a) Centriole
b) Chromatid
c) Centromere
d) Nucleolus
Answer: c) Centromere
Explanation: The centromere is the region where spindle fibers attach during cell division.

Application
Q: Why does crossing over not occur in mitosis?
a) There are no homologous chromosomes in mitosis.
b) Chromosomes do not align during mitosis.
c) Mitosis does not involve genetic variation.
d) Homologous chromosomes do not pair in mitosis.
Answer: d) Homologous chromosomes do not pair in mitosis.
Explanation: Crossing over requires homologous chromosome pairing, which only occurs in meiosis.

Short Answer Type Questions

Recall
Q: Name the phases of the cell cycle in the correct sequence.
Answer: G1 phase, S phase, G2 phase (interphase), and the mitotic phase.

Understanding
Q: What happens during the G1 phase of the cell cycle?
Answer: The G1 phase is a period of cell growth where the cell increases in size, synthesizes
proteins, and prepares for DNA replication.

Recall and Understanding

Q: What is the significance of the S-phase in the cell cycle?
Answer: The S-phase is crucial for DNA replication, ensuring that each daughter cell receives a
complete set of genetic material after cell division.

Application
Q: A cell fails to replicate its DNA in the S-phase. How will this affect mitosis?
Answer: If DNA replication does not occur, the cell will not have enough genetic material for two
daughter cells, leading to defective or non-viable cells.

Recall
Q: What are the two main phases of the cell cycle?
Answer: Interphase and Mitotic phase.

Understanding and Application

Q: Why is mitosis important for multicellular organisms?
Answer: Mitosis is essential for growth, repair, and replacement of damaged or dead cells,
maintaining genetic consistency.
Analysis
Q: If spindle fibers are not formed during mitosis, what will happen?
Answer: Chromosomes will not align or separate correctly, leading to unequal distribution of
chromosomes in daughter cells.

Recall and Understanding

Q: What are sister chromatids?
Answer: Sister chromatids are identical copies of a chromosome, connected by a centromere,
formed during the S-phase of interphase.

Understanding
Q: What happens during metaphase of mitosis?
Answer: In metaphase, chromosomes align at the equatorial plane of the cell, and spindle fibers
attach to their centromeres.

Analysis and Application

Q: How is cytokinesis different in plant and animal cells?
Answer: In animal cells, cytokinesis occurs through the formation of a cleavage furrow, while in
plant cells, a cell plate forms due to the presence of a rigid cell wall.

Recall
Q: Define homologous chromosomes.
Answer: Homologous chromosomes are pairs of chromosomes that have the same genes at the
same loci but may carry different alleles.

Understanding and Application

Q: Explain how crossing over in meiosis leads to genetic variations.
Answer: During crossing over, segments of genetic material are exchanged between non-sister
chromatids of homologous chromosomes, creating new allele combinations.

Recall and Understanding

Q: What is reduction division?
Answer: Reduction division refers to meiosis, where the chromosome number is halved from diploid
(2n) to haploid (n) in gametes.

Application
Q: Why is meiosis important for sexual reproduction?
Answer: Meiosis produces haploid gametes, ensuring that the chromosome number remains
constant in offspring after fertilization.

Analysis
Q: A cell with 46 chromosomes undergoes meiosis. How many chromosomes will each gamete
have?
Answer: Each gamete will have 23 chromosomes.
Recall and Understanding
Q: Differentiate between mitosis and meiosis based on the number of daughter cells produced.
Answer: Mitosis produces two daughter cells, while meiosis produces four daughter cells.

Understanding
Q: Why are the daughter cells produced by meiosis genetically diverse?
Answer: Genetic diversity arises from crossing over during prophase I and independent assortment
of chromosomes during metaphase I of meiosis.

Analysis and Application

Q: A multicellular organism has a wound. What type of cell division will aid in its healing, and why?
Answer: Mitosis will aid in healing as it produces identical cells for repair and replacement.

Recall and Understanding

Q: Mention two differences between mitotic and meiotic cell division.
Answer:
Mitosis: Produces two identical daughter cells; occurs in somatic cells.
Meiosis: Produces four genetically diverse daughter cells; occurs in germ cells.

Application and Analysis

Q: A person has a genetic disorder caused by a chromosomal abnormality. Which type of cell
division error might have occurred, and how?
Answer: An error during meiosis, such as nondisjunction (failure of chromosomes to separate),
could lead to chromosomal abnormalities in gametes, causing the disorder.
 Structure of Chromosomes
Basic Structure of Chromosome : Chromosomes are thread-like
structures located in the nucleus of cells, carrying genetic
information in the form of genes.

Chromosomes play a vital role in hereditary, variation and

evolutionary development of the species. 
They were discovered by the German scientist Walther
Fleming in 1882. 
Each chromosome has a centromere which holds together the
two sister chromatids

Key Components of Chromosomes :

Chromatin:
Uncoiled and relaxed form of DNA present in the nucleus during the
non-dividing phase of the cell.
Made up of DNA and proteins (histones).

Chromatid:
Each chromosome consists of two identical chromatids joined by a
centromere during cell division.
Formed during DNA replication.

Gene:
Functional unit of heredity located on chromosomes.
Made up of DNA sequences that code for specific proteins.

Structure of DNA ( Deoxyribonucleic Acid )

DNA is a macromolecule composed of two
complementary strands twisted around each other.

Double-helix model proposed by Watson and Crick.

Made of two complementary strands of nucleotides

held together by hydrogen bonds.

Nucleotides consist of:

A sugar molecule (deoxyribose),
A phosphate group,
A nitrogenous base (Adenine, Thymine, Cytosine,
Guanine).
 Structure of DNA ( Deoxyribonucleic Acid )
Adenine (A), Cytosine (C), Thymine (T)
and Guanine (G).
Centromere:
Constricted region of the chromosome
that holds sister chromatids together.
Plays a crucial role in chromosome
movement during cell division.

Functions of Chromosomes:
Store and transmit genetic information.
Regulate cell division and inheritance.

Multiple Choice Questions

Recall
What is the main function of a gene?
a) Replicate DNA
b) Carry genetic information
c) Form histones
d) Produce energy
Answer: b) Carry genetic information
Explanation: Genes are segments of DNA that carry the information necessary for synthesizing proteins,
which determine traits.

Recall
What is chromatin?
a) Condensed DNA during cell division
b) A protein that holds chromosomes together
c) Uncoiled form of chromosomes during interphase
d) The region where the centromere is located
Answer: c) Uncoiled form of chromosomes during interphase
Explanation: Chromatin is the uncoiled form of chromosomes found during interphase, allowing DNA
replication and transcription to occur.

Recall
What is the structure of DNA?
a) Double helix
b) Single strand
c) Triple helix
d) Circular
Answer: a) Double helix
Explanation: DNA has a double-helix structure, consisting of two strands that twist around each other.
Recall
What connects the two sister chromatids in a chromosome?
a) Telomere
b) Chromatin
c) Centromere
d) Gene
Answer: c) Centromere
Explanation: The centromere is the region that connects two sister chromatids, allowing them to segregate
during cell division.

Understanding
What is a chromatid?
a) The basic unit of genetic information
b) The coiled structure of DNA
c) One of the two identical halves of a chromosome
d) A protein that organizes DNA
Answer: c) One of the two identical halves of a chromosome
Explanation: A chromatid is one of the two identical copies of a chromosome formed after DNA replication
during the S-phase of the cell cycle.

Understanding
What happens to chromatin during cell division?
a) It breaks down into nucleotides.
b) It condenses to form chromosomes.
c) It remains uncoiled.
d) It replicates into a new form.
Answer: b) It condenses to form chromosomes.
Explanation: During cell division, chromatin condenses to form visible chromosomes, ensuring proper
segregation of genetic material.

Understanding
What is the role of histones in the structure of chromatin?
a) To bind DNA to the cell membrane
b) To condense chromatin into chromosomes
c) To provide a scaffold for chromatin structure
d) To form the centromere
Answer: c) To provide a scaffold for chromatin structure
Explanation: Histones are proteins that help DNA coil around them, forming nucleosomes, which are the
structural units of chromatin.

Understanding
Which of the following is true about the gene structure of DNA?
a) A gene is a sequence of amino acids.
b) A gene is a sequence of nucleotides in DNA.
c) A gene is a protein molecule.
d) A gene is located only in the cytoplasm.
Answer: b) A gene is a sequence of nucleotides in DNA.
Explanation: A gene consists of a specific sequence of nucleotides in the DNA, which provides instructions for
making proteins.
Application
Which part of the chromosome is important for its proper separation during mitosis?
a) Chromatin
b) Chromatid
c) Gene
d) Centromere
Answer: d) Centromere
Explanation: The centromere is crucial during cell division as it holds the sister chromatids together
and ensures their proper alignment and separation.

Application
A mutation in the centromere could lead to which of the following?
a) Failure of chromatids to segregate properly
b) Faster DNA replication
c) Formation of additional chromosomes
d) Condensation of chromatin
Answer: a) Failure of chromatids to segregate properly
Explanation: If the centromere is mutated, chromatids may fail to attach to spindle fibers, leading to
improper chromosome segregation.

Application
Which of the following would most likely occur if histones were removed from chromatin?
a) Chromatin would remain condensed.
b) Chromatin would remain uncoiled and inaccessible.
c) Chromatin would form centromeres.
d) Chromosomes would break into pieces.
Answer: b) Chromatin would remain uncoiled and inaccessible.
Explanation: Histones are responsible for coiling the DNA into a compact structure. Without
histones, DNA would not condense into chromosomes.

Analysis
If a chromosome lacks a centromere, what is likely to happen during cell division?
a) The chromosome will replicate more times.
b) The chromosome will not align properly at the metaphase plate.
c) The chromosome will be easily copied.
d) The chromosome will be ignored during the division.
Answer: b) The chromosome will not align properly at the metaphase plate.
Explanation: The centromere is essential for chromosome alignment during metaphase. Without it,
the chromosome may not properly attach to the spindle fibers.
Analysis
Why is it important for chromatids to be identical before cell division?
a) To ensure genetic variation in daughter cells
b) To ensure that each daughter cell receives a complete set of genetic information
c) To prevent DNA replication errors
d) To increase mutation rates
Answer: b) To ensure that each daughter cell receives a complete set of genetic information
Explanation: Identical chromatids ensure that each daughter cell receives an exact copy of the genetic
material during cell division.

Understanding and Application

Why do chromosomes condense during cell division?
a) To facilitate the process of gene transcription
b) To ensure the chromosome is protected from damage
c) To prevent the DNA from getting tangled during separation
d) To allow DNA replication to occur more efficiently
Answer: c) To prevent the DNA from getting tangled during separation
Explanation: Chromosomes condense during cell division to prevent the DNA from becoming tangled or
damaged, facilitating proper segregation.

Understanding and Application

In a laboratory experiment, DNA is denatured. How does the structure of DNA facilitate this process?
a) The DNA strands are linked by covalent bonds.
b) The strands are held together by hydrogen bonds between complementary bases.
c) The DNA is held tightly by histones.
d) The structure is resistant to heat.
Answer: b) The strands are held together by hydrogen bonds between complementary bases.
Explanation: The hydrogen bonds between complementary nitrogenous bases (A-T, G-C) are relatively weak,
allowing the strands to separate during denaturation.

Application and Analysis

What would happen if a chromatin fiber was not properly coiled?
a) The cell would not be able to replicate DNA.
b) The chromosome would be unstable and unable to divide.
c) The cell would divide too quickly.
d) The chromosomes would be too small to be observed.
Answer: b) The chromosome would be unstable and unable to divide.
Explanation: Proper coiling of chromatin ensures that chromosomes are stable and can segregate correctly
during cell division.

Application and Analysis

A researcher observes a mutation in the gene encoding the protein that forms the centromere. What might be
the outcome of this mutation?
a) Proper chromosome segregation will occur.
b) The chromosome will break during cell division.
c) Chromosomes will fail to align at the metaphase plate.
d) DNA replication will not occur.
Answer: c) Chromosomes will fail to align at the metaphase plate.
Explanation: The centromere is crucial for chromosome alignment and proper segregation. A mutation in this
region can result in errors during cell division.
Recall and Understanding
What is the shape of the chromosomes during interphase?
a) Coiled
b) Uncoiled
c) Circular
d) X-shaped
Answer: b) Uncoiled
Explanation: During interphase, chromosomes are in the form of uncoiled chromatin, which allows for
transcription and replication.

Recall and Understanding

Where are genes located?
a) Only in the cytoplasm
b) On the centromere
c) Along the length of the chromatid
d) In the ribosomes
Answer: c) Along the length of the chromatid
Explanation: Genes are sequences of nucleotides that are found along the length of the chromatid, which is
part of the chromosome.

Recall and Understanding

Which process involves the condensation of chromatin into chromosomes?
a) DNA replication
b) Transcription
c) Mitosis
d) Meiosis
Answer: c) Mitosis
Explanation: During mitosis, chromatin condenses into visible chromosomes to ensure accurate distribution
of genetic material to daughter cells.

Short Answer Type Questions

Recall
What is the basic structure of a chromosome?
Answer: A chromosome consists of two identical sister chromatids joined at a region called the centromere.
The chromatids are made up of DNA wrapped around proteins called histones, forming a structure known as
chromatin.

Recall
What is a chromatid?
Answer: A chromatid is one half of a chromosome, formed during DNA replication. After replication, each
chromosome consists of two identical chromatids joined by the centromere.

Understanding
Define chromatin and its role in the chromosome structure.
Answer: Chromatin is the uncoiled form of DNA found in the nucleus during interphase. It helps in DNA
replication and transcription and condenses to form visible chromosomes during cell division.
Understanding
Explain the function of the centromere in a chromosome.
Answer: The centromere is the region that holds the two sister chromatids together and plays a crucial role in
chromosome movement during cell division by attaching to the spindle fibers.

Understanding
Describe the gene structure of DNA.
Answer: A gene is a specific sequence of nucleotides in the DNA that carries the instructions for synthesizing
proteins. It is located on the chromosome and is made up of a sequence of base pairs: adenine (A), thymine
(T), cytosine (C), and guanine (G).

Understanding
How does the structure of DNA enable it to carry genetic information?
Answer: The structure of DNA, with its double helix and complementary base pairing (A-T, C-G), ensures the
accurate transmission of genetic information during cell division. The sequence of nitrogenous bases in the
DNA serves as a code for protein synthesis.

Understanding
What is the difference between chromatin and chromatid?
Answer: Chromatin is the uncoiled, relaxed form of DNA found in the nucleus during interphase, while
chromatid is the condensed, coiled form of chromatin that is visible during cell division.

Understanding
Why is it necessary for chromosomes to condense during cell division?
Answer: Chromosome condensation is necessary to prevent the DNA from tangling or breaking during cell
division, ensuring that the genetic material is accurately distributed between daughter cells.

Understanding
How does the DNA in a chromosome differ from the chromatin in terms of structure?
Answer: DNA in a chromosome is tightly coiled and condensed into chromatids, while chromatin is a more
relaxed and uncoiled form of DNA. Chromatin allows for DNA replication and gene expression during
interphase.

Application
Explain the process of DNA replication.
Answer: DNA replication involves the unwinding of the double helix, followed by the separation of the two
strands. Each strand serves as a template for the formation of a new complementary strand, resulting in two
identical DNA molecules
.
Application
How does the centromere contribute to the proper segregation of chromosomes?
Answer: The centromere provides a point of attachment for spindle fibers during cell division, ensuring that
the sister chromatids are pulled apart and equally distributed between the daughter cells.

Application
What happens to the chromatin during the cell cycle?
Answer: During interphase, chromatin is in a relaxed, uncoiled state. As the cell enters mitosis, chromatin
condenses to form visible chromosomes, which ensures proper chromosome segregation during cell division.
Analysis
What role does the DNA sequence in genes play in protein synthesis?
Answer: The sequence of nucleotides in a gene determines the sequence of amino acids in a protein. This
genetic code is read and translated by ribosomes, directing the synthesis of proteins that determine the
organism's traits.

Analysis
How do mutations in the DNA affect chromosomes and heredity?
Answer: Mutations in DNA can alter the sequence of bases in genes, potentially changing the structure of
proteins. These changes can be inherited and may lead to genetic disorders or contribute to evolutionary
changes.

Analysis
How is the structure of a chromosome related to its function in heredity?
Answer: The chromosome’s structure allows it to carry genetic information in the form of genes. During cell
division, the condensation and separation of chromosomes ensure the accurate transmission of genetic
material to offspring.

Understanding and Application

Why are chromosomes described as a "vehicle" for genetic material?
Answer: Chromosomes are considered vehicles for genetic material because they carry genes, which contain
the instructions for making proteins and determining an organism's traits. These instructions are passed on
to the next generation during reproduction.

Understanding and Application

Describe the relationship between DNA, chromatin, and chromosomes.
Answer: DNA is the genetic material that contains the instructions for protein synthesis. In its relaxed form, it
is called chromatin. During cell division, chromatin condenses to form chromosomes, which carry the DNA to
daughter cells.

Understanding and Analysis

What is the significance of histones in the structure of chromatin?
Answer: Histones are proteins around which DNA wraps, forming nucleosomes. They help in organizing the
DNA into a compact structure, allowing it to fit within the nucleus and also play a role in regulating gene
expression.

Understanding and Analysis

What role does the nucleosome play in the structure of chromatin?
Answer: The nucleosome is the basic structural unit of chromatin, consisting of DNA wrapped around histone
proteins. It helps in compacting the DNA into a manageable form and regulates gene expression.

Recall and Understanding

Why is the condensation of chromosomes important during cell division?
Answer: The condensation of chromosomes is important to prevent the DNA from tangling or breaking during
cell division. It ensures that each daughter cell receives an exact copy of the genetic material
 Genetics
It is the study of transmission of characters from parents to offspring
and the laws relating to such transmission.
Mendel’s Laws of Inheritance :

First Law (Law of Segregation)

Each organism has two alleles for each trait, one
Mendel experimented on garden pea
inherited from each parent.
These alleles segregate (separate) during the
plant (Pisum sativum) having many
formation of gametes, and each gamete receives visible contrasting characters.
only one allele. He used seven contrasting pairs of
Example: In a monohybrid cross, if a parent has a characters or traits in garden pea.
genotype of Aa, gametes will have either A or a.

Second Law (Law of Independent Assortment)

Genes for different traits are inherited
independently of each other, provided they are on
different chromosomes.
Example: The inheritance of seed color does not
affect the inheritance of seed shape in pea plants.

Third Law (Law of Dominance)

In a heterozygous condition, the dominant allele
expresses its trait while the recessive allele is
masked.
Example: In the case of pea plant flower color,
purple (P) is dominant over white (p), so the
genotype Pp will show purple flowers.

Monohybrid Cross Dihybrid Cross

A monohybrid cross involves the A dihybrid cross involves the inheritance of
inheritance of a single trait. two traits simultaneously.
Example: Crossing a homozygous Example: Cross between a plant with
tall plant (TT) with a homozygous genotype (RRYY) for round, yellow
short plant (tt). seeds and (rryy) for wrinkled, green
seeds.
Phenotypic ratio: The ratio of different
physical traits in offspring. Phenotypic ratio: In the F2 generation, the
For this cross, all F1 offspring will phenotypic ratio for the two traits is
be tall (Tt), so the phenotypic ratio 9:3:3:1:
is 100% tall. 9 Round, Yellow
3 Round, Green
Genotypic ratio: The ratio of different 3 Wrinkled, Yellow
genetic combinations. 1 Wrinkled, Green
The genotypic ratio for F1 offspring
(Tt x Tt) is 1 TT : 2 Tt : 1 tt.
Key Terminology
Gene: A segment of DNA that determines a particular trait.

Allele: Different forms of a gene (e.g., A and a, where A is the dominant allele
and a is the recessive allele).

Heterozygous: An individual with two different alleles for a trait (e.g., Aa).

Homozygous: An individual with two identical alleles for a trait (e.g., AA or

aa).

Dominant: An allele that masks the expression of the recessive allele in a

heterozygous individual (e.g., A).

Recessive: An allele that is masked by the dominant allele in a heterozygous

individual (e.g., a).

Mutation: A change in the DNA sequence that may lead to a change in the
organism's traits.

Variation: The differences between individuals of the same species due to

genetic differences.

Phenotype: The physical appearance or expression of a trait in an organism

(e.g., tall, short).

Genotype: The genetic makeup of an organism, represented by the alleles it

carries (e.g., AA, Aa, aa).

Sex Determination in Humans

Sex Chromosomes: Humans have 23 pairs of chromosomes, 22 pairs of

autosomes (non-sex chromosomes) and 1 pair of sex chromosomes.

XY system: Females have two X chromosomes (XX), and males have one X and
one Y chromosome (XY).

Male offspring: Males inherit an X chromosome from their mother and a Y

chromosome from their father (XY).

Female offspring: Females inherit one X chromosome from both their mother
and father (XX).
Sex-linked Inheritance of Diseases (X-linked)
Some genetic diseases are carried on the X chromosome and are known as X-
linked diseases.

Haemophilia: A genetic disorder where the blood doesn’t clot properly. It is

caused by a mutation in a gene on the X chromosome. Since males have only
one X chromosome, they are more likely to be affected. Females are typically
carriers if they have one affected X chromosome.

Colour Blindness: A condition where individuals cannot distinguish certain

colors. This is caused by a mutation in the gene for color vision on the X
chromosome. Like haemophilia, males are more frequently affected because
they have only one X chromosome.

Multiple Choice Questions

Recall
Which of the following is true about Mendel’s Law of Dominance?
A) The dominant allele can be masked by the recessive allele.
B) The dominant allele expresses its trait only in a heterozygous condition.
C) The recessive allele expresses its trait in a homozygous condition.
D) Both alleles contribute equally to the phenotype.
Answer: C) The recessive allele expresses its trait in a homozygous condition.
Explanation: The Law of Dominance states that the dominant allele expresses its phenotype in both
homozygous and heterozygous conditions, while the recessive allele expresses its phenotype only when
present in a homozygous condition.

Understanding
In a monohybrid cross between two heterozygous pea plants (Tt × Tt), what is the genotypic ratio of the
offspring?
A) 1 TT : 2 Tt : 1 tt
B) 1 TT : 1 Tt : 1 tt
C) 2 TT : 1 Tt : 1 tt
D) 2 TT : 2 Tt : 2 tt
Answer: A) 1 TT : 2 Tt : 1 tt
Explanation: The Punnett square for Tt × Tt gives a genotypic ratio of 1 TT : 2 Tt : 1 tt.

Recall
What does the term ‘heterozygous’ refer to?
A) Two identical alleles for a gene.
B) Two different alleles for a gene.
C) A gene that is not expressed.
D) A gene that always expresses the dominant trait.
Answer: B) Two different alleles for a gene.
Explanation: Heterozygous refers to having two different alleles for a particular gene, e.g., Tt.
Understanding and Application
In a dihybrid cross, the phenotypic ratio of the F2 generation in a heterozygous cross (AaBb × AaBb)
is:
A) 9:3:3:1
B) 1:2:3:4
C) 3:1
D) 1:1:1:1
Answer: A) 9:3:3:1
Explanation: In a dihybrid cross, the typical phenotypic ratio of the F2 generation is 9:3:3:1, where 9
show both dominant traits, 3 show the first dominant and second recessive, 3 show the first
recessive and second dominant, and 1 shows both recessive traits.

Understanding
What is the phenotypic ratio observed in a monohybrid cross of two heterozygous organisms (Tt ×
Tt)?
A) 3 tall : 1 short
B) 1 tall : 1 short
C) 2 tall : 2 short
D) 3 dominant : 1 recessive
Answer: A) 3 tall : 1 short
Explanation: The phenotypic ratio in a monohybrid cross between two heterozygous individuals (Tt
× Tt) is 3 tall : 1 short.

Recall and Understanding

What term describes the physical appearance or expression of an organism’s genotype?
A) Genotype
B) Heterozygous
C) Phenotype
D) Allele
Answer: C) Phenotype
Explanation: The phenotype refers to the physical expression or appearance of an organism based
on its genotype.

Application
Which of the following best describes sex-linked inheritance?
A) Traits that are controlled by genes on the X or Y chromosome.
B) Traits that are inherited from both parents equally.
C) Traits controlled by genes located in the nucleus.
D) Traits controlled by genes on the autosomes.
Answer: A) Traits that are controlled by genes on the X or Y chromosome.
Explanation: Sex-linked inheritance involves genes located on the X or Y chromosomes, and the
traits they control are passed down through the sex chromosomes.
Analysis
Which of the following individuals would be most likely to inherit a sex-linked recessive disorder like
hemophilia?
A) A male with a normal X chromosome and a Y chromosome.
B) A female with two X chromosomes carrying the normal allele.
C) A male with one X chromosome carrying the hemophilia allele and a Y chromosome.
D) A female with two X chromosomes carrying the hemophilia allele.
Answer: C) A male with one X chromosome carrying the hemophilia allele and a Y chromosome.
Explanation: Males inherit only one X chromosome, so if it carries a recessive allele for a sex-linked
disorder like hemophilia, the disorder will be expressed.

Recall
Which of the following is an example of a dominant allele?
A) b (blue eyes)
B) T (tall height)
C) t (short height)
D) r (round seeds)
Answer: B) T (tall height)
Explanation: The dominant allele for tall height in Mendel’s pea plant experiment was represented
by “T”.

Understanding
What does the term "genotype" refer to?
A) The physical appearance of an organism.
B) The genetic constitution of an organism.
C) The environmental influence on traits.
D) The inheritance pattern of traits.
Answer: B) The genetic constitution of an organism.
Explanation: The genotype refers to the specific genetic makeup of an organism, represented by the
combination of alleles inherited from both parents.

Application and Analysis

In human beings, if a male inherits a defective X-linked gene for color blindness, what would be his
condition?
A) He will be a carrier of color blindness.
B) He will be colorblind.
C) He will have normal color vision.
D) He will be unaffected by the condition.
Answer: B) He will be colorblind.
Explanation: Since males have only one X chromosome, if it carries the defective gene for color
blindness, the male will express the disorder.
Analysis and Application
In a cross between a female carrier of color blindness (XᴄX) and a normal male (XY), what is the
probability of having a colorblind child?
A) 25%
B) 50%
C) 100%
D) 0%
Answer: B) 50%
Explanation: The female carrier (XᴄX) can pass either the normal X (X) or the colorblind X (Xᴄ), while
the male passes the Y chromosome. The possibilities include normal or colorblind sons (50%
chance), and normal or carrier daughters (50% chance).

Understanding and Application

Which of the following terms refers to a change in the DNA sequence that can lead to genetic
variation?
A) Mutation
B) Phenotype
C) Allele
D) Homozygous
Answer: A) Mutation
Explanation: Mutations are changes in the DNA sequence that can lead to new genetic variations,
some of which may be inherited.

Understanding
What is the relationship between genotype and phenotype?
A) The genotype directly determines the phenotype, but environmental factors can influence it.
B) Genotype has no effect on phenotype.
C) Phenotype determines genotype.
D) There is no relationship between genotype and phenotype.
Answer: A) The genotype directly determines the phenotype, but environmental factors can
influence it.
Explanation: The genotype determines the potential phenotype, but environmental influences can
sometimes modify the phenotype.

Recall
What is the term for an organism that has two identical alleles for a trait?
A) Heterozygous
B) Homozygous
C) Recessive
D) Dominant
Answer: B) Homozygous
Explanation: Homozygous refers to an organism having two identical alleles for a particular trait
(e.g., TT or tt).
Understanding
In a monohybrid cross between a homozygous dominant and a homozygous recessive organism (TT × tt),
what will be the genotype of the F1 generation?
A) TT
B) Tt
C) tt
D) 50% TT and 50% tt
Answer: B) Tt
Explanation: In a cross between TT and tt, all the F1 offspring will have the genotype Tt (heterozygous).

Analysis
If a mutation occurs in the DNA of a gamete, what will be the consequence for the offspring?
A) The mutation will affect the offspring only if it is dominant.
B) The mutation will be passed to the offspring if it occurs in the gametes.
C) The mutation will affect the parent, not the offspring.
D) The mutation will not affect the offspring if it is recessive.
Answer: B) The mutation will be passed to the offspring if it occurs in the gametes.
Explanation: Mutations in the DNA of gametes (sperm or egg cells) are passed to the offspring, potentially
affecting their phenotype or genotype.

Understanding
Which of the following is true about a sex-linked recessive trait?
A) It is expressed only in females.
B) It is expressed in males even if they inherit only one copy of the gene.
C) It is inherited equally by both male and female offspring.
D) It is more common in females than in males.
Answer: B) It is expressed in males even if they inherit only one copy of the gene.
Explanation: Males have only one X chromosome, so if it carries a recessive allele for a sex-linked disorder, it
will be expressed.

Application
If a mother is a carrier for hemophilia (XᴄX) and the father has normal blood clotting (XY), what is the
probability of their son being affected by hemophilia?
A) 25%
B) 50%
C) 0%
D) 100%
Answer: B) 50%
Explanation: Sons inherit their X chromosome from their mother and Y chromosome from their father. If the
mother is a carrier (XᴄX), there is a 50% chance her son will inherit the Xᴄ allele and be affected by hemophilia.

Recall
Which term describes an organism's genetic makeup, represented by alleles?
A) Phenotype
B) Genotype
C) Heterozygous
D) Mutation
Answer: B) Genotype
Explanation: The genotype is the genetic makeup of an organism, represented by the combination of alleles.
Short Answer Type Questions
Recall
Q: What are the three laws of Mendel?
Solution: The three laws of Mendel are:
1. Law of Dominance: In a pair of alleles, one allele may dominate over the other, and the recessive allele will
not be expressed in the presence of the dominant allele.
2. Law of Segregation: During the formation of gametes, the two alleles for a gene segregate or separate, so
each gamete carries only one allele for a particular trait.
3. Law of Independent Assortment: Alleles for different traits assort independently of one another during
gamete formation.

Understanding
Q: Define the terms "phenotype" and "genotype" with an example.
Solution:
Phenotype refers to the observable characteristics or traits of an organism, such as height, color, or shape.
For example, the phenotype of a pea plant could be "tall" or "short."
Genotype refers to the genetic makeup or the specific alleles an organism carries for a particular trait. For
example, the genotype of a pea plant for height could be "Tt" (heterozygous) or "TT" (homozygous
dominant).

Application
Q: In a monohybrid cross between two heterozygous pea plants (Tt × Tt), what is the phenotypic ratio of the F2
generation?
Solution: The phenotypic ratio in a monohybrid cross between two heterozygous plants (Tt × Tt) will be:
3 Tall (dominant phenotype) : 1 Short (recessive phenotype)
This is because the Punnett square gives the genotypic ratio 1 TT : 2 Tt : 1 tt, and the tall phenotype is dominant.

Analysis
Q: What will be the genotypic and phenotypic ratios of the F1 generation in a dihybrid cross (AaBb × AaBb)?
Solution: In a dihybrid cross between two heterozygous individuals (AaBb × AaBb), the phenotypic ratio of the
F1 generation will be:
9:3:3:1
9 individuals with both dominant traits
3 individuals with the first dominant and second recessive trait
3 individuals with the first recessive and second dominant trait
1 individual with both recessive traits

Recall and Understanding

Q: Differentiate between "homozygous" and "heterozygous" organisms with examples.
Solution:
Homozygous: An organism is homozygous when it has two identical alleles for a particular trait. For
example, TT (homozygous dominant) or tt (homozygous recessive).
Heterozygous: An organism is heterozygous when it has two different alleles for a particular trait. For
example, Tt (heterozygous).
Application
Q: Explain how a mutation in a gene can lead to genetic variation.
Solution: A mutation is a sudden, permanent change in the DNA sequence. Mutations can introduce new
alleles into a population, leading to genetic variation. If the mutation is beneficial, it may increase the
organism's fitness and be passed on to the next generation. For example, a mutation in a flower color gene
may result in a new color, which could provide a survival advantage.

Understanding
Q: What is a monohybrid cross? Illustrate with an example.
Solution: A monohybrid cross involves the inheritance of a single trait. For example, crossing two
heterozygous pea plants (Tt) for the trait of height:
Parental cross: Tt × Tt
Punnett square result:
1 TT (Tall)
2 Tt (Tall)
1 tt (Short)
Phenotypic ratio: 3 Tall : 1 Short

Application and Analysis

Q: How does the inheritance of color blindness follow a sex-linked pattern?
Solution: Color blindness is an X-linked recessive disorder. Since males have only one X chromosome (XY), if
they inherit the X chromosome carrying the defective gene for color blindness, they will be affected. Females
have two X chromosomes (XX), so they must inherit the defective gene from both parents to be affected.
Females who inherit the gene from only one parent are carriers.

Recall
Q: What is the role of the Y chromosome in human sex determination?
Solution: The Y chromosome plays a crucial role in male sex determination. It carries the SRY gene, which
triggers the development of male characteristics during embryonic development. Males have one X and one
Y chromosome (XY), while females have two X chromosomes (XX).

Analysis
Q: Explain the difference between dominant and recessive traits with an example.
Solution:
Dominant trait: A dominant trait is expressed even if only one allele is present. For example, the allele for
tall height (T) is dominant. So, both TT and Tt will result in tall plants.
Recessive trait: A recessive trait is expressed only when both alleles are recessive. For example, the allele
for short height (t) is recessive, so only tt will result in a short plant.

Analysis
Q: Explain the difference between dominant and recessive traits with an example.
Solution:
Dominant trait: A dominant trait is expressed even if only one allele is present. For example, the allele for
tall height (T) is dominant. So, both TT and Tt will result in tall plants.
Recessive trait: A recessive trait is expressed only when both alleles are recessive. For example, the allele
for short height (t) is recessive, so only tt will result in a short plant.
Recall and Understanding
Q: What is a gene?
Solution: A gene is a segment of DNA that codes for a specific protein or trait. It is the basic unit of heredity,
responsible for the transmission of traits from parents to offspring.

Application
Q: In a cross between a normal male (XY) and a colorblind female carrier (XᴄX), what is the probability that
their son will be colorblind?
Solution:
Male offspring inherit the Y chromosome from their father and one X chromosome from their mother.
If the mother is a carrier (XᴄX), there is a 50% chance of passing the Xᴄ (colorblind allele) to her son.
Therefore, the probability of the son being colorblind is 50%.

Understanding and Application

Q: How would the F1 generation of a cross between two homozygous pea plants (TT × tt) look like?
Solution: In the cross between two homozygous pea plants (TT × tt), all the offspring in the F1 generation will be
heterozygous (Tt). Since T is dominant, all offspring will exhibit the dominant trait, tall.

Understanding
Q: What is a dihybrid cross and how is it different from a monohybrid cross?
Solution: A dihybrid cross involves two traits, whereas a monohybrid cross involves one trait. For example, in a
dihybrid cross of two heterozygous pea plants for height and seed color (AaBb × AaBb), four different
phenotypic combinations are possible. In contrast, a monohybrid cross focuses on just one trait.

Recall and Understanding

Q: What is a carrier in terms of genetic inheritance?
Solution: A carrier is an individual who has one copy of a recessive allele for a genetic disorder but does not
express the disorder themselves. For example, a female carrier of color blindness has one normal X (X) and
one X carrying the color blindness allele (Xᴄ).

Analysis
Q: If a female is colorblind, what would be the genotypic ratio of her children when crossed with a normal
male?
Solution:
The female will have the genotype XᴄXᴄ (homozygous for the colorblind allele).
The male will have the genotype XY (normal vision).
The possible offspring will be:
Sons: Will inherit the Y chromosome from their father and one X chromosome (Xᴄ) from their mother.
So, all sons will be colorblind (XᴄY).
Daughters: Will inherit one X chromosome from each parent, so all daughters will be carriers (XᴄX).
Therefore, the genotypic ratio of the children is:
Sons: 100% colorblind (XᴄY)
Daughters: 100% carriers (XᴄX)
Understanding
Q: What is the significance of genetic variation?
Solution: Genetic variation is essential for the survival and evolution of species. It increases the chances of
survival in changing environments, as some individuals may have traits that allow them to better adapt to
new conditions. For example, mutations can create new alleles, leading to variation in traits that may provide
a survival advantage.

Application
Q: What would happen if a dominant allele for a trait is present in both parents in a monohybrid cross?
Solution: If a dominant allele is present in both parents, the offspring will inherit at least one dominant allele
from each parent, resulting in a dominant phenotype. Even if the dominant allele is inherited from one parent,
the trait will be expressed.

Understanding
Q: How does sex determination occur in human beings?
Solution: In humans, sex determination is based on the presence of the X and Y chromosomes. Females have
two X chromosomes (XX), and males have one X and one Y chromosome (XY). The Y chromosome carries the
SRY gene, which triggers the development of male characteristics.

Recall
Q: Define a mutation. How can it affect an organism?
Solution: A mutation is a change in the DNA sequence that can lead to genetic variation. Mutations can be
harmful, beneficial, or neutral. For example, a mutation could result in a genetic disorder or it could provide a
beneficial trait, such as resistance to a disease.
 Absorption by roots
Absorption by Roots
Root Function: Roots absorb water and minerals
from the soil and transport them to the rest of the
plant.
Root Hair Adaptations: Root hairs increase the
surface area for water absorption.

Active and Passive Transport:

Passive Transport (e.g., Osmosis, Diffusion):
Movement of substances without energy
expenditure.
Active Transport: Movement of substances
against a concentration gradient, requiring
energy (ATP).

Imbibition : The process of

absorbing water by dry Diffusion : The movement of
substances (e.g., seeds, wood) molecules (liquids or gases)
due to the affinity of water from an area of higher
molecules for the surface of the
concentration to an area of
substance.
lower concentration until
Characteristics: equilibrium is reached.
It leads to swelling.
It is a physical process and Example in plants: Movement
does not involve energy. of gases (O₂, CO₂) through
Essential for seed germination. stomata during respiration and
photosynthesis.

Osmosis : The diffusion of water molecules through a selectively

permeable membrane from a region of lower solute
concentration to a region of higher solute concentration.

Key Terms: Endosmosis: Water

Osmotic Pressure: The pressure exerted by the solvent enters the cell.
(water) as it moves into the more concentrated solution. Exosmosis: Water
leaves the cell.
Turgidity: The state of being swollen or firm due to water
uptake (cell is turgid when full of water).

Flaccidity: The state of being soft or limp due to water loss

(cell becomes flaccid when water is lost).

Plasmolysis: Shrinkage of the cytoplasm due to water loss

when placed in a hypertonic solution.

Deplasmolysis: Re-entry of water into a plasmolysed cell

when placed in a hypotonic solution.
Root Pressure : The pressure exerted by the root cells as they absorb water
from the soil, pushing water upwards into the xylem.

Characteristics:
It is a result of active absorption of water.
It contributes to the upward movement of water in plants, especially
during the night.

Forces Responsible for Ascent of

Sap
Cohesion: Water molecules
The ascent of sap refers to the
stick together.
upward movement of water and
Adhesion: Water molecules
dissolved minerals (collectively
stick to the walls of xylem
called sap) from the roots to the
vessels.
leaves and other aerial parts of
Transpirational Pull: Loss of
the plant through the xylem.
water through transpiration
creates a suction force, pulling
water upwards.

Root Structure for Water Absorption

Characteristics of Roots:
Root hairs increase surface area for absorption.
Thin cell walls facilitate water entry.
Large vacuoles store absorbed water.

Structure of a Single Root Hair:

Long, tubular extension of an epidermal cell.
Thin cell wall and semi-permeable membrane.
Vacuole contains cell sap with high solute concentration.

Root Structure for Water Absorption

Experiments to Show Conduction of Water Through Xylem
Experiment 1:
Place a plant stem in colored water.
Observe the colored water rising through the xylem, staining the stem.

Experiment 2:
Cut a transverse section of the stem and observe under a microscope.
Colored rings indicate water movement through xylem vessels.
Multiple Choice Questions
Recall and Understanding
Q1. What is the process by which water enters root hairs from the soil?
(a) Diffusion
(b) Osmosis
(c) Active transport
(d) Imbibition
Answer: (b) Osmosis
Explanation: Water moves from a region of higher water potential (soil) to lower water potential (root hair)
through a semi-permeable membrane.

Recall and Understanding

Q2. Root hairs are extensions of which part of the root?
(a) Cortex
(b) Epidermis
(c) Pericycle
(d) Endodermis
Answer: (b) Epidermis
Explanation: Root hairs are tubular extensions of epidermal cells that increase the surface area for water
absorption.

Application
Q3. Which condition will lead to plasmolysis in a plant cell?
(a) Placing it in a hypertonic solution
(b) Placing it in a hypotonic solution
(c) Keeping it in distilled water
(d) Exposing it to bright light
Answer: (a) Placing it in a hypertonic solution
Explanation: In a hypertonic solution, water leaves the cell, causing the cytoplasm to shrink.

Application
Q4. What causes root pressure to develop in plants?
(a) Loss of water from leaves
(b) Active absorption of ions by roots
(c) Cohesion and adhesion of water molecules
(d) Transpirational pull
Answer: (b) Active absorption of ions by roots
Explanation: Root pressure develops due to osmotic movement of water caused by the active uptake of
minerals.

Analysis
Q5. A plant placed in a saline environment starts wilting. What explains this phenomenon?
(a) Loss of turgidity due to plasmolysis
(b) Excessive transpiration
(c) Lack of mineral uptake
(d) Reduced photosynthesis
Answer: (a) Loss of turgidity due to plasmolysis
Explanation: The saline environment is hypertonic, causing water loss from cells, leading to wilting.
Analysis
Q6. Which of the following combinations is responsible for the ascent of sap?
(a) Osmosis and active transport
(b) Transpirational pull, cohesion, adhesion
(c) Root pressure and plasmolysis
(d) Active and passive transport
Answer: (b) Transpirational pull, cohesion, adhesion
Explanation: These forces work together to move water upward through the xylem.

Recall
Q7. What is the main component of xylem that conducts water?
(a) Phloem fibers
(b) Tracheids and vessels
(c) Sieve tubes
(d) Companion cells
Answer: (b) Tracheids and vessels
Explanation: Tracheids and vessels are specialized structures in xylem for water conduction.

Recall
Q8. What is the term for the pressure exerted by the cell contents against the cell wall?
(a) Osmotic pressure
(b) Root pressure
(c) Turgor pressure
(d) Atmospheric pressure
Answer: (c) Turgor pressure
Explanation: Turgor pressure is crucial for maintaining cell rigidity.

Understanding and Application

Q9. Why is the root hair cell sap more concentrated than soil water?
(a) To facilitate active transport
(b) To lower water potential for osmosis
(c) To increase transpiration rate
(d) To absorb minerals effectively
Answer: (b) To lower water potential for osmosis
Explanation: The concentration gradient facilitates water movement into root hair cells.

Understanding and Application

Q10. Why is active transport essential for mineral absorption in roots?
(a) Minerals are present in soil in high concentrations
(b) Minerals move against the concentration gradient
(c) It requires less energy
(d) It is a passive process
Answer: (b) Minerals move against the concentration gradient
Explanation: Active transport ensures mineral absorption even when soil concentration is low.

Analysis and Application

Q11. What will happen to a plant cell placed in distilled water?
(a) It will plasmolyze
(b) It will become turgid
(c) It will remain unchanged
(d) It will shrink
Answer: (b) It will become turgid
Explanation: Water enters the cell due to osmosis, increasing turgor pressure.
Analysis and Application
Q12. Which force prevents the breaking of water columns in xylem during ascent of sap?
(a) Transpiration
(b) Adhesion
(c) Cohesion
(d) Root pressure
Answer: (c) Cohesion
Explanation: Cohesion between water molecules prevents the column from breaking.

Recall and Understanding

Q13. What is the primary site for water absorption in plants?
(a) Root tip
(b) Root hairs
(c) Cortex
(d) Xylem
Answer: (b) Root hairs
Explanation: Root hairs increase surface area for water absorption.

Recall and Understanding

Q14. What is deplasmolysis?
(a) Shrinking of cytoplasm
(b) Swelling of plasmolyzed cells
(c) Movement of water out of the cell
(d) Death of root hair cells
Answer: (b) Swelling of plasmolyzed cells
Explanation: When a plasmolyzed cell is placed in a hypotonic solution, it regains turgidity.

Understanding and Analysis

Q15. Which of these experiments demonstrates water conduction in xylem?
(a) Wilting of leaves
(b) Dye rising in a cut stem
(c) Root hair absorbing water
(d) Leaf curling
Answer: (b) Dye rising in a cut stem
Explanation: The dye highlights the path of water through xylem.

Understanding and Analysis

Q16. How does transpirational pull aid in water movement?
(a) By reducing root pressure
(b) By creating a suction force in the xylem
(c) By pushing water from roots to leaves
(d) By reducing adhesion forces
Answer: (b) By creating a suction force in the xylem
Explanation: Transpiration creates a negative pressure that pulls water upward.

Application
Q17. Which of the following best describes the function of adhesion in xylem?
(a) Preventing water loss
(b) Attracting water molecules to cell walls
(c) Reducing transpiration rate
(d) Breaking water columns
Answer: (b) Attracting water molecules to cell walls
Explanation: Adhesion helps water molecules cling to xylem walls, aiding upward movement.
Application
18. In a plant experiment, why does a wilting leaf regain turgidity after watering?
(a) Increase in atmospheric pressure
(b) Osmosis restores turgor pressure
(c) Root pressure stops water loss
(d) Photosynthesis resumes
Answer: (b) Osmosis restores turgor pressure
Explanation: Water enters cells, restoring their turgid state.

Recall
Q19. What is the major driving force for water movement from roots to leaves?
(a) Root pressure
(b) Cohesion and adhesion
(c) Transpirational pull
(d) Osmotic pressure
Answer: (c) Transpirational pull
Explanation: Transpiration generates the force required for upward water movement.

Recall
Q20. What is the term for the movement of water into root hairs?
(a) Plasmolysis
(b) Osmosis
(c) Diffusion
(d) Active transport
Answer: (b) Osmosis
Explanation: Osmosis drives water movement from soil to root hairs due to the water potential gradient.

Short Answer Type Questions

Recall
Q1. Define osmosis.
Solution: Osmosis is the movement of water molecules from a region of higher water potential to a
region of lower water potential through a semi-permeable membrane.

Recall
Q2. What is the main function of root hairs?
Solution: The main function of root hairs is to increase the surface area of the root for efficient
absorption of water and minerals from the soil.

Understanding
Q3. Why does a plasmolyzed cell become turgid when placed in distilled water?
Solution: A plasmolyzed cell becomes turgid in distilled water because water enters the cell by
osmosis, increasing the turgor pressure.

Understanding
Q4. Explain the role of cohesion and adhesion in the ascent of sap.
Solution: Cohesion helps water molecules stick together, forming a continuous column, while
adhesion helps water molecules adhere to the walls of the xylem, preventing the column from
breaking.
Application
Q5. How does a hypertonic solution affect plant cells?
Solution: A hypertonic solution causes water to move out of the plant cells by osmosis, leading to
plasmolysis, where the cytoplasm shrinks away from the cell wall.

Application
Q6. Why does root pressure occur mostly at night?
Solution: Root pressure occurs at night due to the continuous absorption of minerals and water by
roots when transpiration rates are low.

Analysis
Q7. A plant wilts even after watering. What could be the reason?
Solution: The soil might be waterlogged, depriving roots of oxygen needed for respiration, which is
essential for active absorption of minerals and water.

Analysis
Q8. What would happen to the rate of water absorption if root hairs were absent?
Solution: The rate of water absorption would decrease significantly as root hairs increase the
surface area for water absorption.

Recall and Understanding

Q9. What is the significance of turgor pressure in plants?
Solution: Turgor pressure helps maintain the rigidity of plant cells, supports the plant structure, and
plays a role in opening and closing stomata.

Recall and Understanding

Q10. Differentiate between turgidity and flaccidity.
Solution: Turgidity is the state where cells are swollen due to water absorption, while flaccidity
occurs when cells lose water, causing them to become limp.

Application and Analysis

Q11. How can you demonstrate water conduction through the xylem?
Solution: Place a cut stem in a colored dye solution. After some time, the dye will travel upward,
highlighting the xylem's role in water conduction.

Application and Analysis

Q12. What adaptation allows root hairs to absorb water efficiently?
Solution: Root hairs are thin-walled and elongated, increasing the surface area for efficient
absorption of water and dissolved minerals.

Recall and Application

Q13. What is the role of active transport in mineral absorption?
Solution: Active transport allows the absorption of minerals against their concentration gradient,
requiring energy from ATP.
Recall and Application
Q14. How does transpiration help in the ascent of sap?
Solution: Transpiration creates a negative pressure in the xylem, generating a suction force
that pulls water upward from the roots to the leaves.

Understanding and Analysis

Q15. Explain why plants placed in saline soil wilt faster.
Solution: Saline soil creates a hypertonic environment, causing water to move out of plant
cells by osmosis, leading to loss of turgidity and wilting.

Understanding and Analysis

Q16. Why is cohesion between water molecules essential for transpiration?
Solution: Cohesion keeps water molecules linked in a continuous column, preventing the
column from breaking as water moves upward through the xylem.

Recall
Q17. What is plasmolysis?
Solution: Plasmolysis is the process where the cytoplasm shrinks and detaches from the
cell wall due to the loss of water in a hypertonic solution.

Recall
Q18. Name the two main forces responsible for the ascent of sap in tall trees.
Solution: Transpirational pull and root pressure are the two main forces responsible for the
ascent of sap in tall trees.

Application and Understanding

Q19. Why is it necessary for root hair cells to have a high concentration of solutes?
Solution: A high concentration of solutes lowers the water potential in root hair cells,
allowing water to enter from the soil by osmosis.

Application and Understanding

Q20. How does the experiment with a celery stalk in colored water demonstrate xylem
function?
Solution: The colored water travels through the xylem, staining the veins of the celery,
which visibly demonstrates the pathway of water conduction.
 Transpiration
Transpiration: The process by which plants lose
water vapor from their aerial parts, primarily
through stomata.

Importance:
1. Cooling: Reduces leaf temperature during hot
conditions.
2. Water and Nutrient Movement: Creates a
suction pull for water and dissolved minerals.
3. Turgor Maintenance: Helps maintain turgidity
of cells.
4. Gas Exchange: Facilitates opening of stomata
for photosynthesis.

Ganong’s Potometer and Its Limitations

1. Limitations: Ganong’s Potometer: Used
Not an accurate representation of to measure the rate of water
transpiration since some water is used for uptake, indirectly indicating
photosynthesis. transpiration rate.
Air bubbles can disrupt the apparatus.
Requires a perfectly cut stem to prevent Principle: Water lost by
leakage. transpiration is replaced by
water uptake.
Factors Affecting the Rate of Transpiration

Internal Factors
External Factors
Leaf Surface Area:
Larger surface area increases transpiration Light:
due to more exposure. Increases stomatal opening, accelerating
transpiration during the day.
Stomatal Number and Distribution:
More stomata or stomata concentrated on Temperature:
the lower surface (dorsiventral leaves) Higher temperatures increase evaporation
enhance transpiration. and diffusion rates.
Cuticle Thickness: Humidity:
A thick waxy cuticle reduces water loss by Low humidity enhances the water vapor
limiting evaporation. gradient, increasing transpiration.
Structure of Guard Cells: Wind Speed:
Efficient guard cell functioning aids in Strong winds remove the water vapor
regulating stomatal opening and closing. around leaves, increasing transpiration.

Soil Water Availability:

Adequate water in the soil maintains
transpiration; drought conditions decrease
it.
Experiments related to transpiration:
Loss in Weight Experiment:
Setup: A potted plant or a leafy shoot in a test tube is weighed initially
and after a fixed time.
Observation: The weight decreases due to water loss by transpiration.
Conclusion: Confirms water loss through transpiration.

Cobalt Chloride Paper Test:

Setup: Place dry cobalt chloride paper on both sides of a
dorsiventral leaf.
Observation: Paper on the lower surface turns pink faster.
Conclusion: Transpiration is more from the lower surface due to
higher stomatal density.

Mechanism of Stomatal Transpiration

(Potassium Ion Exchange Theory)
Adaptations in Plants to Reduce Transpiration
Stomatal Opening:
1. Thick waxy cuticle to minimize water
In light, guard cells actively absorb K⁺ ions.
loss.
Water enters guard cells by osmosis,
2. Sunken stomata reduce exposure to air
making them turgid, and the stomata
currents.
open.
3. Reduced leaf area (spines in cacti).
4. Hairy leaf surface traps moisture and
Stomatal Closing:
lowers transpiration.
At night, K⁺ ions exit guard cells.
Water moves out, making guard cells
flaccid, and the stomata close.

A Brief Idea of Guttation and Bleeding

Guttation:
Loss of liquid water through specialized
structures called hydathodes.
Occurs at night or early morning when soil
moisture is high.

Bleeding:
Oozing of sap from injured plant parts.
Common in plants like rubber or grapevine.
Multiple Choice Questions
Recall

1. What is the primary function of transpiration in plants?

A. Absorption of nutrients
B. Cooling the plant
C. Transport of food
D. Photosynthesis
Answer: B. Cooling the plant
Explanation: Transpiration helps regulate the temperature of the plant by cooling it through the
evaporation of water.

Recall and Understanding

2. Which of the following is a key feature of Ganong’s Potometer?

A. It measures root pressure.
B. It measures water absorption and loss by transpiration.
C. It only measures transpiration from leaves.
D. It directly measures water vapor released.
Answer: B. It measures water absorption and loss by transpiration.
Explanation: Ganong’s Potometer is used to measure the rate of water absorption by a plant
shoot, which is an indirect measure of transpiration.

Understanding and Application

3. Which experiment demonstrates the loss in weight of a plant due to transpiration?

A. Use of cobalt chloride paper
B. Ganong’s Potometer
C. Loss in weight of a potted plant or leafy shoot
D. Water absorption in a beaker
Answer: C. Loss in weight of a potted plant or leafy shoot
Explanation: In this experiment, the plant’s weight decreases as water is lost through
transpiration, which can be measured.

Analysis and Application

4. Which factor would most likely increase the rate of transpiration in plants?
A. Low humidity
B. Higher cuticle thickness
C. Reduced light intensity
D. Higher soil moisture
Answer: A. Low humidity
Explanation: Low humidity increases the concentration gradient between the leaf and the
surrounding air, which accelerates the rate of transpiration.

Recall

5. What is guttation?
A. Loss of water vapor through stomata
B. Loss of liquid water through hydathodes
C. Loss of water through the roots
D. Loss of nutrients through leaves
Answer: B. Loss of liquid water through hydathodes
Explanation: Guttation is the process of water being exuded from the edges of leaves as liquid,
typically during the night or early morning.
Recall and Understanding

6. Which of the following conditions would likely reduce the rate of transpiration in a plant?
A. High wind speed
B. Increased temperature
C. High humidity
D. Large surface area of leaves
Answer: C. High humidity
Explanation: High humidity reduces the concentration gradient of water vapor between the leaf
and the surrounding air, thus slowing down transpiration.

Application

7. The unequal rate of transpiration in a dorsiventral leaf can be demonstrated using which
material?
A. Potometer
B. Cobalt chloride paper
C. Hydathodes
D. Water in a test tube
Answer: B. Cobalt chloride paper
Explanation: Cobalt chloride paper turns from blue to pink in the presence of water vapor,
demonstrating the unequal rate of transpiration between the upper and lower surfaces of a
dorsiventral leaf.

Understanding and Application

8. How do potassium ions play a role in stomatal transpiration?

A. They increase water uptake by root cells.
B. They regulate the opening and closing of stomata.
C. They convert water into glucose.
D. They reduce transpiration by closing guard cells.
Answer: B. They regulate the opening and closing of stomata
Explanation: Potassium ions are involved in the process that controls the turgidity of guard cells,
thereby regulating stomatal opening and transpiration.

Application and Analysis

9. Which adaptation helps plants reduce transpiration in hot and dry climates?
A. Thick cuticle
B. Larger stomatal openings
C. Increased leaf surface area
D. Higher rate of photosynthesis
Answer: A. Thick cuticle
Explanation: A thick cuticle reduces water loss by preventing excessive evaporation from the
surface of the leaf.

Understanding and Application

10. How does wind speed affect the rate of transpiration?

A. It decreases the rate by closing the stomata.
B. It increases the rate by removing moisture from around the leaf.
C. It has no effect on the rate of transpiration.
D. It decreases the rate by reducing the concentration gradient.
Answer: B. It increases the rate by removing moisture from around the leaf
Explanation: Wind removes the water vapor surrounding the stomata, maintaining a steep
gradient that accelerates transpiration.
Recall
11. What is the main factor that drives the process of transpiration?
A. Root pressure
B. Capillary action
C. Water potential difference between the leaf and air
D. Osmosis
Answer: C. Water potential difference between the leaf and air
Explanation: The difference in water potential between the leaf cells and the surrounding air
creates a driving force for water to move out of the leaf, resulting in transpiration.

Recall and Understanding

12. Which of the following best explains the significance of transpiration in plants?
A. It helps absorb minerals from the soil.
B. It aids in the cooling of the plant.
C. It directly facilitates photosynthesis.
D. It supports the process of fertilization.
Answer: B. It aids in the cooling of the plant
Explanation: Transpiration helps cool the plant by evaporating water, preventing overheating in
high temperatures.

Application
13. Which of the following will most likely decrease the rate of transpiration?
A. Increase in temperature
B. Decrease in soil moisture
C. Increase in humidity
D. Increase in light intensity
Answer: C. Increase in humidity
Explanation: High humidity reduces the water vapor gradient between the leaf and surrounding
air, thus slowing down transpiration.

Analysis and Application

Why does the rate of transpiration decrease at night?
A. Stomata close at night.
B. Temperature is lower at night.
C. Both A and B are correct.
D. The plant is not actively photosynthesizing.
Answer: C. Both A and B are correct
Explanation: At night, stomata close and the temperature drops, reducing the rate of
transpiration.

Recall
15. Which part of the plant is primarily responsible for the loss of water during transpiration?
A. Roots
B. Leaves
C. Flowers
D. Stem
Answer: B. Leaves
Explanation: Most transpiration occurs through the stomata on the leaves, where water vapor
escapes into the atmosphere.

Application and Analysis

16. How does the presence of a thick waxy cuticle on the leaf surface help in reducing
transpiration?
A. It increases the evaporation rate.
B. It blocks the flow of water through the leaf.
C. It reduces water loss by preventing evaporation.
D. It increases stomatal opening.
Answer: C. It reduces water loss by preventing evaporation
Explanation: A thick cuticle prevents excessive water evaporation by forming a protective barrier
on the leaf surface.
Recall
17. What happens to transpiration when a plant is exposed to direct sunlight?
A. Transpiration decreases.
B. Transpiration increases.
C. Transpiration stops.
D. Transpiration becomes irregular.
Answer: B. Transpiration increases
Explanation: Direct sunlight increases the temperature and causes more water to evaporate from
the leaf surface, accelerating transpiration.

Application and Understanding

18. Which of the following experiments would demonstrate unequal transpiration from the upper
and lower surfaces of a dorsiventral leaf?
A. Potometer experiment
B. Cobalt chloride paper experiment
C. Water absorption experiment
D. Loss in weight of a potted plant experiment
Answer: B. Cobalt chloride paper experiment
Explanation: Cobalt chloride paper changes color in the presence of moisture, indicating the
higher rate of transpiration from the lower surface of a dorsiventral leaf.

Recall
19. Which structure in plants regulates the opening and closing of stomata?
A. Epidermis
B. Guard cells
C. Xylem
D. Phloem
Answer: B. Guard cells
Explanation: Guard cells regulate the opening and closing of stomata, controlling the rate of
transpiration.

Understanding and Application

20. How does the process of transpiration benefit the plant in terms of water and nutrient
transport?
A. Transpiration creates a negative pressure, aiding in water and nutrient uptake.
B. Transpiration causes a positive pressure that pushes water and nutrients to the roots.
C. Transpiration does not affect water and nutrient transport.
D. Transpiration helps in storing nutrients in leaves.
Answer: A. Transpiration creates a negative pressure, aiding in water and nutrient uptake
Explanation: The loss of water through transpiration creates a negative pressure that draws water
and nutrients from the roots up through the plant.

Short Answer Type Questions

Understanding
Q1: What is transpiration, and why is it important for plants?
Answer: Transpiration is the process of water loss from plants, mainly through the
stomata. It is important because it helps in water and nutrient transport, cooling the
plant, and maintaining turgor pressure.

Understanding
Q2: Explain the role of stomata in the process of transpiration.
Answer: Stomata are small pores on the surface of leaves that allow water vapor to
escape during transpiration. They also regulate gas exchange (CO2 and O2) for
photosynthesis.
Application
Q3: How does the rate of transpiration change in plants under dry conditions? Explain why
this happens.
Answer: The rate of transpiration increases under dry conditions as the plant loses water to
compensate for the lack of moisture in the environment. However, the plant may eventually
close its stomata to conserve water.

Analysis
Q4: Analyze how temperature affects the rate of transpiration in plants.
Answer: As temperature increases, the rate of transpiration increases because heat causes
water to evaporate more quickly from the stomata. However, excessive heat can lead to
excessive water loss and dehydration.

Understanding and Application

Q5: How does wind speed influence transpiration in plants? Provide examples.
Answer: Wind increases the rate of transpiration by removing the humid air around the
stomata, which allows more water vapor to escape. For example, in coastal areas, wind
speeds are higher, leading to greater water loss from plants.

Understanding
Q6: Describe the process of guttation in plants. How does it differ from transpiration?
Answer: Guttation is the exudation of water droplets from the edges of leaves, usually at
night, when root pressure is high. Unlike transpiration, which occurs mainly through
stomata, guttation is through specialized structures called hydathodes.

Application
Q7: You are conducting an experiment to measure the rate of transpiration using a
potometer. What factors could cause inaccuracies in your results?
Answer: Inaccuracies could arise from air bubbles in the potometer, improper sealing of
joints, or incorrect measurement of water loss due to external environmental factors like
temperature or humidity.

Understanding and Application

Q8: Explain the mechanism of stomatal transpiration based on the potassium ion exchange
theory.
Answer: According to the potassium ion exchange theory, the opening and closing of
stomata depend on the movement of potassium ions into guard cells, which causes water
to enter by osmosis, resulting in the expansion and opening of the stomata.

Analysis and Application

Q9: How do adaptations in desert plants help reduce water loss through transpiration?
Answer: Desert plants have adaptations like reduced leaf surface area, thick waxy cuticles,
and stomata that open at night to minimize water loss and conserve moisture during the
day.

Understanding
Q10: What is the significance of the cuticle in reducing transpiration in plants?
Answer: The cuticle is a waxy layer that covers the epidermis of leaves. It acts as a barrier,
reducing water loss and preventing excessive transpiration, especially in arid conditions.

Understanding and Application

Q11: Explain how cobalt chloride paper is used to demonstrate unequal rates of transpiration
on a dorsiventral leaf.
Answer: Cobalt chloride paper changes color when it absorbs moisture. By placing the
paper on the upper and lower surfaces of a dorsiventral leaf, you can demonstrate that the
lower surface (with more stomata) loses water more rapidly than the upper surface.
Application
Q12: How can Ganong’s potometer be used to study the rate of transpiration?
Answer: Ganong’s potometer measures the rate of water absorption by a plant, which is
proportional to the rate of transpiration. By observing the movement of air bubbles in a
water-filled tube, the rate at which water is drawn through the plant can be determined.

Analysis
Q13: Analyze how high humidity affects the rate of transpiration in plants.
Answer: High humidity reduces the rate of transpiration because the air surrounding the
stomata is already saturated with water vapor, leading to a reduced gradient for water loss.

Understanding
Q14: What are the factors that determine the rate of transpiration in plants?
Answer: The factors include temperature, humidity, wind speed, light intensity, soil
moisture, and the number of stomata present on the leaves.

Understanding and Application

Q15: How does light intensity affect the rate of transpiration? Provide a practical example.
Answer: Light intensity increases the rate of transpiration as it stimulates the stomata to
open for gas exchange during photosynthesis. For example, in the daytime, plants transpire
more as stomata open to take in CO2 for photosynthesis.

Application
Q16: If a plant is placed in a sealed container with high humidity, what do you expect to
happen to the rate of transpiration?
Answer: The rate of transpiration would decrease because the air inside the container
would be saturated with water vapor, reducing the moisture gradient between the inside of
the leaf and the surrounding air.

Understanding
Q17: What is the role of guard cells in regulating transpiration?
Answer: Guard cells control the opening and closing of stomata. When they are turgid, the
stomata open, allowing transpiration to occur. When they lose water and become flaccid,
the stomata close to conserve water.

Application
Q18: Describe an experiment to demonstrate the loss in weight of a potted plant due to
transpiration.
Answer: Place a potted plant in a closed container and measure its initial weight. After a
period, measure the weight again. The difference in weight is due to the loss of water
through transpiration.

Understanding and Application

Q19: How do plants in tropical rainforests adapt to prevent excessive transpiration?
Answer: Rainforest plants have large, broad leaves with a thick cuticle, and many have
stomata on the lower surface to reduce direct exposure to sunlight, thus minimizing water
loss.

Application
Q20: What would happen to the rate of transpiration in a plant if the stomata were blocked
by a chemical substance? Explain why.
Answer: If the stomata were blocked, transpiration would be reduced or stopped because
water vapor cannot escape through the stomata, disrupting the normal process of water
loss and gas exchange.
 Photosynthesis
Photosynthesis is the process by which plants, algae, and some bacteria
convert light energy into chemical energy, producing glucose and oxygen
from carbon dioxide and water.

Importance:
It is crucial for life on Earth as it produces oxygen, which is essential for
respiration.
It forms the base of the food chain by synthesizing glucose, which is the
primary energy source for organisms.
Photosynthesis helps regulate the levels of carbon dioxide in the
atmosphere.
Internal Structure of Chloroplast:
Chloroplasts are the organelles responsible for
photosynthesis. They contain chlorophyll, the
green pigment that absorbs light.

Structure:

Thylakoids: Membranous sacs where the light

reaction occurs.

Stroma: The fluid surrounding the thylakoids

where the dark reaction (Calvin cycle) occurs.

The chloroplast is the site where both the light

and dark reactions of photosynthesis take place.

Opening and Closing of Stomata:

Stomata open and close based on the potassium ion exchange theory.
During the day, light causes the guard cells to take in potassium ions, leading to
water influx and turgor pressure, causing stomata to open.
At night, potassium ions are actively pumped out, leading to water loss and closing
of the stomata.

Balanced Chemical Equation for Photosynthesis:

NADPH : Nicotinamide Adenine

Dinucleotide Phosphate Hydrogen
CO₂: Carbon dioxide from the air.
H₂O: Water absorbed by roots. ATP : Adenosine triphosphate
Glucose (C₆H₁₂O₆): Produced as food for the plant.
O₂: Released into the atmosphere as a by-product. NADP : Nicotinamide Adenine
Dinucleotide Phosphate
Light Reaction (Photochemical Phase):

Activation of Chlorophyll: Chlorophyll absorbs light energy, exciting electrons.

Photolysis of Water: Water molecules are split to release oxygen, protons (H⁺), and
electrons.

Formation of ATP and NADPH: Energy from light is used to form ATP (through
photophosphorylation) and NADPH, which are used in the dark reaction.

Dark Reaction (Biosynthetic Phase):

Calvin Cycle: The combination of Photochemical Phase: Refers to the

hydrogen from NADPH and carbon light-dependent reactions where light
dioxide (CO₂) forms glucose. energy is converted to chemical
energy.
No light is required for the dark reaction,
but it relies on the ATP and NADPH Biosynthetic Phase: Refers to the dark
reaction where CO₂ is converted to
produced during the light reaction.
glucose.

Adaptations in Plants for Photosynthesis:

Leaf Structure: Broad leaves with a large surface area for maximum light absorption.
Chloroplasts: Concentrated in the upper layers of leaves to absorb sunlight efficiently.
Veins: Transport water to the leaves and carry glucose away.
Stomata: Regulate the exchange of gases (CO₂ and O₂) and water vapor.

Experiments to Show the Necessity of Light, Carbon Dioxide, Chlorophyll, and Formation
of Starch:

Experiment to Show the Need for Light:

Procedure: Place a potted plant in a dark room for 48 hours to destarch it. Then,
expose it to light for a few hours and perform a starch test.
Observation: No starch will form in the leaf kept in the dark, while starch will form in
the leaf exposed to light, demonstrating the necessity of light for photosynthesis.

Experiment to Show the Need for Carbon Dioxide:

Procedure: Place a potted plant in a bell jar with sodium hydroxide (which absorbs
CO₂) and expose it to light.
Observation: The plant will not produce starch, indicating that CO₂ is essential for
photosynthesis.

Experiment to Show the Need for Chlorophyll:

Procedure: Boil a leaf in water, then immerse it in iodine solution to test for starch.
Observation: Only the green parts of the leaf will show starch presence,
demonstrating that chlorophyll is necessary for photosynthesis.

Experiment to Show the Formation of Starch:

Procedure: Perform a destarching experiment, then expose a leaf to sunlight and
conduct a starch test.
Observation: The leaf will show a blue-black color when iodine is applied, proving
that starch is formed during photosynthesis.
Carbon Cycle:

The carbon cycle is the process by which carbon is exchanged between the atmosphere,
plants, animals, and the earth's surface.
1. Photosynthesis: Plants absorb CO₂ from the atmosphere and convert it into glucose.
2. Respiration: Animals and plants release CO₂ back into the atmosphere when they
respire.
3. Decomposition: Dead plants and animals release CO₂ as they decay.
4. Combustion: The burning of fossil fuels releases CO₂ into the atmosphere.

Multiple Choice Questions

Recall
Question: What is the main product of the process of photosynthesis?
A) Oxygen
B) Carbon dioxide
C) Glucose
D) Nitrogen
Answer: C) Glucose
Explanation: Photosynthesis primarily produces glucose (C₆H₁₂O₆) which serves as the
plant's energy source. Oxygen is released as a byproduct.

Understanding
Question: Which of the following is required for photosynthesis to occur?
A) Sunlight
B) Chlorophyll
C) Carbon dioxide
D) All of the above
Answer: D) All of the above
Explanation: Photosynthesis requires sunlight, chlorophyll, and carbon dioxide to produce
glucose and oxygen.
Application
Question: In an experiment to demonstrate the necessity of light for photosynthesis, a
plant is kept in the dark for 48 hours. What would be the expected result of the starch test?
A) The leaf will turn blue-black
B) The leaf will remain yellow
C) The leaf will show no change
D) The leaf will turn green
Answer: C) The leaf will show no change
Explanation: When a plant is kept in the dark, it cannot carry out photosynthesis, so no
starch will be formed in the leaf.

Analysis
Question: Which part of the chloroplast is the site for the light reactions of photosynthesis?
A) Stroma
B) Thylakoid membrane
C) Inner membrane
D) Cytoplasm
Answer: B) Thylakoid membrane
Explanation: The light reactions of photosynthesis occur in the thylakoid membrane of the
chloroplast, where chlorophyll absorbs sunlight.

Understanding and Application

Question: What happens to the carbon dioxide during the dark reaction of photosynthesis?
A) It is used to form glucose
B) It is released into the atmosphere
C) It is converted into oxygen
D) It is stored as starch
Answer: A) It is used to form glucose
Explanation: During the dark reaction (Calvin cycle), carbon dioxide is fixed and combined
with hydrogen from NADPH to form glucose.

Recall
Question: Which pigment is primarily responsible for the absorption of light during
photosynthesis?
A) Carotene
B) Xanthophyll
C) Chlorophyll
D) Phycobilin
Answer: C) Chlorophyll
Explanation: Chlorophyll is the primary pigment responsible for absorbing light in
photosynthesis, especially in the blue and red wavelengths.

Application
Question: If a plant is kept in a sealed container with an indicator solution for carbon
dioxide and exposed to light, what would be the expected result?
A) The solution will turn pink
B) The solution will turn blue
C) The solution will remain yellow
D) The solution will remain neutral
Answer: A) The solution will turn pink
Explanation: In the presence of carbon dioxide, the solution typically turns yellow. In
photosynthesis, CO₂ is consumed, and the solution turns pink as the CO₂ concentration
decreases.
Understanding
Question: In the process of photosynthesis, which of the following is the source of oxygen?
A) Carbon dioxide
B) Water
C) Glucose
D) Sunlight
Answer: B) Water
Explanation: Water molecules undergo photolysis during the light reaction, releasing oxygen as a by-
product.

Understanding
Question: The light reaction of photosynthesis produces which of the following?
A) ATP and NADPH
B) Oxygen and Carbon dioxide
C) Glucose and Oxygen
D) Water and ATP
Answer: A) ATP and NADPH
Explanation: The light reactions of photosynthesis produce ATP and NADPH, which are used in the dark
reactions (Calvin cycle).

Application
Question: What will happen to the rate of photosynthesis if a plant is exposed to increased concentrations
of carbon dioxide?
A) The rate will decrease
B) The rate will increase
C) The rate will remain constant
D) The rate will fluctuate
Answer: B) The rate will increase
Explanation: Increased carbon dioxide concentrations provide more raw material for photosynthesis,
thus increasing the rate of the process, up to a certain point.

Recall and Understanding

Question: What is the role of chlorophyll in photosynthesis?
A) It absorbs light energy
B) It transports water
C) It stores glucose
D) It absorbs oxygen
Answer: A) It absorbs light energy
Explanation: Chlorophyll absorbs light energy, which is then used in the light reactions of photosynthesis
to produce ATP and NADPH.

Analysis
Question: If a plant is exposed to light but kept in an environment without carbon dioxide, what would
happen to its photosynthesis?
A) It will continue normally
B) It will stop completely
C) It will increase rapidly
D) It will decrease but not stop
Answer: B) It will stop completely
Explanation: Carbon dioxide is a key reactant in photosynthesis, and without it, the plant cannot carry out
the process, even if light is present.

Recall
Question: In the Calvin cycle, what is the main product formed from the fixation of carbon dioxide?
A) Oxygen
B) Glucose
C) ATP
D) NADPH
Answer: B) Glucose
Explanation: The Calvin cycle uses carbon dioxide and hydrogen (from NADPH) to form glucose, which is
the final product.
Understanding and Application
Question: What is the significance of the process of photosynthesis for life on Earth?
A) It helps in producing oxygen
B) It produces glucose, which is a source of energy
C) It reduces the carbon dioxide concentration in the atmosphere
D) All of the above
Answer: D) All of the above
Explanation: Photosynthesis plays a critical role in producing oxygen, glucose, and reducing carbon
dioxide, which supports life on Earth.

Recall
Question: Which of the following is not a product of the light reaction of photosynthesis?
A) Oxygen
B) Glucose
C) ATP
D) NADPH
Answer: B) Glucose
Explanation: Glucose is not directly produced in the light reaction; it is produced in the dark reaction
using ATP and NADPH from the light reaction.

Analysis and Application

Question: If a plant's chloroplasts are destroyed, what effect will this have on photosynthesis?
A) It will have no effect
B) It will stop the light reaction only
C) It will stop the dark reaction only
D) It will stop photosynthesis completely
Answer: D) It will stop photosynthesis completely
Explanation: Chloroplasts are essential for photosynthesis as they contain chlorophyll. Without
chloroplasts, the plant cannot carry out either the light or dark reactions.

Understanding
Question: What happens to the stomata during the day in plants?
A) They remain closed
B) They open to allow CO₂ entry
C) They open to release oxygen
D) They close to conserve water
Answer: B) They open to allow CO₂ entry
Explanation: During the day, the stomata open to allow the plant to take in carbon dioxide for
photosynthesis.

Application
Question: In an experiment to demonstrate the necessity of chlorophyll for photosynthesis, a green
leaf is boiled and tested for starch. What would be the result?
A) The leaf will turn blue-black
B) The leaf will remain colorless
C) The leaf will turn red
D) The leaf will remain green
Answer: B) The leaf will remain colorless
Explanation: Chlorophyll is necessary for photosynthesis to produce glucose. Without chlorophyll, no
starch will be produced in the leaf.

Recall
Question: What is the function of the stomata in photosynthesis?
A) Absorption of sunlight
B) Exchange of gases
C) Transport of water
D) Synthesis of glucose
Answer: B) Exchange of gases
Explanation: The stomata allow the exchange of gases (CO₂ and O₂) necessary for photosynthesis.
Understanding and Application
Question: How does increased light intensity affect photosynthesis?
A) It increases the rate of photosynthesis
B) It decreases the rate of photosynthesis
C) It has no effect
D) It causes the plant to lose energy
Answer: A) It increases the rate of photosynthesis
Explanation: Increased light intensity provides more energy for the light reactions, thus increasing
the rate of photosynthesis up to a certain limit.

Short Answer Type Questions

Recall
Question: What are the main products of photosynthesis?
Solution: The main products of photosynthesis are glucose (C₆H₁₂O₆) and oxygen (O₂).

Understanding
Question: Explain the significance of photosynthesis for life on Earth.
Solution: Photosynthesis is vital as it produces oxygen, which is essential for the survival of aerobic
organisms, and glucose, which serves as an energy source for plants and animals. It also helps in
reducing the concentration of carbon dioxide in the atmosphere.

Application
Question: How can the necessity of light for photosynthesis be demonstrated experimentally?
Solution: One experiment to demonstrate this is by placing a leaf in a dark room for 48 hours and
then conducting a starch test. If no light is present, starch will not form in the leaf, proving that light is
essential for photosynthesis.

Analysis
Question: Why does a plant need chlorophyll to perform photosynthesis?
Solution: Chlorophyll absorbs sunlight, which is essential for the light reactions of photosynthesis.
Without chlorophyll, the plant would not be able to absorb light energy effectively to carry out the
process of photosynthesis.

Understanding and Application

Question: What is the role of stomata in photosynthesis?
Solution: Stomata are small openings in the leaves that allow the exchange of gases. They allow
carbon dioxide to enter the leaf for photosynthesis and release oxygen as a byproduct.

Recall
Question: What is the overall balanced equation for photosynthesis?
Solution: The overall balanced equation for photosynthesis is:
6CO2 + 6H2O + light energy → C6H12O6 + 6O2

Application
Question: Describe the light reaction of photosynthesis.
Solution: In the light reaction, chlorophyll absorbs light energy, which activates it and leads to the
photolysis of water, releasing oxygen (O₂). This energy is used to produce ATP and NADPH, which are
then used in the dark reactions.

Understanding
Question: What are the dark reactions of photosynthesis?
Solution: The dark reactions, or Calvin cycle, occur in the stroma of the chloroplast. In these
reactions, carbon dioxide is fixed and combined with hydrogen from NADPH to form glucose.

Application
Question: How does an increase in carbon dioxide concentration affect the rate of photosynthesis?
Solution: An increase in carbon dioxide concentration typically increases the rate of photosynthesis,
as carbon dioxide is a raw material for the process. However, this increase is limited by other factors
such as light intensity and temperature.
Understanding and Application
Question: Explain how the potassium ion exchange theory helps in the opening and closing of
stomata.
Solution: According to the potassium ion exchange theory, stomatal opening and closing are
regulated by the movement of potassium ions. When potassium ions are actively transported
into the guard cells, water follows by osmosis, causing the guard cells to swell and open the
stomata. When potassium ions leave, the cells lose water and shrink, closing the stomata.

Recall
Question: What is the function of NADPH in photosynthesis?
Solution: NADPH is produced during the light reactions of photosynthesis. It acts as a carrier of
hydrogen atoms in the dark reactions, where it combines with carbon dioxide to form glucose.

Application
Question: How can the necessity of chlorophyll for photosynthesis be demonstrated
experimentally?
Solution: An experiment to demonstrate the necessity of chlorophyll is by using a variegated leaf
(a leaf with both green and non-green areas). When the leaf is tested for starch after being
exposed to light, only the green areas will show starch, indicating that chlorophyll is essential for
photosynthesis.

Analysis and Application

Question: What is the significance of the light reaction in photosynthesis?
Solution: The light reaction is significant because it provides the ATP and NADPH required for the
dark reactions (Calvin cycle), which are necessary for the synthesis of glucose. It also produces
oxygen as a byproduct.

Recall and Understanding

Question: What is the role of water in the light reaction of photosynthesis?
Solution: Water molecules are split during the light reaction in a process called photolysis. This
releases oxygen (O₂) and provides electrons and protons, which are used to form ATP and
NADPH.

Application
Question: How would you demonstrate the necessity of carbon dioxide for photosynthesis in a
plant?
Solution: A plant can be placed in a bell jar with a carbon dioxide-absorbing substance (like
potassium hydroxide) and then exposed to light. Since there is no carbon dioxide available, no
photosynthesis will occur, and no starch will be produced.

Analysis
Question: What would happen if a plant is exposed to light but kept in a carbon dioxide-free
environment?
Solution: If a plant is kept in a carbon dioxide-free environment, the rate of photosynthesis will
decrease or stop completely, as carbon dioxide is a necessary raw material for the process.

Understanding and Application

Question: How does the structure of chloroplasts help in photosynthesis?
Solution: Chloroplasts have a double membrane structure with inner membranes called
thylakoids, which contain chlorophyll. The light reactions occur in the thylakoid membranes,
while the dark reactions occur in the stroma. This compartmentalization allows for efficient
photosynthesis.

Recall
Question: What is the carbon cycle, and why is it important?
Solution: The carbon cycle is the process by which carbon is exchanged between the
atmosphere, oceans, soil, and living organisms. It is important because it regulates the levels of
carbon dioxide, which is essential for photosynthesis and the balance of Earth's ecosystems.
Understanding
Question: What adaptations do plants have to reduce transpiration?
Solution: Plants have adaptations such as the presence of a waxy cuticle, reduced number of
stomata, and stomatal closure during the hottest parts of the day to reduce water loss through
transpiration.

Application
Question: How would you perform an experiment to show that light is necessary for the
formation of starch in plants?
Solution: A plant can be placed in the dark for 48 hours to destarch it. Then, it can be exposed to
light for a few hours. After boiling the leaf and testing it with iodine solution, the leaf will turn
blue-black, indicating that starch has been formed, proving the necessity of light for
photosynthesis.
 Chemical Coordination in Plants
Physiological Effects of Auxins
Promote growth of plants 
Secreted by the cells present in the tips of stems and roots Plant growth regulators
Synthetic auxins are used in horticulture are chemical substances
Example: Indole Acetic Acid (IAA).
that influence various
physiological processes in
Physiological Effects of Gibberellins plants, such as growth,
Promote cell differentiation in the presence of auxins  development, and
Break seed dormancy  responses to stimuli.
Stimulate elongation of shoots
Example: Gibberellic Acid (GA₃).

Physiological Effects of Cytokinins

Promote cell division in plants 
Delay ageing of leaves 
Promote opening of stomata 
Promote fruit growth
Example: Zeatin.

Physiological Effects of Abscisic Acid 

Acts as a growth inhibitor 
Promotes dormancy in seeds and buds 
Promotes closing of stomata 
Promotes wilting and falling of leaves 
Detachment of flowers and fruits from the plants is due
to abscisic acid

Physiological Effects of Ethylene

A gaseous hormone that promotes fruit ripening.
Enhances senescence and abscission of leaves and fruits.
Stimulates flowering in certain plants like pineapple.

Tropic Movements in Plants : Tropic movements are directional movements of plants in response
to external stimuli.

Phototropism Geotropism
Movement of plants in response to light. Movement of plants in response to gravity.
Example: Shoots grow towards light Example: Roots grow downwards (positive
(positive phototropism), roots grow away geotropism), shoots grow upwards
from light (negative phototropism). (negative geotropism).
Hydrotropism
Movement of plants in response to water. Thigmotropism
Example: Roots grow towards water
sources. Movement of plants in response to touch.
Example: Tendrils of climbers coil around a
Chemotropism support.
Movement of plants in response to
chemicals.
Example: Growth of pollen tubes towards
the ovule in response to chemical signals.
Multiple Choice Questions
Recall
Q1. Which plant hormone promotes cell elongation and is responsible for phototropism?
a) Gibberellins
b) Auxins
c) Cytokinins
d) Ethylene
Answer: b) Auxins
Explanation: Auxins promote cell elongation and accumulate on the shaded side of the plant,
causing bending toward the light (phototropism).

Recall and Understanding

Q2. Name the plant hormone responsible for inducing seed dormancy.
a) Gibberellins
b) Auxins
c) Cytokinins
d) Abscisic Acid
Answer: d) Abscisic Acid
Explanation: Abscisic Acid (ABA) induces dormancy in seeds and buds and helps plants survive
under stress conditions.

Understanding
Q3. What is the role of cytokinins in plants?
a) Promote ripening of fruits
b) Induce seed dormancy
c) Delay leaf senescence
d) Stimulate flowering
Answer: c) Delay leaf senescence
Explanation: Cytokinins promote cell division and delay leaf aging (senescence) by maintaining
chlorophyll content.

Application
Q4. A gardener sprays auxin on a plant. What effect will it have on the plant?
a) It will ripen the fruits.
b) It will promote apical dominance.
c) It will induce seed dormancy.
d) It will trigger stomatal closure.
Answer: b) It will promote apical dominance.
Explanation: Auxins enhance apical dominance by suppressing lateral bud growth, allowing the
main shoot to grow taller.

Analysis and Application

Q5. Why does a shoot bend toward the light in phototropism?
a) Due to even distribution of auxins
b) Due to higher concentration of auxins on the shaded side
c) Due to absence of auxins
d) Due to evaporation of water on the illuminated side
Answer: b) Due to higher concentration of auxins on the shaded side
Explanation: Auxins accumulate on the shaded side, causing cells to elongate more on that side
and leading to bending toward the light.

Recall
Q6. Which plant hormone helps in breaking seed dormancy?
a) Abscisic Acid
b) Ethylene
c) Gibberellins
d) Auxins
Answer: c) Gibberellins
Explanation: Gibberellins promote germination by breaking seed dormancy and activating
enzymes that mobilize stored nutrients.
Understanding and Application
Q7. What type of tropic movement occurs when a pollen tube grows toward an ovule?
a) Phototropism
b) Chemotropism
c) Geotropism
d) Thigmotropism
Answer: b) Chemotropism
Explanation: Chemotropism refers to plant growth in response to a chemical stimulus, as in the
case of pollen tubes growing toward ovules due to chemical signals.

Recall and Understanding

Q8. Which hormone is responsible for ripening of fruits?
a) Ethylene
b) Cytokinins
c) Auxins
d) Gibberellins
Answer: a) Ethylene
Explanation: Ethylene is a gaseous hormone that accelerates fruit ripening by breaking down cell
walls and converting starches into sugars.

Analysis
Q9. Why do roots grow downward in geotropism?
a) Due to accumulation of auxins on the lower side of the root
b) Due to even distribution of cytokinins
c) Due to the absence of light
d) Due to inhibition of gibberellins
Answer: a) Due to accumulation of auxins on the lower side of the root
Explanation: In roots, auxins inhibit cell elongation on the lower side, causing the root to bend
downward.

Application
Q10. Which tropic movement is exhibited by a vine coiling around a support?
a) Phototropism
b) Geotropism
c) Thigmotropism
d) Hydrotropism
Answer: c) Thigmotropism
Explanation: Thigmotropism refers to the growth movement of plants in response to touch, such as
tendrils coiling around a support.

Recall
Q11. Name the hormone responsible for the closure of stomata during water stress.
a) Gibberellins
b) Auxins
c) Cytokinins
d) Abscisic Acid
Answer: d) Abscisic Acid
Explanation: Abscisic Acid triggers the closing of stomata to reduce water loss during drought
conditions.

Analysis and Application

Q12. What happens to a plant if gibberellins are deficient?
a) Leaves turn yellow prematurely.
b) The plant grows abnormally tall.
c) Seed germination is delayed.
d) Fruits ripen too quickly.
Answer: c) Seed germination is delayed.
Explanation: Gibberellins are essential for breaking seed dormancy and initiating germination.
Understanding
Q13. Which hormone is used in agriculture to induce flowering in pineapples?
a) Cytokinins
b) Ethylene
c) Auxins
d) Gibberellins
Answer: b) Ethylene
Explanation: Ethylene is widely used in agriculture to induce uniform flowering in plants like
pineapples.

Recall and Understanding

Q14. What is the response of roots toward water called?
a) Geotropism
b) Phototropism
c) Hydrotropism
d) Thigmotropism
Answer: c) Hydrotropism
Explanation: Hydrotropism refers to the growth of roots toward a water source to ensure the plant's
survival.

Recall
Q15. Which hormone is known as the "stress hormone" in plants?
a) Auxins
b) Ethylene
c) Abscisic Acid
d) Cytokinins
Answer: c) Abscisic Acid
Explanation: Abscisic Acid helps plants survive stress conditions by inducing dormancy and
closing stomata to conserve water.

Understanding and Application

Q16. How do auxins help in preventing the premature dropping of fruits?
a) By delaying leaf senescence
b) By promoting apical dominance
c) By strengthening the attachment of fruits to the plant
d) By ripening the fruit
Answer: c) By strengthening the attachment of fruits to the plant
Explanation: Auxins maintain the connection between the fruit and the plant, preventing early fruit
drop.

Analysis
Q17. Why do roots show positive geotropism?
a) To grow toward light
b) To grow away from water
c) To anchor the plant and absorb nutrients
d) To enhance auxin concentration
Answer: c) To anchor the plant and absorb nutrients
Explanation: Positive geotropism ensures roots grow downward for anchorage and absorption of
water and nutrients.

Application
Q18. What would happen if a plant was sprayed with gibberellins?
a) The plant would grow taller.
b) The fruits would ripen.
c) The leaves would yellow prematurely.
d) The plant would grow laterally.
Answer: a) The plant would grow taller.
Explanation: Gibberellins stimulate stem elongation and are often used in agriculture to increase
plant height.
Analysis and Application
Q19. Why do seeds in a dry environment fail to germinate?
a) Lack of nutrients
b) Absence of gibberellins
c) Lack of water to activate enzymes
d) Excessive ethylene
Answer: c) Lack of water to activate enzymes
Explanation: Water is essential to activate enzymes that mobilize stored nutrients for seed
germination.

Recall and Understanding

Q20. What is the directional growth response of plants toward a chemical stimulus called?
a) Thigmotropism
b) Hydrotropism
c) Chemotropism
d) Phototropism
Answer: c) Chemotropism
Explanation: Chemotropism is the growth response of plants toward a chemical stimulus, such as
pollen tube growth toward ovules.

Short Answer Type Questions

Recall
Q1. Name two plant hormones that promote cell division.
Solution: Cytokinins and Auxins.
Explanation: Cytokinins and auxins are involved in promoting cell division and growth in plants.

Recall
Q2. What is phototropism? Provide one example.
Solution: Phototropism is the growth movement of a plant in response to light. For example, a
sunflower bending toward sunlight.

Understanding
Q3. Explain why roots show positive geotropism.
Solution: Roots exhibit positive geotropism because they grow downward toward gravity, helping
in anchorage and absorption of water and nutrients.

Application
Q4. How does ethylene help in fruit ripening?
Solution: Ethylene stimulates the conversion of starches to sugars, softens cell walls, and
accelerates the ripening process.

Understanding and Application

Q5. How do auxins affect plant growth when exposed to sunlight?
Solution: Auxins accumulate on the shaded side of a plant, causing those cells to elongate, which
results in the plant bending toward the light.

Analysis
Q6. Why does seed dormancy benefit plants in unfavorable conditions?
Solution: Seed dormancy ensures that seeds remain inactive during unfavorable conditions and
germinate only when conditions are suitable, increasing survival chances.

Recall and Understanding

Q7. Name one hormone responsible for delaying leaf senescence and explain its importance.
Solution: Cytokinins delay leaf senescence by maintaining chlorophyll content, ensuring longer
photosynthetic activity.
Application
Q8. What happens to a plant if abscisic acid levels increase significantly?
Solution: High levels of abscisic acid cause stomatal closure, seed dormancy, and reduced growth, helping
the plant survive stress conditions like drought.

Recall
Q9. What is chemotropism? Give one example.
Solution: Chemotropism is the directional growth of a plant in response to a chemical stimulus. For
example, pollen tubes growing toward ovules.

Analysis and Application

Q10. A farmer applies gibberellins to a crop. What change will likely occur?
Solution: The plants will grow taller due to enhanced stem elongation. Additionally, gibberellins might
induce early flowering and improve fruit size.

Recall and Understanding

Q11. How do gibberellins help in seed germination?
Solution: Gibberellins break seed dormancy and activate enzymes that convert stored starch into sugars,
providing energy for germination.

Analysis
Q12. Why do plants growing in a shady area tend to be taller than those in sunlight?
Solution: In shady areas, plants produce more auxins, promoting cell elongation and upward growth to
reach sunlight.

Understanding
Q13. Differentiate between positive and negative phototropism.
Solution: Positive phototropism: Growth of plant parts toward light (e.g., stems).
Negative phototropism: Growth of plant parts away from light (e.g., roots).

Application
Q14. How does thigmotropism help climbing plants like peas?
Solution: Thigmotropism allows tendrils to coil around a support, providing stability and enabling the plant
to grow upward.

Recall and Understanding

Q15. Name one hormone responsible for apical dominance and explain its effect.
Solution: Auxins are responsible for apical dominance by inhibiting lateral bud growth, allowing the main
shoot to grow taller.

Understanding and Application

Q16. A gardener sprays cytokinins on leaves. What result can be expected?
Solution: Cytokinins delay leaf senescence, resulting in greener and healthier leaves for a longer time.

Analysis and Application

Q17. Why is ethylene used in agriculture for fruit harvesting?
Solution: Ethylene is used to ripen fruits uniformly and quickly, making them market-ready for sale.

Recall
Q18. What is hydrotropism? Provide an example.
Solution: Hydrotropism is the growth of plant roots toward a water source. For example, roots growing
toward underground water.

Understanding
Q19. Explain the role of auxins in phototropism.
Solution: Auxins migrate to the shaded side of the plant, promoting elongation of cells on that side and
causing the plant to bend toward the light source.

Application
Q20. Why are gibberellins sprayed on seedless grapes?
Solution: Gibberellins increase the size of seedless grapes by promoting cell elongation and division,
resulting in larger and juicier fruits.
 Circulatory System
Blood is a specialized fluid connective tissue that circulates through the body,
delivering essential substances like oxygen, nutrients, hormones, and enzymes to cells
and tissues while removing waste products like carbon dioxide and metabolic
byproducts.
Functions of Blood
Transportation: Oxygen from lungs to
tissues and carbon dioxide back to the Colour : Bright red when taken
lungs. from an artery and deep red when
Nutrients from the digestive system to taken from a vein.
cells. Volume : An average adult human
Hormones from glands to target organs. has 5 to 6 litres blood.
Regulation: Maintains body temperature, Taste Salty.
pH balance, and water balance in tissues. Blood is slightly alkaline with a pH
Protection: WBCs protect against of 7.3 to 7.45.
infections.
Platelets and plasma proteins aid in Red Blood Cells (RBCs/Erythrocytes)
clotting to prevent blood loss.
Composition of Blood Structure: Biconcave, no nucleus or
mitochondria in mammals.
Plasma (55%): Mature RBCs do not have nuclei.
It is a light yellow-coloured alkaline Functions: Transport oxygen using hemoglobin;
fluid that is 90% water and contains some carbon dioxide transport.
dissolved proteins, glucose, hormones, The average life of RBCs is 120 days.
ions, and waste products. In Adults : Produced in Long bones like ribs
Functions: Transporting nutrients, In children, RBCs are produced in the bone
hormones, and waste products. marrow until 5 years of age.
It is a light yellow-coloured alkaline
liquid.

White Blood Cells (WBCs/Leucocytes)

Structure: Irregular shape, nucleus present.
Functions: Immunity and defense against pathogens
Types: Lymphocytes (antibody production), Phagocytes (engulf bacteria).
Phagocytosis, Inflammation, diapedesis, Formation of Antibodies are functions of WBCs

Types of WBCs
Granulocytes : Contain granules in their cytoplasm and a lobed nucleus.

Neutrophils (62%) :
Most abundant (60-70% of WBCs).
Function: Engulf and destroy bacteria (phagocytosis).
Produced In Bone marrow

Eosinophils (2.3%) :
Stain with acidic dyes : eosin (acid dye)
Function: Fight parasitic infections; involved in allergic
responses.Destroy bacteria
Produced In Bone marrow

Basophils (0.4%) :
Stain with basic dyes;(methylene blue) least abundant (<1%).
Function: Release histamine and heparin; mediate allergic and
inflammatory responses.
Produced In Bone marrow
Agranulocytes : Do not have granules in their cytoplasm and have a non-lobed nucleus.

Types:
Lymphocytes (30%) :
20-25% of WBCs.
Function:
B-cells: Produce antibodies.
T-cells: Attack infected or cancerous cells.
Natural Killer (NK) Cells: Destroy virus-infected and abnormal cells.

Monocytes (5.3%) :
Largest WBCs.
Function: Engulf pathogens and debris; differentiate into
macrophages when they move into tissues.

Blood Platelets (Thrombocytes) :

Blood platelets are minute, oval or
round, non-nucleated structures
floating in the blood. 
Platelets are derived from
megakaryocytes in the red bone
marrow. 
Their life span is 3 to 5 days.  Blood
Phagocytosis is the process
platelets play an important role in
by which certain cells, called
blood clotting.
phagocytes, engulf and
destroy foreign particles,
Increase in Efficiency of Mammalian Red Blood Cells (RBCs)
pathogens (like bacteria
Mammalian RBCs exhibit higher efficiency in transporting
and viruses), and cellular
oxygen due to the absence of certain organelles such as the
debris. It is a crucial
nucleus, mitochondria, and endoplasmic reticulum. This
mechanism of the immune
unique structure maximizes their ability to carry and
system to protect the body
deliver oxygen throughout the body.
from infections.
Key Features of RBC Efficiency
Absence of Nucleus:
Reason: Lack of a nucleus creates more space inside the
cell for hemoglobin, the oxygen-carrying protein.
Efficiency: Allows RBCs to carry a greater amount of
oxygen per cell.

Absence of Mitochondria:
Reason: RBCs rely on anaerobic respiration (glycolysis)
Diapedesis is the process by
for energy production. which white blood cells
Efficiency: Prevents RBCs from using the oxygen they (WBCs), particularly
transport, ensuring that all oxygen is delivered to neutrophils and monocytes,
tissues. migrate from the bloodstream
into the tissues to combat
Biconcave Shape: infections or respond to
Reason: Absence of rigid organelles allows RBCs to injuries. This movement occurs
by squeezing through the walls
maintain their flexible, biconcave shape.
of blood vessels, specifically
Efficiency: Increases the surface area-to-volume ratio, the capillaries or venules,
enhancing gas exchange and allowing RBCs to squeeze without causing damage to the
through narrow capillaries. vessel wall.

Absence of Endoplasmic Reticulum:

Reason: Reduces internal complexity, leaving more
space for hemoglobin.
Efficiency: Facilitates oxygen transport without
interference from metabolic processes.
Blood Coagulation : Formation of a clot to prevent bleeding.
Injured cells and platelets disintegrate at the site of the wound and release
thrombokinase or thromboplastin.

Thrombokinase with the help of calcium ions converts prothrombin of the plasma into
thrombin.

Thrombin in the presence of calcium ions reacts with the soluble fibrinogen and
converts it into insoluble fibrin. Fibrin forms threads and a meshwork at the site of
the wound.

Blood cells are trapped in the network of the fibrin. The blood shrinks and squeezes
out the rest of the plasma in the form of a clear liquid. The solid mass which is left
behind is called a clot or thrombus.
Haemoglobin is a respiratory pigment Tissue Fluid and Lymph
present in the stroma of RBCs. It combines Tissue Fluid:
readily with oxygen to form an unstable Plasma leaks out of capillaries; bathes cells to provide
nutrients and remove waste.
compound oxyhaemoglobin. This compound
delivers oxygen to tissues. Lymph:
Colorless fluid, part of the immune system, rich in
Haemoglobin has a very strong affinity for WBCs.
carbon monoxide. When combined with Functions: Transport fats, return excess fluid to blood,
carbon monoxide, it forms a stable immunity.
compound carboxyhaemoglobin. Most of the tissue fluid enters another set of vessels
Carboxyhaemoglobin reduces the capacity called lymphatic vessels, and this fluid is called lymph. 
Lymph vessels drain lymph into lymph nodes. 
of the blood in transporting oxygen,
From lymph nodes, through lymph vessels again,
sometimes even resulting in death. lymph enters the vena cava just before its entry into
the right auricle.
Structure and Working of the Composition of Lymph : Cellular Part: Leukocytes
(mostly lymphocytes) + Non-cellular Part: Water 94%
Heart Solids 6%
The heart is a muscular, hollow organ located in
the chest cavity, slightly tilted to the left. It is
divided into four chambers:

Atria (Upper Chambers):

Right Atrium (RA) Blood in our body circulates in a closed manner, i.e.
through blood vessels, all the time. Such type of
Left Atrium (LA)
blood circulation is called a closed vascular system. 
Ventricles (Lower Chambers):
In animals such as insects, the blood mostly flows
Right Ventricle (RV) through open spaces, and such type of circulation is
Left Ventricle (LV) called open vascular system. 
Key Features The human blood circulatory system consists of
Walls: Made of cardiac muscle; the left heart, arteries, veins and blood capillaries.
ventricular wall is thicker to pump blood to
the entire body.

Valves: Prevent backflow of blood:

Tricuspid Valve: Between RA and RV.
Bicuspid/Mitral Valve: Between LA and LV.
Pulmonary Valve: Between RV and pulmonary artery.
Aortic Valve: Between LV and aorta.
Septum: Divides the heart into left and right halves.
Blood Vessels Entering and Leaving the Heart

Entering the Heart:

Superior and Inferior Vena Cava: Bring
deoxygenated blood from the body to the RA.

Pulmonary Veins: Bring oxygenated blood from the

lungs to the LA.

Leaving the Heart:

Pulmonary Artery: Carries deoxygenated blood from
the RV to the lungs.

Aorta: Carries oxygenated blood from the LV to the

entire body.
Working of the Heart

Blood Flow Pathway:

Right Side (Pulmonary Circulation): Main Blood Vessels of Liver and Kidney
1. Deoxygenated blood enters the RA
through the vena cava. Liver:
2. Blood flows to the RV via the tricuspid Hepatic Artery: Brings oxygenated blood to the
valve. liver.
3. RV pumps blood to the lungs through the Hepatic Vein: Carries deoxygenated blood away
pulmonary artery for oxygenation. from the liver.
Hepatic Portal Vein: Brings nutrient-rich blood
Left Side (Systemic Circulation): from the digestive organs to the liver.
1. Oxygenated blood enters the LA via the
pulmonary veins. Kidney:
2. Blood flows to the LV via the bicuspid Renal Artery: Supplies oxygenated blood to the
valve. kidneys.
3. LV pumps blood to the body through the Renal Vein: Carries filtered, deoxygenated blood
aorta. away from the kidneys.

Cardiac Cycle:
Systole: Contraction phase; pumps blood
out of the heart.
Diastole: Relaxation phase; chambers fill
with blood.

Double Circulation:
Pulmonary Circulation: Blood flows
between the heart and lungs.
Systemic Circulation: Blood flows
between the heart and the rest of the
body.
Pulse Blood Pressure (BP)
The pulse is the rhythmic throbbing of Blood pressure is the force exerted by blood against
arteries caused by the contraction and the walls of arteries as the heart pumps it.
relaxation of the heart as it pumps blood. Key Features:
Key Features:
Measurement:
Location: Commonly felt at areas where Systolic Pressure: Pressure during heart
arteries are close to the skin, such as the contraction (normal: ~120 mmHg).
wrist (radial artery) or neck (carotid Diastolic Pressure: Pressure during heart
artery). relaxation (normal: ~80 mmHg).
Expressed as Systolic/Diastolic, e.g., 120/80
Normal Pulse Rate: mmHg.
Adults: 60–100 beats per minute (bpm).
Higher in children and decreases with Factors Influencing BP:
age. Age: BP tends to increase with age.
Lifestyle: Diet, stress, and exercise affect BP.
Significance: Health Conditions: Hypertension (high BP) or
Indicates the heart rate and rhythm. hypotension (low BP).
Changes with activity, emotions, and
health conditions. Significance:
Indicates cardiovascular health.
Helps diagnose conditions like hypertension and
heart disease.
Relationship Between Pulse
and Blood Pressure Blood Vessels:
Pulse reflects the heart's Blood vessels are an integral part of the circulatory
rhythm, while BP system, responsible for transporting blood throughout
measures the force of
the body. There are three main types of blood vessels:
blood flow.
Both are critical
arteries, veins, and capillaries. Their structures are
indicators of the closely related to their functions.
circulatory system's 1. Arteries
health. Function: Carry oxygenated blood away from the heart to
various parts of the body (except the pulmonary artery,
which carries deoxygenated blood to the lungs).

Structure and Features:

Thick, Elastic Walls: To withstand high pressure from the
heart's pumping action.
Small Lumen: Helps maintain high blood pressure.
No Valves: Blood flow is driven by the pressure
generated by the heart.
Pulsating Blood Flow: Due to rhythmic contraction and
relaxation of the heart.

2.Veins
Function: Carry deoxygenated blood back to the heart
(except the pulmonary vein, which carries oxygenated
blood from the lungs to the heart).

Structure and Features:

Thin Walls with Less Elastic Tissue: As blood pressure is
lower in veins.
Wide Lumen: To accommodate a large volume of blood.
Valves Present: Prevent backflow of blood, ensuring
one-directional flow.
Steady Blood Flow: No pulsing as in arteries.
3.Capillaries
Function: Facilitate exchange of gases, nutrients, and waste products
between blood and tissues.

Structure and Features:

One-Cell Thick Walls: Allows efficient diffusion of substances.
Very Narrow Lumen: Enables close contact with tissues for
exchange.
Extensive Network: Increases surface area for exchange.
No Valves: Blood flow is slow, ensuring effective exchange.

Spleen
Location: The spleen is located on the left side of the abdomen, just below the diaphragm.
Functions:
Filter Blood: Removes old and damaged red blood cells from circulation.
Immune Response: Contains white blood cells (such as lymphocytes) that help fight infections.
Storage of Blood: Acts as a reservoir for blood, storing platelets and red blood cells.
Recycling Iron: The spleen recycles iron from old red blood cells and returns it to the bone
marrow.

Tonsils
Location: Tonsils are located in the throat and are part of the body’s first line of defense against
ingested or inhaled pathogens.
Types of Tonsils:
1. Palatine Tonsils: Located on each side of the throat.
2. Pharyngeal Tonsil (Adenoid): Located at the back of the nasal cavity.
3. Lingual Tonsils: Located at the base of the tongue.

Functions:
Trap Pathogens: Tonsils help trap and filter out bacteria and viruses from the air, food, and
liquids that enter the body.
Immune Response: Contain lymphocytes that produce antibodies to fight infections.
First Line of Defense: Tonsils serve as a first defense mechanism, preventing infections from
spreading to the respiratory system.

ABO Blood Group System

According to the ABO blood group system, there are four blood groups A, B, AB and O. 
O type blood can be given to persons of all types of blood, i.e. O, A, B and AB. Hence, a person
with O type of blood is called a universal donor. 
A person with AB type of blood can receive blood from all types, i.e. AB, A, B and O. Hence,
such a person is called a universal recipient.

Rh Factor

The blood of most people contains a substance called Rh factor.


Rh stands for Rhesus, our common primate ancestor in which this factor was first discovered. 
When the blood of an Rh positive (Rh+) individual is transfused into a person lacking the Rh
factor, the blood of the recipient develops antibodies against the Rh factor which may even
lead to death.
Significance of the Hepatic Portal System
The hepatic portal system is a vital part of the circulatory system that carries blood from the
digestive organs to the liver. It ensures that substances absorbed from food in the intestines are
processed before entering the general circulation.

Structure:
The hepatic portal system consists of the hepatic portal vein, which transports blood from the
stomach, intestines, spleen, and pancreas to the liver.
The liver then processes the nutrients, toxins, and other substances in the blood before it is
sent to the heart and the rest of the body through the inferior vena cava.

Significance:

Nutrient Processing:
After digestion, nutrients like glucose, amino acids, vitamins, and minerals are absorbed into
the blood from the small intestine. The portal vein carries this nutrient-rich blood to the liver,
where nutrients are stored or converted for use by the body.
For example, excess glucose is stored as glycogen in the liver, and amino acids are used for
protein synthesis.

Detoxification:
The liver detoxifies harmful substances (like alcohol, drugs, and metabolic waste) absorbed
from the digestive tract. The hepatic portal system ensures that these substances are filtered
and neutralized before they can enter general circulation.

Metabolism Regulation:
The liver helps maintain homeostasis by regulating blood sugar levels, producing proteins
such as albumin, and processing fats and lipids.
The hepatic portal system allows the liver to adjust these levels based on nutrient intake.

Hormone Regulation:
The liver also regulates hormones like insulin and glucagon, which are involved in maintaining
blood glucose levels. The portal blood ensures that the liver has access to signals and
precursors needed for hormone regulation.

Immune Defense:
The liver contains immune cells (Kupffer cells) that help filter out bacteria, pathogens, and
dead cells from the blood coming from the digestive organs, contributing to immune defense.
Multiple Choice Questions
Understanding
Which part of the heart pumps oxygenated blood to the body?
a) Right atrium
b) Left ventricle
c) Right ventricle
d) Left atrium
Answer: b) Left ventricle
Explanation: The left ventricle pumps oxygenated blood to the entire body through the aorta.

Understanding
What is the main function of red blood cells (RBCs)?
a) To fight infections
b) To transport oxygen
c) To aid in clotting
d) To carry nutrients
Answer: b) To transport oxygen
Explanation: RBCs contain hemoglobin, which binds with oxygen and carries it from the lungs to
tissues throughout the body.

Understanding
Where does gas exchange occur in the lungs?
a) Bronchi
b) Alveoli
c) Trachea
d) Diaphragm
Answer: b) Alveoli
Explanation: The alveoli are tiny air sacs in the lungs where the exchange of oxygen and carbon
dioxide takes place.

Application
If a person has a deficiency of platelets, what is most likely to happen?
a) Increased oxygen delivery
b) Increased risk of bleeding
c) Decreased blood pressure
d) Increased white blood cell count
Answer: b) Increased risk of bleeding
Explanation: Platelets are involved in blood clotting; a deficiency leads to difficulty in clotting,
increasing the risk of bleeding.

Application
A person has a blood pressure reading of 140/90 mmHg. What does this indicate?
a) Normal blood pressure
b) High blood pressure
c) Low blood pressure
d) Risk of diabetes
Answer: b) High blood pressure
Explanation: A reading of 140/90 mmHg or higher is considered hypertension, a condition of high
blood pressure.

Application
In which of the following scenarios would the liver’s role in detoxification be most active?
a) After eating a meal rich in proteins
b) After drinking alcohol
c) After strenuous exercise
d) After a balanced meal
Answer: b) After drinking alcohol
Explanation: The liver detoxifies harmful substances, including alcohol, by breaking them down
into less harmful products.
Analysis
If a person has low levels of hemoglobin, which organ will likely respond by producing more red
blood cells?
a) Kidneys
b) Heart
c) Liver
d) Lungs
Answer: a) Kidneys
Explanation: When oxygen levels are low, the kidneys release erythropoietin, which stimulates the
bone marrow to produce more red blood cells.

Analysis
What could be the consequence of a blockage in the coronary arteries?
a) Stroke
b) Heart attack
c) Kidney failure
d) Asthma
Answer: b) Heart attack
Explanation: Blockage in the coronary arteries can restrict blood flow to the heart muscle, leading
to a heart attack due to lack of oxygen.

Understanding and Application

How does the absence of a nucleus in red blood cells (RBCs) increase their efficiency?
a) Increases the size of the RBCs
b) Increases the oxygen-carrying capacity
c) Increases the lifespan of RBCs
d) Allows RBCs to produce more hemoglobin
Answer: b) Increases the oxygen-carrying capacity
Explanation: The absence of a nucleus allows RBCs to have more space for hemoglobin, thereby
increasing their ability to carry oxygen.

Understanding and Application

What would happen if the body's lymphatic system is blocked?
a) Increased red blood cell count
b) Accumulation of tissue fluid leading to edema
c) Increased production of white blood cells
d) Reduced blood clotting
Answer: b) Accumulation of tissue fluid leading to edema
Explanation: Blockage of the lymphatic system prevents the drainage of lymph and tissue fluid,
leading to swelling (edema).

Recall and Understanding

Which blood vessels carry oxygenated blood away from the heart?
a) Veins
b) Arteries
c) Capillaries
d) Lymph vessels
Answer: b) Arteries
Explanation: Arteries carry oxygenated blood away from the heart to the body, with the exception
of the pulmonary artery.

Recall and Understanding

What is the function of the spleen in the lymphatic system?
a) To filter blood and remove old RBCs
b) To produce insulin
c) To store bile
d) To produce red blood cells
Answer: a) To filter blood and remove old RBCs
Explanation: The spleen filters blood and removes old red blood cells and pathogens from the
bloodstream.
Understanding
Which of the following is NOT a function of the lymphatic system?
a) Absorbing fats from the digestive system
b) Circulating oxygen in the body
c) Fighting infections
d) Returning tissue fluid to the blood
Answer: b) Circulating oxygen in the body
Explanation: The lymphatic system does not circulate oxygen; that is the function of the
circulatory system.

Analysis and Application

A person with Rh-negative blood receives a transfusion of Rh-positive blood. What could happen?
a) The blood will be accepted without any issues
b) The body will produce antibodies against Rh-positive blood
c) The person will develop diabetes
d) The blood will be filtered out immediately
Answer: b) The body will produce antibodies against Rh-positive blood
Explanation: If an Rh-negative person receives Rh-positive blood, their immune system may
produce antibodies against the Rh factor, leading to a hemolytic reaction.

Analysis and Application

What is the primary function of the hepatic portal system?
a) To filter toxins from the blood
b) To carry blood from the digestive organs to the liver
c) To supply oxygen to the liver
d) To regulate blood pressure
Answer: b) To carry blood from the digestive organs to the liver
Explanation: The hepatic portal system carries blood from the digestive organs to the liver for
detoxification and nutrient processing.

Recall
Which part of the circulatory system carries deoxygenated blood to the lungs?
a) Pulmonary veins
b) Pulmonary artery
c) Aorta
d) Vena cava
Answer: b) Pulmonary artery
Explanation: The pulmonary artery carries deoxygenated blood from the right ventricle to the
lungs for oxygenation.

Recall
Which organ produces the hormone erythropoietin?
a) Heart
b) Liver
c) Kidneys
d) Lungs
Answer: c) Kidneys
Explanation: The kidneys produce the hormone erythropoietin, which stimulates the bone marrow
to produce red blood cells in response to low oxygen levels.

Recall
Which of the following blood vessels is responsible for nutrient and gas exchange at the tissue
level?
a) Arteries
b) Veins
c) Capillaries
d) Lymph vessels
Answer: c) Capillaries
Explanation: Capillaries are the smallest blood vessels where nutrient and gas exchange occurs
between blood and tissues.
Recall
What is the main cause of varicose veins?
a) High blood pressure
b) Valve failure in veins
c) Narrowing of arteries
d) Excessive exercise
Answer: b) Valve failure in veins
Explanation: Varicose veins occur when the valves in the veins fail, causing blood to pool and veins
to become swollen.

Recall
What would happen if a person has a deficiency in white blood cells (WBCs)?
a) Increased clotting ability
b) Increased susceptibility to infections
c) Increased red blood cell count
d) Decreased heart rate
Answer: b) Increased susceptibility to infections
Explanation: White blood cells (WBCs) are part of the immune system, and a deficiency would
impair the body’s ability to fight infections.

Short Answer Type Questions

Understanding
What is the function of hemoglobin in red blood cells?
Answer: The main function of hemoglobin is to bind with oxygen in the lungs and transport
it to tissues throughout the body. It also carries carbon dioxide from the tissues back to the
lungs for exhalation.

Understanding
What is the role of the diaphragm during breathing?
Answer: The diaphragm is a muscular partition that separates the thoracic cavity from the
abdominal cavity. During inhalation, the diaphragm contracts and moves downward,
expanding the chest cavity and allowing air to enter the lungs. During exhalation, it
relaxes and moves upward, helping to push air out of the lungs.

Understanding
Describe the structure and function of capillaries.
Answer: Capillaries are the smallest blood vessels, consisting of a single layer of
endothelial cells. They enable the exchange of gases (oxygen and carbon dioxide),
nutrients, and waste products between the blood and tissues due to their thin walls and
large surface area.

Application
Why is blood flow slower in capillaries than in arteries or veins?
Answer: Blood flow is slower in capillaries because of their large total cross-sectional area.
This allows sufficient time for the exchange of gases, nutrients, and waste products
between the blood and tissues. The reduced speed facilitates these exchanges.

Application
Explain how the structure of red blood cells is adapted to their function.
Answer: Red blood cells (RBCs) have a biconcave shape, which increases their surface
area for oxygen absorption and transport. They also lack a nucleus, allowing more space
for hemoglobin, the protein that binds oxygen, increasing their efficiency in oxygen
transport.
Application
Why do the valves of the heart prevent backflow of blood?
Answer: The valves in the heart (such as the mitral and tricuspid valves) prevent the backflow of
blood by ensuring that blood moves only in one direction. They close tightly after blood passes
through, stopping it from flowing backward when the heart relaxes.

Analysis
What would happen if the coronary arteries get blocked?
Answer: Blockage of the coronary arteries can reduce or completely stop blood flow to the heart
muscle, leading to a heart attack (myocardial infarction). The lack of oxygen and nutrients can
cause damage or death to heart tissue.

Analysis
How would a deficiency in platelets affect the body’s ability to heal wounds?
Answer: A platelet deficiency (thrombocytopenia) would impair the body’s ability to form blood
clots, leading to prolonged or excessive bleeding and difficulty healing wounds, as platelets are
crucial for the blood clotting process.

Analysis
Explain why oxygenated blood and deoxygenated blood do not mix in the heart.
Answer: Oxygenated blood from the lungs enters the left atrium and is pumped into the left
ventricle. Deoxygenated blood from the body enters the right atrium and is pumped into the right
ventricle. The septum (a wall of tissue) separates the two sides of the heart, preventing the mixing
of oxygenated and deoxygenated blood.

Understanding and Application

How does the lymphatic system help in the defense of the body?
Answer: The lymphatic system helps defend the body by transporting lymph, which contains white
blood cells, through lymph nodes where they filter out pathogens. This helps to fight infections. The
system also absorbs and transports fats from the digestive system.

Understanding and Application

Explain how the liver helps in detoxifying harmful substances.
Answer: The liver detoxifies harmful substances by breaking them down into less toxic forms. It
processes alcohol, drugs, and metabolic waste products (like ammonia) into compounds that can
be safely excreted through urine or bile.

Understanding and Application

Why does the human body need two circulatory circuits (pulmonary and systemic circulation)?
Answer: The two circulatory circuits ensure that oxygenated and deoxygenated blood are
efficiently separated and transported. Pulmonary circulation carries blood to the lungs for
oxygenation, while systemic circulation delivers oxygen-rich blood to the body tissues and
organs.

Recall and Understanding

What are the components of the human circulatory system?
Answer: The human circulatory system consists of the heart, blood vessels (arteries, veins, and
capillaries), and blood. It is responsible for transporting oxygen, nutrients, hormones, and waste
products throughout the body.

Recall and Understanding

What is the main function of the white blood cells (WBCs)?
Answer: The main function of white blood cells (WBCs) is to protect the body from infections by
recognizing and attacking pathogens like bacteria, viruses, and fungi. They also play a key role in
immune responses.
Recall and Understanding
What happens when a person with Rh-negative blood receives Rh-positive blood?
Answer: When an Rh-negative person receives Rh-positive blood, their immune system may
recognize the Rh factor as foreign and produce antibodies against it. This can lead to a hemolytic
transfusion reaction, where the new blood cells are destroyed.

Analysis and Application

Why is it important for the kidneys to filter blood?
Answer: The kidneys filter blood to remove waste products (like urea) and excess substances
(such as sodium, water, and ions). This helps maintain the balance of salts, fluids, and electrolytes
in the body, which is crucial for normal cell function.

Analysis and Application

Explain why the heart has a thick muscular wall on the left side.
Answer: The left side of the heart has a thicker muscular wall because it has to pump blood to the
entire body (through the aorta), requiring more force. The right side, which pumps blood only to
the lungs, has a thinner muscular wall.

Analysis and Application

How does the body regulate blood pressure?
Answer: The body regulates blood pressure through mechanisms such as vasoconstriction and
vasodilation of blood vessels, which are controlled by the nervous system and hormones like
adrenaline and angiotensin II. The kidneys also play a role by adjusting fluid balance.

Recall
What is the function of the aorta?
Answer: The aorta is the largest artery in the body. It carries oxygenated blood from the left
ventricle of the heart to the rest of the body, supplying oxygen and nutrients to various organs and
tissues.

Recall
What is the ABO blood group system based on?
Answer: The ABO blood group system is based on the presence or absence of antigens (A and B) on
the surface of red blood cells. People with blood group A have A antigens, group B have B antigens,
group AB have both, and group O have neither.
 Excretory System
Excretion is the removal of harmful and unwanted substances, especially nitrogenous
wastes from the body.

Excretory Organs in Humans

1. Lungs: Excretes carbon dioxide and water vapor during respiration.

2. Skin: Removes urea, salts, and water through sweat glands.
3. Liver: Converts ammonia into urea (deamination), which is excreted by the
kidneys.
4. Kidneys: Main excretory organ, filters blood to form urine.

The human urinary system consists of

1. A pair of kidneys
2. A pair of ureters
3. Urinary bladder
4. Urethra
5.Blood Vessels:
Renal Artery: Carries oxygenated, unfiltered blood to the kidneys.
Renal Vein: Carries deoxygenated, filtered blood away from the kidneys.

A Pair of Kidneys : 
Dark red, bean shape,
10 cm long, 6 cm wide. 
The right kidney is slightly lower in position due to
the presence of the liver. 
The renal artery supplies oxygenated blood to the
kidneys. 
The renal veins take away deoxygenated blood
from the kidneys.
A Pair of Ureters
Ureters are tube-like structures which arise from the
notch, i.e. the hilum of each kidney. 
The ureters connect behind with the urinary bladder. 
The ureters carry the urine produced to the urinary
bladder

Urinary Bladder 
Muscular sac-like structure. 
It stores urine temporarily.

Urethra 
Short muscular tube which expels urine out of the
body. 
It is long in males and very short in females. 
The opening is guarded by sphincters which open at
the time of urination.
Internal Structure of the Kidneys
Cortex: Outer granular layer containing
nephrons.
Medulla: Inner striated region with renal
pyramids.
Pelvis: Funnel-shaped cavity leading to
the ureter.
The medulla is composed of conical
pyramids. 
The apex of each pyramid, i.e. papilla,
projects into the pelvis.
External:
Bean-shaped, reddish-brown.
Located in the abdominal cavity, one on each side of the vertebral column.

Uriniferous Tubule :
The kidneys have an enormous number
of uriniferous tubules. They are also
known as nephrons, renal tubules or
kidney tubules. Uriniferous tubules are
the structural and functional units of the
kidneys.

Malpighian Capsule
The Malpighian Capsule is a crucial
component of a nephron, responsible for
the filtration of blood in the kidneys. It
consists of:
Bowman’s Capsule : It is a thin-walled, cuplike depression.  A knot-like mass of blood
capillaries called glomerulus is located in the concave depression of the Bowman’s
capsule.  The Bowman’s capsule and the glomerulus together are called Malpighian
tubule or renal tubule.
Collects the filtrate during the process of ultra-filtration.

Function of the Malpighian Capsule

Performs ultra-filtration by filtering small molecules like water, glucose, urea, and
salts from blood plasma.

Larger molecules (proteins, blood cells) are retained in the blood.

Proximal Convoluted Tubule (PCT) : It is also known as the first convoluted tubule. 
It is the first part of the convoluted region of the tubule. 
PCT lies in the cortex.

Loop of Henle : It is the Ushaped middle part of the tubule.

Distal Convoluted Tubule (DCT) :  It is the end part of the kidney tubule.  It opens into
the collecting duct.

Ultra-filtration :
Ultra-filtration is the first step in the process of urine formation,
occurring in the Malpighian Capsule of the nephron.
Mechanism:
Blood enters the glomerulus through the afferent arteriole (wider diameter) and
leaves through the efferent arteriole (narrower diameter).
The difference in diameter creates high blood pressure in the glomerulus.
This pressure forces small molecules (water, glucose, salts, urea) through the semi-
permeable walls of the glomerular capillaries into the Bowman’s capsule.

Filtrate Composition:
The filtrate in the Bowman’s capsule is called glomerular filtrate and contains water,
glucose, urea, salts, and other small molecules.
Proteins, blood cells, and large molecules remain in the blood due to their size.

Reabsorption :
Selective reabsorption is the process by which useful substances are absorbed back into
the blood from the filtrate after ultra-filtration. It occurs in different parts of the
nephron.

The glomerular filtrate passes down the tubule; water and other substances required by
the body are reabsorbed. 
This entire process is called selective reabsorption.  Potassium ions and certain
substances such as penicillin are passed into the urine through the distal convoluted
tubule

Tubular secretion.
The cells of the walls of DCT are involved in bringing back into the renal tubule
potassium ions and other substances; hence, this process is known as tubular secretion

Renal Tubule Activity

Glomerulus Ultrafiltration

Bowman’s Capsule Bowman’s Capsule

Proximal Convoluted Tubule (PCT) Reabsorbs water, glucose, sodium and chloride ions
Loop of Henle Absorption of water and sodium ions

Distal Convoluted Tubule (DCT) Reabsorption of chloride ions and water

Multiple Choice Questions
Recall
Question: Which blood vessel brings oxygenated blood to the kidney?
a) Renal vein
b) Aorta
c) Renal artery
d) Inferior vena cava
Answer: c) Renal artery
Explanation: The renal artery is responsible for carrying oxygenated blood to the kidneys
for filtration.

Understanding
Question: What is the primary function of the nephron?
a) Production of red blood cells
b) Filtration of blood and formation of urine
c) Production of hormones
d) Absorption of oxygen
Answer: b) Filtration of blood and formation of urine
Explanation: The nephron, the functional unit of the kidney, filters blood and forms urine by
processes like ultrafiltration, reabsorption, and secretion.

Application
Question: If the nephron is damaged, which of the following functions would be most
affected?
a) Transporting oxygen to tissues
b) Regulating body temperature
c) Removing nitrogenous wastes
d) Controlling muscular movements
Answer: c) Removing nitrogenous wastes
Explanation: Nephrons remove nitrogenous wastes like urea from blood during urine
formation. Damage would impair this critical function.

Analysis
Question: Why is the afferent arteriole wider than the efferent arteriole in the nephron?
a) To decrease blood pressure in the glomerulus
b) To increase filtration pressure in the glomerulus
c) To allow the reabsorption of water
d) To prevent urine backflow
Answer: b) To increase filtration pressure in the glomerulus
Explanation: The difference in diameters creates high pressure in the glomerulus, aiding
ultrafiltration.

Recall and Understanding

Question: The Bowman’s capsule and the glomerulus together are known as:
a) Nephron loop
b) Malpighian body
c) Renal tubule
d) Collecting duct
Answer: b) Malpighian body
Explanation: The Malpighian body (renal corpuscle) comprises the Bowman’s capsule and
glomerulus, where ultrafiltration occurs.
Understanding and Application
Question: What would happen if the tubular reabsorption process stopped functioning?
a) Excess water would remain in the body
b) Essential nutrients would be lost in the urine
c) Blood would not reach the kidneys
d) Urine production would stop
Answer: b) Essential nutrients would be lost in the urine
Explanation: Tubular reabsorption ensures that essential substances like glucose and water are
reabsorbed from the filtrate into the blood.

Recall
Question: Which structure carries urine from the kidney to the urinary bladder?
a) Urethra
b) Renal tubule
c) Ureter
d) Collecting duct
Answer: c) Ureter
Explanation: The ureter transports urine from the renal pelvis in the kidney to the urinary bladder.

Analysis and Application

Question: Why does the nephron selectively reabsorb glucose but not urea?
a) Urea is non-toxic and does not need removal.
b) Urea has a smaller molecular size.
c) Glucose is essential for energy, whereas urea is a waste product.
d) The nephron lacks specific carriers for urea.
Answer: c) Glucose is essential for energy, whereas urea is a waste product.
Explanation: Glucose is reabsorbed for metabolic needs, while urea, being toxic, is excreted in
urine.

Recall and Understanding

Question: The process of ultrafiltration in the nephron occurs in:
a) Loop of Henle
b) Malpighian capsule
c) Distal convoluted tubule
d) Collecting duct
Answer: b) Malpighian capsule
Explanation: Ultrafiltration occurs in the Malpighian capsule, specifically in the Bowman’s capsule
and glomerulus.

Application
Question: A patient has high glucose levels in urine. What does this indicate?
a) Malfunctioning nephron
b) Reduced urea production
c) Normal kidney function
d) Diabetes mellitus
Answer: d) Diabetes mellitus
Explanation: High glucose in urine suggests that the kidneys are unable to reabsorb glucose, a
common symptom of diabetes.

Understanding and Application

Question: Why is water reabsorbed in the nephron?
a) To dilute the blood
b) To maintain body hydration
c) To increase urine concentration
d) To remove salts
Answer: b) To maintain body hydration
Explanation: Water reabsorption ensures the body retains adequate hydration and prevents
dehydration.
Recall
Question: The structural and functional unit of the kidney is the:
a) Ureter
b) Nephron
c) Glomerulus
d) Bowman’s capsule
Answer: b) Nephron
Explanation: The nephron is the smallest unit that performs kidney functions like filtration and
reabsorption.

Analysis
Question: How does tubular secretion help maintain pH balance?
a) By reabsorbing glucose
b) By secreting excess H⁺ ions into the filtrate
c) By retaining proteins in the blood
d) By secreting water into the filtrate
Answer: b) By secreting excess H⁺ ions into the filtrate
Explanation: Tubular secretion removes excess hydrogen ions, maintaining the blood’s pH.

Recall and Understanding

Question: Which part of the nephron is involved in the maximum water reabsorption?
a) Loop of Henle
b) Proximal convoluted tubule
c) Bowman’s capsule
d) Distal convoluted tubule
Answer: b) Proximal convoluted tubule
Explanation: Most water reabsorption occurs in the proximal convoluted tubule due to its high
permeability.

Application
Question: If a person drinks excessive water, which process is most likely to decrease?
a) Ultrafiltration
b) Tubular reabsorption
c) Tubular secretion
d) Filtration in the glomerulus
Answer: b) Tubular reabsorption
Explanation: Excess water reduces the need for reabsorption as the body works to expel the
surplus.

Recall
Question: Urochrome, the pigment that gives urine its yellow color, is derived from:
a) Hemoglobin breakdown
b) Protein metabolism
c) Glucose metabolism
d) DNA synthesis
Answer: a) Hemoglobin breakdown
Explanation: Urochrome is produced from the breakdown of hemoglobin in the liver.

Analysis
Question: What would happen if the glomerular filtration rate decreases?
a) Increase in urine output
b) Accumulation of waste products in the blood
c) Dehydration
d) Increased reabsorption of nutrients
Answer: b) Accumulation of waste products in the blood
Explanation: A lower filtration rate results in inefficient waste removal, leading to toxic
accumulation.
Understanding
Question: What prevents proteins from being filtered into the Bowman’s capsule?
a) Active transport in the nephron
b) Large size of protein molecules
c) Low blood pressure in the glomerulus
d) High concentration of proteins in urine
Answer: b) Large size of protein molecules
Explanation: Proteins are too large to pass through the pores of the glomerular capillaries.

Recall and Understanding

Question: Which structure stores urine before it is excreted?
a) Kidney
b) Bladder
c) Ureter
d) Urethra
Answer: b) Bladder
Explanation: The bladder temporarily stores urine until it is excreted through the urethra.

Application
Question: In case of kidney failure, what artificial process mimics the filtration of blood?
a) Dialysis
b) Osmosis
c) Respiration
d) Peristalsis
Answer: a) Dialysis
Explanation: Dialysis is a medical procedure that artificially filters the blood when kidneys fail.

Short Answer Type Questions

Recall
Question: Name the blood vessels associated with the kidneys and their primary functions.
Solution:
Renal artery: Brings oxygenated blood to the kidney.
Renal vein: Carries deoxygenated blood and filtered waste products away from the kidney.

Recall and Understanding

Question: What is the primary function of the urinary bladder?
Solution: The urinary bladder temporarily stores urine before it is expelled from the body through
the urethra.

Application
Question: What will happen if the loop of Henle is damaged in a nephron?
Solution: The concentration of urine will be affected because the loop of Henle is responsible for
reabsorbing water and salts, maintaining the osmotic balance.

Understanding and Application

Question: How does the structure of the nephron help in ultrafiltration?
Solution: The glomerulus has thin, porous capillary walls and high blood pressure created by the
afferent arteriole, which facilitates ultrafiltration of blood into the Bowman’s capsule.

Recall
Question: What are the excretory products of human kidneys?
Solution: Urea, uric acid, creatinine, excess salts, and water.

Analysis
Question: Why is selective reabsorption necessary in the nephron?
Solution: Selective reabsorption ensures essential substances like glucose, water, and ions are
returned to the blood, while waste products like urea are excreted in urine.
Understanding
Question: What role does the proximal convoluted tubule play in urine formation?
Solution: The proximal convoluted tubule reabsorbs most of the filtered glucose, amino acids,
water, and salts back into the blood, ensuring minimal loss of essential nutrients.

Recall and Understanding

Question: What is ultrafiltration, and where does it occur?
Solution: Ultrafiltration is the process of filtering blood under high pressure to remove water, salts,
and waste materials. It occurs in the glomerulus and Bowman’s capsule.

Application
Question: Why is the afferent arteriole wider than the efferent arteriole in a nephron?
Solution: The afferent arteriole is wider to create high blood pressure in the glomerulus, aiding in
the ultrafiltration process.

Analysis and Application

Question: A patient’s urine contains glucose. Which part of the nephron is likely malfunctioning?
Solution: The proximal convoluted tubule is malfunctioning as it is responsible for the reabsorption
of glucose from the filtrate.

Recall
Question: Name two nitrogenous wastes excreted by the human kidneys.
Solution: Urea and uric acid.

Understanding
Question: What is the significance of tubular secretion in urine formation?
Solution: Tubular secretion removes excess ions, drugs, and wastes like hydrogen and potassium
ions from the blood into the filtrate, helping maintain pH and electrolyte balance.

Recall and Understanding

Question: What are the main components of the nephron?
Solution: The main components of the nephron include the glomerulus, Bowman’s capsule,
proximal convoluted tubule, loop of Henle, distal convoluted tubule, and collecting duct.

Analysis
Question: Why is the composition of glomerular filtrate different from urine?
Solution: The glomerular filtrate contains water, glucose, salts, and waste products. After selective
reabsorption and tubular secretion, essential substances are reabsorbed, and waste products are
concentrated to form urine.

Recall and Understanding

Question: Draw and label the internal structure of the kidney. Identify the region where
ultrafiltration occurs.
Solution:
Label: Cortex, medulla, renal pelvis, ureter, renal artery, renal vein.
Ultrafiltration occurs: In the Malpighian capsule within the cortex.

Understanding and Application

Question: What happens if the kidney stops functioning?
Solution: Waste products like urea and toxins will accumulate in the blood, leading to conditions
like uremia, which can be fatal without dialysis or kidney transplant.

Recall
Question: What is the function of the collecting duct in the nephron?
Solution: The collecting duct collects urine from nephrons, and it also reabsorbs water to
concentrate the urine before it is transported to the renal pelvis.
Application
Question: Why does the kidney reabsorb water during urine formation?
Solution: Water reabsorption ensures the body maintains hydration and conserves water,
especially in cases of low water intake or dehydration.

Recall
Question: Name two organs other than kidneys involved in excretion in humans.
Solution:
Lungs: Excrete carbon dioxide and water vapor.
Skin: Excretes sweat, which contains water, salts, and small amounts of urea.

Analysis and Application

Question: Explain the significance of maintaining the pH balance of blood through tubular
secretion.
Solution: Tubular secretion removes hydrogen ions and ammonia, helping to neutralize the blood’s
pH and maintain homeostasis, preventing conditions like acidosis or alkalosis.
 Nervous System
Structure of Neuron
A neuron is the structural and functional
unit of the nervous system.

Parts of a Neuron:
1. Cell Body (Soma): Contains the
nucleus and cytoplasm. Responsible
for metabolic activities.
2. Dendrites: Branched extensions from
the cell body that receive signals.
3. Axon: A long projection that
transmits impulses away from the
cell body.
4. Myelin Sheath: Fatty layer covering
the axon, increases the speed of
nerve impulse transmission.
5. Nodes of Ranvier: Gaps in the myelin
sheath aiding in impulse conduction.
6. Synaptic Knobs: Terminal endings
that release neurotransmitters.

External Structure of the

Brain and Its Primary Parts

Primary Parts and Functions:

Medulla Oblongata:
Controls involuntary
actions like breathing,
heartbeat, and
swallowing.
Cerebrum: Largest part;
controls voluntary actions,
intelligence, memory, and
sensory perception.

Cerebellum: Maintains balance, posture, and coordination of muscle

movements.
Thalamus: Relays sensory and motor signals to the cerebral cortex;
regulates consciousness and alertness.
Hypothalamus: Regulates body temperature, hunger, thirst, and emotions;
links the nervous system to the endocrine system.
Pons: Connects different parts of the brain and assists in controlling
breathing.
Cerebrum : The largest portion of the brain. 
It is divided into two cerebral hemispheres connected to each other by the
corpus callosum. 
The cortex contains cell bodies of the neuron and is greyish in colour; hence, it is
called grey matter. 
The grey matter has many folds (i.e. gyri) and grooves (i.e. sulci). 
The medulla consists of the axons of the nerve fibres and is called white matter.
Cerebellum 
Located at the base of the cerebrum. 
In a median section, its white matter appears like a branching tree.
Medulla Oblongata 
Located at the base of the skull. 
It is roughly triangular. 
It continues behind the brain as the spinal cord. 
Injury to the medulla oblongata results in death.

Distribution of White and Gray Matter:

Brain:
Gray matter forms the outer layer (cerebral cortex) and is involved in
processing information, decision-making, and controlling voluntary
movements.
White matter lies beneath the gray matter and contains nerve fibers that
transmit signals between different brain regions and the spinal cord.

Spinal Cord:
Gray matter is located centrally in a butterfly-shaped pattern and contains cell
bodies of neurons involved in reflex actions and local processing.
White matter surrounds the gray matter and consists of myelinated fibers that
facilitate communication between the brain and peripheral nervous system.

Involuntary Actions:
Voluntary Actions:
Meaning: Actions that
Meaning: Actions
occur automatically
controlled consciously
without conscious
by the brain.
control.
Examples: Walking,
Examples: Heartbeat,
writing, speaking,
digestion, reflex
and playing an
actions like blinking
instrument.
or sneezing.
Reflex Arc
A pathway through
which a reflex action
occurs.

Components:
Receptor: Detects
stimulus.
Sensory Neuron:
Transmits impulse to
spinal cord.
Interneuron:
Processes impulse in
the spinal cord.
Motor Neuron: Transmits impulse to effector.
Effector: Performs the response (e.g., muscle contraction).

Peripheral and Autonomic Nervous Systems

Peripheral Nervous System (PNS):
Comprises cranial and spinal nerves.
Connects the CNS to limbs and organs.
Transmits sensory and motor signals between the body and central nervous
system.
Autonomic Nervous System (ANS):
Regulates involuntary activities like heartbeat, digestion, and respiration.

Divided into two parts:

Sympathetic Nervous System: Prepares the body for "fight or flight" by
increasing heart rate, dilating pupils, and inhibiting digestion.
Parasympathetic Nervous System: Promotes "rest and digest" functions by
slowing the heart rate, constricting pupils, and stimulating digestion.

Together, the PNS and ANS coordinate voluntary and involuntary body activities
to maintain homeostasis.

Natural Reflex: Acquired Reflex:

Definition: Inborn, Natural vs. Acquired Definition: Learned
automatic response to Reflex response developed
a stimulus. through practice or
Examples: Blinking experience.
when an object Examples: Cycling, typing
approaches the eye, on a keyboard, playing a
withdrawal of hand musical instrument.
upon touching
something hot.
External and Internal structure and functions of the
Eye
External Structure:

Eyelids and Eyelashes: Protect the eye

from dust and foreign particles.
Conjunctiva: Thin transparent membrane
that protects the cornea.

Internal Structure:

Cornea: Transparent, curved layer that

refracts and focuses light entering the eye.
Iris: Colored part of the eye; regulates the
size of the pupil based on light intensity.
Pupil: Opening in the iris through which
light enters the eye.
Lens: Flexible, transparent structure that
focuses light onto the retina.
Retina: Inner layer of the eye containing:

Rods: Detect dim light and black-and-

white vision.
Cones: Detect bright light and color
vision.
Optic Nerve: Carries visual information from the retina to the brain.
Aqueous Humor: Maintains the shape of the cornea and provides nutrients.
Vitreous Humor: Gel-like substance that helps maintain the eye's shape and
supports the retina.
Functions:
1. Vision: The eye captures light, focuses it on the retina, and sends signals to the
brain for image processing.
2. Adaptation: Adjusts to varying light intensities (pupil size changes).
3. Accommodation: Lens adjusts its shape to focus on objects at different
distances.

Key Concepts:
Stereoscopic Vision: Ability to perceive depth and 3D structures due to
binocular vision. Provides depth perception by combining slightly different
images from both eyes. The brain interprets these differences to perceive
distance and depth.

Adaptation: Pupil dilation and constriction based on light intensity.The eye

adjusts to varying light intensities using the iris. In bright light, the pupil
constricts; in dim light, it dilates.

Accommodation: Focusing mechanism for near and far objects. The lens
changes shape to focus on objects at different distances. For near objects, the
lens becomes thicker; for distant objects, it flattens.
Defects of the Eye and Corrective Measures
Myopia (Nearsightedness):
Distant objects appear blurry.
Caused by elongation of the eyeball or excessive curvature of the cornea.
Corrected with concave lenses.

Hyperopia/Hypermetropia (Farsightedness):
Near objects appear blurry.
Caused by a short eyeball or a flat cornea.
Corrected with convex lenses.

Presbyopia:
Age-related difficulty in focusing on near objects.
Caused by the loss of elasticity in the lens.
Corrected with bifocal or progressive lenses.

Astigmatism:
Blurred vision caused by irregular curvature of the cornea or lens.
Corrected with cylindrical lenses.

Cataract:
Clouding of the lens leading to blurred vision.
Treated by surgical removal and replacement with an artificial lens.

The Ear: Structure and Functions

External Ear:
Structure:
Pinna (Auricle): The visible,
cartilaginous outer part of
the ear.
External Auditory Canal: A
tubular structure leading to
the eardrum.
Earwax (Cerumen):
Produced by glands in the
ear canal to trap dust and
microorganisms.

Functions:
Collects sound waves from the environment.
Funnels sound waves into the auditory canal toward the eardrum.
Earwax protects the canal by trapping debris and has antimicrobial properties.
Middle Ear:
Structure:
Tympanic Membrane (Eardrum): A thin membrane that vibrates in response to
sound waves.

Ossicles: A chain of three tiny bones:

Malleus (Hammer): Connected to the eardrum.
Incus (Anvil): Transmits vibrations from the malleus to the stapes.
Stapes (Stirrup): Transfers vibrations to the oval window of the cochlea.
Eustachian Tube: A narrow passage connecting the middle ear to the throat
(nasopharynx).

Functions:
Amplifies sound vibrations.
Transmits vibrations from the eardrum to the cochlea via the ossicles.
Equalizes air pressure between the middle ear and the atmosphere (via the
Eustachian tube).

Inner Ear:
Structure:

Cochlea:
A spiral-shaped, fluid-filled structure.
Contains hair cells (mechanoreceptors) in the Organ of Corti.

Vestibular System:
Semicircular Canals: Three fluid-filled loops oriented in different planes.
Otolith Organs: The utricle and saccule, which detect linear acceleration and gravity.

Auditory Nerve (Cochlear Nerve): Transmits sound signals to the brain.

Functions:
Hearing (Cochlea):
Hair cells in the cochlea convert sound vibrations into electrical signals.
The auditory nerve transmits these signals to the auditory cortex in the brain.

Balance (Vestibular System):

Semicircular canals detect rotational movements of the head.
Otolith organs sense linear motion and orientation relative to gravity.

The Course of Perception of Sound in the Human Ear

1. Collection of Sound Waves:
The pinna (auricle) collects sound waves from the environment and directs them into
the external auditory canal.
The sound waves travel through the canal to reach the tympanic membrane
(eardrum).

2. Conversion to Mechanical Vibrations:

The sound waves cause the tympanic membrane to vibrate.
These vibrations are transmitted to the ossicles (malleus, incus, stapes) in the middle
ear, amplifying the sound energy.
The stapes vibrates against the oval window, a membrane that leads to the cochlea.
3. Conversion to Fluid Waves:
Vibrations at the oval window generate pressure waves in the fluid-filled cochlea
(inner ear).
The fluid waves travel through the scala vestibuli and scala tympani of the cochlea.

4. Stimulation of Hair Cells:

The pressure waves cause the basilar membrane to vibrate at specific locations
depending on the frequency of the sound:
High-frequency sounds stimulate the base of the cochlea.
Low-frequency sounds stimulate the apex.
These vibrations deflect the hair cells (mechanoreceptors) in the Organ of Corti.
The deflection of hair cells opens ion channels, generating electrical signals.

5. Transmission of Electrical Signals:

Electrical signals are transmitted to the brain via the auditory nerve (cochlear
nerve).
The signals travel to the brainstem, then to the auditory cortex in the temporal lobe
for interpretation as sound.

Role of the Ear in Maintaining Balance

The inner ear plays a vital role in maintaining the body's balance through the vestibular
system, which detects motion, orientation, and spatial positioning.

1. Components of the Vestibular System:

Semicircular Canals:
Three fluid-filled loops oriented in different planes (horizontal, anterior,
posterior).
Detect rotational movements of the head.
Otolith Organs:
Utricle: Detects horizontal motion.
Saccule: Detects vertical motion.

2. Mechanism of Balance Maintenance:

Semicircular Canals:
Rotational movements cause the fluid in the canals to move.
This movement bends the hair cells in the ampullae, generating electrical signals.
Signals are transmitted to the brain to perceive head rotation.
Otolith Organs:
Contain tiny calcium carbonate crystals (otoliths) that move in response to
gravity or linear acceleration.
Movement of otoliths deflects hair cells, signaling changes in head position or
linear motion.

3. Integration with the Nervous System:

Signals from the vestibular system are sent to the vestibular nuclei in the brainstem.
These signals are integrated with input from the eyes (visual system) and
proprioceptors (sensors in muscles and joints).
The brain processes this information to maintain posture, balance, and coordination.
 4. Reflex Actions:
Vestibulo-Ocular Reflex (VOR):
Stabilizes vision during head movement by adjusting eye position.
Postural Reflexes:
Triggered by vestibular input to maintain body equilibrium.

Multiple Choice Questions

Recall
Q1. What is the structural and functional unit of the nervous system?
a) Axon
b) Neuron
c) Synapse
d) Dendrite
Answer: b) Neuron
Explanation: The neuron is the basic unit of the nervous system, responsible for
transmitting signals.

Recall
Which part of the brain controls voluntary actions?
a) Cerebellum
b) Medulla Oblongata
c) Cerebrum
d) Pons
Answer: c) Cerebrum
Explanation: The cerebrum is responsible for voluntary actions, reasoning, and
decision-making.

Recall and Understanding

Q3. What part of the brain is primarily responsible for maintaining balance and
coordination?
a) Thalamus
b) Cerebellum
c) Medulla Oblongata
d) Hypothalamus
Answer: b) Cerebellum
Explanation: The cerebellum ensures smooth and balanced muscular activities and
coordination.

Recall and Understanding

Q4. The reflex arc pathway includes which of the following structures in order?
a) Receptor → Sensory neuron → Spinal cord → Effector → Motor neuron
b) Receptor → Sensory neuron → Spinal cord → Motor neuron → Effector
c) Sensory neuron → Receptor → Motor neuron → Spinal cord → Effector
d) Motor neuron → Spinal cord → Receptor → Sensory neuron → Effector
Answer: b) Receptor → Sensory neuron → Spinal cord → Motor neuron → Effector
Explanation: Reflex arcs follow this sequence to perform involuntary actions.
Understanding and Application
Q5. What happens to the lens during accommodation when focusing on a nearby
object?
a) Lens becomes thinner
b) Lens becomes thicker
c) Pupil dilates
d) Pupil constricts
Answer: b) Lens becomes thicker
Explanation: The ciliary muscles contract, allowing the lens to thicken and focus on
nearby objects.

Understanding and Application

Q6. Which corrective lens is used for myopia, and how does it function?
a) Convex lens; diverges light
b) Concave lens; converges light
c) Concave lens; diverges light
d) Convex lens; converges light
Answer: c) Concave lens; diverges light
Explanation: Myopia causes light to focus in front of the retina. Concave lenses
diverge light to bring it onto the retina.

Application
Q7. A person has difficulty hearing due to an obstruction in the external auditory
canal. Which process is affected first?
a) Vibration of the eardrum
b) Transmission of sound by ossicles
c) Conversion of sound to nerve impulses
d) Movement of fluid in the cochlea
Answer: a) Vibration of the eardrum
Explanation: Sound waves cannot reach the eardrum, preventing vibrations.

Application
Q8. If the hypothalamus malfunctions, which of these is most likely to be disrupted?
a) Memory processing
b) Balance and coordination
c) Regulation of body temperature
d) Heartbeat regulation
Answer: c) Regulation of body temperature
Explanation: The hypothalamus controls body temperature, hunger, and other
homeostatic functions.

Analysis
Q9. Why does damage to the medulla oblongata result in life-threatening
conditions?
a) It controls emotions.
b) It regulates reflex actions like coughing.
c) It controls vital functions like heartbeat and respiration.
d) It processes sensory information.
Answer: c) It controls vital functions like heartbeat and respiration.
Explanation: The medulla regulates involuntary activities critical for survival.
Analysis
Q10. Why does cataract surgery improve vision?
a) It reshapes the cornea.
b) It removes the cloudy lens and replaces it with an artificial one.
c) It strengthens the ciliary muscles.
d) It clears the vitreous humor.
Answer: b) It removes the cloudy lens and replaces it with an artificial one.
Explanation: Cataracts cloud the lens, impairing light transmission to the retina.

Recall and Application

Q11. Which nerve transmits signals from the retina to the brain?
a) Optic nerve
b) Auditory nerve
c) Vestibular nerve
d) Trigeminal nerve
Answer: a) Optic nerve
Explanation: The optic nerve carries visual signals from the retina to the brain.

Recall and Application

Q12. What part of the ear is responsible for detecting rotational motion?
a) Cochlea
b) Tympanic membrane
c) Semicircular canals
d) Oval window
Answer: c) Semicircular canals
Explanation: The semicircular canals detect rotational head movements using fluid
and hair cells.

Application and Analysis

Q13. If the ciliary muscles are damaged, which visual ability will be most affected?
a) Seeing distant objects
b) Adjusting focus on nearby objects
c) Detecting colors
d) Adapting to light changes
Answer: b) Adjusting focus on nearby objects
Explanation: Ciliary muscles control lens shape for accommodation.

Application and Analysis

Q14. Which reflex action prevents choking while eating?
a) Coughing
b) Blinking
c) Swallowing
d) Sneezing
Answer: c) Swallowing
Explanation: Swallowing reflex ensures food enters the esophagus instead of the
airway.
Analysis and Application
Q15. Why does hyperopia occur more frequently with age?
a) Weakening of ciliary muscles
b) Elongation of the eyeball
c) Hardening of the lens
d) Loss of retinal sensitivity
Answer: c) Hardening of the lens
Explanation: With age, the lens loses elasticity, making near focusing difficult.

Analysis and Application

Q16. How does the vestibulo-ocular reflex help maintain balance?
a) By coordinating eye movements with head movements
b) By stimulating ear fluid movement
c) By detecting changes in body posture
d) By interpreting sound signals
Answer: a) By coordinating eye movements with head movements
Explanation: The reflex stabilizes vision during head movements, aiding balance.

Recall and Understanding

Q17. What is the difference between natural and acquired reflexes?
a) Natural reflexes are learned, acquired are instinctive.
b) Acquired reflexes require memory, natural reflexes do not.
c) Natural reflexes develop over time, acquired are present from birth.
d) Both types are unrelated to learning.
Answer: b) Acquired reflexes require memory, natural reflexes do not.
Explanation: Acquired reflexes involve learned responses, while natural reflexes are innate.

Recall and Understanding

Q18. In the spinal cord, where is gray matter found?
a) Surrounding the white matter
b) In the central region
c) Exclusively in the dorsal region
d) As an outer layer
Answer: b) In the central region
Explanation: In the spinal cord, gray matter forms a central "H" shape, surrounded by white
matter.

Understanding and Application

Q19. If the optic nerve is damaged, what happens to vision?
a) Complete blindness in one or both eyes
b) Blurry peripheral vision
c) Difficulty in distinguishing colors
d) Loss of depth perception
Answer: a) Complete blindness in one or both eyes
Explanation: The optic nerve transmits visual information; damage disrupts vision entirely.

Understanding and Application

Q20. Why do people with astigmatism see blurred images?
a) The retina is damaged.
b) The cornea or lens has an irregular curvature.
c) The optic nerve is blocked.
d) The pupil cannot dilate properly.
Answer: b) The cornea or lens has an irregular curvature.
Explanation: Uneven curvature causes light to focus unevenly, blurring the image.
Short Answer Type Questions
1. Recall
Q1. Name the three parts of a neuron and their primary functions.
Answer:
Dendrites: Receive signals from other neurons.
Cell Body (Soma): Processes the information.
Axon: Transmits the signal to other neurons or effectors.

2. Recall
Q2. What are the two types of reflexes, and how do they differ?
Answer:
Natural Reflex: Inborn and involuntary, e.g., blinking.
Acquired Reflex: Learned through experience, e.g., cycling.

3. Understanding
Q3. Why is the cerebrum referred to as the "seat of intelligence"?
Answer: The cerebrum controls higher functions such as reasoning, memory, learning, and
voluntary actions, which are central to intelligence.

4. Recall and Understanding

Q4. Differentiate between white matter and gray matter.
Answer:
White Matter: Composed of myelinated axons, found on the outside of the spinal cord and
inside the brain.
Gray Matter: Composed of neuron cell bodies and dendrites, found inside the spinal cord
and outside the brain.

5. Recall
Q5. What are the primary functions of the medulla oblongata?
Answer:
Controls involuntary functions like breathing, heartbeat, and digestion.
Regulates reflexes such as coughing and sneezing.

6. Application
Q6. Why do myopic people have difficulty seeing distant objects clearly? How is it corrected?
Answer:
Reason: In myopia, the image forms in front of the retina because the eyeball is
elongated.
Correction: Using concave lenses to diverge light before it reaches the eye.

7. Recall and Application

Q7. What is the function of the semicircular canals in the ear?
Answer: The semicircular canals detect rotational movement of the head, helping maintain
balance.

8. Application
Q8. Why is the reflex arc important for survival?
Answer: Reflex arcs allow the body to respond quickly to harmful stimuli without the delay of
conscious thought, protecting it from injury.

9. Understanding
Q9. What is the role of the hypothalamus in the brain?
Answer: The hypothalamus regulates homeostasis, including body temperature, hunger,
thirst, and hormone secretion through the pituitary gland.
10. Recall
Q10. Name the parts of the ear responsible for: a) Hearing
b) Balance
Answer:
a) Hearing: Cochlea
b) Balance: Semicircular canals and otolith organs (utricle and saccule)

11. Analysis
Q11. Why does damage to the spinal cord often result in paralysis?
Answer: The spinal cord contains pathways that transmit motor commands from the
brain to the body and sensory signals from the body to the brain. Damage disrupts these
pathways, causing loss of movement and sensation.
12. Application
Q12. How does the lens change during accommodation when viewing a distant object?
Answer: The ciliary muscles relax, making the lens thinner to focus light onto the retina.

13. Understanding and Application

Q13. Why is the autonomic nervous system divided into sympathetic and
parasympathetic systems?
Answer:
Sympathetic: Prepares the body for "fight or flight" responses (e.g., increases heart
rate).
Parasympathetic: Promotes "rest and digest" activities (e.g., reduces heart rate).

14. Recall
Q14. Define stereoscopic vision.
Answer: Stereoscopic vision refers to the ability to perceive depth and three-dimensional
structures, enabled by the overlapping fields of vision from both eyes.

15. Understanding
Q15. How does the thalamus act as a relay center?
Answer: The thalamus processes and relays sensory information from the body to the
appropriate areas of the cerebrum for interpretation.

16. Analysis
Q16. Why do cataracts cause blurred vision? How are they treated?
Answer:
Reason: The lens becomes cloudy, blocking or scattering light entering the eye.
Treatment: Cataract surgery to replace the cloudy lens with an artificial one.

17. Recall and Understanding

Q17. What is the role of rods and cones in the retina?
Answer:
Rods: Detect dim light and black-and-white vision.
Cones: Detect bright light and color vision.

18. Application and Analysis

Q18. Explain why astigmatism causes distorted vision. How is it corrected?
Answer:
Reason: Irregular curvature of the cornea or lens causes uneven refraction of light.
Correction: Using cylindrical lenses to focus light correctly on the retina.
19. Understanding
Q19. What is the function of the auditory nerve?
Answer: The auditory nerve transmits electrical signals from the cochlea to the brain for
interpretation as sound.

20. Application and Understanding

Q20. Why is the reflex action faster than voluntary action?
Answer: Reflex actions bypass the brain and involve only the spinal cord, allowing a
quicker response, whereas voluntary actions require brain processing, causing a delay.
 Endocrine System
Endocrine and Exocrine Glands

Endocrine Glands: Ductless glands that release hormones directly into the
bloodstream. Example: Thyroid, Adrenal.

Exocrine Glands: Glands with ducts that secrete substances to specific

locations. Example: Sweat glands, Salivary glands.

Location and Shape of Major Endocrine Glands

Adrenal Glands: Two triangular glands located on top of each kidney.

Pancreas: Elongated organ behind the stomach; has both endocrine and
exocrine functions.

Thyroid Gland: Butterfly-shaped gland in the neck, in front of the trachea.

Pituitary Gland: Small, pea-shaped gland at the base of the brain, below the
hypothalamus.

Pancreas Adrenal Glands

Insulin: Lowers blood
glucose levels by Adrenal Glands
promoting glucose Cortical Hormones (Cortisol, Aldosterone):
Cortisol: Regulates metabolism, stress response.
uptake in cells. Aldosterone: Maintains blood pressure and
Glucagon: Increases electrolyte balance.
blood glucose levels by
breaking down Adrenaline: Prepares the body for "fight or flight"
glycogen in the liver. response by increasing heart rate and blood glucose
levels.

Thyroid Gland
Thyroxine (T4):
Regulates metabolism, Pituitary Gland
growth, and
development. Growth Hormone (GH): Stimulates body growth
and cell repair.
Tropic Hormones: Regulate the activity of other
glands (e.g., TSH for the thyroid, ACTH for
adrenal glands).
ADH (Antidiuretic Hormone): Regulates water
balance by promoting water reabsorption in
kidneys.
Oxytocin: Stimulates uterine contractions during
childbirth and milk release during breastfeeding.
Effects of Hormonal Imbalance
a) Pancreas
Insulin Deficiency (Hyposecretion): Causes diabetes mellitus (high blood sugar).
Excess Insulin (Hypersecretion): Causes hypoglycemia (low blood sugar).

b) Thyroid Gland
Hypothyroidism (Deficiency of Thyroxine):
Stunted growth (cretinism in children).
Weight gain, fatigue, goiter in adults.
Hyperthyroidism (Excess Thyroxine): Increased metabolic rate, weight loss,
irritability.

c) Adrenal Glands
Hyposecretion:
Cortisol deficiency: Addison’s disease (fatigue, low blood pressure).
Aldosterone deficiency: Imbalance in salt and water levels.
Hypersecretion:
Excess cortisol: Cushing’s syndrome (weight gain, high blood pressure).
Excess adrenaline: Increased heart rate, high blood pressure.

d) Pituitary Gland
Hyposecretion of GH: Dwarfism.
Hypersecretion of GH: Gigantism in children, acromegaly in adults.

Feedback Mechanism (with reference to TSH)

Feedback Mechanism: A regulatory system where the secretion of a
hormone is controlled by its own levels in the blood.

Example:
The hypothalamus secretes TRH (Thyrotropin-releasing hormone),
stimulating the pituitary to release TSH (Thyroid-stimulating hormone).
TSH stimulates the thyroid gland to produce thyroxine.
High thyroxine levels inhibit TRH and TSH production, maintaining
hormonal balance.
Multiple Choice Questions
Recall
Q1. Which gland is known as the "master gland" of the body?
a) Thyroid
b) Pituitary
c) Adrenal
d) Pancreas
Answer: b) Pituitary
Explanation: The pituitary gland controls the functioning of other endocrine glands
through its tropic hormones.

Recall and Understanding

Q2. Where is the thyroid gland located?
a) On top of the kidneys
b) Behind the stomach
c) In the neck, in front of the trachea
d) At the base of the brain
Answer: c) In the neck, in front of the trachea
Explanation: The thyroid gland is butterfly-shaped and situated in the neck.

Understanding
Q3. What is the function of insulin secreted by the pancreas?
a) Breaks down glycogen to glucose
b) Lowers blood glucose levels
c) Increases metabolic rate
d) Regulates water balance
Answer: b) Lowers blood glucose levels
Explanation: Insulin promotes glucose uptake by cells, reducing blood sugar levels.

Recall
Q4. Which hormone is secreted by the adrenal medulla?
a) Thyroxin
b) Oxytocin
c) Adrenaline
d) Cortisol
Answer: c) Adrenaline
Explanation: Adrenaline is produced by the adrenal medulla and helps in the "fight or
flight" response.

Analysis
Q5. Why does hypothyroidism lead to weight gain?
a) It decreases insulin production.
b) It lowers metabolic rate.
c) It causes excess adrenaline secretion.
d) It reduces cortisol levels.
Answer: b) It lowers metabolic rate.
Explanation: Thyroxine regulates metabolism. A deficiency decreases metabolism,
leading to weight gain.
Recall
Q6. Which hormone regulates water reabsorption in the kidneys?
a) Adrenaline
b) ADH (Antidiuretic Hormone)
c) Oxytocin
d) Glucagon
Answer: b) ADH (Antidiuretic Hormone)
Explanation: ADH promotes water reabsorption in the kidneys, maintaining fluid
balance.

Understanding and Application

Q7. A person has high blood sugar levels. Which hormone is likely deficient?
a) Glucagon
b) Insulin
c) Cortisol
d) Thyroxin
Answer: b) Insulin
Explanation: Insulin lowers blood sugar. Its deficiency leads to high blood glucose,
causing diabetes.

Application
Q8. How does adrenaline prepare the body for emergency situations?
a) By lowering blood pressure
b) By increasing heart rate and blood glucose levels
c) By reducing metabolic rate
d) By promoting digestion
Answer: b) By increasing heart rate and blood glucose levels
Explanation: Adrenaline provides energy and prepares the body for "fight or flight".

Recall and Understanding

Q9. Which hormone stimulates uterine contractions during childbirth?
a) Oxytocin
b) ADH
c) Growth Hormone
d) Thyroxin
Answer: a) Oxytocin
Explanation: Oxytocin stimulates uterine contractions and helps in milk release
during breastfeeding.

Recall
Q10. Which gland secretes glucagon?
a) Thyroid
b) Pituitary
c) Pancreas
d) Adrenal
Answer: c) Pancreas
Explanation: The pancreas secretes glucagon, which increases blood glucose
levels by breaking down glycogen.
Analysis and Application
Q11. A child is experiencing stunted growth. Which hormone is likely deficient?
a) Thyroxin
b) Adrenaline
c) Growth Hormone (GH)
d) Cortisol
Answer: c) Growth Hormone (GH)
Explanation: GH is responsible for growth and cell repair. Its deficiency leads to
stunted growth.

Recall
Q12. What is the primary function of thyroxin?
a) Regulates blood pressure
b) Maintains water balance
c) Controls metabolic rate
d) Stimulates uterine contractions
Answer: c) Controls metabolic rate
Explanation: Thyroxin regulates the body\u2019s metabolism and energy levels.

Application
Q13. Why does cortisol deficiency cause low blood pressure?
a) It increases insulin levels.
b) It decreases salt and water retention.
c) It reduces adrenaline secretion.
d) It lowers metabolic rate.
Answer: b) It decreases salt and water retention.
Explanation: Cortisol regulates blood pressure by maintaining salt and water
balance.

Recall and Understanding

Q14. What does the feedback mechanism regulate in the endocrine system?
a) Blood pressure only
b) Hormone secretion levels
c) Nerve impulses
d) Digestion
Answer: b) Hormone secretion levels
Explanation: The feedback mechanism maintains hormonal balance by adjusting
hormone levels.

Recall
Q15. What does TSH stimulate?
a) Pancreas to release insulin
b) Thyroid to release thyroxin
c) Adrenal gland to release adrenaline
d) Pituitary to release growth hormone
Answer: b) Thyroid to release thyroxin
Explanation: TSH (Thyroid Stimulating Hormone) regulates thyroxin secretion
from the thyroid gland.
Understanding
Q16. How does hyperthyroidism affect the body?
a) Reduces metabolic rate and weight gain
b) Increases metabolic rate and weight loss
c) Causes low blood sugar levels
d) Reduces heart rate
Answer: b) Increases metabolic rate and weight loss
Explanation: Excess thyroxin increases metabolism, leading to weight loss and
irritability.

Application
Q17. A person with diabetes has low blood sugar after an insulin dose. What
condition is this?
a) Hyperglycemia
b) Hypoglycemia
c) Hyperthyroidism
d) Hypothyroidism
Answer: b) Hypoglycemia
Explanation: Hypoglycemia occurs due to excess insulin, causing low blood
glucose levels.

Recall
Q18. Which hormone helps break down glycogen into glucose?
a) Insulin
b) Glucagon
c) Thyroxin
d) ADH
Answer: b) Glucagon
Explanation: Glucagon increases blood sugar by converting glycogen to glucose.

Understanding and Application

Q19. Why is the pituitary gland called the "master gland"?
a) It secretes digestive enzymes.
b) It produces hormones that regulate other endocrine glands.
c) It controls voluntary movements of the body.
d) It regulates only the adrenal glands.
Answer: b) It produces hormones that regulate other endocrine glands.
Explanation: The pituitary gland secretes tropic hormones (e.g., TSH, ACTH) that
control the activity of other endocrine glands, making it the "master gland."

Analysis
Q20. A persons adrenal glands are hyperactive. What symptoms might they
show?
a) High blood pressure and increased heart rate
b) Low blood sugar and fatigue
c) Weight gain and slowed metabolism
d) Stunted growth
Answer: a) High blood pressure and increased heart rate
Explanation: Excess adrenaline and cortisol increase heart rate and blood
pressure.
Short Answer Type Questions
Recall
Q1. Define a hormone.
Solution: A hormone is a chemical messenger secreted by endocrine glands directly into
the bloodstream, which regulates various physiological activities in the body.

Recall and Understanding

Q2. Name the hormones secreted by the pancreas and their functions.
Solution:
Insulin: Lowers blood glucose levels by facilitating glucose uptake by cells.
Glucagon: Increases blood glucose levels by converting glycogen into glucose in the
liver.

Understanding and Application

Q3. Why is the pancreas considered both an endocrine and exocrine gland?
Solution:
Endocrine: It secretes hormones like insulin and glucagon into the blood.
Exocrine: It secretes digestive enzymes through ducts into the small intestine.

Analysis
Q4. What would happen if thyroxin is secreted in excess in the body?
Solution: Excess thyroxin leads to hyperthyroidism, characterized by weight loss, high
metabolic rate, increased heartbeat, and irritability.

Recall
Q5. Name the gland located on top of the kidneys. What hormones does it secrete?
Solution: The adrenal gland.
Adrenaline (emergency hormone).
Cortical hormones (regulate metabolism and salt balance).

Application
Q6. A person is experiencing excessive thirst and frequent urination. Which hormone
might be deficient?
Solution: The hormone ADH (Antidiuretic Hormone) might be deficient, leading to a
condition called diabetes insipidus.

Recall
Q7. Which hormone is responsible for uterine contractions during childbirth?
Solution: Oxytocin, secreted by the posterior pituitary gland.

Understanding
Q8. What are tropic hormones? Provide one example.
Solution: Tropic hormones are secreted by the pituitary gland and regulate the functions
of other endocrine glands. Example: TSH (Thyroid Stimulating Hormone).

Analysis and Application

Q9. Explain how insulin and glucagon maintain blood glucose levels.
Solution: Insulin lowers blood glucose by facilitating its uptake by cells, while glucagon
raises glucose levels by converting stored glycogen into glucose. Together, they
maintain homeostasis.
Recall and Understanding
Q10. What is the difference between endocrine and exocrine glands?
Solution:
Endocrine: Ductless, release hormones directly into the blood (e.g., thyroid).
Exocrine: Have ducts, release substances locally (e.g., salivary glands).

Application
Q11. Why do individuals with hypothyroidism gain weight?
Solution: Hypothyroidism decreases metabolic rate, leading to reduced energy expenditure and
fat accumulation.

Recall
Q12. Name one hormone secreted by the adrenal medulla and its function.
Solution: Adrenaline: Prepares the body for "fight or flight" by increasing heart rate and energy
supply.

Recall and Understanding

Q13. What happens in the condition called dwarfism?
Solution: Dwarfism occurs due to the hyposecretion of growth hormone (GH) in childhood,
leading to stunted growth.

Analysis
Q14. Why is negative feedback important in hormone regulation?
Solution: Negative feedback prevents over-secretion of hormones by reducing their production
when optimal levels are reached, maintaining homeostasis.

Understanding and Application

Q15. Explain the role of TSH in thyroxin production.
Solution: TSH (Thyroid Stimulating Hormone), secreted by the pituitary gland, stimulates the
thyroid to produce thyroxin. Increased thyroxin levels suppress TSH production (negative
feedback).

Recall
Q16. What is Addison\u2019s disease, and which gland is affected?
Solution: Addison\u2019s disease is caused by the hyposecretion of adrenal cortical hormones,
leading to fatigue, low blood pressure, and salt imbalance.

Analysis and Application

Q17. A child has abnormally large hands and feet. Which hormone is responsible, and what
condition does this indicate?
Solution: The hormone growth hormone (GH) is overproduced, leading to acromegaly, which
causes abnormal growth in adulthood.

Recall
Q18. Name the hormones secreted by the posterior pituitary gland.
Solution: ADH (Antidiuretic Hormone) and Oxytocin.

Application
Q19. Why might a diabetic patient need insulin injections?
Solution: Diabetic patients may lack sufficient insulin, leading to high blood glucose levels.
Injecting insulin helps regulate glucose levels.

Understanding
Q20. What is the function of ADH, and which organ does it target?
Solution: ADH (Antidiuretic Hormone) promotes water reabsorption in the kidneys, reducing
water loss through urine.
 Reproductive System
Male Reproductive System:
Primary Organs:
Testes:
Located in the scrotum, which keeps them
at a temperature lower than body
temperature for optimal sperm
production.
Each testis is encased in a capsule. The
capsule is internally divided into 15–20
lobules. Each lobule contains seminiferous
tubules.
Sperms are produced in the seminiferous
tubules by the process of
spermatogenesis.
Secrete the hormone testosterone,
responsible for secondary sexual
characteristics in males. Accessory Glands:

Epididymis: Seminal Vesicles:

A long, coiled tube situated on the back of Produce a fluid rich in fructose, providing
each testis. energy for sperm.
Stores sperm, allowing them to mature The fluid also contains enzymes that help
and gain motility. in sperm motility.

Vas Deferens: Prostate Gland 

A muscular tube that transports mature It is a bilobed structure. 
sperm from the epididymis to the urethra It pours an alkaline secretion into the
during ejaculation. semen. This secretion constitutes about
It is about 45 cm long.  The two vas 13–33% of the semen.
deferens loop over the ureters and join
the urethra. Bulbourethral Glands (Cowper's Glands):
Secrete mucus that lubricates the urethra
Ejaculatory Duct  and neutralizes traces of acidic urine.
The vas deferens and the seminal vesicles
unite to form the ejaculatory duct. 
It ejects sperms into the urethra just
before ejaculation

Penis:
External reproductive organ responsible
for delivering sperm into the female
reproductive system
It is the passage for both urine and
semen. 
It is a highly vascular organ with erectile
tissues and vascular spaces. 
Under the influence of sexual stimulation,
blood flows in large amounts into the
vascular spaces of the penis, which makes
it erect. Such a condition is called
erection.
Female Reproductive System
Primary Organs:
Ovaries:
Two ovaries are present in the pelvic
cavity, one on each side of the uterus. 
Ovaries produce ova by the process of
oogenesis.
Paired organs that produce ova (eggs)
through oogenesis.
Secrete the hormones oestrogen and
progesterone, regulating the
menstrual cycle and secondary sexual
characteristics.

Fallopian Tubes (Oviducts):

Tubular structures where fertilization
occurs.
Cilia lining the tubes help transport the
egg from the ovary to the uterus.
The two oviducts or fallopian tubes are about 12 cm long and attached to the lateral ends of
the ovaries. 
The open distal end of the ducts is funnel-shaped and called oviduct funnel, infundibulum or
ostium. 
The infundibulum has finger-like projections called fimbriae which help to push the released
ovum into the oviduct.
Uterus (Womb):
Hollow, muscular organ where the fertilized egg implants and the embryo develops.
The internal wall of the uterus is lined by tissue layers. The innermost layer is called the
endothelium which is lined by the ciliated epithelium.  It protects and nourishes the
developing embryo.
The inner lining (endometrium) thickens during the menstrual cycle to support implantation.
Cervix:
The lower, narrow part of the uterus that opens into the vagina.
Produces mucus that facilitates sperm movement during ovulation.

Vagina:
Muscular canal that serves as the birth canal and the site where sperm is deposited during
intercourse.

Gametes: Sperm and Egg

Sperm Structure and Function
Head:
The nucleus of sperms contains genetic
material (22 + X/22 + Y chromosomes).

Acrosome at the tip contains enzymes that

help penetrate the egg's outer layers during
fertilization.

Mitochondria  The mitochondria are

contained in the middle piece.  It provides
energy (ATP) for the swimming activity of
the sperm.

Tail: A long, whip-like structure (flagellum) enabling the sperm to swim toward the egg.
Egg Structure and Function
Egg Structure and Function
Nucleus:
Contains 23 chromosomes (haploid), ready to fuse with the sperm's nucleus.

Cytoplasm:
Rich in nutrients to support the early stages of embryonic development.

Zona Pellucida:
A glycoprotein layer surrounding the egg that ensures only one sperm fertilizes the egg.

Fertilization, Implantation, and Embryonic Development

Fertilization:
Occurs in the fallopian tube.
Fertilisation is the fusion of the male gamete (sperm) and the female gamete (ovum) to form a
zygote. 
During copulation, the sperms are released into the vagina near the cervix of the uterus. 
These sperms actively pass through the passage of the cervix into the uterine cavity.  Of the
millions of sperms released into the vagina, very few are able to reach the upper parts of the
oviducts. The rest die on the way and are absorbed.

Implantation:
The zygote undergoes multiple divisions (cleavage) to form a blastocyst.
The blastocyst attaches to the uterine wall approximately 7 days after fertilization.
It is the process during which the developing embryo adheres itself to the endometrial lining of
the uterus.
The embryo is a growing egg after fertilisation until the main parts of the body and the
internal organs have started to take shape.
The foetus is the stage when the embryo starts looking like a baby, usually from 7 weeks of
gestation.

Gestation:
Refers to the period of fetal
development in the uterus.
In humans, gestation lasts
approximately 280 days or 9 months.
During this time, the embryo develops
into a fully formed baby, with all
organ systems functioning.

Placenta:
A temporary organ that connects the mother and
embryo via the umbilical cord.

Functions:
Nutrition: Transfers glucose, amino acids, and other
nutrients to the embryo.
Respiration: Facilitates the exchange of oxygen and
carbon dioxide between maternal and fetal blood.
Excretion: Removes waste products like urea from the
embryo's blood.
Endocrinal Function: Secretes hormones (e.g., hCG,
progesterone) to maintain pregnancy.
Parturition:
The process of childbirth, triggered by hormonal and
physical changes.

Stages:
Dilation Stage:
The cervix dilates (widens) due to uterine contractions.
Amniotic sac ruptures, releasing amniotic fluid
(commonly referred to as the "water breaking").

Expulsion Stage:
Strong uterine contractions push the baby through the
birth canal.
The baby is delivered.

Placental Stage:
After some time, the umbilical cord shrinks and can be tied and cut.
After about 15 minutes, the placenta breaks from the uterus and is expelled out after birth.

Hormonal Role:
Oxytocin, released by the pituitary gland, stimulates uterine contractions during labor.

Foetal Membranes and Amniotic Fluid:

The amniotic sac surrounds the embryo, filled with amniotic fluid.

Functions:
It is a sac which develops around the embryo even before the formation of allantois. 
The amniotic fluid fills the space between the amnion and embryo. 
The amniotic fluid protects the embryo from physical damage by jerks and mechanical shocks.
Protects the embryo from physical shocks.
Prevents desiccation.
Maintains a constant temperature.

Menstrual Cycle
Phases:
a. Menstrual Phase (Day 1-5):
The uterine lining (endometrium) is shed, resulting in bleeding.
Triggered by a drop in progesterone levels.
b. Follicular Phase (Day 6-13):
Follicle-stimulating hormone (FSH) stimulates the growth of ovarian follicles.
Oestrogen levels rise, thickening the endometrium.
c. Ovulation (Day 14):
A surge in luteinizing hormone (LH) causes the release of a mature egg from the
ovary.
d. Luteal Phase (Day 15-28):
The ruptured follicle forms the corpus luteum, which secretes progesterone.
Progesterone prepares the endometrium for implantation.
If fertilization does not occur, the corpus luteum degenerates, causing progesterone
levels to drop.
Role of Sex Hormones
Testosterone:
Production: Secreted by the interstitial cells (Leydig cells) in the testes under the influence of
luteinizing hormone (LH) from the pituitary gland.
Functions:

Sperm Production: Stimulates spermatogenesis in the seminiferous tubules.

Development of Secondary Sexual Characteristics:
Growth of facial and body hair.
Deepening of the voice due to enlargement of the larynx.
Increased muscle mass and strength.
Development of male pattern baldness in some individuals (genetic predisposition).
Sexual Drive: Plays a crucial role in regulating libido in males.
Bone and Muscle Growth: Promotes bone density and muscle development.
Erythropoiesis: Enhances the production of red blood cells by stimulating the bone marrow.
Maintenance of Male Reproductive Organs: Ensures proper functioning of structures such as
the testes, prostate gland, and seminal vesicles.

Oestrogen:
Secreted by the ovaries.
Regulates the menstrual cycle and promotes the development of female secondary sexual
characteristics (e.g., breast development, widening of hips).

Progesterone:
Secreted by the corpus luteum and placenta.
Maintains pregnancy by thickening the uterine lining and preventing uterine contractions.

Identical and Fraternal Twins

Identical Twins:
Formed when a single fertilized egg splits into two embryos.
Share the same genetic material and are always of the same sex.

Fraternal Twins:
Result from the fertilization of two separate eggs by two different sperm.
Genetically different and can be of the same or different sexes.

Multiple Choice Questions

Recall and Understanding
Which organ produces sperm in the male reproductive system?
A) Prostate gland
B) Testis
C) Seminal vesicle
D) Epididymis
Answer: B) Testis
Explanation: The testis is the primary reproductive organ in males responsible for
producing sperm and the hormone testosterone.
Recall and Understanding
What is the function of amniotic fluid?
A) Provides nutrition to the embryo
B) Protects the embryo from mechanical shocks
C) Supplies oxygen to the embryo
D) Facilitates fertilization
Answer: B) Protects the embryo from mechanical shocks
Explanation: Amniotic fluid acts as a cushion, protecting the developing embryo from external
impacts.

Understanding and Application

Which structure in the female reproductive system is the site of fertilization?
A) Uterus
B) Vagina
C) Fallopian tube
D) Cervix
Answer: C) Fallopian tube
Explanation: Fertilization typically occurs in the fallopian tube, where the sperm meets the egg.

Understanding and Application

What is the primary role of the placenta in fetal development?
A) Hormonal regulation of the mother
B) Mechanical support for the fetus
C) Exchange of nutrients, gases, and waste between mother and fetus
D) Protection against infections
Answer: C) Exchange of nutrients, gases, and waste between mother and fetus
Explanation: The placenta ensures the transfer of essential substances and waste products between
maternal and fetal blood.

Analysis
Why are identical twins genetically identical, whereas fraternal twins are not?
A) Identical twins share the same egg and sperm; fraternal twins do not.
B) Identical twins share a placenta, while fraternal twins do not.
C) Fraternal twins are a result of genetic mutation.
D) Fraternal twins share the same amniotic sac, while identical twins do not.
Answer: A) Identical twins share the same egg and sperm; fraternal twins do not.
Explanation: Identical twins result from the splitting of a single fertilized egg, whereas fraternal twins
arise from two separate eggs fertilized by different sperms.

Application
A disruption in the menstrual cycle could be caused by a deficiency in which hormone?
A) Adrenaline
B) Testosterone
C) Progesterone
D) Thyroxine
Answer: C) Progesterone
Explanation: Progesterone regulates the menstrual cycle and prepares the uterus for implantation. A
deficiency can lead to irregularities.

Application
If a sperm lacks an acrosome, what function will it fail to perform?
A) Penetrate the egg membrane
B) Move toward the egg
C) Divide into multiple cells
D) Produce energy
Answer: A) Penetrate the egg membrane
Explanation: The acrosome contains enzymes that help the sperm penetrate the egg membrane for
fertilization.
Analysis and Application
If the placenta fails to function properly, what is the most immediate consequence for the fetus?
A) Hormonal imbalance in the mother
B) Reduced oxygen and nutrient supply to the fetus
C) Premature labor
D) Development of fraternal twins
Answer: B) Reduced oxygen and nutrient supply to the fetus
Explanation: The placenta ensures the transfer of oxygen and nutrients. Its failure affects fetal growth
and development.

Recall
What is the duration of the menstrual cycle in an average female?
A) 21 days
B) 28 days
C) 30 days
D) 14 days
Answer: B) 28 days
Explanation: The menstrual cycle is approximately 28 days, but it can vary slightly among
individuals.

Recall
Which hormone is responsible for the development of secondary sexual characteristics in males?
A) Oestrogen
B) Progesterone
C) Testosterone
D) Follicle Stimulating Hormone
Answer: C) Testosterone
Explanation: Testosterone triggers the development of male secondary sexual characteristics like a
deeper voice and facial hair.

Understanding
What is gestation?
A) The process of implantation of the embryo
B) The process of fertilization
C) The period of development of the fetus in the uterus
D) The delivery of the baby
Answer: C) The period of development of the fetus in the uterus
Explanation: Gestation refers to the time during which the fetus develops inside the uterus.

Recall and Understanding

What is the role of the prostate gland?
A) Produces sperm
B) Secretes fluid that nourishes and protects sperm
C) Stores sperm temporarily
D) Stimulates hormone production
Answer: B) Secretes fluid that nourishes and protects sperm
Explanation: The prostate gland contributes to seminal fluid, providing a medium for sperm to move
and survive.

Application
What is the likely outcome if fertilization does not occur in a menstrual cycle?
A) The zygote is implanted in the uterus
B) The menstrual cycle stops permanently
C) The uterine lining is shed during menstruation
D) The fallopian tubes are blocked
Answer: C) The uterine lining is shed during menstruation
Explanation: If fertilization does not occur, the uterine lining breaks down and is shed, resulting in
menstruation.
Analysis
Why are fraternal twins genetically different?
A) They develop from two different eggs fertilized by two different sperms.
B) They share the same egg but different sperms.
C) They are formed due to a genetic mutation.
D) They develop from the same zygote.
Answer: A) They develop from two different eggs fertilized by two different sperms.
Explanation: Each fraternal twin has a unique genetic composition, like any two siblings, because
they originate from different eggs and sperms.

Understanding and Application

What role does the placenta play in the excretion of fetal waste products?
A) It produces enzymes to digest waste products.
B) It transfers waste from the fetal blood to the maternal blood.
C) It stores waste products until birth.
D) It prevents waste from accumulating in the fetal body.
Answer: B) It transfers waste from the fetal blood to the maternal blood.
Explanation: The placenta facilitates the removal of waste products from the fetal blood, transferring
them to the mother's circulatory system for excretion.

Application
How does a lack of oestrogen affect the menstrual cycle?
A) Ovulation stops, leading to infertility.
B) The uterine lining thickens excessively.
C) The menstrual cycle becomes shorter.
D) Fertilization becomes impossible.
Answer: A) Ovulation stops, leading to infertility.
Explanation: Oestrogen is crucial for the growth and release of eggs during ovulation. Without it,
ovulation ceases, impacting fertility.

Recall and Understanding

What is the meaning of the term "parturition"?
A) The process of fertilization
B) The process of childbirth
C) The process of implantation
D) The process of placenta formation
Answer: B) The process of childbirth
Explanation: Parturition is the medical term for the process of delivering a baby, marking the end of
pregnancy.

Recall
Which structure connects the fetus to the placenta?
A) Amniotic sac
B) Fallopian tube
C) Umbilical cord
D) Chorionic villi
Answer: C) Umbilical cord
Explanation: The umbilical cord connects the fetus to the placenta, facilitating the exchange of
nutrients, gases, and waste products.

Understanding and Application

If the amniotic fluid is significantly reduced, what is the most likely consequence for the fetus?
A) Restricted movement and growth
B) Early onset of labor
C) Increased risk of genetic abnormalities
D) Development of identical twins
Answer: A) Restricted movement and growth
Explanation: Amniotic fluid cushions the fetus and allows free movement. Its reduction can lead to
growth restrictions and other complications.
Analysis and Application
A woman is experiencing irregular menstrual cycles and infertility. Which hormone is most likely
deficient?
A) Thyroxine
B) Progesterone
C) Insulin
D) Adrenaline
Answer: B) Progesterone
Explanation: Progesterone is essential for regulating the menstrual cycle and preparing the uterus for
pregnancy. Its deficiency can result in irregular cycles and infertility.

Short Answer Type Questions

Recall
What is the function of the testis in the male reproductive system?
Answer: The testis produces sperm and the hormone testosterone, which regulates male
sexual development and reproductive function.

Recall
What is the role of the placenta in pregnancy?
Answer: The placenta facilitates the exchange of nutrients, oxygen, and waste products
between the mother and fetus.

Understanding
Explain the process of fertilization.
Answer: Fertilization is the fusion of a sperm cell from the male and an egg cell from the
female, resulting in the formation of a zygote.

Understanding
What is the function of the fallopian tube in the female reproductive system?
Answer: The fallopian tube is the site where fertilization occurs. It transports the egg from
the ovary to the uterus.

Application
How does the menstrual cycle affect fertility?
Answer: The menstrual cycle regulates ovulation and the thickening of the uterine lining.
Fertility is highest during ovulation when an egg is released.

Application
What would happen if the sperm's acrosome is damaged?
Answer: If the acrosome is damaged, the sperm will be unable to release the enzymes
required to penetrate the egg, preventing fertilization.

Analysis
Why is the role of progesterone crucial during pregnancy?
Answer: Progesterone helps maintain the uterine lining, preventing its shedding, and
supports the implantation of the fertilized egg. Without it, miscarriage could occur.

Analysis
Compare the roles of the testes and ovaries in the reproductive process.
Answer: The testes produce sperm and testosterone, whereas the ovaries produce eggs
and hormones like estrogen and progesterone, which regulate the menstrual cycle and
support pregnancy.
Understanding and Application
How do identical twins differ from fraternal twins genetically?
Answer: Identical twins are genetically identical because they originate from the
same fertilized egg that splits into two, while fraternal twins come from two
different eggs fertilized by separate sperm cells, so they are genetically distinct.

Understanding and Application

Why is the amniotic fluid important for the developing fetus?
Answer: Amniotic fluid provides a protective cushion for the fetus, prevents
dehydration, and helps regulate temperature, allowing the fetus to grow and
develop safely.

Application and Analysis

What might happen if there is a failure in the implantation of the fertilized egg?
Answer: If implantation fails, the fertilized egg is not able to develop in the uterus,
leading to the loss of the pregnancy.

Application and Analysis

Explain the consequences of insufficient estrogen in the female reproductive
system.
Answer: Low levels of estrogen can lead to irregular menstruation, difficulty in
ovulation, and potential infertility, as estrogen regulates the menstrual cycle and
prepares the body for pregnancy.

Recall and Understanding

What is the function of the male accessory glands?
Answer: The male accessory glands (prostate gland, seminal vesicles, and
bulbourethral glands) secrete fluids that nourish and protect sperm, facilitating
their movement and survival.

Recall and Understanding

What is the significance of the menstrual cycle?
Answer: The menstrual cycle regulates the release of eggs and prepares the
uterine lining for pregnancy. It lasts approximately 28 days and includes stages
such as menstruation, ovulation, and the luteal phase.

Understanding and Recall

What is gestation, and how long does it last in humans?
Answer: Gestation is the period of fetal development in the uterus, lasting about
40 weeks (9 months) in humans.

Understanding and Recall

Explain the role of testosterone in male reproduction.
Answer: Testosterone is responsible for the development of male secondary
sexual characteristics such as facial hair, deep voice, and increased muscle
mass. It also stimulates sperm production.
Analysis and Application
What could happen if the placenta does not develop properly during pregnancy?
Answer: Improper development of the placenta can lead to complications such as
insufficient nutrient and oxygen supply to the fetus, growth restriction, and
potential miscarriage or premature birth.

Analysis and Application

How would a lack of progesterone affect pregnancy?
Answer: A lack of progesterone can lead to the shedding of the uterine lining,
causing miscarriage or preventing the fertilized egg from implanting.

Recall
What is parturition?
Answer: Parturition is the process of childbirth, involving labor and the delivery of
the baby from the mother's uterus.

Recall
What is the primary function of the ovary in the female reproductive system?
Answer: The ovary produces eggs (ova) and secretes hormones like estrogen and
progesterone, which regulate the menstrual cycle and support pregnancy.
 Population
Population Explosion in India
Population Explosion refers to the sharp and rapid increase in the human population over a
short period. It has led to concerns regarding the strain on resources, environmental impact,
and the overall quality of life. India is one of the countries experiencing the most significant
population growth, and the government has been emphasizing the need for effective
population control measures.

The causes of the population explosion in India can be attributed to the rapid decline in the
death rate and an increase in the birth rate.

Main Reasons for the Sharp Rise in Human Population in India and the
World
Improved Healthcare Systems:
Medical advancements, such as vaccines, antibiotics, and improved disease control, have
significantly reduced mortality rates, especially infant mortality.
Better access to healthcare services, including maternal care, has contributed to a higher
survival rate, thus boosting population growth.

Improved Sanitation and Hygiene:

The provision of clean drinking water, sanitation facilities, and waste disposal has
drastically reduced the spread of infectious diseases, further lowering the death rate and
improving life expectancy.

Advancements in Agriculture:
With the Green Revolution, agricultural productivity increased, ensuring that the rising
population had enough food. Better irrigation, the use of high-yielding variety seeds, and
fertilizers have played a crucial role in feeding a growing population.

Decreased Death Rate:

The introduction of vaccines, antibiotics, and better public health practices has drastically
lowered death rates, particularly in infants and young children. As a result, the population
continues to grow.

Lack of Awareness about Family Planning:

In many regions, the awareness and use of family planning measures are still limited. As a
result, families tend to have more children, contributing to a high birth rate.

Key Terms Related to Population

Demography: The scientific study of human populations, including their size, distribution,
structure, and changes over time. Demographic studies help in understanding trends like
birth rates, death rates, and migration, which can influence population control policies.

Population Density: Population density refers to the number of individuals living per unit of
area, usually per square kilometer. Areas with high population density face greater
pressure on resources, leading to issues like overcrowding, resource depletion, and
increased competition for jobs and housing.

Birth Rate: The birth rate is the number of live births per 1,000 people in a given year. A high
birth rate indicates a growing population, while a low birth rate indicates a stable or
declining population. India, for example, has a high birth rate contributing to the population
explosion.
 Death Rate: The death rate refers to the number of deaths per 1,000 individuals in a given
year. In the past, India had a high death rate due to widespread diseases and poor
healthcare. However, medical advancements have led to a decrease in death rates over the
years.

Growth Rate of Population: The population growth rate is the difference between the birth
rate and the death rate. A positive growth rate indicates an increasing population. The rapid
increase in population in India is due to the high birth rate and declining death rate.

Problems Faced Due to Population Explosion

Unemployment: A rapidly increasing population creates a larger labor force, but there are
not enough jobs to accommodate everyone. This leads to higher unemployment rates, lower
wages, and social instability.

Over-exploitation of Natural Resources: As the population grows, the demand for resources
such as water, food, and energy increases. Over-exploitation of these resources can lead to
their depletion, soil degradation, deforestation, and loss of biodiversity.

Low Per Capita Income: When the population grows faster than economic development, the
per capita income (income per individual) decreases. This leads to poverty, low standards of
living, and insufficient access to basic needs like education, healthcare, and sanitation.

Price Rise (Inflation): A larger population leads to increased demand for goods and services,
which can drive up prices. Inflation results in reduced purchasing power, making life difficult
for the average person, especially those in the lower-income brackets.

Pollution: A large population produces a significant amount of waste, including solid waste,
air pollutants, and water contaminants. The increased use of fossil fuels leads to air
pollution, while industrialization and urbanization contribute to water and soil pollution,
impacting the environment and public health.

Unequal Distribution of Wealth: The wealth generated by a growing economy is often

unequally distributed, with the rich becoming richer and the poor becoming poorer. This
exacerbates economic inequality and creates social divisions.

Surgical Methods of Population Control

Tubectomy (Female Sterilization):

A surgical procedure where the fallopian tubes are blocked, cut, or tied to
prevent eggs from reaching the uterus for fertilization. This method is
considered permanent, as it prevents any future pregnancies.

Vasectomy (Male Sterilization):

A surgical procedure where the vas deferens (the sperm ducts) are cut or
sealed, preventing sperm from being released during ejaculation. This is also
a permanent method of contraception for men.
Non-Surgical Methods or Contraceptive Methods:

Oral Contraceptives (Pills): Hormonal pills taken by females to

prevent ovulation and pregnancy.
Condoms (Male and Female): Physical barriers that prevent sperm
from entering the female reproductive tract.
Intrauterine Devices (IUDs): Devices placed inside the uterus to
prevent pregnancy.
Injectable Contraceptives: Hormonal injections that prevent
ovulation for a period of time.

Awareness Programs:
Education on Family Planning: Informing individuals and
communities about the benefits of smaller family sizes and
providing information on contraception methods.

Government Campaigns: Many countries, including India, have

launched awareness campaigns like "Hum Do, Hamare Do" to
encourage family planning and population control.

Government Policies:
Incentives for Small Families: Providing financial incentives,
healthcare benefits, and tax reductions for families that limit the
number of children.

Legislation and Family Planning: Laws to promote delayed

marriages, family planning programs, and restrictions on the
number of children in some cases.

Multiple Choice Questions

Recall
Q1. Which of the following terms refers to the number of people living per unit area?
A) Birth Rate
B) Death Rate
C) Population Density
D) Growth Rate
Answer: C) Population Density
Explanation: Population density refers to the number of individuals living per unit area (usually
per square kilometer). It helps assess how crowded an area is.

Understanding
Q2. What is the primary cause for the rapid rise in the human population in India?
A) Increased death rate
B) Improved healthcare and sanitation
C) Reduced birth rate
D) Decreased migration
Answer: B) Improved healthcare and sanitation
Explanation: Advances in healthcare and sanitation have reduced mortality rates, allowing
more people to live longer, contributing to the rise in population.
Application
Q3. If a country has a high birth rate and a low death rate, what will be the expected result in the
population?
A) Population will remain stable
B) Population will decline
C) Population will increase rapidly
D) Population will fluctuate
Answer: C) Population will increase rapidly
Explanation: A high birth rate and low death rate indicate that more individuals are being born
than dying, leading to rapid population growth.

Understanding and Application

Q4. What can be a direct consequence of overpopulation in urban areas?
A) Economic prosperity
B) Increased pollution and waste
C) Improved infrastructure
D) Higher literacy rate
Answer: B) Increased pollution and waste
Explanation: Overpopulation often leads to more waste generation, higher pollution levels, and
strain on public services like waste management in urban areas.

Recall
Q5. Which of the following terms refers to the scientific study of populations?
A) Population Density
B) Demography
C) Population Growth Rate
D) Family Planning
Answer: B) Demography
Explanation: Demography is the study of the structure, distribution, and dynamics of human
populations.

Application
Q6. What could be the possible impact of a low birth rate on the population of a country?
A) Rapid population growth
B) Population decline
C) No change in population
D) Increased migration
Answer: B) Population decline
Explanation: A low birth rate results in fewer births, which, if not compensated by immigration, can
lead to a declining population.

Analysis
Q7. How does over-exploitation of natural resources contribute to the problems caused by
population explosion?
A) It reduces economic growth
B) It leads to depletion of resources like water, fossil fuels, and minerals
C) It improves agricultural productivity
D) It increases population density
Answer: B) It leads to depletion of resources like water, fossil fuels, and minerals
Explanation: Over-exploitation of resources due to high population pressures can lead to their
depletion, affecting sustainability.

Understanding
Q8. Which of the following is not a method of controlling population growth?
A) Tubectomy
B) Vasectomy
C) Increased birth rate
D) Family planning education
Answer: C) Increased birth rate
Explanation: Increasing the birth rate is the opposite of controlling population growth. Tubectomy,
vasectomy, and family planning education are methods of control.
Recall and Understanding
Q9. Which of the following is a direct effect of the rising population on employment?
A) Decrease in unemployment rates
B) Increase in job opportunities
C) Rise in unemployment rates
D) Stable employment situation
Answer: C) Rise in unemployment rates
Explanation: With the rise in population, the number of job seekers increases, but job opportunities
may not keep up, leading to higher unemployment rates.

Application and Analysis

Q10. A country experiences a high birth rate and a low death rate, resulting in rapid population
growth. Which of the following problems is most likely to arise?
A) Increased literacy rate
B) Decreased unemployment
C) Depletion of natural resources
D) Improved healthcare services
Answer: C) Depletion of natural resources
Explanation: Rapid population growth increases demand for resources like water, food, and
energy, leading to overuse and depletion of natural resources.

Analysis
Q11. What could be the effect of reduced birth rates on the economy of a country?
A) Economic prosperity due to a smaller labor force
B) Economic growth due to higher consumer demand
C) Decline in workforce, leading to economic challenges
D) No significant change in the economy
Answer: C) Decline in workforce, leading to economic challenges
Explanation: A reduced birth rate can lead to a shrinking workforce, which can cause challenges in
economic growth due to a lack of young workers.

Recall
Q12. Which of the following factors leads to a decrease in the death rate in a country?
A) High birth rate
B) Better healthcare services
C) High unemployment
D) Increased migration
Answer: B) Better healthcare services
Explanation: Improved healthcare reduces mortality by treating diseases and preventing early
deaths, contributing to a lower death rate.

Understanding and Application

Q13. What is the main objective of the population control methods like tubectomy and vasectomy?
A) To prevent genetic disorders
B) To prevent the birth of more children
C) To promote family planning education
D) To regulate migration
Answer: B) To prevent the birth of more children
Explanation: Tubectomy (female sterilization) and vasectomy (male sterilization) are surgical
methods designed to permanently prevent pregnancy by stopping the reproductive process.

Recall
Q14. Which of the following is the best definition of the 'growth rate of population'?
A) The number of births in a given year
B) The number of deaths in a given year
C) The difference between birth rate and death rate
D) The average age of the population
Answer: C) The difference between birth rate and death rate
Explanation: The population growth rate is calculated by subtracting the death rate from the birth
rate, indicating how fast the population is increasing.
Recall and Understanding
Q15. What is the consequence of a high population density on the environment?
A) Reduced pollution
B) Increased resource use and waste generation
C) Greater biodiversity
D) Reduced deforestation
Answer: B) Increased resource use and waste generation
Explanation: High population density leads to higher resource consumption and waste production,
contributing to pollution and environmental degradation.

Application
Q16. How can awareness programs help in controlling population growth?
A) By encouraging higher birth rates
B) By informing people about the benefits of family planning
C) By promoting migration to other countries
D) By reducing healthcare access
Answer: B) By informing people about the benefits of family planning
Explanation: Awareness programs educate individuals about family planning options, leading to
smaller families and slower population growth.

Application and Analysis

Q17. Which of the following is a consequence of unequal distribution of wealth in overpopulated regions?
A) Equal access to resources
B) Reduced economic disparity
C) Widening gap between the rich and poor
D) Increased standard of living for all
Answer: C) Widening gap between the rich and poor
Explanation: In overpopulated regions, the unequal distribution of wealth leads to greater economic
disparity, leaving many people in poverty.

Understanding and Application

Q18. What is the role of government policies in controlling population growth?
A) To encourage larger families
B) To provide incentives for smaller families
C) To promote an increase in birth rates
D) To discourage family planning
Answer: B) To provide incentives for smaller families
Explanation: Government policies often provide incentives like financial benefits, healthcare, and
education to encourage smaller families and control population growth.

Recall and Understanding

Q19. Which of the following is the most likely effect of a population explosion on the environment?
A) Increased pollution and resource depletion
B) Decreased waste generation
C) Improved resource management
D) Enhanced biodiversity
Answer: A) Increased pollution and resource depletion
Explanation: A growing population demands more resources, leading to overuse and environmental
damage, such as pollution and resource depletion.

Analysis and Application

Q20. Which method would be most effective in controlling population growth in a region with a high
birth rate and low access to healthcare?
A) Increased agricultural productivity
B) Improved access to family planning and healthcare
C) Economic incentives for large families
D) Increased migration
Answer: B) Improved access to family planning and healthcare
Explanation: Providing better access to family planning and healthcare services can reduce birth rates
by preventing unplanned pregnancies and improving maternal and child health.
Short Answer Type Questions
Recall
Q1. Define the term 'population density.'Answer:
Population density is the number of individuals living per unit area, typically expressed
as the number of people per square kilometer. It indicates how crowded a specific area
is.

Recall
Q2. What is 'demography'?Answer:
Demography is the scientific study of human populations, focusing on their size,
structure, distribution, and changes over time due to birth, death, migration, and aging.

Understanding
Q3. What are the primary factors contributing to population explosion in India?Answer:
The main factors contributing to population explosion in India are:
Improved healthcare: Better medical facilities have reduced the death rate.
Improved sanitation: Better living conditions have reduced the spread of diseases.
High birth rate: Cultural practices and lack of awareness about family planning lead
to more births.
Decreased infant mortality rate: Fewer children are dying due to advancements in
healthcare.

Understanding
Q4. Explain the difference between 'birth rate' and 'death rate.'Answer:
Birth rate refers to the number of live births per 1,000 people in a given year.
Death rate refers to the number of deaths per 1,000 people in a given year. The
difference between these two rates determines the growth rate of a population.

Application
Q5. How can a high birth rate lead to overpopulation?Answer:
A high birth rate means more individuals are being born than are dying, which leads to a
rapid increase in the population size. If the resources and infrastructure are not sufficient
to support this growing population, it can lead to overpopulation.

Application
Q6. How does overpopulation contribute to the over-exploitation of natural resources?
Answer:
Overpopulation increases the demand for essential resources such as food, water, and
energy. This leads to over-exploitation, resulting in depletion of natural resources,
deforestation, and environmental degradation.

Analysis
Q7. What are the socio-economic problems that arise due to population explosion?
Answer:
Socio-economic problems include:
Unemployment: More people need jobs, but there aren't enough opportunities.
Unequal distribution of wealth: A large population means that wealth becomes more
concentrated in fewer hands.
Price rise: Increased demand for goods leads to inflation.
Low per capita income: Resources become stretched, leading to lower income for
individuals.
Pollution: A larger population produces more waste and pollution, straining the
environment.
Analysis
Q8. Why does a high population density cause environmental degradation?Answer:
High population density leads to increased consumption of resources, excessive waste
generation, and higher demand for land, water, and energy. These factors contribute to
environmental degradation, such as air pollution, water contamination, and loss of
biodiversity.

Understanding and Application

Q9. What role does improved healthcare play in controlling population growth?Answer:
Improved healthcare reduces mortality rates, especially infant mortality. When fewer
people die, the overall population continues to grow. Additionally, better healthcare can
also include family planning services, which help to control birth rates.

Understanding and Application

Q10. How can the increase in birth rate lead to a rise in unemployment?Answer:
A high birth rate means more individuals will enter the workforce over time. If there
aren’t enough job opportunities to match the growing labor force, unemployment rises,
leading to social and economic issues.

Application and Analysis

Q11. How can family planning reduce population growth?Answer:
Family planning involves educating individuals about birth control methods and
providing access to contraceptives. This helps reduce birth rates, giving families the
ability to plan and space the births of their children, which leads to slower population
growth.

Application and Analysis

Q12. What effect does population explosion have on the economy of a country?Answer:
Population explosion leads to increased demand for resources, services, and
infrastructure. It can result in inflation, higher unemployment, and lower per capita
income. The economy may struggle to provide for the needs of the growing population,
leading to poverty and social instability.

Recall and Understanding

Q13. What are 'surgical methods' of population control?Answer:
Surgical methods of population control include procedures like tubectomy (female
sterilization) and vasectomy (male sterilization). These are permanent methods that
prevent further pregnancies by surgically blocking the reproductive organs.

Recall
Q14. What is a 'growth rate' of population?Answer:
The growth rate of population is the difference between the birth rate and death rate in a
given population. It indicates the rate at which the population is increasing or
decreasing.

Understanding
Q15. How can the government help control the population explosion in India?Answer:
The government can help by:
Promoting family planning programs and educating the public about contraceptive
methods.
Providing healthcare services to reduce infant mortality.
Offering financial incentives for small families.
Implementing laws that regulate the number of children per family, such as tax
benefits and subsidies.
Understanding and Application
Q16. Why is reducing the death rate important for controlling population growth?Answer:
Reducing the death rate helps increase the life expectancy of individuals. However, if the
birth rate remains high while the death rate is reduced, the population will continue to
grow rapidly. Hence, balancing both birth and death rates is essential to controlling
population growth.

Analysis and Application

Q17. What are the consequences of unequal distribution of wealth in a highly populated
country?Answer:
In a highly populated country, the unequal distribution of wealth can lead to:
Poverty for the majority of the population, despite economic growth.
Social unrest due to the disparity in living standards.
Unequal access to essential services like healthcare, education, and sanitation.

Application
Q18. How do tubectomy and vasectomy help in controlling population growth?Answer:
Tubectomy (female sterilization) and vasectomy (male sterilization) are surgical
procedures that prevent further pregnancies by blocking or cutting the reproductive
organs. These are permanent methods that effectively reduce birth rates and help
control population growth.

Analysis
Q19. What impact does overpopulation have on the natural environment?Answer:
Overpopulation puts pressure on natural resources, leading to their depletion. It causes
deforestation, air and water pollution, and habitat destruction. This increases the
demand for energy, water, and food, ultimately harming the environment and reducing
biodiversity.

Recall
Q20. What is the relationship between birth rate and population growth?Answer:
The birth rate is directly related to population growth. A high birth rate contributes to
faster population growth, while a low birth rate slows population growth. If the birth rate
exceeds the death rate, the population will increase rapidly.
 Human Evolution
Evolution can be defined as the formation of more complex organisms from
pre-existing simpler organisms over a certain period. It is a slow, but
progressive, natural, sequential development or transformation of animals
and plants from ancestors of different forms and functions.

Key Characteristics of Human Evolution

Bipedalism:
Walking upright on two legs.
Frees the hands for tool-making and carrying objects.
First observed in Australopithecus.

Increasing Cranial Capacity:

Gradual increase in brain size, leading to higher intelligence.
Cranial capacity in humans: approximately 1200-1600 cc.

Reduction in the Size of Canine Teeth:

Indicating a shift from hunting and tearing meat to a more omnivorous diet.

Development of Forehead and Reduction of Brow Ridges:

Prominent in Neanderthals but reduced in modern humans (Homo sapiens ), reflecting
advanced brain development.

Development of Chin:
Present only in modern humans, aiding in better speech articulation.

Reduction in Body Hair:

A shift from a hairy body to smoother skin, aiding thermoregulation and reducing
parasite load.

Height and Posture:

Evolutionary trend toward increased height and upright posture.

Key Human Ancestors

Australopithecus (4-2 million years ago): Homo erectus (1.9 million - 110,000 years
Earliest bipedal primates. ago):
Small cranial capacity (~400-500 cc). First to use fire and create advanced
Short stature (3.5–4.5 feet). tools.
Cranial capacity ~850-1100 cc.

Homo habilis (2.4-1.4 million years ago):

Known as "handy man" due to tool usage. Neanderthals (400,000–40,000 years
Cranial capacity ~600-800 cc. ago):
Lived in Europe and Western Asia.
Adapted to cold climates; robust body
structure.
Cro-Magnon (40,000–10,000 years ago):
Early modern humans in Europe.
Skilled in art and tool-making.

Homo sapiens sapiens (Modern Humans):

Advanced tool-making, language, and culture.
Cranial capacity ~1200-1600 cc

Theories of Evolution
A. Lamarck’s Theory of Inheritance of Acquired Characteristics
Proposed by Jean-Baptiste Lamarck, this theory suggests that traits acquired during
an organism's lifetime can be passed on to its offspring.

1. Use of Organs:
Organs used frequently become more developed.
Example: The long neck of giraffes evolved because they stretched their necks
to reach higher branches.
2. Disuse of Organs:
Organs not used frequently shrink or disappear over generations.
Example: Vestigial organs in humans like the appendix, wisdom teeth, and ear
pinnae.
3. Criticism:
Lamarck's theory was later disproven because acquired traits cannot alter an
organism's DNA.

B. Darwin’s Theory of Evolution by Natural Selection

Proposed by Charles Darwin, this theory is based on the concept of "Survival of the
Fittest."

1. Key Principles:
Variation: Differences exist among individuals in a population.
Struggle for Existence: Organisms compete for limited resources.
Natural Selection: Individuals with advantageous traits survive and reproduce.
Adaptation: Over generations, favorable traits become more common in the
population.

Example: Peppered Moth

During the Industrial Revolution in England, pollution caused tree trunks to
darken.
Before pollution: Light-colored moths were camouflaged and survived.
After pollution: Dark-colored moths were better camouflaged, and light-
colored moths were preyed upon.
This is an example of adaptation through natural selection.
Multiple Choice Questions
Understanding
Q1. What is the significance of bipedalism in human evolution?
a) It allowed humans to develop larger canines.
b) It enabled humans to walk upright, freeing the hands for other activities.
c) It increased the cranial capacity in early humans.
d) It helped humans develop language skills.
Answer: b) It enabled humans to walk upright, freeing the hands for other activities.
Explanation: Bipedalism helped in tool-making, carrying objects, and other evolutionary
advancements

Understanding
Which ancestor is referred to as the "handy man" due to their ability to make tools?
a) Australopithecus
b) Homo habilis
c) Homo erectus
d) Neanderthals
Answer: b) Homo habilis
Explanation: Homo habilis was the first to use tools, earning the nickname "handy man."

Application
Q3. Which evolutionary trait helped early humans adapt to colder climates?
a) Reduction in body hair
b) Use of tools
c) Development of fire-making skills
d) Increasing cranial capacity
Answer: c) Development of fire-making skills
Explanation: Fire allowed early humans like Homo erectus to survive cold climates by providing
warmth and protection.

Application
What does the adaptation of the peppered moth demonstrate?
a) Lamarck’s theory of use and disuse
b) Darwin’s theory of natural selection
c) Development of vestigial organs
d) Migration of species
Answer: b) Darwin’s theory of natural selection
Explanation: The peppered moth’s color change during the Industrial Revolution is a classic
example of survival of the fittest.

Recall
Q5. Which human ancestor was the first to use fire?
a) Australopithecus
b) Homo habilis
c) Homo erectus
d) Neanderthals
Answer: c) Homo erectus
Explanation: Homo erectus is known for using fire for warmth, protection, and cooking.

Recall
Q6. What is the approximate cranial capacity of modern humans (Homo sapiens sapiens)?
a) 400–500 cc
b) 800–1000 cc
c) 1200–1600 cc
d) 2000–2500 cc
Answer: c) 1200–1600 cc
Explanation: Modern humans have a significantly larger brain compared to their ancestors.
Analysis
Q7. How does the development of a chin distinguish modern humans from their ancestors?
a) It allows for better speech articulation.
b) It increases cranial capacity.
c) It helps in chewing food more effectively.
d) It improves posture.
Answer: a) It allows for better speech articulation.
Explanation: The chin supports tongue movement and speech, a feature unique to modern
humans.

Analysis
Q8. Why are wisdom teeth considered vestigial in humans?
a) They no longer serve a significant purpose in our diet.
b) They are larger than necessary for modern jaws.
c) They are prone to infections.
d) They grow earlier than other teeth.
Answer: a) They no longer serve a significant purpose in our diet.
Explanation: Modern humans consume softer food that doesn’t require extra molars for grinding.

Understanding and Application

Q9. Which characteristic is not associated with Australopithecus?
a) Bipedalism
b) Cranial capacity of 400–500 cc
c) Use of fire
d) Short stature
Answer: c) Use of fire
Explanation: Fire usage was first observed in Homo erectus, not Australopithecus.

Understanding and Application

Q10. How does the reduction in body hair benefit modern humans?
a) It improves sensory functions.
b) It aids in thermoregulation.
c) It reduces predator attacks.
d) It enhances physical strength.
Answer: b) It aids in thermoregulation.
Explanation: Reduced body hair helps in sweat evaporation and temperature control.

Analysis and Application

Q11. What evidence supports Darwin’s theory of evolution by natural selection?
a) Fossil records showing transitional species
b) Increasing cranial capacity in modern humans
c) Survival of dark-colored peppered moths during industrial pollution
d) Development of vestigial organs
Answer: c) Survival of dark-colored peppered moths during industrial pollution
Explanation: This shows how favorable traits allow survival and reproduction.

Analysis and Application

Q12. Why are Homo habilis and Homo erectus considered milestones in human evolution?
a) They developed the first languages.
b) They were the first to migrate out of Africa.
c) They made and used tools and fire.
d) They were the first to display bipedalism.
Answer: c) They made and used tools and fire.
Explanation: Homo habilis used tools, and Homo erectus utilized fire, both critical developments in
human evolution.
Recall and Understanding
Q13. Which of the following is not a vestigial organ in humans?
a) Appendix
b) Wisdom teeth
c) Pinna
d) Pancreas
Answer: d) Pancreas
Explanation: The pancreas is a functional organ, unlike the appendix or wisdom teeth.

Recall and Understanding

Q14. Which ancestor is associated with the development of art and culture?
a) Australopithecus
b) Neanderthals
c) Cro-Magnon
d) Homo habilis
Answer: c) Cro-Magnon
Explanation: Cro-Magnons were early modern humans skilled in art and cultural activities.

Recall
Q15. What is the key principle of Darwin’s theory of natural selection?
a) Inheritance of acquired traits
b) Survival of the fittest
c) Development of vestigial organs
d) Use and disuse of organs
Answer: b) Survival of the fittest
Explanation: Natural selection is based on advantageous traits aiding survival and reproduction.

Recall
Q16. Which ancestor had the smallest cranial capacity?
a) Homo habilis
b) Australopithecus
c) Neanderthals
d) Homo erectus
Answer: b) Australopithecus
Explanation: Australopithecus had a cranial capacity of 400–500 cc, the smallest among listed
ancestors.

Understanding
Q17. Why did Darwin reject Lamarck’s theory of evolution?
a) Acquired traits do not alter genetic material.
b) Use and disuse of organs have no evolutionary impact.
c) Vestigial organs are not influenced by behavior.
d) Evolution occurs in isolated species.
Answer: a) Acquired traits do not alter genetic material.
Explanation: Darwin emphasized genetic inheritance rather than behavior-induced changes.

Understanding
Q18. What characteristic distinguishes Neanderthals from modern humans?
a) Brow ridges
b) Bipedalism
c) Use of fire
d) Reduced body hair
Answer: a) Brow ridges
Explanation: Neanderthals had prominent brow ridges, unlike modern humans.
Application
Q19. Why is the development of tools considered a significant evolutionary step?
a) It reduced dependency on natural resources.
b) It marked the beginning of human culture.
c) It enhanced survival by aiding in food acquisition.
d) It allowed migration to other continents.
Answer: c) It enhanced survival by aiding in food acquisition.
Explanation: Tools helped early humans hunt, gather, and process food efficiently.

Application
Q20. Which evolutionary feature allowed the development of advanced speech in humans?
a) Larger cranial capacity
b) Development of a chin
c) Bipedal posture
d) Reduced body hair
Answer: b) Development of a chin
Explanation: The chin supported speech articulation, a key feature in human communication.

Short Answer Type Questions

Understanding
Q1. What is bipedalism, and why is it considered a significant milestone in human
evolution?
Answer:
Bipedalism refers to the ability to walk upright on two legs. It is significant as it freed the
hands for tool-making, carrying objects, and increased efficiency in locomotion.

Understanding
Q2. Name any two features that distinguish Homo habilis from Australopithecus.
Answer:
1. Homo habilis had a larger cranial capacity (about 600–800 cc) compared to
Australopithecus.
2. Homo habilis used tools, earning them the nickname "handy man."

Application
Q3. How did the adaptation of the peppered moth during the Industrial Revolution
demonstrate natural selection?
Answer:
During the Industrial Revolution, trees darkened due to soot, making dark-colored
moths better camouflaged. They survived and reproduced more, while light-colored
moths were preyed upon, demonstrating survival of the fittest.

Application
Q4. Explain how the reduction of body hair was beneficial in human evolution.
Answer:
The reduction of body hair helped humans regulate body temperature more effectively
through sweating, which is essential for thermoregulation in hot climates.

Recall
Q5. Which human ancestor is known for using fire for the first time?
Answer:
Homo erectus was the first human ancestor to use fire.
Recall
Q6. Define the term "cranial capacity."
Answer: Cranial capacity refers to the volume of the braincase, which indicates the brain size of
a species.

Analysis
Q7. Why is the presence of vestigial organs in humans considered evidence of evolution?
Answer: Vestigial organs like the appendix and wisdom teeth are remnants of ancestral features
that no longer serve a significant function, showing evolutionary changes over time.

Analysis
Q8. Analyze the role of increasing cranial capacity in the evolution of human ancestors.
Answer: Increasing cranial capacity allowed human ancestors to develop advanced cognitive
abilities, such as problem-solving, tool-making, and communication, which contributed to their
survival and evolution.

Understanding and Application

Q9. How does the concept of "survival of the fittest" relate to Darwin’s theory of natural selection?
Answer: ‘Survival of the fittest" means individuals with advantageous traits are more likely to
survive, reproduce, and pass on their traits to the next generation, forming the basis of Darwin's
theory.

Understanding and Application

Q10. Compare the cranial capacities of Australopithecus and Homo sapiens sapiens.
Answer:
Australopithecus: 400–500 cc
Homo sapiens sapiens: 1200–1600 cc
The increase in cranial capacity reflects advanced cognitive development in modern
humans.

Application
Q11. Why did the giraffe’s neck become longer according to Lamarck’s theory?
Answer: Lamarck suggested that giraffes stretched their necks to reach higher leaves, and this
acquired trait was passed on to their offspring.

Application
Q12. Describe how the chin's development contributed to human evolution.
Answer: The chin supports the tongue and jaw, aiding in better speech articulation, a critical
aspect of communication in modern humans.

Analysis and Application

Q13. How do the differences in canine teeth size among human ancestors show dietary
adaptation?
Answer: Reduction in canine size indicates a shift from a diet requiring tearing of flesh
(carnivorous) to a more omnivorous or plant-based diet, reflecting changes in food habits and
tools.

Analysis and Application

Q14. What evolutionary advantage did the development of tools provide early humans?
Answer: The development of tools helped early humans hunt, process food, and build shelters,
improving their chances of survival and adaptation to different environments.

Recall and Understanding

Q15. Name any two human ancestors and their defining characteristics.
Answer:
1. Homo habilis: Known for tool-making; cranial capacity of 600–800 cc.
2. Neanderthals: Adapted to cold climates; robust bodies and prominent brow ridges.
Recall and Understanding
Q16. What does the term "natural selection" mean?
Answer: Natural selection is the process by which organisms with advantageous traits survive
and reproduce, passing those traits to their offspring.

Recall
Q17. Which human ancestor is closely related to modern humans?
Answer: Cro-Magnon is closely related to modern humans (Homo sapiens sapiens).

Recall
Q18. What is the significance of the peppered moth in the study of evolution?
Answer: It provides evidence of natural selection, showing how traits that enhance survival in a
changing environment become more common.

Understanding
Q19. Explain the term "forehead and brow ridges" in the context of human evolution.
Answer: Forehead development and the reduction of prominent brow ridges in modern humans
(Homo sapiens sapiens) allowed for a larger braincase and advanced cognitive functions.

Understanding
Q20. Why is the use of organs important in Lamarck’s theory?
Answer: Lamarck proposed that frequent use of an organ strengthens it, leading to its
development over generations, while disuse causes it to diminish.
 Pollution
Pollution is the introduction of harmful
substances or energy into the
environment, causing adverse effects on
living organisms and ecosystems. It can
be classified into several types based on
the affected area or medium.
Air Pollution
Sources:
Vehicular emissions: Motor vehicles release
carbon monoxide (CO), hydrocarbons, and
nitrogen oxides due to incomplete combustion
of fuel.
Industrial emissions: Factories and power plants emit harmful gases like
sulphur dioxide (SO₂) and particulate matter during production processes.

Burning garbage: Produces toxic gases such as carbon monoxide (CO) and
volatile organic compounds (VOCs).

Brick kilns: Emit fine particulate matter and greenhouse gases like CO₂.

Major Pollutants: Carbon monoxide (CO), Sulphur dioxide (SO₂), Nitrogen

oxides (NOx), Particulate matter, Hydrocarbons.

Water Pollution
Sources:
Household detergents: Contain phosphates, leading to eutrophication in
water bodies.

Sewage: Discharge of untreated waste containing organic matter and

pathogens.

Industrial waste: Toxic chemicals, heavy metals, and dyes released into rivers
and lakes.

Oil spills: Accidental leaks from oil tankers or rigs that harm aquatic
ecosystems.

Major Pollutants: Nitrates, phosphates, heavy metals, oil, and pathogens.

Thermal Pollution
Sources:
Industries and power plants release hot water into rivers and lakes,
raising the water temperature.

Effects: Reduces dissolved oxygen levels in water, affecting aquatic life.

Alters breeding cycles of aquatic organisms.

Soil Pollution
Sources:
Industrial waste: Dumping of hazardous chemicals into soil. Urban,
commercial, and domestic waste: Improper disposal of plastics, glass,
and other non-biodegradable items.

Chemical fertilizers and pesticides: Contaminate the soil, reducing

fertility and harming microorganisms.

Major Pollutants: Heavy metals, pesticides, plastics, fertilizers.

Biomedical Waste
Sources:
Hospitals and clinics produce waste such as used needles, syringes,
soiled dressings, and other medical equipment.

Effects:
Spread of infectious diseases and contamination of soil and water.

Radiation Pollution
Sources:
X-rays: Excessive medical exposure can harm tissues

Radioactive fallout: From nuclear power plants, accidents, or weapons

testing.

Effects:
Causes genetic mutations, cancers, and harm to the immune system.

Noise Pollution
Sources:
Motor vehicles, industrial machinery, construction activities, and
loudspeakers.

Effects:
Leads to hearing loss, stress, sleep disturbances, and harm to wildlife.
Biodegradable and Non-biodegradable Wastes
Biodegradable Wastes
Substances that can be broken down by microorganisms into harmless substances.
Examples: Paper, vegetable peels, food waste, and animal waste.
Impact:
Decomposes naturally, enriching the soil with nutrients.
Can cause foul odor if not managed properly.

Non-biodegradable Wastes
Substances that cannot be decomposed by microorganisms and persist in the
environment for long periods.
Examples: Plastics, glass, Styrofoam, pesticides like DDT.
Impact:
Accumulates in landfills, harming soil and water quality.
Pesticides and chemicals may enter the food chain, affecting health.

Effects of Pollution

Climate
Greenhouse Effect: Environment
Greenhouse gases (CO₂, CH₄) Acid Rain:
trap heat in the Earth's Sulphur and nitrogen oxides
atmosphere, leading to combine with water vapor to form
increased temperatures. acids, which damage soil, water
Contributes to global warming. bodies, plants, and buildings.

Global Warming: Ozone Layer Depletion:

Results in melting glaciers, Chlorofluorocarbons (CFCs) break
rising sea levels, and extreme down ozone molecules, leading to
weather events like cyclones an increase in harmful UV
and droughts. radiation.
Causes skin cancer, cataracts, and
harm to aquatic ecosystems.
Human Health
Respiratory Problems: Asthma, Other Organisms
bronchitis, and lung cancer due Pollution disrupts food chains,
to polluted air. reduces biodiversity, and destroys
Waterborne Diseases: Cholera, habitats.
typhoid, and dysentery caused
by contaminated water. Harmful chemicals accumulate in
Radiation Exposure: Can cause organisms, leading to
cancers, genetic mutations, and bioaccumulation and
immune system damage. biomagnification.
Control Measures for Pollution

Air Pollution
1. Use of Unleaded Petrol and CNG: Reduces harmful emissions from vehicles.
2. Switching Off Engines: Reduces fuel consumption and emissions at traffic
signals.
3. Euro Bharat Vehicular Standards: Regulate emissions from vehicles.

Water Pollution
1. Sewage Treatment Plants: Treat wastewater before releasing it into water
bodies.
2. Industrial Effluent Treatment: Proper treatment and recycling of industrial
waste.

Soil Pollution
1. Organic Farming: Avoids the use of chemical fertilizers and pesticides.
2. Ban on Plastics: Reduces non-biodegradable waste.

Forestry and Conservation

1. Social Forestry: Increases green cover, absorbs CO₂, and provides habitats for
wildlife.

Noise Pollution
1. Enforce laws on noise levels at construction sites and industrial areas.
2. Limit the use of loudspeakers and horns.

Swachh Bharat Abhiyan

Launched: October 2, 2014, by the Government of India.

Objective: Promote cleanliness and hygiene across the country.

Key Goals:
a. Eliminate open defecation.
b. Improve solid waste management.
c. Create awareness about cleanliness.

Achievements: Construction of toilets, cleaning campaigns, and a shift

towards a cleaner and healthier India.
Multiple Choice Questions
Recall
Q1. Which of the following is a source of air pollution?
a) Oil spills
b) Brick kilns
c) Biomedical waste
d) Plastic waste
Answer: b) Brick kilns
Explanation: Brick kilns release particulate matter and harmful gases into the air, making them a
source of air pollution.

Understanding
Q2. What is the main pollutant responsible for eutrophication in water bodies?
a) Carbon monoxide
b) Phosphates
c) Nitrogen oxides
d) Heavy metals
Answer: b) Phosphates
Explanation: Phosphates from detergents and fertilizers promote excessive algae growth in water
bodies, causing eutrophication.

Application
Q3. Which measure would most effectively reduce vehicular pollution?
a) Planting more trees
b) Using unleaded petrol or CNG
c) Constructing sewage treatment plants
d) Avoiding oil spills
Answer: b) Using unleaded petrol or CNG
Explanation: Switching to cleaner fuels like unleaded petrol or CNG significantly reduces harmful
emissions from vehicles.

Analysis
Q4. Which pollutant is most likely to cause damage to the ozone layer?
a) Carbon monoxide
b) Chlorofluorocarbons (CFCs)
c) Sulphur dioxide
d) Methane
Answer: b) Chlorofluorocarbons (CFCs)
Explanation: CFCs release chlorine atoms that break down ozone molecules, leading to ozone
depletion.

Recall and Understanding

Q5. Which of the following is a biodegradable waste?
a) Styrofoam
b) Vegetable peels
c) Plastic bottles
d) Glass
Answer: b) Vegetable peels
Explanation: Biodegradable waste, such as vegetable peels, decomposes naturally by microbial
action.

Understanding
Q6. Noise pollution can directly cause which of the following health issues?
a) Skin irritation
b) Hearing loss
c) Respiratory problems
d) Bone fractures
Answer: b) Hearing loss
Explanation: Prolonged exposure to high noise levels damages hearing and may lead to partial or
complete hearing loss.
Recall
Q7. What is the full form of CNG?
a) Compressed Natural Gas
b) Clean Natural Gas
c) Controlled Natural Gas
d) Converted Natural Gas
Answer: a) Compressed Natural Gas
Explanation: CNG stands for Compressed Natural Gas, a cleaner alternative fuel.

Application and Analysis

Q8. Which of the following control measures would be most effective for soil pollution
caused by plastic waste?
a) Organic farming
b) Banning polythene bags
c) Using unleaded petrol
d) Social forestry
Answer: b) Banning polythene bags
Explanation: Banning non-biodegradable plastics like polythene reduces soil pollution.

Recall and Understanding

Q9. What is the main source of biomedical waste?
a) Factories
b) Hospitals
c) Households
d) Vehicles
Answer: b) Hospitals
Explanation: Hospitals produce biomedical waste such as used syringes, needles, and soiled
dressings.

Application
Q10. How does social forestry help in controlling pollution?
a) It reduces water usage.
b) It increases soil fertility.
c) It absorbs carbon dioxide.
d) It improves traffic management.
Answer: c) It absorbs carbon dioxide.
Explanation: Social forestry increases green cover, absorbing CO₂ and reducing air pollution.

Analysis
Q11. Which pollutant causes acid rain?
a) Carbon dioxide
b) Nitrogen oxides
c) Chlorofluorocarbons
d) Phosphates
Answer: b) Nitrogen oxides
Explanation: Nitrogen oxides combine with water vapor to form acids, leading to acid rain.

Understanding
Q12. What is the primary greenhouse gas responsible for global warming?
a) Methane
b) Carbon dioxide
c) Sulphur dioxide
d) Chlorine
Answer: b) Carbon dioxide
Explanation: CO₂ traps heat in the atmosphere, contributing significantly to global warming.
Recall
Q13. Which pollutant is associated with thermal pollution?
a) Oil spills
b) Hot water from industries
c) Sewage
d) CFCs
Answer: b) Hot water from industries
Explanation: Industries release hot water into rivers, disrupting aquatic ecosystems.

Application
Q14. The Swachh Bharat Abhiyan aims to address which of the following issues?
a) Vehicle emissions
b) Open defecation
c) Industrial waste
d) Noise pollution
Answer: b) Open defecation
Explanation: Swachh Bharat Abhiyan focuses on eliminating open defecation and
promoting cleanliness.

Analysis
Q15. Which of the following pollutants accumulates in food chains, causing
biomagnification?
a) Vegetable waste
b) DDT
c) Glass waste
d) Sewage
Answer: b) DDT
Explanation: Persistent pesticides like DDT accumulate in organisms, magnifying as they
move up the food chain.

Recall and Understanding

Q16. What is the primary aim of setting up sewage treatment plants?
a) Generate electricity
b) Treat wastewater before discharge
c) Produce fertilizers
d) Store rainwater
Answer: b) Treat wastewater before discharge
Explanation: Sewage treatment plants process wastewater to remove contaminants before
releasing it.

Understanding
Q17. How does the greenhouse effect benefit life on Earth?
a) Provides oxygen for breathing.
b) Maintains Earth's temperature for survival.
c) Reduces water pollution.
d) Increases soil fertility.
Answer: b) Maintains Earth's temperature for survival.
Explanation: The greenhouse effect keeps Earth's temperature suitable for life.

Application
Q18. What is the role of Euro Bharat standards in pollution control?
a) Treat sewage effectively.
b) Regulate vehicle emissions.
c) Reduce industrial waste.
d) Ban biomedical waste.
Answer: b) Regulate vehicle emissions.
Explanation: Euro Bharat standards ensure vehicles meet specific emission norms to control
pollution.
Recall
Q19. Which pollutant is most harmful in radiation pollution?
a) X-rays
b) Nitrogen oxides
c) Phosphates
d) Methane
Answer: a) X-rays
Explanation: X-rays, when overused or improperly handled, can damage living tissues and
DNA.

Analysis and Application

Q20. Why is organic farming promoted as a pollution control measure?
a) It reduces pesticide and fertilizer use.
b) It increases food production.
c) It saves water.
d) It reduces noise pollution.
Answer: a) It reduces pesticide and fertilizer use.
Explanation: Organic farming avoids synthetic chemicals, reducing soil and water pollution.

Short Answer Type Questions

Recall
Q1. Define pollution and name any two types of pollution.
Answer: Pollution is the introduction of harmful substances or energy into the environment,
causing adverse effects.
Examples: Air pollution, Water pollution.

Understanding
Q2. What is thermal pollution, and how does it affect aquatic ecosystems?
Answer: Thermal pollution is the increase in water temperature due to industrial discharge
or power plants. It reduces oxygen levels in water, affecting aquatic life.

Recall and Understanding

Q3. List two sources of noise pollution.
Answer:
Motor vehicles
Construction sites

Application
Q4. How can using unleaded petrol help reduce air pollution?
Answer: Unleaded petrol reduces the emission of harmful lead compounds, improving air
quality and reducing health hazards.

Analysis
Q5. Why are chemical fertilizers considered a source of soil pollution?
Answer: Excessive use of chemical fertilizers contaminates soil with toxic substances,
leading to decreased fertility and harming microorganisms.

Recall
Q6. Give one example each of biodegradable and non-biodegradable waste.
Answer:
Biodegradable: Vegetable peels
Non-biodegradable: Plastics
Understanding
Q7. What is the greenhouse effect, and why is it important?
Answer: The greenhouse effect is the trapping of heat in the Earth’s atmosphere by
greenhouse gases. It maintains the Earth's temperature, making it habitable.

Application and Understanding

Q8. Why is switching off engines at traffic signals recommended?
Answer: Switching off engines reduces fuel consumption and air pollution by lowering
emissions of harmful gases like carbon monoxide.

Analysis and Application

Q9. Suggest one measure to control soil pollution caused by plastics and explain its
effectiveness.
Answer: Measure: Ban on polythene bags.
Explanation: Reduces non-biodegradable waste accumulation, preventing soil
contamination.

Recall
Q10. What is the role of sewage treatment plants in pollution control?
Answer: Sewage treatment plants remove contaminants from wastewater before
discharging it into water bodies, reducing water pollution.

Understanding and Application

Q11. Explain how social forestry can mitigate air pollution.
Answer: Social forestry involves planting trees on community lands, which absorb carbon
dioxide, release oxygen, and improve air quality.

Recall and Understanding

Q12. Name two pollutants that cause acid rain.
Answer:
Sulphur dioxide (SO₂)
Nitrogen oxides (NOₓ)

Application
Q13. Why is organic farming considered environmentally friendly?
Answer: Organic farming avoids synthetic chemicals, reducing soil and water pollution and
promoting biodiversity.

Analysis
Q14. What are the long-term effects of DDT accumulation in organisms?
Answer: DDT causes biomagnification, leading to toxic accumulation in organisms and
affecting reproductive and nervous systems.

Recall and Understanding

Q15. What is the primary objective of the "Swachh Bharat Abhiyan"?
Answer: The primary objective is to achieve cleanliness by eliminating open defecation and
improving waste management in India.

Analysis and Application

Q16. Why are X-rays considered harmful if overused?
Answer: Overuse of X-rays exposes the body to radiation, damaging tissues and increasing
the risk of cancer.
Recall
Q17. Name any two effects of ozone layer depletion.
Answer:
Increased UV radiation reaching Earth
Higher risk of skin cancer and cataracts

Application
Q18. How does the use of CNG in automobiles reduce pollution?
Answer: CNG burns cleaner than petrol or diesel, emitting fewer pollutants such as carbon
monoxide and nitrogen oxides.

Understanding
Q19. Why are oil spills considered a serious environmental issue?
Answer: Oil spills coat marine organisms, disrupt their breathing, and contaminate water,
affecting aquatic ecosystems and biodiversity.

Analysis
Q20. How can banning polythene and plastics benefit the environment?
Answer: Banning plastics reduces non-biodegradable waste, preventing soil and water
pollution and protecting wildlife from ingestion hazards.