LEARING OBJECTIVES

At the end of this lesson, Students should be able to:

- Explain the meaning of biology

- Say the meaning of the Greek words bio and logos
- Mention the major fields of biology
- State the usefulness of biology
-
INTRODUCTION TO BIOLOGY
The term “biology” is derived from the Greek words “bio” meaning life and
“logos” meaning study. Therefore, biology is defined as the study living things.
Biology is a branch of natural science that deals with the study of living things,
including their origin, structure, function, maturation, evolution and
classification.
Biology is described as a branch of natural science that studies how living
things interact with one another and their environment.

Branches of Biology
Even though all of the subcategories of biology are connected by fundamental
principles, they are split into different branches for ease of study. Examples
are:

 Anatomy: this is the study of how bodily structures are put together in
an organism. These structures include bones, muscles, organs, and
tissues.
  Botany: Botany is the scientific study of plants. Some of the aspects
studied in botany are morphology, taxonomy, evolution and ecology of
plant life and other relevant details.
 Zoology: Zoology is the branch of biology that studies the animal
kingdom, including the structure, embryology, evolution, classification,
habits, and distribution of all animals.
 Microbiology: Microbiology is the branch of biology that deals with the
study of microorganisms, such as bacteria, archaea, and protists.
 Genetics: Genetics is the study of genes, inheritance, and variation in
living organisms. It’s about how traits are passed from one generation
to the next.
 Biochemistry: Biochemistry is the study of chemical processes within
living organisms.
 Biotechnology: Biotechnology is a branch of biology that exploits
biological processes and techniques to produce substances of biological
origin, or to modify organisms or their products, or to develop
microorganisms for specific uses, or for other industrial purposes.
 Marine Biology: Marine Biology is the study of marine life and marine
ecosystems. The field focuses on the study of organisms and other
related variables that inhabit the world’s oceans.

Importance of Biology
There are numerous indications of the importance of biology.
1. Biology is primarily concerned with studying life.
2. It offers a thorough scientific explanation of how all living and nonliving
things interact with one another.
3. It provides information about various life forms.
4. Biology includes various areas of study concerned with the
sustainability of life, such as the study of the human body and the
environment, the ecosystem, the quality of food, the causes of disease,
and the discovery of new medications.
LEARING OBJECTIVES
At the end of this lesson, Students should be able to:

- Identify the seven characteristics of living things.

- Describe the seven characteristics of living organisms.

CHARACTERISTICS OF LIVING THINGS

Definition of Living Things

 Living things refer to organisms that are alive. Hence, all human beings, animals,
birds, plants, insects, bacteria, and more are living things. All these living
things have common traits in them.

Definition of Non-living Things

A non-living thing in biology means any form without a life, such as an

inanimate body or object. Compared with the entity that has a life, a non-living
thing lacks the features that characterize a living thing.

The Characteristics of Living Things

MRS. GREN

M - Movement

R - Respiration

S - Sensitivity

G - Growth

R - Reproduction

E - Excretion

N - Nutrition

Movement

 Muscles provide movement for all animals.

 Animals move to find food, shelter, and to avoid predators.

 Some animals may move to mate, reproduce or give birth.

Respiration
 A process where food is converted to energy.

 It is a chemical reaction within our bodies.

 Glucose reacts with oxygen to release energy, along with carbon dioxide and

water.

 Breathing is inhaling and exhaling - moving air in and out of our bodies.

Respiration should NOT be confused with this.

 Plants photosynthesize to produce food, and they also respire.

Sensitivity

 Animals detect changes with their sense organs.

 Skin (feel), Eyes (see), Ears (listen), Tongue (taste), and Nose (smell).

 Insects have long antennae - which they use to touch the ground in front of

them, to decide if it is safe to move or not.

 Growth and reproduction

 Food is important to grow, repair damaged body parts, and to live.

 Reproduction is important to keep a plant/animal species in existence.

 If the elephants in a herd stopped producing offspring, the herd would

eventually disappear (become extinct), as the old elephants died.

 Every single species in the world is important to maintain the balance.

 Excretion

All living things excrete. As a result of the many chemical reactions occurring

in cells, they have to get rid of waste products which might poison the cells.

Excretion is defined as the removal of toxic materials, the waste products of

metabolism and substances in excess from the body of an organism.

Nutrition

Living things take in materials from their surroundings that they use for

growth or to provide energy. Nutrition is the process by which organisms

obtain energy and raw materials from nutrients such as proteins,

carbohydrates and fats..

Characteristics of Plants

 Plants move as they grow and spread out over the ground.

 Plants respire and gaseous exchange happens through leaves.

 Green plants are sensitive towards light and grow towards it.

 Plants reproduce by making seeds or spores some make copies of themselves -

plantlets.

 Waste may be stored in leaves.

 Plants make food from carbon dioxide and water.

Important Difference between Plants and Animals

Basis of
Plants Animals
Comparison

Green-coloured living Living organisms

things capable of that feed on organic
Definition
preparing their own food material and contain
through photosynthesis. an organ system.

Movement Cannot move as they are Can move freely

 rooted in the ground. from one place to the
Exceptions- Volvox and other. Exception-
Chlamydomonas. Sponges and Corals.

Digestive
Absent Present
System

Store food in the form of Store food in the

Food Storage
starch form of glycogen

Contains cell wall, Do not have cell

Structure of chloroplast, walls, have other
Cell plasmodesmata, plastids organelles like tight
and other organelles junction and cilia.

Take in oxygen and

Take in Carbon Dioxide
Respiration release carbon
and release Oxygen
dioxide

Occurs through
Medium of
Occurs through stomata lungs, gills, skin and
Respiration
more.

The meristematic system Organs and organ

Growth in the tip of roots and system support the
stems supports growth growth
 Animals reproduce
Asexual reproduction by
sexually whereas
Reproduction budding, vegetative
some lower animals
Method methods, wind, spores,
like algae have
insects.
asexual reproduction

The proper nervous

Show response through
Response system allows
touch and light
responding quickly

Sensitive Less sensitive Highly sensitive

Cactus, moss, conifers, Vertebrate, Insects,

Examples flowering plants, vascular Reptiles, Mammals,
plants, etc. Amphibians, etc.

LEARING OBJECTIVES
At the end of this lesson, Students should be able to:

- Sort, group and classify organisms through observations

 - Construct dichotomous keys
- Use dichotomous keys to classify species and groups of related
organism

IDENTIFYING SPECIES

Classification Systems Definition

In life, many things are classified, that is, to put into categories or groups
based on their characteristics. Of course, biology, being the study of life and
living things, also has an order of classification. The classification of living
things helps us in many ways to organize and group organisms based on their
characteristics.

What is a classification system? The classification system is the system used

for the scientific classification of organisms and other activities in science
based on the characteristics, behaviors, and methods used.

There are different types of classification systems and they are all used for
different purposes. Organism classification takes place in the form of a
taxonomic system. This is called the Linnaean classification.

Linnaean system of classification

This system was developed in the eighteenth century by Carl Linnaeus. The
Linnaean classification involves the usage of the grouping organisms using a
hierarchy called taxa. This animal classification system contains taxonomic
levels and taxonomic groups that animals are placed in based on their features
and even shared ancestry.

These levels of biological classification are as follows:

Species » Genus » Family » Order » Class » Phylum » Kingdom » Domain

These were listed from the least inclusive to the most inclusive. Figure 1
below shows the taxonomical ranking.
Figure 1: The hierarchy of different taxonomic ranks in the Biological
Classification System.

Levels of the Classification System

The classification of organisms takes place in the different taxonomic levels.

They will be defined and listed according to their inclusiveness in groups.

Domain

The domain classification is the highest level of taxonomic classification in

the organism classification system. The domain can be broken down into
three types:

 Bacteria (true bacteria)

 Archaea (primitive bacteria usually living in extreme environments)

 Eukaryotic (including protists, fungi, plants, and animals)

These can be seen in Figure 2 below. These individual domains are based on
their evolution over the years and the different attributes they contain.
Figure 2: The three domains of life.

Kingdom

The kingdom classification is the second-highest ranking in the taxonomic

groupings of organisms. There are five kingdoms. The five kingdoms consists
of:

1. Animals (all multicellular animals)

2. Plants (all green plants)

3. Fungi (moulds, mushrooms, yeast)

4. Protists (Amoeba, Chlorella, and Plasmodium)

5. Monerans (bacteria, blue-green algae)

1. The kingdom Animalia: is the most diverse out of the kingdoms and this is
because it has evolved the most. This kingdom is generally divided
into invertebrates and vertebrates (animals that have a backbone and those
that do not).

2. The kingdom Plantae: is made up of all trees, flowers, bushes, and

vegetation. It is the oldest of all the kingdoms. Its members are characterized
by having limited movement, eukaryotic features, and autotrophic abilities.

3. The kingdom Fungi: is made up of yeasts, toadstools, molds and

mushrooms. These organisms are carnivores that have chitin in their cell
walls yet reproduce in a sporic manner.
4. The kingdom Protista: can be considered the mother of all eukaryotes as
all of them are descendants of this kingdom. It can be a very difficult kingdom
to distinguish as it is intertwined with many of the others.

5. The monera kingdom: consists of all archaea and bacteria as it deals with
all microscopic organisms.

Figure 3: An illustration depicting the diversity of living organisms classified

into 5 major kingdoms

Phylum

In the kingdom-phylum ranking system, the next classification is phylum. This

taxonomic rank, sometimes termed as “division” lies after the kingdom and
further classifies based on phenetic and phylogenetic. Phenetics is based on
the number of shared characteristics using a numerical system and
phylogenetics is based on evolution and shared relationships but using a
systematic study. Each kingdom is broken down into numerous phyla.
Examples:

1. Chordata, which have backbones

2. Arthropod, which has jointed legs and an exoskeleton

3. Annelids, which are segmented worms

Class

The class falls just between the phylum and order classifications. Just like
kingdoms contain multiple phyla, each phylum can contain multiple classes.
For example, results in the Chordata phylum being divided into:

i. Mammals

ii. Birds

iii. Amphibians

iv. Fish

v. Reptiles

Order

Order is the classification that consists of several families. An order consists

of multiple families that share many characteristics and evolutionary traits.
Example, mammals can be further subdivided into a variety of different
groups such as:

 Carnivores
 Primates

Family

When a group of genera with similar characteristics and traits are pulled
together it is called a family. Here are a few examples of which carnivores can
be divided into:
  Canidae - dogs
 Felidae - cats

Genus

Genus is the systematic unit in the organism classification that helps

determine the species of organisms as the genus groups multiple species
together. The Felidae family can be further sub-divided into four genuses.
Examples are:

 Acinonyx - cheetah
 Panthera - lion and tiger
 Neofelis - clouded leopard
 Felis - domestic cats

Species

Species classification is the final ranking for the biological classification of

living things. A species is defined as a group of organisms with similar
characteristics that are able to procreate or interbreed with one another. The
offspring they produce must be sustainable and also being able to create a
new generation of the species as well. The genus Panthera can be divided into:

 Panthera Leo (lion)

 Panthera tigris (tiger)

Examples of classification systems

All organisms can be classified based on the classification system. For

instance, a simple household pet such as a cat;

A cat would belong to the domain eukarya, being a multicellular organism.

This would be further divided into the kingdom Animalia as a cat is obviously
an animal. Being an animal that has a flexible rod that supports its backbone,
it would be a member of the phylum Chordata.

The class of the domestic cat would be Mammalia being an organism that
carries it’s young in a womb and also lactates to feed its offspring. The house
cat then follows the path of being a member of the order Carnivora and the
family of Felidae. Finally, we come to the genus, which in this case is Felis and
the species is catus. So a cat, using the classification system is called Felis
catus.

Binomial System of Nomenclature

Carolus Linnaeus also introduced a system of naming living things which is

popularly used by biologists today. This system is called binomial system of
nomenclature. In this system, each organism or living thing is given two
names. The first name is the generic name (common to the genus) and it
always begins with a capital letter.
The second name is the specific name which begins with a small letter. These
scientific names are written in italics or are underlined. Examples of scientific
name of some organisms are given below;
i. Man. : Homo sapiens
ii. Lion: Panthera leo
iii. Maize: Zea mays
iv. Rat: Rattus rattus
v. Dog: Canis domestica

Dichotomous key
A dichotomous key is a method of identification whereby groups of organisms
are divided into two categories repeatedly.
 With each sequential division, more information is revealed about the specific
features of a particular organism
 When the organism no longer shares its totality of selected characteristics
with any organism, it has been identified

When using a dichotomous key to identify specimens it is preferable to use

immutable features (i.e. features that do not change)
 Size, colouration and behavioural patterns may all vary amongst individuals
and across lifetimes
 Physical structures (e.g number of limbs) and biological processes (e.g.
reproduction methods) make for better characteristics

Dichotomous keys are usually represented in one of two ways:

 As a branching flowchart (diagrammatic representation)
 As a series of paired statements laid out in a numbered sequence (descriptive
representation)

Below are some examples of dichotomous keys represented as both diagrams

and descriptions
WEEK 5-6
LEARING OBJECTIVES
At the end of this lesson, Students should be able to:

- Understand that all organisms are made of cells

- Understand microorganisms are typically single celled
- Identify and describe the functions of cell structures (limited to cell
membrane, cytoplasm, nucleus, cell wall, chloroplast, mitochondria and
sap vacuole)
- Explain how the structure of cells are related to their functions
- Describe the similarities and differences between the structures of
plants and animals

CELL

A cell can be defined as the basic structural and functional unit of life. The
protoplasm is the organized complex material of which living cells are made.
All characteristics of living things are possessed by the protoplasm.
Types of cells
Cells can be divided into two categories called

 Prokaryotic and
 Eukaryotic cells.

Prokaryotic cells: are simple cells that lack nucleus and membrane-
bound organelles.

Eukaryotic cells: are complex cells comprising nuclear and cytoplasmic

material sheathed by a cell membrane. Both plants and animals come
under eukaryotic cells. Eukaryotic cells have a standard set of features;
however, plant and animal cells do have their differences.
Animal Cell Structure

Animal cells are generally smaller than plant cells. Another defining
characteristic is its irregular shape. This is due to the absence of a cell wall.
But animal cells share other cellular organelles with plant cells as both have
evolved from eukaryotic cells.

Plant Cell Structure

Just like different organs within the body, plant cell structure includes various
components known as cell organelles that perform different functions to
sustain itself.
THE CELL ORGANELLES AND THEIR FUNCTIONS

A. THE CYTOPLASM

All living materials outside the nucleus are classified is cytoplasm. The
cytoplasm is semi-fluid and consists of endoplasmic reticulum, mitochondria,
lysosomes, Golgi apparatus, centrosome, and vacuoles, all bounded by the cell
membrane or plasma membrane.

FUNCTIONS OF THE CYTOPLASM

1. All the living substances including nucleus are suspended in the semi-fluid
cytoplasm.

2. The streaming of the content of the cytoplasm brings about interchange of

materials between the organelles within the cytoplasm.

B. CELL WALL

The cell wall is the non-living outer boundary of the cell and is made up of
cellulose. It has tiny pores or pits through which nutrients pass from one cell
to another. It is important to note that cell wall is absent in animal cell

FUNCTIONS
1. The cell wall gives rigidity to cell and the plant as a whole

2. It allows free passage of materials.

C. CELL MEMBRANE (PLASMA MEMBRANE)

This is a thin and flexible living layer that surrounds the entire cytoplasm and
separates the cell from neighbouring cells.

FUNCTIONS

1. The cell membrane regulates the movement of substances in and our of the
cell.

2. It protects the cytoplasm.

It delimits the content of the cytoplasm.

4. It forms a barrier between the cell and its surrounding.

D. MITOCHONDRIA (SINGULAR MITOCHONDRION)

This is known as the power house of the cell. They are tiny rod-shaped bodies
or granules in the cytoplasm. They are more concentrated in very active cells
such as the liver cells.

FUNCTIONS

1. They are the centre of cellular respiration in which food substances are
oxidized to release energy for the activities of the cells. This is the reason why
mitochondria are referred to as the power house of the cells.

2. They contain enzymes and decoy ribonucleic acid (DNA). The enzymes
carry out oxidative phosphorelation of adenosine diphosphate (ADP) to
adenosine triphosphate (ATP).

3. The DNA helps to code the synthesis of protein in mitochondria

membranes.

E. LYSOSOMES
Lysosomes derived it name from “lysis” meaning breaking down. These are
minute and rounded bodies containing enzymes found in animal cells.

FUNCTIONS

1. They destroy worn out parts of cells by discharging enzymes into the and
thereby clearing the area for new healthy cells to grow.

2. Lysosomes discharge enzymes to degenerated tissues causing the

breakdown of the cells. For example, the absorption of the tail of tadpole when
it is changing to the adult toad is caused by lysosomes. The products if the
disintegrated cells are used for the growth of other cells.

3. Enzymes released by Lysosomes destroy bacteria and cells.

F. CHLOROPLAST

These only occur in green plants. They contain green pigments called
chlorophyll. A chloroplast is surrounded by a membrane. In leaves,
chloroplasts are oval or disc-shaped while in algae they are cup-like ribbon or
plate-like.

FUNCTION

Chloroplast is the site for photosynthesis where organic foods are

synthesized.

G. VACUOLES

Vacuoles are found in plant cells. They are very large in plant cells but when
they occur in animal cells, they are usually small. A vacuole is surrounded by a
membrane called tonoplast and is filled with water, mineral salts, sugars and
pigments called cell sap.

FUNCTIONS

1. The cell sap is osmotic in function.

2. It stores nutrients and waste products.

3. Some substances dissolved in the vacuoles (such as sucrose and minerals)
are food reserves which could be used by cytoplasm in time of need.

4. Tannins and alkaloids in vacuoles prevent herbivorous animals from eating

plants due to such chemicals.

H. NUCLEUS

The nucleus is bounded by a thin living nuclear membrane which separates it

from the cytoplasm. The nuclear membrane has many tiny pores orpits which
allow substances to go in and out of the nucleus. The nucleus floats in the
cytoplasmic fluid.

Within the nucleus is a small spherical body called nucleolus (sometimes

more than one) and chromatin materials which condense during cell division
into chromosomes (hereditary units). Inside the nuclear membrane and
surrounding the chromatin materials and nucleolus is a semi-fluid material
called nuclear fluid or nucleoplasm. The chromosomes are made up of DNA
(deoxyribonucleic acid).

FUNCTIONS

1. The nucleus control directly or indirectly most of the activities of a living

cell. The removal of the nucleus results in the death of the cytoplasm.

2. The nucleus carries chromosomes on which hereditary materials (genes)

are coded.

3. The DNA in chromosomes gives information for the manufacture of the

proteins in the cell.

4. The nucleolus produces several kinds of RNA (Ribonucleic acids) which are
passed out of the nucleus to the cytoplasm to manufacture proteins (DNA does
not pass out of the nucleus).

SIMILARITIES BETWEEN PLANT AND ANIMAL CELLS

Both plant and animal cells are similar because they both possess cytoplasm,
cell membrane, endoplasmic reticulum, Golgi apparatus, mitochondria,
ribosomes, nuclear membrane, nucleus, chromosomes, nucleoplasm and
nucleolus. They both carry out mitosis in somatic cells and meiosis in
reproductive cells.

DIFFERENCES BETWEEN PLANT AND ANIMAL CELLS

1. Pant cells has cellulose cell wall hence definite in shape however, animal
cell has living cell membrane hence it can change its shape.

2. Chloroplasts are present in plant cells but absent in animal cells.

3. Plant cells have large permanent central vacuole while vacuoles are usually
absent and when present, they small and temporary.

4. Food is stored as starch in plant cell whereas food is stored as glycogen and
fat in animal cells.

5. Centriole is present in animal cell but absent in plant cell.

6. Cytoplasm of plant cell is pushed to the cell wall but in animal cell, it is
spread all over the cell.
LEARNING OBJECTIVES
At the end of this lesson, Students should be able to:

- Define a microscope
- State the main parts of a microscope
- Calculate the magnification of an object using the formula: a. Total
microscope magnification = magnifying power of eyepiece x
magnifying power of objective lens b. Magnification= size in picture ÷
actual size
THE MICROSCOPE

Microscope Definition
Microscopes are instruments that are used in science laboratories to visualize
very minute objects such as cells, and microorganisms, giving a contrasting
image that is magnified. Microscopes are made up of lenses for magnification,
each with its own magnification powers. Depending on the type of lens, it will
magnify the specimen according to its focal strength.

Their ability to function is because they have been constructed with special
components that enable them to achieve high magnification levels. They can
view very small specimens and distinguish their structural differences, for
example, the view of animal and plant cells, viewing microscopic bacterial
cells.

Types of Microscopes
The different types of microscopes are as follows:

Light Microscopes
These are basic microscopes that use light to magnify objects. The lenses in
these microscopes refract the light for the objects beneath them to appear
closer. The different types of light or optical microscopes are:

 Compound microscope
 Simple microscope
  Dissection or stereo microscope

Electron Microscopes
Instead of light, these microscopes use beams of electrons to generate images.
The two well-known electron microscopes are:

 TEM (Transmission Electron Microscope) – the electrons transmit or

pass through a very thin specimen.
 SEM (Scanning Electron Microscope) – It scans through the surface of
the specimen by focusing the electron beam.

Structural Parts of a Microscope and their Functions

Structural Parts

There are three structural parts of the microscope i.e. head, base, and arm.
1. Head – This is also known as the body. It carries the optical parts in the
upper part of the microscope.
2. Base – It acts as microscopes support. It also carries microscopic
illuminators.
3. Arms – This is the part connecting the base and to the head and the
eyepiece tube to the base of the microscope. It gives support to the head of
the microscope and it is also used when carrying the microscope. Some
high-quality microscopes have an articulated arm with more than one joint
allowing more movement of the microscopic head for better viewing.

Optical Parts of a Microscope and their Functions

The optical parts of the microscope are used to view, magnify, and produce an
image from a specimen placed on a slide. These parts include:
1. Eyepiece – also known as the ocular. This is the part used to look through
the microscope. It is found at the top of the microscope.
2. Eyepiece tube – it’s the eyepiece holder. It carries the eyepiece just above
the objective lens. In some microscopes such as the binoculars, the eyepiece
tube is flexible and can be rotated for maximum visualization, for variance
in distance. For monocular microscopes, they are none flexible.
3. Objective lenses – These are the major lenses used for specimen
visualization. They have a magnification power of 40x-100X. There are
about 1- 4 objective lenses placed on one microscope, in that some are rare
facing and others face forward. Each lens has its own magnification power.
4. Nose piece – also known as the revolving turret. It holds the objective
lenses. It is movable hence it can revolve the objective lenses depending on
the magnification power of the lens.
5. The Adjustment knobs – These are knobs that are used to focus the
microscope. There are two types of adjustment knobs i.e. fine adjustment
knobs and coarse adjustment knobs.
6. Stage – This is the section in which the specimen is placed for viewing. They
have stage clips that hold the specimen slides in place. The most common
stage is the mechanical stage, which allows the control of the slides by
moving the slides using the mechanical knobs on the stage instead of
moving them manually.
7. Aperture – This is a hole on the microscope stage, through which the
transmitted light from the source reaches the stage.
8. Microscopic illuminator – This is the microscopes light source, located at
the base. It is used instead of a mirror. It captures light from an external
source of a low voltage of about 100v.
9. Diaphragm – it’s also known as the iris. It is found under the stage of the
microscope and its primary role is to control the amount of light that
reaches the specimen. It’s an adjustable apparatus, hence controlling the
light intensity and the size of the beam of light that gets to the specimen. For
high-quality microscopes, the diaphragm comes attached with an Abbe
condenser and combined they are able to control the light focus and light
intensity that reaches the specimen.

Magnification Formula

Calculating magnification and specimen size using millimetres as units

 Magnification is calculated using the following equation:

Magnification = Image size ÷ Actual size

 A better way to remember the equation is using an equation triangle:

Magnificati
on equation

 Rearranging the equation to find things other than the magnification

becomes easy when you remember the triangle - whatever you are
trying to find, place your finger over it and whatever is left is what you
do, so:
o Magnification = image size / actual size
o Actual size = image size / magnification
o Image size = magnification x actual size
Remember magnification does not have any units and is just written as ‘x 10’
or ‘x 5000’
Worked example
An image of an animal cell is 30 mm in size and it has been magnified by a
factor of x 3000. What is the actual size of the cell?
To find the actual size of the cell:

Worked example using the magnification equation

Converting units of measurement

 There are 1000 nanometers (nm) in a micrometre (µm)

 There are 1000 micrometres (µm) in a millimetre (mm)
 There are 1000 millimetres (mm) in a metre (m)
Worked example

Step 1: Check that units in magnification questions are the same

Remember that 1mm = 1000µm

2000 / 1000 = 2, so the actual thickness of the leaf is 2 mm and the drawing
thickness is 50 mm

Step 2: Calculate Magnification

Magnification = image size / actual size = 50 / 2 = 25

So the magnification is x 25

How do you prepare a microscope slide for viewing?

The basic steps for preparing a microscope slide are to place the specimen on
the slide, apply a drop of water or oil (if preparing a wet mount slide), and
then gently lowering a cover slip over the specimen.
LEARNING OBJECTIVES
At the end of this lesson, students should be able to:

- Understand that cells can be grouped together to form tissues, organs

and organ systems.

CELLS, TISSUES, ORGANS AND ORGANISMS

Organization of Life

All living things are highly organized. This organization occurs in levels. The
simplest structures are found at the lowest levels and they interact to build up
more complex structures at the next level and so on.

There are four levels of organization of life in organisms. These are the cells,
tissues, organs and systems. The simplest of all these levels is the cell.

Cells (First Level)

The cell is defined as the smallest unit of living organism. It is the first level of
organization of life. All plants and animals are made of only one cell hence
they are unicellular organism while others are made up of many cells and are
therefore called multicellular organisms. Examples of unicellular organisms
are Amoeba, Euglena, Paramecium, Plasmodium, Trypanosome,
Chlamydomonas. These organisms have only one cell each and are capable of
carrying our all life processes such as movement, respiration and
reproduction. Examples of cells in higher plants are phloem cells, xylem
vessels, while examples of cells in higher animals are rod and cone cells in the
eyes, ova or eggs, spermatozoa cells, nerve cells, red blood cells, white blood
cells and epidermis cells.

Tissues (Second level)

A tissue is a group of similar cells forming a layer in an organism which

performs a particular function. In other words, a tissue consist of two or more
different types of cells aggregating together to perform a specific function.
Examples of tissues in higher plants are mesophyll layer in leaves, epidermal
tissue, sclerenchyma tissue, xylem tissue, parenchyma tissues in stem.
Examples of tissues in higher animals include muscles, bone, cartilages and
blood (a liquid tissue). Examples of organisms which exist at the tissue level of
organism of life are Hydra, Algae, sponges and fungi.
Organs (Third Level)

An organ is a group of similar tissues forming a layer in an organism which

performs a specific function. Examples of organs in plants are leaves, flowers,
roots, stems and seeds. Examples of organs in animals are skin, eyes, ears,
stomach, brain, kidney, liver and heart. These organs are known to perform
specific functions in the body.

Systems (Fourth Level)

A system is a group of similar organs which work together to perform specific

functions. Examples of systems in plant are the shoot system and root system.
Examples of systems in animals are digestive, reproductive, respiratory,
skeletal, nervous, excretory and circulatory systems. These systems work
together to make up an organism. For an organism to perform well, all the
cells, tissues, organs and systems must also function normally.
ORGANISM

Complex, multicellular organisms, like humans, are made of many cells, which
are organized into tissues, which make up organs, which organize into organ
systems to perform our life functions. The function of each of these structures
relies on the properties of the components it is made of.
 LEARNING OBJECTIVES
At the end of this lesson, students should be able to:

- List the organs of a flowering plant

- Explain the functions of the organs of a flowering plant

MAJOR ORGAN SYSTEM

Organs of a flowering plant

 Root
 Stem
 Leaf
 Flower
 Bud

1. Functions of the Roots

 Anchors the plant in place.

 Takes up water and minerals from the soil.

 Roots also take in oxygen from the air-pockets in the soil.

 The roots of some plants (example – carrots), store food.

 Tap root – the main root grows downwards, and lateral roots grow sideways.

 Fibrous root – all roots are the same size and can grow downwards and

sideways.

2. Functions of the Stem

 Transports water and food.

 Supports the leaves and flowers.

 Some plants who don’t have a strong stem, grow up on the sides of larger

plants.
 Some plants (example – trees), store food in their stems/trunks.

 Some plants (example – ginger), have underground stems, which store food.

3. Functions of the Leaf

 Produces food.

 Traps sunlight to make food.

 Controls amount of water inside the plant.

 Controls Carbon dioxide and Oxygen entering and leaving.

 Different leaves are shaped differently – and come in various sizes and

colours, based on the plant’s needs.

4. Functions of the Flower

 Contains the reproductive organs of the plant.

 Many flowers use insect’s help to reproduce and have brightly coloured

flowers to attract them.

 Flowers are shaped differently in different plants, based on their habitat.

5. Functions of the Bud

 Contains tiny new branches, leaves and flowers ready to grow.

 LEARNING OBJECTIVES
At the end of this lesson, students should be able to:

- List the organs of humans

- Explain the organ systems in humans

THE ORGAN SYSTEMS OF THE HUMAN BODY

The organs of the human body are:

 Skeletal System

 Muscle System

 Circulatory System

 Respiratory System

 Digestive System

 Nervous System

 Excretory System

 Sensory System

 Endocrine System

Skeletal system
 There are 206 bones in the human skeleton.

 Each arm and hand together has 30 bones.

 Each leg and foot together has 29 bones.

 The skeleton accounts for 15% of the body's mass.

 Tissue of the skeleton (bone) is hardened as it takes calcium from digested

food.

FUNCTIONS OF THE SKELETAL SYSTEM

1. Protection

The brain and spinal cord form the CNS (Central Nervous System) and are

made from soft tissue. They can be damaged without a hard covering. The

bones of the skull are fused together to make a strong barrier around the

brain.

The backbone is made of 33 bones known as vertebrae (singular : vertebra).

There's a hole in each vertebra through which the spinal cord runs. The

column of Vertebrae makes a tube of bone around the spinal cord. There are

gaps between the vertebrae through which nerves pass from the spinal cord

to the body. The ribs and backbone form a protective structure around the

lungs and heart. The ribs aren't heavy to allow for the movements of the heart.

C
 2. Support

 The organs form systems (digestive, circulatory, excretory, and respiratory)

account for 20% of the body's weight. The organs are made from soft material

and have no supporting material inside them. The bones of the skeleton

provide a strong structure to which the organs are attached. They allow the

organs to be spread out in the body without squashing into each other.

3. Movement

Joint - the place where bones meet. In some joints (skull), the bones are fused

together and cannot move. Most joints allow some movement.

Types of Joints

 Hinge joints: Joints at the elbow or knee are called hinge joints - as

they move like the hinge on a door. They can only move back and forth.

 Ball-and-socket: joints Joints at the hip and shoulder are called ball-

and-socket joints - the end of the bone forms a round structure like a

ball that fits into a cup-shaped socket. These allow more movement.

Ligament - fibres that prevent the bones from coming apart.

Cartilage - a hard, slippery surface that prevents bones from wearing out

when they rub against each other. Reduces friction, and allows ease of

movement.
 Synovial Fluid: a liquid present in joints where a lot of movement occurs

(knees). It spreads out over the surface of the cartilage and acts like oil. It

reduces friction, and wear.

Muscles: This is a tissue that can move. It can contract and expand. A muscle
is attached to two bones across a joint, with the help of Tendons. The action
of one muscle produces an opposite effect to the other muscle and causes
movement in the opposite direction. These 2 muscles are called
as Antagonistic Muscle Pairs.
Smooth Muscle - Found in other organ systems such as the digestive system,

where it moves food down the alimentary canal.

 Cardiac Muscle - The heart is made of this muscle. Its movement pumps

blood throughout the body.

 The nervous system controls the movement of these 2 muscles, so that you

don't have to voluntarily perform an action.

Circulatory system
 The heart is located near the centre of the chest - closer to your left.

 It is made of Cardiac Muscles - which makes the heart beat.

 The heart pushes blood into the arteries and draws blood from the veins

 The beating of the heart gives pressure to the blood, to flow throughout your

body.

 The heart and the blood vessels make up the circulatory system.

 The beating of the heart can be checked by taking the pulse.

Check your pulse

1. Hold out your right hand with your palm up.

2. Put the thumb of your left hand under your wrist.

3. Let the first two fingers of your left-hand rest on top of your wrist.

4. Feel around the wrist to find a throbbing artery. This is your pulse.

5. You can measure your pulse rate by counting how many times your pulse

beats in a minute.

Respiratory system
 Diaphragm - is a muscle that moves up and down to help you breathe.

 The ribs are light-weight and move as you inhale and exhale.

 The number of breaths you take in a certain time is called the rate of

breathing.

 The oxygen taken in as you inhale, is used to release energy from food - and to

keep other cells alive.

1. Air enters through your nose/mouth.

2. Passes down the back of the mouth and into the voice box and windpipe

(trachea)

3. The bottom of the windpipe divides into 2 tubes

called bronchi (singular: bronchus)

4. The bronchi carry the air into the lungs.

5. Here, the oxygen passes through the walls of the lungs and into the blood.

6. Carbon dioxide from the blood passes through the walls of the lung and into

the air as you exhale.

Digestive system
Alimentary canal - is the main part of the digestive system. It is a tube that

runs throughout the body. It includes the :

 Oesophagus (food pipe)

 Stomach

 Intestines (Large and Small)

 The alimentary canal is approximately 9 metres long - and it folds inside your

abdomen to fit in there.

 It takes between 24 and 48 hours for the food to completely travel throughout

the alimentary canal.

Process of mechanical and chemical digestion

 Your teeth break down the food into small chunks.

 Saliva in the mouth breaks the chunks into smaller molecules.

 The saliva helps moisten the food (now called the bolus) - so they travel down

the oesophagus smoothly.

 In the stomach, acids help turn the bolus into a creamy liquid called chyme.

 The small intestines absorb nutrients in the food.

 The large intestines absorb water. This now then gets excreted after the whole

process.

Nervous System
 Comprises of the brain, spinal cord, and nerves.

 The brain is enclosed in the skull.

 The spinal cord is enclosed in the backbone.

 Nerves connect the brain to the eyes, ears, tongue, nose, skin, and to all the

other organs in your body.

 Messages travel through the nervous system in tiny electrical signals

(called impulses).

 The sense organs send signals to the spinal cord and the brain.

 The brain can also send signals to your muscles - to move so you can walk,

dance, raise your hand, nod etc.

Excretory system
 Waste produced by the body in chemical reactions collect in the blood.
 As the blood passes through the kidneys, a waste product called urea is

filtered from the blood with water.

 The mixture of urea and water is called as urine.

 On a hot day, little urea and water are released from the blood - through the

skin. This is your sweat. As the sweat evaporates, your skin cools down.

 As the blood passes through the lungs, carbon dioxide is removed and passed

into the air.

Sensory system
 The sensory system is made of sense organs - the eyes, ears, nose, tongue, and

skin.

 These are the organs of sight, hearing, smell, taste, and touch respectively.

 The function of the system is to provide information about the surrounding of

an animal.

 The information is sent along in the form of electrical impulses along

the nerves to the brain.

Endocrine system
 This is made of glands- which release chemicals called hormones into the

blood.

 The adrenal gland is found above the kidneys and releases/secretes a

hormone called adrenaline.

 You may feel the effect of adrenaline when you are asked to talk in front of the

class, or face something you're scared of.

 It makes your heartbeat faster and directs more blood into your muscles - so

your body is prepared to run in case of danger.

 Hormones also control your growth, and your body's development.

 The hormone insulin helps the body store a sugar that has been absorbed

from digested food.

 A lack of this hormone, or less of it - leads to a disease called diabetes.

 This can be controlled by taking in extra insulin into the body.

Key Points about the Human Body

Every human being, tissues, human body parts and the organ systems are
made up of cells- the fundamental unit of life. Anatomy is the science of
understanding the structure and the parts of living organisms. Physiology, on
the other hand, deals with the internal mechanisms and the processes that
work towards sustaining life.
These can include biochemical and physical interactions between various
factors and components in our body. With the progress of evolution,
organisms began to exhibit advanced characteristics and features that enabled
them to be more efficient and thrive in their respective environment.
The human structure can be described as bipedal, with hair covering the body,
presence of mammary glands and a set of extremely well-developed sense
organs. With respect to human body anatomy, we have a specialized
circulatory system that enables the efficient transport of materials and
nutrients within the body.
The presence of a well-developed digestive system helps to extract essential
nutrients and minerals required by the body. A well developed respiratory
system ensures the efficient gas exchange and the nervous system enables
coordination and interaction within the body and also the external
environment, thereby ensuring survival.