Lecture 1

Bio 103
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Biology I
Introduction to Biology

✓ Biology: General concept

✓ History of biology
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✓ What is life?

✓ Characteristics of living things.

Biology: General concept

Greek words “bios” means Life

“Logos” means knowledge / study

Biology is the “scientific study of life”.

 History of Biology
➢ Prehistoric humans had to rely on their senses alone to make observations.

➢ They had no laboratories, microscopes, dissecting kits, or other equipment.

Modern Biology

➢ Modern biology began during the 17th century.

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➢ Robert Hooke (1635-1703) and Anton van Leeuwenhoek (1632-1723) introduced
a new tool, the microscope, to the scientific world and discovered microorganisms.

➢ William Harvey (1578-1657), an English physician who traced the pattern of

circulation of blood in humans and showed that it travelled in one direction
through the arteries and veins in a circular path.
 Biology Today
✓ Modern biology is vast science.

✓ Over 1,500,000 (1.5 million) different kinds or species of organisms have been identified
and new ones are still being discovered.

✓ They range in size and complexity from tiny bacteria to trees and humans.

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https://www.discoverwildlife.com/news/new-species-in-2021/
Group of organisms being studied

Botany :The study of plants.

Zoology :The study of animals.
Microbiology :The study of microscopic organisms.
Bacteriology :The study of bacteria.
Virology :The study of viruses.
Mycology :The study of fungi.
Entomology :The study of insects.
Ornithology :The study of birds.
Approaches taken to study Biology
Taxonomy The classification of organisms.
The study of the external form and structure
Morphology
of organisms.
The study of the internal structure of
Anatomy
organisms.
Physiology The study of the function of organisms.
Cytology The study of cells.
The study of the relationship of organisms
Ecology
to their environment.
Genetics The study of inheritance.
Pathology The study of diseases.
How do you define life?
NOT ALIVE ALIVE
ALIVE?

NOT ALIVE?
Life
 Life means something alive. The structural and functional unit of life is “cell”.

 So, what are the special characteristics of a living things?

 Characteristics of a living things
There are nine main characteristics of living things.

1. Cellular structure and organization

2. Growth
3. Metabolism
4. Movement
5. Nutrition
6. Reproduction
7. Respiration
8. Sensitivity / Response to Stimuli
9. Variation and adaptation
1. Cellular Structure & Organization

❖ The cell is the basic structural and functional unit of all known living organisms.

❖ Cells are self-contained and self-maintaining entity.

❖ Cell reproduces by ‘cell division’.

❖ Some organisms, such as most bacteria, are unicellular (single cell).

❖ Other organisms, such as humans, plants and animals are multicellular.

 Component Function

Pinocytotic vesicle Helps to uptake liquid material.

Cross section of animal cell
Contains digestive enzymes that destroy damaged
Lysosome organelles and invaders.
Golgi Body (Vesicles + Processes and packages materials for the cell.
Apparatus)
Ribosome Helps make protein for the cell.

Rough Endoplasmic Builds and transports substances through the cell. Has
Reticulum ribosomes on it.
Smooth Endoplasmic Builds and transports substances through the cell. Does not
Reticulum have ribosomes.
A double layer that supports and protects the cell. Allows
Cell membrane materials in and out.

The “Powerhouse”. Breaks down food to produce energy in

Mitochondria the form of ATP.

Nucleolus A round structure in the nucleus that makes ribosomes.

Nucleus The control center of the cell. Contains the DNA

Nuclear Membrane Surrounds the nucleus.

Centrioles Organize microtubules which serves as the cell's skeletal

system and help with cell division in animal cells.
Cytoplasm Jelly-like fluid that surrounds and protects the organelles.

Vacuole Stores food and water.

Cytosol Provide shape and fills the cell and gives it shape

Microtubules Maintain cell shape.

Cross section of animal cell
 Component Function
Cell Wall Gives shape and protection to plant cells.
Cross section of plant cell
Cell Membrane A double layer that supports and protects the cell. Allows materials
in and out.

Mitochondria The “Powerhouse”. Breaks down food to produce energy in the

form of ATP.

Nucleolus A round structure in the nucleus that makes ribosomes.

Nucleus The control center of the cell. Contains the DNA

Nuclear Membrane Surrounds the nucleus.

Chloroplast Changes sunlight into sugar for plant cells. Contains a green
pigment called chlorophyll.

Amylosplast Responsible to starch synthesis and storage

Cytoplasm Jelly-like fluid that surrounds and protects the organelles.

Vacuole Stores food and water.

Centrosome Cell division and regulating mitosis

Rough Endoplasmic Builds and transports substances through the cell. Has ribosomes
Reticulum on it.

Smooth Endoplasmic Builds and transports substances through the cell. Does not have
Reticulum ribosomes.

Ribosome Helps make protein for the cell.

Golgi Body Processes and packages materials for the cell.

Lysosome Contains digestive enzymes that destroy damaged organelles and

invaders.
Cross section of bacterial cell Component Function

Cell wall The outer covering of bacterial cell, provide protection from
osmotic stress, helps maintain cell shape.

Capsule Resistance to phagocytosis, help to maintain cell shape.

Plasma membrane Selectively permeable barrier, mechanical boundary of cell,

nutrient and waste transport, location of many metabolic
processes, detection of environment cues for chemotaxis.

Cytoplasm Cellular contents inside the cell membrane, excluding the nucleus.

Plasmid Covalently closed, circular piece of DNA which, as an

extrachromosomal genetic element, is not essential for growth.

DNA Polymer of nucleotides connected via a phosphate-deoxyribose

sugar backbone; the genetic material of the cell.

Pili Fimbria-like structure that is present on fertile cells and is involved

in DNA transfer during conjugation

Ribosome Helps make protein for the cell.

Flagellum Whiplike tubular structure attached to a microbial cell responsible

for motility.
Hierarchical organization
Hierarchical organization
Living things have a level of complexity and organization not found in lifeless objects.

The following definitions will help us understand this complex level of organization:

❖ Atom : The building blocks of all matter (the smallest unit of an element).

❖ Elements: The simplest form of matter. They cannot be broken down chemically;
For example: Carbon (C ) Oxygen (O), Nitrogen (N) etc.

❖ Molecules: Two or more atoms combined chemically (the smallest unit of a compound);
For example: O2, N2, C6H12O6 etc.

❖ Cells: The smallest unit of a living thing. In fact, living organisms are made of a limited
number of types of atom which combine to form molecules, the building blocks of life.

❖ Organelles: Structures within cells that perform specific functions.

❖ Tissues: A group of similar cells that perform a similar function. (muscle tissue, bone tissue,
skin tissue, xylem tissue, phloem tissue).
❖ Organs: a group of tissues that work together to perform a specific task. (brain, stomach, heart,
etc.)

❖ Systems: a group of organs that work together to perform a specific task. (skeletal system,
digestive system, etc.)

❖ Organisms: An organism is a complex series of various systems. Like animals, plants etc.
However, some may exist as single cells as in case of bacteria

❖ Population: a group of organisms of the same species in a particular place at a particular time.
(organisms that can interbreed)

❖ Communities: different populations that live in the same area. (all the living things)

❖ Ecosystems: a community of living things and its non-living environment.

❖ Biosphere: The part of the earth’s crust, water and atmosphere that supports life.
2. Growth

➢ All living organisms must grow.

➢ Living organisms grow using food that they
obtain from nutrition.
➢ Growth is a permanent increase in body size.
➢ Plants carry on growing all their lives.
➢ Animals stop growing when they reach a
certain size.
3. Metabolism
Metabolism is the sum of all biochemical reactions in a cell, both
anabolic and catabolic.

Anabolic reaction Catabolic reaction

Metabolism has two distinct phases:

1. Anabolism: Building up.

2. Catabolism: Breaking down.

4. Movement
Movement is the characteristic of organisms that they or some part of
them are capable of moving themselves. We can identify movement in living organisms
at different levels. For example:

❑ Whole organism can move: a mammal can run.

❑ Organs inside organism can move: a heart beats, intestines move food
along them using squeezing movements.
❑ Individual cell can move: an amoeba can move from place to place using
pseudopod.
❑ In plant, when a leaf grows towards the sun or a flower closes at night.
5. Nutrition

❑ All living organisms need food, which is used as a source of energy and
growth.

❑ Plants make their own food by means of photosynthesis. They use sunlight
to turn carbon dioxide and water into sugars.

❑ Animals eat plants or other animals.

6. Reproduction

❑ Only living things can produce off-springs identical.

❑ Reproduction can be either asexual, involving a single parent organism,
or sexual, requiring two parents.
❑ Plants makes seeds that grow into new plants.
❑ Animals lay eggs or have babies.
7. Respiration

❑ All life processes require energy and getting the energy out of the food we eat
is called respiration.

❑ The energy is released during the breakdown of certain energy-rich

compounds in the process of respiration.

❑ The energy that released is stored in molecules of adenosine triphosphate

(ATP). This compound had been found to occur in all living cells and is sometimes
referred to as the “Universal Energy Carrier”
8. Sensitivity / Response to Stimuli

❑ Living organisms are sensitive. They reacts to things happening around them.

Examples:
❑ The growth of a plant towards light, Flowers of many plants open in the
morning and close at night when it is dark.
❑ The rapid withdrawal of one’s hand from a hot object.
➢ Animal have nervous system and they use eye, nose, ear to respond.

➢ Plant do not have nervous system and slow response to light,

oxygen, nutrient etc.

➢ Microorganisms also response to nutrients, enviornments.

9. Variation and Adaptation
Variation

❑ Variation refers to an individual that possesses characteristics different from the others of the
same kind.

❑ Variation comes from random mutations. These are changes in the DNA code.

❑ Offspring always differ in some ways from one another and from their parents. These differences are
called variations.

❑ Most variations do not affect an organism’s chances of survival.

For example, the fact that your hair is a different color from your parents will not likely affect your
chances of survival.
 Adaptation

❑ The process by which a certain type of organisms becomes better suited to

survive in its environment is called adaptation.

❑ Adaptations are physical or behavioral traits that make an organism better suited
to its environment.

❑ Ex. Penguins are adapted to an aquatic existence in the Antarctic.

➢ Penguins often slide on their bellies across the snow in order to conserve
energy when moving quickly.
➢ Their eggs-one or at most two are carried on the feet, where they are
protected by a pouch of skin and incubate for hatching.