SSS1 Biology - Meaning of Biology

BEHAVIOURAL OBJECTIVES:

By the end of the lesson, students should be able to:

i. Define Biology.
ii. State and explain two(2) main branches of Biology.
iii. State and explain fifteen(15) sub-branches of Biology.
iv. State and explain eight(8) characteristics of living things.
v. State seven(7) differences between plants and animals.

INTRODUCTION: Man has been inquisitive about life since the ancient civilizations through the middle ages into the 17th century until modern civilization. Many scientists have contributed much in the study of Biology such as Hippocrates, Aristotle, Robert Hooke, Antonie Van Leeuwenhoek, Carl Linnaeus, etc.

Definition of Biology

The word “Biology” was derived or coined from two Greek words namely; Bios and Logos
Bios meaning life.
Logos meaning study.

Thus, putting the above meaning together; Biology is defined as the study of life. It is also defined as the science of life, which can be the study of plants and animals.

Main branches of Biology

The two(2) main branches of Biology are;

Botany: This is the study of plants, and a scientist who study botany is called a Botanist.

Zoology: This is the study of animals, and a scientist who study zoology is called a Zoologist.

Sub-branches of Biology

i. Morphology: This is the study of physical and external characteristics of living things in terms of shape and structure.
ii. Anatomy: This is the study of internal structure of living things.
iii. Physiology: This is the study of how the body of living things functions.
iv. Taxonomy(Systematics): This is the branch of biology which deals with the classification of living things.
v. Genetics: This is the study of heredity i.e. how traits are passed from one generation to another.
vi. Microbiology: This is the study of microorganisms.
vii. Entomology: This is the study of insects.
viii. Cytology: This is the study of cell.
ix. Parasitology: This is the study of parasites.
x. Histology: This is the study of body tissues.
xi. Mycology: This is the study of fungi.
xii. Phycology: This is the study of Algae.
xiii. Embryology: This is the study of the early development of a plant or animal, e.g. in man, it covers the period from fertilization to birth.
xiv. Ecology: This is the study of inter-relationship between living organisms and their external environment.
xv. Evolution: This is the study of the origin of living things.

Characteristics of Living things

The general characteristics of living things are recognized or remembered by the formula MR. NIGER D

M – Movement
R - Respiration
N – Nutrition
I – Irritability
G – Growth
E – Excretion
R – Reproduction
D – Death

Movement: This is defined as the ability of an organism to move its own whole body or parts of its body from one place to another. Most living things, e.g. animals move from one place to another in search of food, shelter, mates and escaping from enemies.

Respiration: This is defined as the exchange of gases between organisms and their environment. Animals take in CO₂ and breathe out O₂.

Nutrition: This is defined as the ability of living things to feed. The reason for feeding is to enable living things live and carry out life processes such as growth, respiration and reproduction. The two(2) types of nutrition include:
• Autotrophic/Holophytic/Photosynthetic Nutrition: In this type of nutrition, all green plants are able to manufacture their own food through the process known as Photosynthesis.
• Heterotrophic Nutrition: In this type of nutrition, all animals are unable to manufacture their own food but depend directly of indirectly on plants for their survival.

Irritability: This is defined as the ability of living organisms to respond to stimuli. Stimuli include; heat, cold, light, pain, sound, etc.

Growth: This is defined as the irreversible or permanent increase in the size and mass of an organism.

Reproduction: This is defined as the ability of living organisms to give birth to young ones.

Death: All living things must die because they have a definite and limited period of existence.

Differences between Plants and Animals

S/N	PLANTS	ANIMALS
1.	Nutrition is autotrophic.	Nutrition is heterotrophic.
2.	Growth is indefinite and apical	Growth is definite and intercalary
3.	Organs of movement are absent	Organs of movement are present
4.	Slow response to external stimuli	Fast response to external stimuli
5.	Special sense organs absent	Special sense organs present
6.	Chlorophyll is present	Chlorophyll is absent
7.	Store carbohydrate as starch	Store carbohydrate as glycogen