SSS 1: INTRODUCTION TO BIOLOGY

BIOLOGY is coined from two Greek words:

'bios' means life and 'logos' which means to study.

Biology can be defined as the study of life.

Biology can also be defined as the study of plants and animals.

                Branches of Biology 

Biology is grouped into two major branches, namely:

a. Zoology: Zoology is the study of animals

b. Botany: Botany is the study of plants

Other branches of biology are 

1. Physiology: Physiology is the study of how living things function.

2. Anatomy: Anatomy is the study of the internal structure of living things 

3. Ecology: Ecology is the study of living things and their environment.

4. Morphology: Morphology is the study of external features of living things 

5. Genetics: Genetics is the study of heredity and variation in living things 

6. Histology: Histology is the study of tissues 

7. Cytology: Cytology is the study of cells

8. Microbiology: Microbiology is the study of microorganisms.

Methods or process of scientific approach 

Methods of scientific approach are the systematic sequence of making inquiries about a thing under study in science.

         Procedures for scientific methods 

1. Observation 

2. Classification 

3. Inference 

4. Measurement 

5. Identification 

6. Hypothesis 

7. Experiment 

8. Conclusion 

9. Theory or law 

The laydown procedure for experimenting includes 

1. Aim:  To state the purpose of the experiment 

2. Apparatus: It means the materials that will be used in the experiment 

3. Method: It means to explain in detail, the step-by-step procedures of the setup of the experiment 

4. Observation: It means to record what was seen during and after the experiment has been set up

5. Conclusion: It means to draw a conclusion on the outcome of the whole experiment based on the final result and observation 

          Living and non-living things 

Living things are things that have life e.g. Man, goats, dogs, trees, grass, etc 

Non-living things are things that do not have life e.g. Stone, air, water, chairs, etc 

    

         Characteristics of living things 

The characteristics of living things are 

1. Movement (Locomotion) 

2. Respiration 

3. Nutrition 

4. Irritability(Sensitivity)

5. Growth 

6. Excretion 

7. Reproduction 

8. Death/Lifespan

9. Adaptation 

10. Competition 

                        Movement 

Movement is the ability of an organism to move its own whole body or part of its body from one place to another.

Reasons why animals move from one place to another 

1. To search for food 

2. To escape from predators 

3. To find mates for reproduction 

4. To avoid danger 

5. To find new and favorable habitat 

6. To disperse or reduce competition or overcrowding by moving to a new place 

                         Respiration 

Respiration is the process by which living things break down (oxidize) food substances to release energy for metabolic activities of the body, with or without the use of oxygen.

                           Nutrition 

Nutrition is the process by which living organisms obtain food substances and use them to provide materials necessary for metabolic activities 

                           Irritability 

Irritability (Sensibility) is the response of organisms towards changes in the environment.

                           Growth 

Growth is the irreversible or permanent increase in the size of an organism.

                           Excretion

Excretion is the removal of metabolic waste materials from the body.

                          Reproduction 

Reproduction is the ability of living organisms to give birth to offspring of their kind.

                            Death 

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

                          Competition 

Competition is the ability of living things to struggle for all the necessities of life to survive in their various environments 

                          Adaptation 

Adaptation is the physical or behavioral feature of living things that helps them survive better in their environment.

Differences between plants and animals

Animals	Plants
1. Animals can move the whole of the body from place to place	Plants do not move from place to place. The only parts of plants that move are leaves, stems,   and roots
2. Animals have sense organs	Plants do not have sense organs
3. Animals have heterotrophic modes of nutrition	Plants have an autotrophic mode of nutrition
4. Growth in animals is limited. Growth takes place all over the body	Growth in plants is unlimited. Growth in plants is apical
5. Animals store carbohydrates as glycogen	Plants store carbohydrates as starch
6. Response to stimuli in animals is fast	Response to stimuli in plants is slow
7. Animals have special excretory organs	Plants have no special excretory organs
8. Animals have a fixed number of body parts	Plants have no fixed number of body parts
9. Animal cells do not contain large vacuole	Plant cells contain large vacuole
10. Animals have special respiratory organs	No special respiratory organs
11. Chloroplast is absent in animal cells	Chloroplast is present in plant cells
12. Cellulose cell wall is absent in animal cells	Cellulose cell wall is present in plant cells

             ORGANISATION OF LIFE 

Many individual organisms can be organized into the following levels: 

1. Cells 

2. Tissues 

3. Organs 

4. Systems 

                                Cells 

The cell is the basic structural and functional unit of life.

               Unicellular organisms

Unicellular organisms are plants and animals that are made up of a single cell. They are capable of carrying out all life processes such as movement, respiration, and reproduction.

Examples of organisms that exist at the cellular level

1. Amoeba 

2. Paramecium 

3. Plasmodium 

4. Trypanosome 

5. Euglena 

6. Bacteria 

7. Chlamydomonas 

8. Chlorella 

9. Diatom etc 

              Multicellular organisms

They are plants and animals that are made up of many cells e.g. Dog, goats, man, hibiscus, etc

     

 Examples of cells in higher animals 

1. Eye cells e.g. Rod and cone cells

2. Skin cells e.g. keratinocytes, melanocytes, Merkel cells, and Langerhans cells

3. Blood cells e.g. Red blood cells, white blood cells, platelets

5. fat cells e.g. Adipose cells

6. nerve cells e.g. Sensory neurons, motor neurons, glial cells

7. Reproductive cells e.g. Ovum and spermatozoa

8. Bone cells e.g. Osteoblasts, osteocytes, and osteoclasts

Examples of cells in higher plants 

1. Phloem cells 

2. Xylem cells 

3. Parenchyma cells 

4. Collenchyma cells 

5. Sclerenchyma cells 

6. Meristematic cells 

8. Epidermal cells.

                             Tissues 

A tissue is a group of similar cells working together to perform a specific function in the body.

Examples of organisms that exist at the tissue level 

1. Obelia 

2. algae 

3. Sponges 

4. Fungi 

5. Hydra etc 

Examples of tissues in animals 

1. Blood 

2. Bone 

3. Muscle 

4. Cartilage 

Examples of tissues in plants 

1. Xylem tissue

2. Phloem tissue

3. Mesophyll layer in leaves 

4. Parenchyma tissue

4. Collenchyma tissue

5. Sclerenchyma tissue

6. Meristematic tissue

8. Epidermal tissue 

                              Organs

An organ is a group of similar tissues working together to perform a specific function in the body.

 

1. Ginger 

2. Onion bulb 

3. Rhizome

4. Platyhelminthes e.g. Tapeworm, planaria, liver fluke, blood fluke, etc

Examples of organs in animals 

1. Skin 

2. Eyes 

3. Ears 

4. Tongue 

5. Nose 

6. Stomach 

7. Lungs 

8. Brain 

9. Heart 

10. Liver 

11. Kidney etc 

Examples of organs in flowering plants 

1. Leaves 

2. Flowers 

3. Roots 

4. Stems 

5. Seeds 

                            Systems 

A system is a group of similar organs that work together to perform specific functions. These systems work together to make up an organism.

Examples of systems in animals 

1. Respiratory system 

2. Digestive system 

3. Nervous system 

4. Skeletal system 

5. Excretory system 

6. Reproductive system 

7. Circulatory system 

8. Endocrine system 

9. Lymphatic system 

Examples of systems in plants 

1. Shoot system 

2. Root system 

Complexity of organization in higher organisms 

There is an increase in complexity from unicellular organisms to multicellular organisms.  This increase in complexity is in structure, functions, activities, behaviors, and mode of living. Higher organisms have advantages and some disadvantages in complexity over unicellular organisms.

Advantages of complexity in higher organisms 

1. It leads to growth and development

2. It leads to cellular differentiation to carry out tasks in the body

3. It leads to specialization of the internal structures 

4. It leads to efficiency in carrying out a life process 

5. It leads to adaptation in different habitats

6. It leads to mutual interdependence among component cells 

Disadvantages of complexity in higher organisms 

1. Individual cells cannot exist on their own but depend on one another's activities 

2. It leads to difficulty in reproduction 

3. Decrease in ability to regenerate 

4. The rate of diffusion of oxygen in the body is slow

5. Difficulty in acquiring food materials 

6. Slower rate of removing metabolic waste.