Biology is the study of living things and is divided into several branches including zoology, botany, and microbiology. It involves studying the characteristics of living things such as nutrition, respiration, reproduction, growth, and response to stimuli. Classification systems group organisms based on similarities, with taxonomy being the science of classification. The main taxonomic units are domain, kingdom, phylum/division, class, order, family, genus, and species. Classification is important for identification, understanding evolutionary relationships, and arranging biological information.

1. Introduction to Biology
By Mr. Kanyoro Peter

2. What is Biology?
 Derived from two Greek words; Bios – life and logos – knowledge.
 Therefore, Biology is the study of living things(organisms).
 It is divided in different branches.

3. Branches of Biology
 Are three main branches;
 Zoology – study of animals
 Botany – study of plants
 Microbiology – study of microscopic organisms such as bacteria and
viruses

4. Other branches
 Biotechnology- deals with development of techniques for the
application if biological processes to produce materials for use in
medicine, industry and farming.
 Anatomy – study of internal structure of living things.
 Physiology – study of body functions.
 Genetics – study of inheritance and variation.
 Ecology – study of relationship/interaction between living organisms
and their environment.
 Parasitology – study of parasites.
 Entomology – study of insects.
 Cytology – study of cell

5. Importance of studying Biology
 Study of Biology helps us;
 To understand how our bodies work/function when we are
healthy or diseased.
 To understand our environment and use the natural
resources well/sustainably e.g. forests, water and soil and
avoid pollution.
 To make career choices e.g. medicine, agriculture,
veterinary, dentistry etc. that are based on Biology
knowledge.

6. Importance of studying Biology
 To promote international cooperation in solving pertinent and
emerging problems such as HIV and AIDS, global warming and
depletion of ozone layer.
 To appreciate harmful effects of drugs and substance abuse on
our bodies.
 To understand ways of transmission and control of diseases such
as HIV and AIDS.
 To acquire and utilize scientific skills such observation,
identification and analysis to evaluate everyday life.
 To understand the developmental stages in human body.

7. Characteristics of Living Things
 Nutrition – the process by which living things acquire and utilize
nutrients.
 Plants are autotrophic
 Animals are heterotrophic
Importance;
 Organisms derive nutrients for proper growth and development and
proper functioning of body through nutrition.

8. Characteristics contd.
 Respiration – process by which food substances are broken down in the
mitochondria of the cell to release energy.
Importance
 Organisms derive energy required carry out essential metabolic
activities, for growth and development and reproduction.

9. Characteristics contd.
 Gaseous exchange – process by which respiratory gases pass through
respiratory surfaces.
 The R.Gs include Carbon (IV) Oxide and oxygen.
 The R.Ss include; stomata – leaves, cell membrane – unicellular
organisms e.g. Amoeba, alveoli (lungs) – mammals, gills – fish and skin
– frogs.

10. Characteristics contd.
 Excretion – the process by which living things get rid of/ eliminate metabolic
wastes/harmful materials from their bodies.
 Include such gases as Carbon (IV) Oxide and nitrogenous wastes such as urea.
Importance
 Helps to remove harmful substances which can cause poisoning of living things
if allowed to accumulate in the body.

11. Characteristics contd.
 Growth and development.
 Growth – irreversible increase in size and mass of living organisms.
 Development – irreversible change in complexity of the structure of living things.
Importance
 Organisms attain the appropriate size and mass through growth and mature
through development, which is essential for proper body functioning.

12. Characteristics contd.
 Reproduction – process by which living things give rise to new individuals of
their own kind.
Importance
 Help to perpetuate species and prevent it from becoming extinct………
dinosaurs!
 Sexual reproduction bring about genetic variation thus offspring which better
adaptations for survival.

13. Characteristics contd.
 Irritability – the ability of living organisms to detect and respond
appropriately to changes/stimuli from the environment.
 Changes are experienced in temperature, light, certain chemicals
(pheromones) etc.
Importance
 Living things are able to detect and respond to changes thus can escape
harmful stimuli.

14. Characteristics contd.
 Movement and locomotion
 Movement – change in position by either a part of or the whole living
organism.
 Locomotion – progressive change in position by the whole living organism.
 Animals move/ show locomotion by swimming, flying, walking, hopping,
running.
 Movement in plants change in position by some parts e.g. folding of leaves,
closing of flowers and growing of shoots towards light and roots towards water
or in response to gravity.

15. Importance of movement
 Animals move in search of food and mates.
 Through movement, animals escape harmful environmental stimuli
such as extreme temperatures and seek safe places for survival.
 Plants grow towards favorable factors of survival such as sunlight and
water.

16. Specimen Collection
 A specimen is a whole or a part of an organism under study or examination.
 Specimen are collected for further observation and/or preservation for future
reference in the laboratory while studying organisms.
 It is important to gain knowledge on specimen collection so as to;
 Avoid damage to specimen
 Ensure safety of the collector

17. Precautions taken while collecting and observing specimen
 Collect only the required number of specimens to avoid wastage
 Take care not to harm the specimens during collection so as not to
distort/destroy their features
 Do not destroy the natural habitat of the specimens
 Return the live specimens to their habitat whenever possible to maintain
ecological balance.
 Handle dangerous/injurious specimens e.g. stinging insects with care using a
pair of forceps or hand gloves to avoid injuries to the collector.
 Immobilize highly mobile animals using the suitable chemical substances such
as chloroform ethoxythane for ease of observation

18. Comparison between plants and animals
Plants
 Have chlorophyll) thus make their
own food in presence of sunlight -
autotrophic.
 Respond slowly to changes in the
environment.
 Do not move about, that is they do
not loco mote.
 Growth occur at the meristematic
tissues only.
 Lack complex excretory
organs/system
Animals
 Lack chlorophyll hence feed on
ready made food. They are
heterotrophic
 Respond rapidly to changes in the
environment.
 Most animals move about in search
of food and shelter
 Growth occurs all over the body of
the animal.
 Have complex excretory
organs/system

19. Classification I
 Grouping of living organisms based on their structure and evolutionary relationship
(phylogeny).
 Organisms with similar structures are placed in one group (taxon) – in plural taxa.
 Taxonomy is the science of classification. It involves placing organisms into groups
(taxa) and giving them names.
 Assignment; read and write notes on features used to identify plants and animals

20. Importance of classification
 Helps to bring together living organisms with similar features and separate
those with different for easy identification
 Help to place organisms in their correct taxa for reference.
 Helps to arrange information about organisms in an orderly manner to avoid
chaos and confusion.
 Helps us to understand the evolutionary relationship between different
organisms
 It is important for scientific naming, so as to have universally accepted
names.

21. Taxonomic Units of Classification
 Groups (taxa) into which living organism are placed based on observable
features/characteristics.
 Each unit reflects/shows the position each organism occupy in relation to
others.
 Linnaeus identified seven units of classification in the following order from
the largest to the smallest; Kingdom, Phylum (animals)/Division (plants),
Class, Order, Family, Genus and Species.
 Number of organisms increase from species to kingdom and vise versa

22. Kingdoms
 There are five kingdoms into which organism are placed;
i. Kingdom Monera
ii. Kingdom Protoctista
iii. Kingdom Fungi
iv. Kingdom Plantae
v. Kingdom Animalia

23. Kingdom Monera
 Members include bacteria.

24. Kingdom Protoctista.
 Members include algae such a spirogyra and protozoa such as plasmodium,
paramecium and amoeba.

25. Kingdom Fungi
 Members comprises of moulds, yeasts and mushrooms.

26. Kingdom Plantae
 Comprise all plants; simple plants such as moss plants and higher plants such
as maize, beans, Gravillea robusta etcetera.

27. Kingdom Animalia
 Comprise all animals which includes hydra, tapeworms, bees and human
beings among many others.