Classification of organisms

1. BIOLOGY:
classification of living organisms
BAGALANA STEVEN| S.1 TERM II 2023

2. TAXONOMY
1. Meaning of classification
2. levels of classification
3. Importance of classification
4. Nomenclature of organisms

3. MEANING OF CLASSIFICATION
• Classification refers to the grouping of living organisms
basing of their similar characteristics.
• The science which deals with the study of grouping
organisms basing of their characteristics is known as
Taxonomy.
• The groups under which organisms of similar
characteristics are put are known as taxons
ACTIVITY
• Name six groups under which living organisms in your
community are categorised basing on their
characteristics.

4. LEVELS OF CLASSIFICATION
• There are seven levels of taxonomy. From the smallest,
they are:
• 1. Species: This is a group of organisms with similar
characteristics that are able to breed freely among
themselves and produce fertile offspring. This is a
taxon/group with the fewest organisms. E.g man belongs
to species sapien
• 2. Genus: This is a group made up of a number of similar
or closely related species. (the plural of genus is genera).
E.g man is in genus Homo.
• The genus and species name of an organism are used to
form a Scientific name of an organism as we shall see

5. LEVELS OF CLASSIFICATION
CONTINUES
• 3. Family: This group made up of closely related genera
of organisms. Man belongs to family of Hominidae
• 4. Order: This is group made up of closely related
families. Man belongs to order primate
• 5. Class: This group made up of closely related orders.
Man belongs to class mammalia
• 6. Phylum: This group is made up of closely related
classes. (The plural of phylum is phyla). Man belongs to
phylum chordata.
• 7. Kingdom: It is a group of organisms belonging to
closely related phyla. This is the highest taxon into which
organisms are classified. This group contains the highest
number of organisms. There are five kingdoms of living

6. Hierarchy of classification

8. LEVELS OF CLASSIFICATION
CONTINUES
ACTIVITY 2
• 1. Draw a large inverted isosceles triangle in their
notebooks and divide it horizontally into seven equal
parts. The size of the triangle division represents a
population size.
• 2. On one side of the triangle, write down the places
(from the list of words: continent, village, district, county,
parish, country, region) beginning with the biggest to the
smallest in terms of population size matching with the
divisions in the triangle.
• 3. On the other side of the triangle, starting from the top
to bottom, place the following terms which are the levels
of organisation in the following order; Kingdom, Phylum,
Class, Order, Family, Genus and Species.

9. LEVELS OF CLASSIFICATION
CONTINUES
• 4. Of the terms they have written on the other side of the
triangle, which one would contain the:
• i) Largest number of organisms?
• ii) Smallest number of organisms?
• iii) What happens to the number of organisms in the
levels as you move from kingdom to species? Explain
your answer.

10. IMPORTANCE OF CLASSIFICATION
OF ORGANISMS
• 1. Makes it easy to study organisms by putting them into
correct small groups with similar characteristics.
• 2. Makes it easy to understand the evolutionary
relationship(phylogeny) between different organisms,
• 3. Prevents confusion around the scientific world by
arranging information about organisms in an orderly
way.
• 4. Provide a universal way of arranging information
about organisms.

11. IMPORTANCE OF CLASSIFICATION
OF ORGANISMS CONTINUES
ACTIVITY 3
• Identify six ways through which you can use the
knowledge of classification in your daily life.

12. BINOMIAL SYSTEM OF
ORGANISMS
• This is a system of naming which gives two unique Latin
names to an organism, beginning with genus name
followed by the species name.
• Rules of binomial system (characteristics of scientific
names)
• - The first name is Genus, the second name is species.
• - Scientific names of organisms are written in Latin,
printed in italics or underlined separately when
handwritten.
• - The genus name always starts with a capital letter, and
the species name is always written in small letters.
• - Scientific names rarely change
• - Scientific names are unique i.e. no two organism have

13. SCIENTIFIC NAMES OF
ORGANISMS
Organism Genus name Species name Scientific names
Humans Homo sapien Homo sapien
Cow Bos taurus Bos taurus
Sweet potatoes Ipomea batutus Ipomea batutus
House flies Musca domestica Musca domestica
Cockroach Periplaneta Americana Periplaneta
Americana
Honey bees Apis mellifera Apis mellifera
Onion Allium Cepa Allium cepa
Beans Phaseorus Vulgaris Phaseorus Vulgaris
Mango Mangifera Indica Mangifera indica
Lion Panthera Leo Panthera leo

14. SCIENTIFIC NAMES CONTINUES
The importance of binomial system:
• The binomial system is important because of the
following reasons:
1. Clarification: each organism has a unique name that is
specific to that organism and can be identified.
2. Universal: using same name everywhere to identify the
specific organism.
3. Education: names are short and easier to remember and
learn.
4. Classification: organisms are more easily categorized and
the categories are easier to understand

15. SCIENTIFIC NAMES CONTINUES
• Activity.
• Identify any twenty living organisms in your community
d using any given source of information, research and
Identify the genus, species and scientific name of each of
the named organisms.

16. FLOW CHART AND DICHOTOMOUS
KEY
• Using a flow chart for biological classification
The features/characteristics of organisms can be used to
classify them using a flow chart. The chart usually begins
with two distinct features that distinguish a group of
organisms. Then other features/characteristics can be used
to further separate the organisms until each individual in
the group is identified independently.
Example
Take a look at the chart in the next slide and try to figure
out the domestic animals based on their characteristics.

17. FLOW CHART AND DICHOTOMOUS
KEY

18. FLOW CHART AND DICHOTOMOUS
KEY CONTINUES
• Which one of the domestic animals is a:
a) duck
b) cow
c) cock
d) dog
e) pig
2. Using the above flow chart construct a dichotomous key
to identify the organisms above.

19. ACTIVITY OF INTEGRATION

20. THE FIVE KINGDOMS OF ORGANISMS
By Bagalana Steven 0777 139918 and 0757848094

21. THE FIVE KINGDOMS OF
ORGANISMS
• Organisms are grouped into five big groups, called
kingdoms. The kingdoms are Animals, Plants, Fungi,
Protoctista and Monera.
• The features that are used to group organisms into these
kingdoms are: body structure, method of getting food
and method of reproduction.
• The kingdoms are further divided into smaller groups
called phyla, classes, orders, families, genera and species.
See the on the next slide
• Each kingdom is divided into phyla.each phylum is
divided into classes, each class is divided into orders, each
order is divided into families, each family is divided into
genera, each genus is divided into species.

23. KINGDOM MONERA
• This kingdom includes the simplest and smallest living
organisms known as bacteria. The organisms are single-
celled.

24. KINGDOM MONERA
Characteristics of bacteria:
• The bacteria have the following characteristics:
1. Are unicellular (single celled) organisms
2. Have no true nucleus. Their genetic material is not
enclosed by the nuclear membrane.
3. The bacteria exist in various shapes which can be
rounded (cocci), coiled (Spirilla )or rod-shaped (bacilli)
4. Exist singly or in colonies which can be in pairs (e.g
diplococci and Diplobacilli), cluster (like staphylococci)
or in chain form (e.g streptococci)

25. KINGDOM MONERA
Economic (Useful and Harmful aspects) of importance of
bacteria:
• Some people may tend to fear bacteria, because they
only imagine that bacteria cause harm. However
biological studies show that bacteria can be both
harmful and useful in nature.
Bacteria are harmful because:
 They cause diseases e.g. Tuberculosis and cholera in
humans.
 Action of bacteria on food makes it rot.
 Some bacteria reduce soil fertility by denitrification.

26. KINGDOM MONERA
Bacteria are useful because:
 They help in the process of decomposition by breaking
up organic wastes. This is applied in the production of
composed manure and biogas.
 some bacteria improve soil fertility by fixing nitrogen,
causing decay of organic waste and through nitrification.
 Some bacteria are used in treatment of sewage.
 Some bacteria are used in industry e.g. in making of
food like yoghurt.
 Some bacteria are used in biotechnology and genetic
engineering to produce medicine, hormones and genes.
 Some bacteria in ruminants facilitate digestion of
cellulose in grass by secreting Cellulase.

27. KINGDOM MONERA
Adaptations of bacteria in nature (why bacteria are
abundant or very common in nature)
 Have Ability to live in adverse conditions.
 Ability to respire aerobically and anaerobically.
 Have various modes of feeding reducing competition for
food.
 Bacteria have many strains/mutate very fast.
 Bacteria can easily be dispersed because they are very
small.
 Have higher reproductive rate which increases their
chances of survival
 Ability to thrive in various environments like water Air
and soil