CLASSIFICATION

INTRODUCTION

Have you ever imagined how many living things there are in the world? Indeed there is a greater variety of organisms in the world. How can we organize them so that they are easily recognizable? The
first thing to do is to sort them into smaller and simpler groups. For example, if you were given a collection of books and asked to put them into two groups. How would you do it? What characteristics
would you use? Biologists use the same practice of putting things into groups of related organisms. This is called classification.

Key question
How can you classify the books in the library?
What you do
3.1: Sorting books in a library
Imagine you are in charge of a new library and government has delivered a number of different kinds of textbooks to your school. Someone is going to put the books on shelves in the school library, and
she needs instructions on how to sort them. Write, in not more than 50 words, the instructions to be followed in sorting the books so that the library users can easily get access to the books they need.

Drawing conclusions

1) What characteristics did you look at in order to decide in what group to place a book?
2) Did any book fit into more than one group? Why or why not?
3) Do you think that scientists use classification when they are studying things? If so, how?
4) Why do you think scientists like to classify organisms?
5) Does classifying these organisms into certain groups help scientists study them?
6) How does classification help scientists study organisms?
Levels of Classification
Classification is the act of putting together living organisms into groups based on their common/similar characteristics. Each group of similar organisms is called a taxon (taxa-plural). The branch of biology that
deals with classification of organisms is called taxonomy.
Activity 3.2: Finding out the seven levels of taxonomy of living things
In this activity you are going to discover the different levels of organization of organisms by relating a day to day scenario to a biological concept of classification. The levels are determined by the unique characteristics of the organisms therefore at each level there are a number of organisms that differ.
Key question
How are organisms grouped scientifically?
What you need
i) Notebook
ii) Ruler
iii) Chart with a list of words (county, village, district, continent, world, parish, country)

What to do

1. Draw a large inverted isosceles triangle in your notebook 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 provided) 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 organization in the following order; kingdom, phylum, class, order, family, genus
   and species.
   Of the terms you have written on the other side of the triangle, which one would contain the:
   a. Largest number of organisms?
   b. Smallest number of organisms?
   c. What happens to the number of organisms in the levels as you move from kingdom to species? Explain your answer.
   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.
   Genus: This group consists of a number of similar or closely related species.
   Family: This group is made up of closely related genera (genus singular).
   Order: This group is made up of closely related families.
   Class: This group is made up of closely related orders.
   Phylum: This group is made up of closely related classes.
   Kingdom: This is the highest category into which organisms are classified. It consists of organisms belonging to closely related phyla (phylum-singular). This group contains the highest number of organisms. There are five kingdoms of living organisms today: Monera, Protoctista, Fungi, Plantae and Animalia.

The Two-Name Naming (Binomial) System of Living Organisms

An office/restaurant/bank in a town can easily be located using only two small groups of the address i.e. the name of the street and plot number. In the same way all species are named from the last two groups in the taxonomic levels i.e. the genus and the species. In the two-name naming system every living organism has a unique two part name that consists of two words from the genus name and species
name. 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.

The binomial system is important because of the following reasons:
(i) Clarification: each organism has a unique name that is specific to that organism and can be identified.
(ii) Universal: using same name everywhere to identify the specific organism.
(iii) Education: names are short and easier to remember and learn.
(iv) Classification: organisms are more easily categorized and the categories are easier to understand.

The list below shows the meanings of several Latin prefixes, suffixes, or words that are frequently used in species names. Using the information about Latin word parts, match the scientific name on the left with the correct common name on the right. Draw lines to match them. Then write each pair of names on a separate sheet of paper.

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. Take a look at the chart below and try to figure out the domestic animals based
on their characteristics.
Task: Study the flow chart shown below and answer the questions that follow.

The bacteria have the following characteristics:

• They are unicellular (single celled) organisms
• The bacteria are grouped according to their shapes which can be rounded, coiled or rod-shaped.
• They have no true nucleus. Their genetic material is not enclosed by the nuclear membrane.

Useful and Harmful aspects of Monera

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:

1. They cause diseases e.g. tuberculosis and cholera in humans.
2. Action of bacteria on food makes it rot.
   Bacteria are useful because:
3. They help in the process of decomposition by breaking up organic wastes.
4. They contribute to soil fertility by fixing nitrogen which is important for plant growth.
5. Some bacteria are used in treatment of sewage.
6. Some bacteria are used in industry e.g. in making of food like yoghurt.

Kingdom fungi include mushrooms, yeast and moulds. Some fungi grow in wood and soil, and develop from tiny spores. Fungi have a nucleus and their cells have a cell wall made up of a substance known
as chitin. They do not make their own food; instead feed on the decomposing organic matter of animals and plants.
You may already be aware that some types of fungi like mushrooms are grown and eaten while others like puff balls are poisonous. This informs you that fungi can be useful or harmful in nature.

Useful Aspects of Fungi

1. Fungi keep soil fertile by recycling organic material through decomposition.
2. Some fungi are food for humans, for example, mushrooms.
3. Manufacture of medicine, for example, antibiotic Penicillin Yeast is a type of fungus used in baking of bread and brewing of beer in industries.

Harmful Aspects of Fungi

1. They cause diseases e.g. ringworm, candida, athletes’ foot (in animals), potato blight and leaf rust in coffee.
2. Fungi like moulds when they grow on food they cause food spoilage.
   Activity 3.3: Sorting and identifying organisms in kingdom monera, protoctista and fungi

What you need

Pictures or specimens (bracket fungus, amoeba, bacillus, spirogyra, puff ball, streptococcus, mushroom, paramecium, yeast, spirilla, euglena)

2. Group names (bacteria, fungi, protists)
3. Characteristics of different organisms (single celled, multicellular, nucleus is not surrounded by a membrane, nuclear membrane present, cell wall made up of chitin, feed on decomposing matter).

Project work: Making Yoghurt

In groups of 4 to 6 make yoghurt at school. Use the Internet, cookbooks or ask your teacher to assist you:

• Determine the materials to use.
• Identify the conditions.
• Develop the procedure.
• Write a report including the materials used, explaining the important steps followed and the description of the product. State the living organisms involved in the process. Mention the nutrients found in yogurt and their importance to man.

An example of the format of how a scientific report should be presented or written is given below:

Flowering plants reproduce by seeds which are formed from flowers. The seeds are enclosed in an ovary. Flowering plants are divided into two: monocotyledonous and dicotyledonous plants. Monocotyledonous plants are flowering plants which have only one cotyledon in their seeds. Most have long, narrow leaves with parallel leaf veins. Their flowers have dull coloured petals in multiples of three. Examples include grasses, maize, millet, sorghum. Dicotyledonous plants have two cotyledons in their seeds. Their leaves are usually broad and the leaf veins form a branching network. They have four or five brightly coloured petals on each flower. Examples include; beans, peas, groundnuts.

2. Construct a flow chart for any four organisms based on the

Most reptiles live on land. They have tough dry scales on their bodies which prevent loss of water and are for protection. They use lungs for gas exchange. Like fish and amphibians, reptiles are ectotherms. Reptiles reproduce by laying eggs that have soft shells.

Activity 3.6: Classifying chordates
What you need
Pictures of goat, rat, bat, elephant, human, whale, tortoise, python, gecko, crocodile, crested crane, crow, duck, ostrich, tilapia, shark, catfish, toad, frog, salamander

HIV (Human Immunodeficiency Virus) is what causes AIDS (Acquired Immune Deficiency Syndrome) disease. The virus weakens the immune system of the infected person making it easy to catch
diseases e.g. TB (tuberculosis). The virus is transmitted through: having unprotected sex with an infected person, infected injections, blood transfusion from an infected person and from an infected
mother to her child during pregnancy or birth.

Today, there is no scientifically known cure for AIDS but there are drugs that can make an infected person’s immunity stronger allowing him/her to live a longer and productive life. The most effective way to prevent the spread of HIV and AIDS is abstinence from sex more especially among people who are not in a permanent adult relationship. Hepatitis B and Ebola are transmitted through body contact with fluids from infected persons e.g. kissing. You need to understand that viral diseases are difficult to treat or have no treatment at all. Hepatitis B can be prevented by vaccination; however, Ebola and HIV have no vaccine.
The cassava mosaic virus affects the tubers of the plant resulting in low crop yields. This virus causes the cassava mosaic virus disease. It can be recognized on the cassava leaves which have spots ranging
from light green to yellow. The disease is transmitted from plant to plant by the whitefly.
This disease cannot be cured but it can be avoided. The cassava mosaic virus disease can be prevented by the use of cuttings which have not been attacked by the virus. Farmers are particularly encouraged to plant varieties which are resistant to the disease.

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