learning outcomes;

the learner should be able to;

1. understand the concept of classification of organisms (u)

2. recognise the diversity of living organisms in the environment (k,s)

3. understand that each organism has a Latin name consisting of the genus followed by the species (u)

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.

The branch of biology dealing with naming and classification of living organism is called taxonomy.

Importance of classification: 

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.

Scenario;

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: 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?

What happens to the number of organisms in the levels as you move from kingdom to species? Explain your answer 

The above represent a member from the major five kingdoms of classification.

Test yourself.

1.       How do we know that something is living?

2.       Make a guess about the number of different animals and plants in Uganda. Do you think it is a large number or a small number?

3.       Think of ways in which you could put these organisms into groups.

4.       Do you know the scientific name for some of these organisms?

THE IMPORTANCE OF CLASSIFICATION

      In the introductory activity, you talked about how many different organisms there are in Uganda. No doubt you realised that there are a large number of different living things in our country. In fact, there are more than 2,000 different types of plants and 500 different types of animals in our country.

      Scientists need to sort all living things into groups so that they can recognise and study them more easily. When you were sorting the living things into plants and animals in the activity, you were classifying them. There are so many different organisms on Earth that scientists need to sort them into groups. 

       Classification means sorting things into groups. Think back to how you sorted the living things. You put those that shared certain characteristics into the animal group, and those that shared certain other characteristics into the plant group. Sorting, or classifying, things into groups according to their similarities and differences is called classification, or taxonomy.

Scientists sometimes change the way they classify an organism as they learn more about it. 

       Taxonomists use information from many branches of Biology to classify organisms; for example, genetics, biochemistry and fossils.

Self assessment 2.1

1.   Why is it necessary to group organisms?

2.   What do the scientists consider to do the taxonomy of oganisms?

  The concept of hierarchical classification

Activity . 

By considering the area of administrative entities in Uganda like village, cell, sector, district, province and country and by estimating the number of people in each administrative entity in Uganda.

1.   Which administrative entity has:

a)The largest number of people

b) The smallest number of people

2.   How can you compare this with hierarchy of classification?

In Activity 2.1, you grouped different living organisms into two groups: animals and plants. However, there are thousands of different organisms in these two groups, so scientists must classify them into smaller groups. Taxonomists study more similarities and differences between different organisms so that they can classify them into smaller and smaller groups. This is called hierarchical classification.

 The binomial system

Activity 

By using internet and textbooks, search and explain the nomenclature by binomial system and explain how to write a scientific name of an organism.

Usually, we use an organism’s common name, for example, ‘cat’. However, the word for ‘cat’ is different in different languages. So, people in different parts of the world use different words to describe the same organism. This makes it difficult for scientists to accurately communicate their findings about an organism accurately.

To solve this problem, the biologist Linnaeus developed a system accurately give an organism two Latin names. Using two names is called the binomial system. The first word in the name is the genus to which the organism belongs. 

So for a cat, this would be Felis. The second name is the species to which the organism belongs.

 A species is a group of closely related organisms that are able to breed with one another and produce offspring that can also reproduce. The species name for a cat is domesticus. 

So the scientific name for a domestic cat is Felis domesticus. 

How to write scientific names

Look again at the scientific names you have learnt about in this unit: Ficus carica, Felis domesticus and Commelina africana. What do you notice about how they are written?

•   The first name is the name of the genus the organism belongs to; it starts with a capital letter.

•   The second name is the name of the species the organism belongs to; it starts with a small letter.

When written by hand, the two names must be underlined separately; when they are printed, they must be in italics. 

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.

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 below and try to figure out the domestic animals based on their characteristics.  

1.   Which one of the domestic animals is a: 

a)      duck 

b)      cow 

c)      cock

d)     dog

e)      pig  2

3.  Using the domestic animals in (1) above, create your own flow chart but with features/characteristics different from those given above.