From early time, man has found it convenient to group together, or classify, animals and plants. Many of his groupings are based on utility, or the sharing of a common feature. For example, all types of trees which provide him with orange, sweet-tasting fruits might be associated in his mind.

Living things are classified by dividing them into different kingdoms for example the animal kingdom, the plant kingdom, etc.

Each kingdom is further divided into different phyla for example the animal kingdom is divided into the vertebrates phylum, the arthropods phylum, etc.

Each phylum is further divided into different classes for example the arthropod class is divided into the crustecean class, the arachnid class, the myriapod class and the insect class.

Each class is further divided into different orders for example the insect class is divided into the two-winged Diptera order, the social-casted Hymnenoptera order, the hard-winged Orthoptera order.

Each order is further divided into different families and each family is divided into different genera.

Each genus is then divided into different species.

Members of a species can carry out free reproduction to produce fertile offspring.

FIGURE 2.18

This diagram illustrates the classification categories for organisms with the broadest category Kingdom at the bottom and the most specific category.

 

 

 

 

 

 

 

 

 

 

 

Classification of man:

NAME	GROUP	EXAMPLES
KINGDOM	ANIMALIA	Insects, fish, cow, apes, monkey, early man, modern man
PHYLUM	VERTEBRATE	fish, cow, ape, monkey, early man, modern man
CLASS	MAMMALIA	cow, monkey, ape, early man, modern man
ORDER	PRIMATE	monkey, ape, early man, modern man
FAMILY	HOMINIDAE	ape, early man, modern man
GENUS	HOMO	early man, modern man
SPECIES	SAPIENS	modern man only

Classification of maize:

NAME GROUP EXAMPLES

KINGDOM PLANTAE Mosses, liverworts,

ferns, pine, beans,

sorghum, corn, maize

PHYLUM TRACHEOPHYTA ferns, pine, beans,

sorghum, corn, maize

CLASS SPERMATOPHYTA pine, beans, sorghum,

corn, maize

ORDER ANGIOSPERM beans, sorghum, corn, maize

FAMILY MONOCOTYLEDON sorghum, corn, maize

GENUS ZEA corn, maize

SPECIES MAYS maize

 

Naming of organisms (nomenclature):

Organisms are given common names and scientific names.

Examples of common names are cat, dog, maize. Such common names are misleading because: They are based on superficial resemblances; and secondly, they can refer to many different organisms in different localities.

The standard system of naming organisms used in Biology is called the binomial system.

This method of naming animal and plant types by giving each a double Latin name was developed by Linnaeus, a biologist of the eighteenth century. It is now used by biologists throughout the world. The first of the two is called the generic name, and the second the specific name. It is conventional to write the generic name with a capital letter and the specific name with a small letter.

FIGURE 2.19 These children are all members of the same species Homo sapiens.

The genus name is written starting with a Capital letter and the species name is started with a small letter; and both names are printed in italics.

The 'cat' genus is called Felis; the following are the scientific names of the different cats:

Felis domestica domestic cat Felis tigris tiger Felis leo lion

Felis pardus leopard

The identification (dichotomous) key

This is the key used to identify organisms quickly and accurately. The key commonly used is the Numbered Couplet Key. In this key, each number refers to a characteristic with two contrasting traits of an organism or organisms. An organism with a unique trait is identified and if there are two or more organisms with that trait, they are referred to the next steps where they will be identified individually.

To illustrate the identification key, we shall use the following fowls:

A: Has a wattle, Has a short beak

B: Has a long beak, Has tail feathers

C: Has a long beak

D: Has a comb, Has tail feathers,

E: Has fluffy feathers

F: Has a wattle, Has feathery legs

So the dichotomous key (numbered couplet) would be:

1. Has fluffy feathers .......................... E

Has smooth feathers ....................... 2

2. Has a comb ................................... D

Has no comb... ............................ 3

3. Has feathery legs ............................ F

Has featherless legs ........................ 4

4. Has tail feathers ................................ B

Has no tail feathers ........................... 5

5. Has a long beak ................................ C

Has a short beak ............................... A

For the following drawings of insects, an identification key can be made:

A: Has long antennae B: Has a long style, has long antennae

C: Has hairy antennae, Has short antennae

D: Has short style, Has long antennae

E: Has no style,- Has no antennae

F: Has a long style,- Has long antennae- Has hairy antennae

An identification key (numbered Couplet) could be constructed as below:

1. Has antennae .................. E

Has no antennae .............. 2

2. Has long antennae ............ 3

Has short antennae ........... C

3. Has hairy antennae ........... F

Has smooth antennae......... 4

4. Has style ....................... 5

Has no style ................... A

5. Has long style .................. B

Has short style ................ D