All living organisms can be generally classified as plants or animals. However, plants can be distinguished from animals in the following ways:
| PLANTS | ANIMALS | |
| 1. | Undergo passive movement. | Undergo free or active movement with well developed organs of locomotion. |
| 2. | Gaseous exchange takes place through the entire body. | Gaseous exchange is through special organs. |
| 3. | Green plants photosynthesize i. e. they are autotrophs. | Animals do not photosynthesize i. e. they are heterotrophs. |
| 4. | They exhibit slow response to stimuli. | They exhibit fast response to stimuli. |
| 5. | Growth is apical and indefinite (continuous). | Growth is uniform and definite (limited). |
| 6. | No specialized sense organs. | Possess specialized sense organs. |
| 7. | No specialized excretory systems. | They have special and well developed excretory systems. |
| 8. | Cell has rigid non living cellulose cell wall which provides mechanical support. | Have thin, flexible cell membrane. Mechanical support is provided by external exoskeleton or internal endoskeleton. |
| 9. | They store food (carbohydrates) as starch except fungi which store food as glycogen. | They store carbohydrates as glycogen |
CLASSIFICATION OF LIVING ORGANISIMS
Nature comprises millions of organisms, hence the need for identification, naming and classifying them in a meaningful manner. The present and widely accepted method of classification of organism was introduced by Carolus Linnaeus.
The study of the general principles of classification is called taxonomy or systematic. Classification is an arrangement of organisms into groups, each group is then split into smaller groups and the members of each group have certain features in common which distinguish them from other groups.
The largest group of organisms is the kingdom. The arrangement of living organisms from the highest to the lowest (with decreasing variety of organisms) is as follows:
KINGDOM PHYLUM OR DIVISION CLASS ORDER FAMILY GENUS SPECIES
BINOMIAL NOMENCLATURE
This is the standard system of naming living organisms. Each type of organism is given two names:
- The name of the genus (generic name) to which the organism belongs.
- The name of the species (specific name) to which it belongs.
The generic name is always written first using initial capital letter (underlined or italicized) e.g. Homosapiens is man’s scientific name