Classification of organisms Classification is the grouping of organisms together basing on their observable characteristics. The science of classification is known as Taxonomy. Importance of classification: it enables Biologists to 1. quickly identify organisms belonging to same group and easily establish their characteristic features 2. To provide single scientific name for every group of organism in the world 3. To provide a coherent and universal system of grouping organisms 4. Establish evolutionary relationships existing among organisms Organisms are classified by putting them in various groups called Taxa (singular is taxon) Levels of classification There are 7 major groups in which living things are placed and these are; 1. Kingdom 2. Phylum 3. Class 4. Order 5. Family 6. Genus 7. Species Kingdom has the largest number of organisms while species is the smallest. Species is a group of organisms that are able to interbreed and give rise to fertile off springs e.g. Man belongs to specie called sapiens, houseflies belong to species called domestica. Example of classification; Classification of man Kingdom-Animalia Phylum-Chordata Class-Mammalia Order-Primate Family-Hominidae Genus-Homo Species-Sapiens
The naming of organisms. The binomial system was used where an organism is assigned a name. The first name is a generic name and the second name is species name. This system was suggested by a biologist called Carl Linnaeus. How to write a scientific name Write down the generic name and the first letter must be written in capital. Then write down the species name and it must be written in small letters only. Underline the names separately. If typed it should be in italics Organism Genus Species Scientific Name Man Homo sapiens Homo sapiens Housefly Musca domestica Musca domestica Butterfly Periplantae demodocus Papillio demodocus Cockroach Papillio Americana Periplantae americana Maize Zea Mays Zea mays
Organisms are classified into five kingdoms i.e. 1. Kingdom Monera 2. Kingdom Protoctista 3. Kingdom Fungi 4. Kingdom Plantae 5. Kingdom Animalia
Kingdom Monera
The kingdom is made up of organisms mainly bacteria and blue green algae
The bacteria has the following characteristics
1. They are unicellular (single celled) organisms
2. They are very simple in size, structure and are most abundant and widely distributed organisms.
3. They have no true nucleus. Their genetic material is not enclosed by the nuclear membrane.
4. Have varied methods of feeding i.e. photosynthesis and chemosynthesis
5. They reproduce asexually either by fission or spore formation or sexually by simple conjugation.
Examples of bacteria
List the different types of bacteria and their economic importance
Economic importance of monera 1. Bacteria causes diseases in humans and his animals 2. They help in the process of decomposition by breaking up organic wastes 3. Add soil fertility by fixing nitrogen to nitrates 4. Some bacteria are used in treatment of seawage
Kingdom Protoctista Living things under this kingdom are called protoctists. Examples are: amoeba, euglena, paramecium, chlamydomonas, spirogyra etc.
Main features of protoctists 1. They are unicellular organisms i.e. made of one cell. 2. Have a true nucleus with nuclear membrane organelles. 3. Have double membrane organelles. 4. Some members locomote freely using a pseudopodia, cilia or flagella. 5. They live mostly in water or watery environment. Drawing of an amoeba,
Some features on amoeba Cell membrane: surrounds the whole body Food vacuole: where digestion of food substance takes place Contractile vacuole: used for removal of excess water from the cytoplasm Pseudopodia: used in feeding and in movement
Paramecium
Features on the paramecium 1. They have two nuclei. Macronuclei which controls cell processes and micronuclei which controls reproduction 2. Body is surrounded by cilia on surface and are used for movement 3. Contractile vacuole for excretion of excess water Some economic importance of protoctist 1. Some cause diseases to man and his animals. These diseases are normally called protozoan diseases e.g. Malaria- by plasmodium Trypanasomiasis- trypanosoma Coccidiosis- coccidian Amoebic dysentery- enttamoeba histolytica 2. Algae grow rapidly in water bodies especially dams and lakes leading to algae bloom. This results to death of water animals.