SSS 1: CLASSIFICATION OF LIVING THINGS (I)

Classification of living things is defined as the grouping of living things according to their similar characteristics.
                        Taxonomy 
Taxonomy is a branch of biology that deals with the classification of all living things. It identifies, categorizes, and names all living things.
The scientists who study taxonomy are called taxonomists.
The first scientist who developed the first system of classification was Carolus Linnaeus (1707-1778).

 Reasons for classification of living things
1. To put every living organism into a systematic order or specific group 
2. For easy identification of similar living things 
3. To show the relationship between different categories of living organisms 
4. To show evolutionary trends in different groups of living organisms 
5. To trace the geographical distribution of living organisms 
6. For easy reference 
7. For easy research or study 
             The taxonomic hierarchy 
Living things are grouped or classified by taxonomists in order of hierarchy from the highest level (Kingdom) to the lowest level (species).
There are seven (7) major groups used in the classification of living things. These are:
1. Kingdom 
2. Phylum(for animals) or Division (for plants)
3. Class 
4. Order 
5. Family 
6. Genus 
7. Species
Note: Species is the basic unit of classification of living things. It contains members with the largest number of features and they interbreed among themselves.
Classification of Human and Lion 
   

	Human	Lion
Kingdom	Animalia	Animalia
Phylum	Chordata	Chordata
Class	Mammalia	Mammalia
Order	Primates	Carnivora
Family	Hominidae	Felidae
Genus	Homo	Panthera
Species	Sapiens	Leo

The binomial system of Nomenclature

The binomial system of nomenclature or Binomial nomenclature is defined as the system of giving two names to an organism a genus and a species name.

The first name is the genus name and it always begins with a capital letter. The second name is the species name which begins with a small letter. These scientific names are written in italics or underlined.
Carolus Linnaeus also invented the binomial system of nomenclature 
Examples of scientific names of some organisms 
1. Man           Homo sapiens 
2. Lion           Panthera leo 
3. Rice           Oryza sativa 
4. Maize        Zea mays                        
                          Kingdom 
The five kingdoms are 
1. Monera
2. Protista 
3. Fungi 
4. Plantae 
5. Animalia                            
                               VIRUS

               Characteristics of virus 
1. A virus is a microscopic organism 
2. It possesses either RNA or DNA 
3. It cannot reproduce by binary fission 
4. It does not have structures used in the synthesis of protein 
5. It does not carry out some life processes such as respiration, feed, excretion, irritability, etc
6. It causes chronic diseases like AIDS, influenza, etc
                 Virus as a living thing 
1. Virus can reproduce when present in another living cell 
2. It contains DNA, RNA or nucleic acid
3. It has a protoplasm or protein coat 
                Virus as non-living thing 
1. The virus exists as a crystal in a non-living medium 
2. It lacks organelles 
3. Virus cannot respire, excrete, or respond to stimulus 
                   KINGDOM: MONERA 
The characteristics of the kingdom Monera.
1. They are microscopic in nature

2. They are either motile or non-motile
3. They are unicellular or single-celled
4. The cells are prokaryotic
5. The cells have no definite nucleus with a nuclear membrane
6. They do not have complex chromosomes.
7. They have no mitochondria, no endoplasmic reticulum, and no chloroplast in their cytoplasm.
8. The cell wall does not contain cellulose but polysaccharides and amino acids.
9. Some are motile while others are non-motile.
10. They reproduce by asexual reproduction ( Binary fission)
11. Some are saprophytic i.e. break down food present in dead organisms and absorb it.
12. They cause dead organisms to decay or decompose.

Monera is divided into two namely:
1. Schizophyta e.g bacteria 
2. Cyanophyta (Blue-green algae) e.g. Nostoc, Oscillatoria, and Anabaena

                     

                     Schizophyta

                 Shapes of bacteria
The four basic shapes of bacteria are:
1. Coccus (spherical or ovoid-shaped)
2. Bacillus (rod-like shaped)
3. Vibrio (comma-shaped )
4. spirilla (spiral or helical-shaped)

KINGDOM: PROTISTA

Characteristics:

1. They are unicellular organisms

2. The organisms are eucaryotic

3. They are either motile or non-motile

4. Some protista are heterotrophic, while some are photosynthetic

5. Mode of reproduction is usually asexual (Binary fission) while some have sexual reproduction  (Binary fusion)

There are four phyla in this kingdom. They are:

1. Protophyta

2. Protozoa

3. Chrysophyta

4. Pyrrophyta

The two major phyla are the protophyta and protozoa.

         Phylum: Protophyta.

1. They are the plant-like protist

2. They have cellulose cell wall

3. They contain the organelle called chloroplast

4. They are found in freshwater while some are found in sea water.

Examples: Chlamydomonas, Diatom, Chlorella.

Note: Diatom is found in sea water and it has hard silica coat.

           Phylum: Protozoa.

1. They are animal-like protist

2. They are microscopic organisms

3. They unicellular organisms 

4. They have no cellulose cell wall

5. They have eucaryotic cells i.e cells with membrane

6. They feed on ready-made food

7. They reproduce asexually by binary fission 

8. They are aquatic organisms while few are parasitic

Examples: Amoeba, Paramecium, Trypanosomes and Plasmodium

        Euglena viridis

1. Euglena has both plant-like and animal-like features

2. It is a microscopic organism

3. It is a unicellular organism

4. It is an aquatic organism

Animal characteristics of Euglena

1. Euglena has flagellum for movement

2. It has gullet for feeding or passage of food materials 

3. It has contractile vacuole for osmoregulation and excretion

4. It has eye spot for detecting light intensity

5. It has pellicle which gives it a definite shape

6. Presence of myonemes which aid movement

7. It undergoes holozoic mode of nutrition in the absence of sunlight

Plant characteristics of Euglena

1. Euglena has chloroplast to carry out photosynthesis

2. It has pyrenoids for storing starch. 

3. Starch is stored in form of paramylum granules

4. It has autotrophic (holophytic) mode of nutrition 

                

                

                    

                        KINGDOM: FUNGI

Characteristics of the kingdom fungi

1. They are eucaryotes i.e their cells have cell membrane.

2. Some are unicellular organisms e.g yeast while others are multicellular organism e.g mushroom

3. They have no true root and shoot system

4. They lack chlorophyll and so cannot make their own food by photosynthesis i.e they are non- green plants

5. They are majorly saprophytes while others are parasites

6. They store excess food in the form of glycogen

7. Their cell walls are made of chitin instead of cellulose

8. They are decomposers

9. The body is made of fine thread-like structures called hyphae (singular: hypha)

10. Fungi reproduce asexually by spore formation 

Examples: Bread mould (Rhizopus nigricans), yeast, mushroom, mucor, mildrews, toad stools

    Bread mould (Rhizopus nigricans)

Note: 

1. The hyphae branch into a complicated network known as the mycelium (plural: mycelia). Mycelium is made up of rhizoids, stolons and sporangiospores. 

2. The hypha contains a thin layer of cytoplasm which is multinucleated (several nuclei). The center of the tube of hypha is occupied by vacuole. Hyphae lack cross walls or septa, and therefore described as non-septate or aseptate.

3. There are three types of specialized hyphae:

(a) Stolons: are unbranched hyphae, which grow horizontally on the substrate.

(b) Rhizoids: are root-like structures. They anchor the fungus into its substrate, release digestive enzymes, and absorb nutrients for the fungus

(c) Sporangiophores: are the upright hyphae which bear round reproductive structures called sporangia (singular: sporangium)

                            Yeast cell

                         MUSHROOM 

 Economic importance of fungi

1. They spoil food

2. They cause diseases especially in crop plants

3. They are important decomposers thereby improving soil fertility

4. They are used in industries that uses fermentation processes e.g wine-making and beer-brewing. Yeast is used in bakeries as a raising agent

5. They are used in producing important antibiotics e.g. penicillin 

6. Some mushrooms are edible and serve as food.