Classification of organism

Classification of organism

Overview

This topic involves application of biosystematics principles. These include identification, classification and nomenclature. It indicates the relationship among organisms basing on their characteristics.

It should be noted that although viruses have nonliving characteristics, they show some characteristics of living things when they are within the living cells of an organism.

General objectives

By the end of the topic, learners should be able to trace the relationships between groups of organisms.

Principle of classification

This is an arrangement of organisms into manageable groups based similarities of their structures or appearance. The branch of chemistry that deals with classification is called Taxonomy.

The smallest unit of classification is the species that include organisms that can interbreed. Similar species make a Genus and the next levels are families, order, classes, phyla and finally Kingdoms.

Nomenclature of organisms.

The system of naming organisms is known as binomial system of nomenclature. Here an organism’s name consists of two names. The first name is a genus name which starts with a capital letter and the second name is a species name which starts with a small letter for example, man is Homo sapiens.

Kingdoms

There are five kingdoms

1. Prokaryote
2. Fungi
3. Protoctista
4. Plantae
5. Mammalia

Viruses

Viruses cannot be classified into any Kingdom because, they are on the borderline between living and non-living things. Viruses are smaller than bacteria and cannot be seen with a light microscope. Viruses are living thing because they contain nucleic acid in form of DNA or RNA.

Viruses are made of two components, that is nucleic acid and protein coat. Most viruses are found in animal cells and those that attach bacteria are called bacteriophage. Viruses have a variety of shapes; i.e. spherical such as poliomyelitis, straight rods such as tobacco mosaic (TMV), or flexible rods such as potato viruses.

A diagram of a typical virus

Transmission of viruses

Viruses cannot reproduce outside animal cell and for this reason ae referred to as obligate parasite. Viruses infect body cell, incorporate their DNA into the host DNA and manipulate the cell to synthesize the viruses. Sometimes incorporation of Virus DNA into host DNA or transduction result into new characteristics in the hosts such as antibiotic resistance in bacteria.

Economic importance

1. Viruses cause diseases to plants such as tobacco bright and tomato mosaic by (TMV)
2. Viruses caThe kingdom contains cyanobacteria (blue-green bacteria) and bacteria that are unicellular.Blu-green algae photosynthesize and are capable of fixing nitrogen.Bacteria are classified into gram positive bacteria when their cell wall is stained by gentian violet or gram negative when their cell walls are not stained by gentian violet. Gram negative bacteria are more susceptible to antibiotics than gram negative bacteria.Bacteria are generally distinguished by their shapes, i.e.,
   • Cocci are spherical. Cocci may stick together in chains or streptococci or in clusters or staphylococci,
   • Bacilli are rod shaped
   • Spirilla are spiral shaped (illustrations)

   Common bacterial disease

   use diseases to animals as rabies, flue, polio, HIV and cancers.

3. May lead to antibiotic resistance by bacteria.
4. Used in genetic engineering.

Control of the spread of viral disease

1. Burning infected plants
2. Abstinence or use of a condom to prevent HIV
3. Quarantine for highly infectious virus such small pox.
4. Vaccination
5. Viral diseases are difficult to treat because viruses are continuously changing.

Common bacteria diseases

• For plants
• Bacteria on a plant and fruit

• 

• Bacteria for animals

Importance of bacteria

1. Cause decay and recycling of matter
2. Symbiotic bacteria in intestine synthesize vitamin B12 while those I herbivores produce enzyme cellulase to digest cellulose.
3. Food production: cheese, yoghurt and vinegar, etc.
4. Manufacturing process. E.g. making soap powder, tanning leather.
5. Used in genetic engineering to make useful material.

1. Characteristics
   1. Have no chlorophyll; do not photosynthesize.
   2. Heterotrophic
   3. Cell wall contain chitin rather than cellulose
   4. Body usually a mycelium
   5. Carbohydrates stored as glycogen
   6. Reproduction by means of spores without flagella

Parts of Rhizopus

Parts of mushroom

Economic importance of fungi

Beneficial

1. Decompose and recycle organic matter
2. Production of antibiotics e.g. penicillin
3. Production of alcohols
4. Baking e.g. yeast

Nonbeneficial

1. Cause diseases e.g. ringworm,
2. Food decay

Kingdom Protoctista

The kingdom Protoctista consists of eukaryotic organisms which are assemblages of similar cells. It includes algae, all protozoa and slime moulds.

Characteristics

1. Have no stems, roots or leaves
2. No sclerenchyma
3. No vascular tissue
4. No archegonia

Have other photosynthetic pigments in addition to chlorophyll

Structure of Spirogyra

Reproduction

Asexual reproduction by fragmentation

Sexual reproduction by conjugation

Stages of conjugation in spirogyra

Economic advantage of algae

1. Primary producer
2. Food
3. Provide oxygen in water through photosynthesis.
4. Alginic acid derivatives are used as thickener in foo, cosmetic and drug industry.

Algal bloom cause water to smell and may lead to depletion of oxygen and death of fish.

WATCH THIS VIDEO ON KINGDOM PROTISTA

Kingdom plantae

Characteristics

• Are made of more than one eukaryotic cell.
• Have cell wall containing cellulose
• Have chlorophyll as their main photosynthetic pigment.

Phylum Bryophyta(moss)

1. It is made of small plants generally found in moist terrestrial habitats
2. They have no root and no vascular tissue
3. Show alternation of generation in which the sporophyte and gametophytes are almost equally conspicuous, although the sporophyte is attached to and depends on, gametophyte throughout life.

WATCH THIS VIDEO ON KINGDOM OF PLANTAE  

Parts of a moss

Phylum Filicinophyta (ferns)

Ferns have large leaves with chlorophyll called fronds which are coiled in bud.

Have roots and well developed vascular systems.

Cross section of fern rachis

Phylum Angiospermophyta: Flowering plants

They are made of two classes, monocotyledoneae (monocotyledonous plants) and dicotyledoneae (dicotyledonous plants).

Comparison of monocotyledonous plants and dicotyledonous plants.

Coniferous plant

Economic importance of plants

1. For decoration
2. For food, timber, medicine, raw materials for industries (fruits juices), fibre producing plants (sisal, hemp, cotton)

Kingdom Animalia

The organism included in this kingdom are non-photosynthetic multicellular organism with nervous coordination.

Phylum protozoa

Examples; amoeba, Euglena, paramecium and trypanosome

Characteristics

1. they are single celled.
2. they are microscopic
3. they reproduce by means of binary fission.
4. they move by pseudopodia (amoeba), cilia (paramecium) or flagella (euglena)
5. reproduce by binary cell division or by cell fission

Economic importance

• Entamoeba histolytica cause amoebic dysentery
• They feed and control other disease-causing organisms e.g. bacteria

Economic importance: source of food to other aquatic organisms

Plasmodium

Causes malaria and transmitted by female anopheles mosquito

Life cycle of plasmodium

Prevention of malaria

• Sleeping in mosquito net.
• Using mosquito replant
• Draining stagnant water
• Using insecticide
• Treatment of malaria

MALARIA LIFECYCLE ONE

MALARIA LIFECYCLE TWO

Phylum Platyhelminthes (Flatworms)

Characteristics

1. their bodies are flat with distinct head.
2. they are parasitic
3. are hermaphrodite (have both sexes)
4. They are triploblastic with a body wall composed of an outer epidermis and inner gastrodermis separated by a relatively undifferentiated region of mesoderm called mesenchyme.

They are subdivided into three classes

1. Turbellaria: these are carnivorous flat worms found in flesh water, streams and ponds. It remain under water during day and comes out to feed at night e.g. planarian
2. Trematoda; are generally endo or ecto-parasites e.g. fasciola hepatica or liver fluke is a parasite found in the liver. Blood fluke cause bilharzi