CLASSIFICATION OF ORGANISMS
Science
Introduction
- The modern system of classification was developed by Carolus Linnaeus (1707–1788).
- He introduced a scientific system of naming organisms and classified them based on observable characteristics.
- Modern classification is based on genetics, cell structure, mode of nutrition and evolutionary relationships.
Taxonomic Hierarchy
- Domain
- Kingdom
- Phylum
- Class
- Order
- Family
- Genus
- Species
Five Kingdom Classification
All living organisms are divided into five kingdoms:
1. Monera
2. Protista
3. Fungi
4. Plantae
5. Animalia
KINGDOM MONERA
- Includes unicellular, prokaryotic organisms.
- They lack a true nucleus and membrane-bound organelles.
- Cell wall usually made of peptidoglycan.
- Reproduction occurs mainly through binary fission.
- They can be aerobic or anaerobic.
- Nutrition may be autotrophic or heterotrophic.
Examples:
- Archaebacteria
- These are the most ancient organisms.
- They survive in extreme environments such as high temperature, salinity or acidity.
Eubacteria
- Includes most bacteria found today.
- Can be beneficial or pathogenic.
- Includes gram-positive and gram-negative bacteria.
KINGDOM PROTISTA
- Unicellular eukaryotic organisms.
- Mostly aquatic.
- Some have cell walls made of silica.
- Modes of nutrition include autotrophic and heterotrophic.
Examples:
- Protozoa – Amoeba, Paramecium, Plasmodium, Euglena
- Plant-like protists – Diatoms, algae
- Fungus-like protists – Slime moulds
KINGDOM FUNGI
- Eukaryotic organisms.
- Mostly multicellular except yeast.
- Cell wall made of chitin.
- Reproduce by spores.
- Show alternation of generations.
- Nutrition is heterotrophic and absorptive.
Types of Fungi:
- Sac Fungi – Aspergillus
- Club Fungi – Agaricus (mushroom), Puccinia
- Zygote-forming fungi – Rhizopus, Mucor
- Imperfect fungi – Alternaria, Trichoderma
KINGDOM PLANTAE
- Multicellular eukaryotic organisms.
- Autotrophic with chlorophyll.
- Cell wall made of cellulose.
- Non-motile.
- Plants are classified into:
- Cryptogams – non-flowering plants
- Phanerogams – flowering plants
KINGDOM ANIMALIA
- Multicellular eukaryotic organisms.
- Heterotrophic and holozoic nutrition.
- Most animals are motile.
- Body shows tissue and organ system level of organisation.
Major Phyla:
- Porifera – Sponges
- Coelenterata – Jellyfish, Hydra
- Platyhelminthes – Flatworms
- Nematoda – Roundworms
- Annelida – Earthworm, Leech
- Arthropoda – Insects, Crustaceans
- Mollusca – Pila, Octopus
- Echinodermata – Starfish, Sea urchins
- Chordata – Vertebrates including fish, amphibians, reptiles, birds and mammals
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Subject: Science
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