8th, Chapter 1: Living World and Classification of Microbes.

1. Biodiversity and Biological Classification  

Biological Classification: The process of dividing living organisms into groups and subgroups based on their similarities and differences.

👍Total Species: According to the 2011 census, around 87 million species of living organisms exist on Earth (land and sea).

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✍🏻 Historical Background:

• 1735 (Carl Linnaeus): Divided living world into 2 kingdoms – Vegetabilia and Animalia.
• 1866 (Haeckel): Created 3 kingdoms—Protista, Plants, and Animals.
• 1925 (Chatton): Created 2 main groups—prokaryotes and eukaryotes.
• 1938 (Kopland): Divided organisms into 4 kingdoms—Monera, Protista, Plants, and Animals.

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2. Whittaker's Five Kingdom System

In 1969, American ecologist Robert Harding Whittaker divided living organisms into 5 kingdoms using five primary criteria:

Criteria

1. Cell Complexity: Prokaryotic or Eukaryotic

2. Organism Complexity: Unicellular or Multicellular

3. Mode of Nutrition: Plants: Autotrophic (Photosynthetic) 

Fungi: Saprophytic (absorption from dead matter) 

Animals: Heterotrophic and ingestive

4. Lifestyle 

• Producers: Plants 
• Consumers: Animals 
• Decomposers: Fungi

5. Phylogenetic Relationship 

Prokaryotic to Eukaryotic; Unicellular to Multicellular

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👉Kingdom Classification:

Kingdom 1: Monera – 

• All organisms are unicellular and prokaryotic (lack a well-defined nucleus or cell organelles).
• Can be autotrophic or heterotrophic.

e.g., 

• Lactobacilli, 
• Streptococcus,
• pneumoniae, 
• Salmonella typhi.

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Kingdom 2: Protista – 

• Single-celled (unicellular) eukaryotes with a well-defined nucleus enclosed in a nuclear membrane.
• Possess organs for locomotion like pseudopodia, cilia, or flagella.
• Autotrophs: Euglena, Volvox (contain chloroplasts); 
• Heterotrophs: Amoeba, Paramoecium.

e.g., 

• Amoeba, 

Paramoecium

Euglena, 

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Kingdom 3: Fungi – 

1. Unicellular
2. Multicellular 
3. Non-green, eukaryotic, 
4. heterotrophic, saprophytic (feed on decaying organic matter).
5. The cell wall is made up of a tough and complex sugar called chitin.

e.g., 

• Baker's yeast, 
• Aspergillus, 
• Penicillium, 
• mushrooms.

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Kingdom 4: Plantae—

• Multicellular, 
• Eukaryotic, 
• Autotrophic with cell walls.

e.g., all green plants.

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Kingdom 5: Animalia—

• Multicellular, 
• Eukaryotic, 
• Heterotrophic without cell walls.

e.g., all insects, animals 

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Measurement Units:

1 m = 10 ⁶ µm मायक्रोमीटर 

1 m = 10⁹ nm  

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Microbe Groups:

1. Bacteria

• size: 1 µm to 10 µm
• Unicellular, prokaryotic,
• reproduce by simple binary fission.
• Can double their number in 20 minutes in favorable conditions.
• Shapes: Coccus, Cocco-bacillus, Bacillus, Vibrio (comma-shaped), and Spirillum.

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2. Protozoa 

1. Size: approx. 200 µm 
2. Unicellular eukaryotes,
3. found in soil, fresh water, and seawater.
4. Examples: Amoeba, Paramoecium (free-living); 
5. Entamoeba histolytica (causes amoebiasis); Plasmodium vivax (causes malaria).

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3. Fungi 

• Size: 10 µm to 100 µm 
• Eukaryotic, saprophytic; 
• reproduce sexually and asexually (cell division or budding).

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4. Algae 

1. Size: 10 µm to 100 µm 
2. Aquatic, eukaryotic, 
3. unicellular/multicellular 
4. autotrophs performing photosynthesis via chloroplasts.
5. Examples: Chlorella, Chlamydomonas.

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5. Viruses 

• Size: 10 nm to 100 nm
• Not considered living organisms; considered at the edge of living and non-living.
• 10 to 100 times smaller than bacteria (visible only under electron microscopes).
• Composed of a long molecule of DNA or RNA covered by a protein coat.
• Survive only inside living plant or animal host cells.
• Viruses cause many diseases to plants and animals.

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Important Note / Institutional Work:

National Institute of Virology (NIV), Pune: Established in 1952 under the Indian Council of Medical Research (ICMR) for research on viruses.

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1. Human—polio virus, influenza virus, HIV/AIDS virus, etc.
2. Cattle- picorna virus
3. Plants—Tomato—Wilt virus, Tobacco mosaic virus, etc.
4. Bacteria—Bacteriophage (viruses attack bacteria).

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