Kingdom Monera: Class 11 and NEET 2025/2026 Notes

 

Overview of Kingdom Monera 

• Definition: Bacteria are the sole members of Kingdom Monera.
• Abundance: Most abundant micro-organisms on Earth.
• Habitats: Found in diverse environments – soil, hot springs, deserts, snow, deep oceans, and as parasites on other organisms.

Classification of Bacteria by Shape

1. Coccus (Cocci): Spherical-shaped bacteria.
2. Bacillus (Bacilli): Rod-shaped bacteria.
3. Vibrio (Vibrios): Comma-shaped bacteria.
4. Spirillum (Spirilla): Spiral-shaped bacteria.

Metabolic Diversity of Bacteria

• Autotrophs: Synthesize their own food from inorganic substrates.
• Photosynthetic Autotrophs: Use sunlight to make food.
• Chemosynthetic Autotrophs: Use chemical reactions to make food.
• Heterotrophs: Depend on other organisms or dead organic matter for food.

Types of Bacteria

1. Archaebacteria

• Habitats: Live in extreme environments such as salty areas (halophiles), hot springs (thermoacidophiles), and marshy areas (methanogens).
• Unique Features: Different cell wall structure allowing survival in extreme conditions.
• Examples:
• Methanogens: Found in the gut of ruminant animals (e.g., cows, buffaloes) and produce methane from dung.

2. Eubacteria

• Characteristics: Presence of a rigid cell wall and flagella (if motile).
• Cyanobacteria (Blue-Green Algae):
• Photosynthetic Autotrophs: Contain chlorophyll a similar to green plants.
• Forms: Unicellular, colonial, or filamentous.
• Habitat: Freshwater, marine, or terrestrial.
• Special Features: Capable of fixing atmospheric nitrogen in heterocysts (e.g., Nostoc, Anabaena).
• Chemosynthetic Autotrophic Bacteria:
• Function: Oxidize inorganic substances (nitrates, nitrites, ammonia) for energy (ATP production).
• Role: Nutrient recycling (nitrogen, phosphorus, iron, sulfur).
• Heterotrophic Bacteria:
• Functions: Decomposition, curd production from milk, antibiotic production, nitrogen fixation in legume roots.
• Pathogenic Bacteria: Cause diseases like cholera, typhoid, tetanus, citrus canker.

Reproduction in Bacteria

• Asexual Reproduction: Mainly by fission.
• Spore Formation: Occurs under unfavorable conditions.
• Primitive Sexual Reproduction: DNA transfer between bacteria.

Mycoplasma

• Characteristics: Lack a cell wall, smallest living cells, can survive without oxygen.
• Pathogenicity: Many are pathogenic to animals and plants. 

Key Terms

• Autotrophic Bacteria: Synthesizes its own food.
• Heterotrophic Bacteria: Depends on external sources for food.
• Chemosynthetic: Uses chemical energy for food production.
• Photosynthetic: Uses light energy for food production.
• Archaebacteria: Bacteria living in extreme conditions.
• Eubacteria: True bacteria, including cyanobacteria.
• Methanogens: Methane-producing archaebacteria.
• Mycoplasma: Smallest living cells, lacking cell walls.

 Also Read: 

    Kingdom PROTISTA - Notes