Food chains, food webs, ecological pyramids, biodiversity

1. Food Chains

A food chain is a linear sequence of organisms through which energy and nutrients flow.
It consists of different trophic levels: producers, consumers, and decomposers.
Producers (autotrophs) create food through photosynthesis (e.g., plants, algae).
Primary consumers (herbivores) feed on producers (e.g., deer, rabbits).
Secondary consumers (carnivores) feed on primary consumers (e.g., snakes, frogs).
Tertiary consumers (top predators) feed on secondary consumers (e.g., tigers, eagles).
Decomposers (bacteria, fungi) break down dead organisms and recycle nutrients.
Food chains are usually short due to energy loss at each level.
Example of a simple food chain: Grass → Grasshopper → Frog → Snake → Eagle.

A food web is a complex network of interconnected food chains.
It shows how organisms have multiple feeding relationships.
More stable than a food chain, as energy can flow through multiple pathways.
Example: In a forest, a rabbit may be eaten by a fox or an eagle.
Disruption in a food web (e.g., species extinction) can impact ecosystem balance.

An ecological pyramid is a graphical representation of the structure of an ecosystem.
Three types of ecological pyramids:
- Pyramid of Number: Shows the number of organisms at each trophic level.
- Pyramid of Biomass: Represents the total mass of organisms at each level.
- Pyramid of Energy: Illustrates energy flow from producers to top consumers.
Energy pyramids are always upright due to the loss of energy at each level.
Biomass pyramids may be inverted in aquatic ecosystems (e.g., phytoplankton).

Biodiversity refers to the variety of life forms in an ecosystem.
It includes genetic diversity, species diversity, and ecosystem diversity.
High biodiversity increases ecosystem stability and resilience.
Hotspots are regions rich in biodiversity but threatened by human activities (e.g., Western Ghats, Himalayas).
Threats to biodiversity: deforestation, habitat destruction, pollution, climate change.
Conservation efforts: national parks, wildlife sanctuaries, afforestation.