Structure and function of ecosystems, food chains, and food webs

1. Introduction to Ecosystems

1. An ecosystem is a functional unit of nature that includes both biotic (living organisms) and abiotic (non-living components) factors.
2. It involves interactions between organisms and their environment.
3. Ecosystems can be classified as natural (forests, lakes) or artificial (aquariums, croplands).

2. Structure of an Ecosystem

1. Each ecosystem consists of biotic and abiotic components.
2. Biotic components include:
   • Producers: Green plants and algae that carry out photosynthesis.
   • Consumers: Animals that depend on plants or other animals for food.
   • Decomposers: Bacteria and fungi that break down organic matter.
3. Abiotic components include:
   • Physical factors: Light, temperature, rainfall.
   • Chemical factors: pH, minerals, oxygen, carbon dioxide.

3. Functions of an Ecosystem

1. Energy Flow: Energy is transferred from the sun to producers and then to consumers.
2. Nutrient Cycling: Nutrients like nitrogen, carbon, and phosphorus are cycled between organisms and the environment.
3. Ecological Balance: Maintains stability through interactions between organisms.

4. Food Chains and Food Webs

1. A food chain is a linear sequence of organisms where energy flows from producers to consumers.
2. Types of food chains:
   • Grazing food chain: Starts with plants (e.g., grass → deer → tiger).
   • Detritus food chain: Begins with dead organic matter (e.g., dead leaves → bacteria → fungi).
3. A food web is a network of interconnected food chains that represent feeding relationships in an ecosystem.
4. Trophic levels: Different levels in a food chain, such as:
   • Primary producers: Plants, algae.
   • Primary consumers: Herbivores (e.g., rabbit).
   • Secondary consumers: Carnivores (e.g., fox).
   • Tertiary consumers: Top predators (e.g., lion).
5. Only 10% of energy is passed from one trophic level to the next, as per the 10% Law of Energy Transfer.

5. Ecological Succession

1. Ecological succession is the gradual process of change in the structure of an ecosystem over time.
2. Two main types:
   • Primary Succession: Occurs in areas where life did not exist before, such as lava flows or newly formed sand dunes.
   • Secondary Succession: Occurs in areas where an existing ecosystem has been disturbed (e.g., after a forest fire).
3. Pioneer species like lichens and mosses are the first to colonize barren areas.
4. The final, stable community in succession is called the climax community.

6. Importance of Ecosystems

1. Provides oxygen through photosynthesis.
2. Regulates climate and water cycles.
3. Supports biodiversity and provides habitats for organisms.
4. Essential for food production and medicinal resources.