Science Class 12 - Ecology Notes

Ecology

Welcome to the chapter on Ecology for Class 12. In this chapter, you will learn about the interactions between living organisms and their environment, the structure and function of ecosystems, and the importance of biodiversity. By the end of this chapter, you will understand ecological principles and their applications in solving environmental problems.

Introduction to Ecology

Ecology is the study of how living things interact with each other and with their surroundings. It helps us understand the balance of nature and the impact of human activities on the environment.

Levels of Organization in Ecology

• Organism: An individual living being.
• Population: A group of individuals of the same species living in a given area.
• Community: Different populations living together in an area.
• Ecosystem: A community of living organisms interacting with non-living components (like air, water, soil).
• Biosphere: The part of Earth where life exists.

Ecosystem Structure and Function

• Biotic Components: Living things (plants, animals, microorganisms).
• Abiotic Components: Non-living things (sunlight, water, soil, temperature).
• Producers: Green plants that make food by photosynthesis.
• Consumers: Animals that eat plants or other animals.
• Decomposers: Organisms that break down dead matter (bacteria, fungi).

Energy Flow in Ecosystems

• Energy flows from the sun to producers and then to consumers and decomposers.
• Food chains and food webs show how energy moves through an ecosystem.
• Only about 10% of energy is passed from one trophic level to the next (10% law).

Biogeochemical Cycles

• Water Cycle: Movement of water through evaporation, condensation, and precipitation.
• Carbon Cycle: Circulation of carbon among plants, animals, and the atmosphere.
• Nitrogen Cycle: Conversion of nitrogen between its various chemical forms in the environment.
• Oxygen Cycle: Movement of oxygen within and between its three main reservoirs: the atmosphere, the biosphere, and the lithosphere.

Biodiversity and Conservation

• Biodiversity: The variety of life forms in an area.
• Biodiversity is important for ecosystem stability and human survival.
• Conservation efforts include protecting habitats, endangered species, and sustainable resource use.

Human Impact on the Environment

• Deforestation, pollution, and climate change threaten ecosystems.
• Sustainable development aims to balance human needs with environmental protection.
• Environmental awareness and education are key to solving ecological problems.

Practice Questions

1. Define ecosystem and give two examples.
2. What is the difference between a food chain and a food web?
3. Explain the 10% law of energy transfer in ecosystems.
4. List two ways humans impact the environment.
5. Why is biodiversity important?

Challenge Yourself

• Draw a simple food web showing producers, consumers, and decomposers.
• Research a local endangered species and suggest ways to protect it.

Did You Know?

• Tropical rainforests have the highest biodiversity on Earth.
• Wetlands act as natural water filters and flood protectors.

Glossary

• Ecology: The study of interactions between living things and their environment.
• Biodiversity: The variety of living organisms in an area.
• Producer: An organism that makes its own food (usually a plant).
• Consumer: An organism that eats other organisms.
• Decomposer: An organism that breaks down dead material.
• Food Chain: A sequence showing who eats whom in an ecosystem.
• Food Web: A network of interconnected food chains.

Answers to Practice Questions

1. An ecosystem is a community of living organisms interacting with non-living components. Examples: a pond, a forest.
2. A food chain is a single path of energy flow, while a food web shows many interconnected food chains.
3. Only about 10% of energy is transferred from one trophic level to the next; the rest is lost as heat.
4. Deforestation and pollution (any two human impacts).
5. Biodiversity provides stability to ecosystems and resources for humans.

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Understanding ecology helps us protect our planet for future generations!