Bihar Board - Class 12 Biology - Chapter 14: Ecosystem Handwritten Notes

An ecosystem is a complex network of living organisms and their physical environment, interacting with each other in a balanced way. It can be as small as a pond or as vast as the entire planet. Ecosystems are made up of biotic (living) components such as plants, animals, and microorganisms, as well as abiotic (non-living) components such as sunlight, air, water, and soil. These elements work together in cycles, exchanging energy and nutrients, which are essential for life to thrive.

Key Points:

Definition of Ecosystem:

• An ecosystem is a system formed by the interaction of living organisms (biotic components) with their environment (abiotic components).
• The two main components are biotic (plants, animals, microbes) and abiotic (water, soil, temperature, air).

Types of Ecosystems:

• Terrestrial Ecosystems: These are land-based ecosystems like forests, deserts, and grasslands.
• Aquatic Ecosystems: These include freshwater ecosystems (lakes, rivers) and marine ecosystems (oceans, seas).

Producers, Consumers, and Decomposers:

• Producers (Autotrophs): These are organisms like plants and algae that produce their own food through photosynthesis.
• Consumers (Heterotrophs): These organisms rely on other organisms for food, and include herbivores (plant eaters), carnivores (meat eaters), and omnivores (both).
• Decomposers: Microorganisms and fungi that break down dead plants and animals, recycling nutrients into the ecosystem.

Food Chain and Food Web:

• A food chain shows a linear flow of energy through an ecosystem, from producers to various levels of consumers.
• A food web is a more complex network of food chains, showing how different organisms are interconnected.

Energy Flow in an Ecosystem:

• Energy from the sun is captured by producers (plants) through photosynthesis and passed through the food chain.
• Only about 10% of energy is transferred to the next trophic level (from producers to herbivores, and so on). The rest is lost as heat.

Nutrient Cycle:

• The carbon cycle, nitrogen cycle, and water cycle are key processes that recycle nutrients in ecosystems.
• Decomposers play a crucial role in returning organic material to the soil, making nutrients available for plants again.

Ecological Succession:

• This is the process by which ecosystems change and develop over time. It occurs in two stages:
• Primary succession (starting from a barren environment, like bare rock).
• Secondary succession (following a disturbance, like a forest fire, where soil remains intact).

Balance in Ecosystems:

• An ecosystem's stability depends on the balance between biotic and abiotic factors. Any disturbance, such as pollution, deforestation, or climate change, can disrupt this balance and affect the health of the ecosystem.

Conclusion:

Ecosystems are essential for sustaining life on Earth, as they provide crucial services like food, clean water, air, and regulating climate. Understanding how ecosystems work helps in protecting and preserving these delicate systems for future generations. Conservation efforts are necessary to maintain the balance within ecosystems, preventing degradation caused by human activities such as pollution, overexploitation, and habitat destruction. A healthy ecosystem is vital for maintaining biodiversity and the well-being of all life forms.