Here are the answers to all the Very Important Short Questions (2–3 Marks):

Biotic components are all the living organisms present in an ecosystem. They include producers (plants), consumers (animals), and decomposers (bacteria, fungi). These organisms interact with each other and with the abiotic (non-living) environment to maintain the balance of the ecosystem. They are broadly classified into autotrophs, which make their own food, and heterotrophs, which depend on others for nutrition.

A food chain is a linear sequence that shows how energy and nutrients are transferred from one organism to another in an ecosystem. It begins with a producer (green plant), passes through herbivores (primary consumers), then carnivores (secondary and tertiary consumers). For example: Grass → Grasshopper → Frog → Snake → Eagle. Each level in the food chain is called a trophic level, and energy decreases as it moves up the chain.

Fossil fuels are non-renewable energy sources formed from the remains of ancient plants and animals buried under the earth over millions of years under high pressure and heat. The main types are coal, petroleum (oil), and natural gas. They are widely used for electricity generation, transportation, and industrial processes, but their burning releases carbon dioxide and other pollutants, contributing to air pollution and climate change.

Soil erosion is the process by which the top layer of soil is removed or worn away by natural agents such as wind, water, and ice, or by human activities like deforestation and overgrazing. The topsoil is the most fertile layer, so its loss leads to reduced agricultural productivity, landslides, and desertification. Preventive measures include planting trees, contour farming, and building check dams.

Global warming refers to the gradual rise in the average temperature of the Earth's surface due to the increased concentration of greenhouse gases (such as CO₂, methane, and nitrous oxide) in the atmosphere. These gases trap heat from the sun, creating a "greenhouse effect." It leads to melting of polar ice caps, rising sea levels, extreme weather events, and disruption of ecosystems. The primary cause is the burning of fossil fuels and deforestation.

Acid rain is precipitation (rain, snow, or fog) that has become acidic due to the mixing of water vapor in the atmosphere with pollutants like sulfur dioxide (SO₂) and nitrogen oxides (NOₓ), mainly released by factories and vehicles. Its pH is below 5.6. Acid rain damages forests, harms aquatic life by acidifying lakes and rivers, corrodes buildings and monuments, and can also affect human health by contaminating drinking water.

Biodiversity hotspots are regions of the world that are exceptionally rich in species diversity but are also highly threatened by human activities. To qualify as a hotspot, a region must contain at least 1,500 species of endemic vascular plants and must have lost at least 70% of its original habitat. Examples include the Western Ghats of India, the Amazon Rainforest, and the Mediterranean Basin. Protecting these areas is a priority for global conservation.

Renewable resources are natural resources that can be naturally replenished or regenerated over a short period of time through natural processes. Examples include solar energy, wind energy, water (hydropower), biomass, and tidal energy. Unlike fossil fuels, these resources are sustainable and do not get exhausted with use. They are also considered environmentally friendly as they produce little to no pollution during energy generation.

An ecosystem is a functional unit of nature where living organisms (biotic components) interact with each other and with their non-living environment (abiotic components like soil, water, air, sunlight) in a defined area. Ecosystems can be natural (forest, ocean, pond) or artificial (aquarium, crop field). Energy flows through the ecosystem via food chains and food webs, while nutrients are recycled through biogeochemical cycles.

Decomposers are microorganisms, mainly bacteria and fungi, that break down dead organic matter (dead plants, animals, and waste materials) into simpler inorganic substances like carbon dioxide, water, and minerals. This process is called decomposition. Decomposers play a critical role in nutrient cycling by returning essential nutrients back to the soil, making them available for producers again. Without decomposers, dead matter would accumulate and nutrients would not be recycled in the ecosystem.