Biology

NIOS Biology Chapter 25 Terminal Exercises

The NIOS Class 12 Biology Principles of Ecology chapter explains the interactions between organisms and their environment. Students study ecosystems, food chains, energy flow, and ecological balance. The chapter also highlights conservation and environmental issues.

Solved terminal exercises provide structured answers for practice and revision. This chapter builds awareness about sustainability and prepares students for both exams and real-world ecological understanding in the NIOS Class 12 Biology curriculum.

NIOS Class 12 Biology Principles Of Ecology

1. What are the three physical life support systems on the planet Earth?

The three life support systems on planet Earth are soil, water, and air.

2. Name the various biotic and abiotic components of the environment

Biotic or Living components include all living organisms found in the environment, including plants, animals, and microorganisms.
Abiotic or Non-living components include the physical (climatic), edaphic (nature of soil), and chemical. For example, temperature, light, pressure, humidity, precipitation, wind, mineral elements of soil, and composition of air. Some of these environmental factors serve as resources (air, soil, and water) while others act as regulatory factors (light, temperature, and pressure, etc).

3. Give the differences between natural and human-modified ecosystems

Ecosystems are classified as natural and human-modified depending upon whether they are fully dependent on solar radiation and other natural sources of energy or on fertilizers and fossil fuels.

Natural ecosystems are such as ponds, lakes, meadows, marshlands, grasslands, deserts, and forests. They are our natural resources and provide us with food, fuel, fodder, and medicines.
Human-modified ecosystems are made and managed by human beings for their better living. Urban ecosystem, rural ecosystem, agro-ecosystems, aquaculture, and spaceship aquarium terrarium are some examples of human-modified ecosystems.

4. Why is the number of trophic levels restricted to four or five in a food chain?

The energy in one trophic level is lower than in the higher levels, and it decreases successively at each level. This is why the number of trophic levels is restricted to 4-5 in a food chain.

5. Give only two differences between the freshwater and marine biomes.

Freshwater biomes have low salt content, while marine biomes have 86% saltwater.
The flora in freshwater biomes is classified into three categories: phytoplankton, floating plants, and rooted plants. In marine biomes, there is a larger biodiversity of flora.
While freshwater biomes have insects and vascular plants, they are completely absent in marine biomes.

6. What will happen if all the floating animals are removed from a lake ecosystem?

The elimination of floating animals in a lake ecosystem increases the number of frogs, fish, etc, as the floating animals or zooplankton are their food.

7. What are the benefits of natural ecosystems?

Natural ecosystems are our natural resources and provide us with food, fuel, fodder, and medicines.

8. Give two differences between energy flow and the biogeochemical cycle in an ecosystem.

The flow of energy in an ecosystem is always linear or one-way. But in the biogeochemical cycle, the nutrients are continuously exchanged between the organisms and their physical environment.
The energy flow decreases with successive trophic levels. Because of the biogeochemical cycles, the nutrients are never lost from the ecosystems.