NIOS Class 12 Environmental Science Chapter 5 Ecosystem

NIOS Class 12 Environmental Science Chapter 5 Ecosystem Solutions to each chapter is provided in the list so that you can easily browse throughout different chapters NIOS Class 12 Environmental Science Chapter 5 Ecosystem Notes and select need one. NIOS Class 12 Environmental Science Chapter 5 Ecosystem Question Answers Download PDF. NIOS Study Material of Class 12 Environmental Science Paper Code 333.

NIOS Class 12 Environmental Science Chapter 5 Ecosystem

Also, you can read the NIOS book online in these sections Solutions by Expert Teachers as per National Institute of Open Schooling (NIOS) Book guidelines. These solutions are part of NIOS All Subject Solutions. Here we have given NIOS Class 12 Environmental Science Chapter 5 Ecosystem Solutions, NIOS Senior Secondary Course Environmental Science Solutions for All Chapter, You can practice these here.

Ecosystem

Chapter: 5

Module 2: Ecological Concepts and Issues

Textual Question Answer

INTEXT QUESTIONS 5.1

1. List the abiotic components of ecosystem.

Ans: Physical, inorganic and organic substance.

2. List the biotic components of ecosystem.

Ans: Producer, consumer and decomposers.

3. What role do decomposers play in an ecosystem? 

Ans: They help in decomposing dead organic material and dead plants and animals therefore they are important for recycling of nutrients.

4. Mention two examples of (i) natural ecosystem (ii) man made ecosystem. 

Ans: (i) Pond, lake, forests, ocean (any two).

(ii) Agriculture, aquaculture.

INTEXT QUESTIONS 5.2

1. What are phytoplanktons?

Ans: Microscopic floating vegetation in an aquatic ecosystem.

2. Where will you search for the decomposers in a pond?

Ans: At the bottom of pond.

3. How do nektons differ from zooplanktons? 

Ans: Zooplanktons are free floating and whereas nektons can aquatic animal can swim and narregate.

4. From where do the fishes living at bottom of the pond get their food? 

Ans: Bottom-dwelling fishes get their food from benthic organisms such as worms, beetles, mites, mollusks, and crustaceans. 

INTEXT QUESTIONS 5.3

1. Draw a simple food chain.

Ans: 

2. What is a food web?

Ans: Food web – Inter connected food chains of an area form a food web.

3. Give examples of an inverted pyramids.

Ans: Pyramid of number in case of a tree or in a pond.

4. Which type of pyramid gives the true picture of trophic structure of an ecosystem?

Ans: Pyramid of energy.

INTEXT QUESTIONS 5.4

1. What is the 10% rule of energy transfer in a food chain? 

Ans: 10% rule is i.e. related to ecological efficiency and states that the amount of energy transferred at each tropic level is only 10% of the energy of the previous tropic level.

2. Give formula of Lindman’s efficiency.

Ans: 

3. What is the significance of studying food chains? 

Ans: Studying food chains is important because they explain how energy and nutrients flow through an ecosystem, show the interdependence of organisms, and highlight effects like biomagnification of pollutants at higher trophic levels. 

INTEXT QUESTIONS 5.5

1. What is a sedimentary cycle? 

Ans: Sedimentary cycle It is a type of biogeochemical cycle where the main reservoir is lithosphere.

2. Give an example of gaseous cycle.

Ans: Nitrogen (N₂) and carbon.

3. Why do forest acts as reservoir? 

Ans: Forests trees have long life and therefore the carbon fixed by them cycles very slowly.

4. Name a symbiotic nitrogen fixing bacteria.

Ans: Rhizobium.

5. What is precipitation? 

Ans: Condensation of water vapours to form clouds.

TERMINAL EXERCISE

1. Define the following terms.

(i) Autotrophs.

Ans: Autotrophs are those organisms that can make their food by themselves. Example – green plants and algae.

(ii) Heterotrophs.

Ans: Heterotrophs are those organisms that cannot make their food by themselves and are dependent on the autotrophs. Example – Humans

(iii) Primary carnivores.

Ans: Primary carnivore is an organism that will eat the herbivore only or eat the other plant-eaters.

(iv) Saprotophs.

Ans: Saprotrophs are organisms that feed/grow upon the detritus/dead material. Example-fungi.

(v) Omnivores.

Ans: Omnivores eat both plants and animals. They obtain nutrients and energy from plant and animal matters and can metabolize them.

2. Give reasons whether the following statements are true or false.

(i) Food chains are more stable than food webs.

Ans: Food web is move stable then the food chain. The predator animal has choices for its prey. The food chain is the linear arrangement of organisms, and a decrease in the population of organisms of one trophic level badly affects the animals of upper trophic levels. The statement is false.

(ii) Pyramids of energy are never inverted where as pyramid of biomass may be inverted.

Ans: Pyramids of energy are upright always. Pyramid of biomass are upright in the terrestrial ecosystem and inverted in the aquatic ecosystem. The statement is true.

(iii) A detritus food chain begins with autotrophs.

Ans: The statement is false. The Detritus food chain always starts with a dead and decaying matter. It aims at the decomposition of the dead matter and recycling of nutrients.

(iv) Phytoplankton is the term applied to floating organisms in a pond.

Ans: The statement is true. The phytoplankton remains suspended in the water. They produce oxygen at a much faster rate than the atmospheric oxygen dissolves into the water in a pond.

(v) Aphotic is the upper zone of a pond.

Ans: Aphotic is present beneath the euphotic zone. A little or no sunlight enters the zone. The statement is false.

3. Give reasons for the following statements:

(i) We see more wall lizards near the tube light during summer.

Ans: Lizards are attracted to their prey bugs.Those bugs are found attracted towards the light.

(ii) Energy pyramids are never inverted.

Ans: The energy pyramid is always upright. The higher trophic level gets only 10% of the energy from the lower trophic level. The producers have the highest energy, and only 10% of total energy from the producers passes into the consumers.

(iii) We can not directly use atmospheric nitrogen.

Ans: Atmospheric nitrogen is converted by biological, physical, and industrial fixation into usable forms like nitrates and nitrites.

(iv) There is higher concentration of carbon dioxide in the aphotic zone.

Ans: The carbon dioxide accumulation occurs in the aphotic zone. There is no sunlight, and hence no vegetation grows. The oxygen concentration is less and has acidic pH.

(v) Food chains have a limited number of steps.

Ans: A food chain represents a linear sequence of producers and consumers, thus. There are limited steps. The Food web connects many food chains, and steps are not limited in the food web.

4. What is an ecosystem? Explain its structural components.

Ans: An ecosystem is a functionally independent unit of abiotic and biotic components of the biosphere.

The components of an ecosystem are producers, consumers, decomposers, and abiotic components. Producers include the green plants. In an aquatic ecosystem, certain algae and phytoplanktons are the producers. Consumers are those organisms that obtain their food from producers. They are divided and primary, secondary, tertiary, as well as quaternary consumers. Primary consumers feed upon the herbivore animals. Secondary consumers eat the primary consumer, and so on. Decomposers are bacteria and fungi. They decompose the dead material. The complex substances are converted into simpler ones. The air, water, and salts are abiotic components.

5. Define decomposers and give their role in sustaining an ecosystem.

Ans: Decomposers are bacteria and fungi. They feed upon the detritus atters. And helps in cleaning the environment. The remains of plants and animals are degraded by the microorganism. The pile-up of animal waste and the residues of plants will occur if decomposers were not in the ecosystem. Nutrients are recycled with the help of decomposers.

6. Why are ecosystems dynamic in nature? Give the various functional components of an ecosystem.

Ans: Continuous changes occur in the ecosystem. The abiotic and biotic components result in the changes, Characteristics of the ecosystem, either terrestrial or aquatic, vary with time. The ecosystem is affected by internal and external factors, Climate is the external factor that affects the population of an ecosystem. The ecosystem comprises biotic and abiotic components. Abiotic components are water, soil, and air. Any change in the quality of soil, water, or air affects the particular ecosystem and causes alterations in it. Biotic components are the plants, animals, and the microorganism. The decreased forest land results in declination in the population of wild animals.

7. What is an ecological pyramid? Define and differentiate between different pyramid of energy and pyramid of numbers.

Ans: An ecological pyramid is a way of representing the trophic levels in graphical forms. The base is made from producers, and then consumers lie above the producers. The pyramid of numbers represents the number of organisms present at a particular trophic level. It can be upright or inverted as well. Inverted when the consumers’ are more than the producers. Example – The caterpillars are feeding on the leaves of a tree. A pyramid of energy shows the flow of energy in an ecosystem. It is always upright.

8. List the various steps of nitrogen cycle in a sequence.

Ans: The steps in the nitrogen cycle are:

(i) Nitrogen fixation: The atmospheric nitrogen is converted into usable forms. It can be fixed either by bacteria, like Rhizobium, Physical agents such as thunderstorms and lightning or by industrial nitrogen fixation.

(ii) Nitrification: The conversion of ammonia into nitrates and nitrites by the bacterium, Nitrosomonas, and Nitrococcus. These are the usable forms of nitrogen for the plants. The Nitrobacter converts the nitrate into nitrites.

(iii) Assimilation: The conversion of nitrogen into proteins and other molecules that make tissues in plants and animals.

(iv) Ammonification: Ammonifying bacteria helps in the conversion of wastes and dead matter into ammonia.

(v) Denitrification: Denitrification is the opposite of nitrogen fixation. Denitrifying bacteria convert the nitrate again into gaseous nitrogen.

9. The following organisms were identified in a pond ecosystem-Spirogyra, Euglena, Hydra, Daphnia, arthropod larvae, bass and sunfish. Make a food web and identify the trophic level of each one of them.

Ans: Bass is at the highest trophic level. Sunfish is a secondary consumer, is at the third trophic level. Arthropod larvae are also secondary consumers. They eat plant-eating insects and are at the third trophic level. Hydra and Daphnia are primary consumers, are at the second trophic level. Spirogyra and Euglena are producers and are at the first trophic level.

Diagram with labelling: