Get summaries, questions, answers, solutions, notes, extras, PDF and guide of Chapter 2 Energy Flow and Its Balance, NBSE Class 9 Environmental Education textbook, which is part of the syllabus of students studying under Nagaland Board. These solutions, however, should only be treated as references and can be modified/changed.
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Summary
Energy is the foundation of life on Earth. The Sun is the main source of energy. All living things get their energy directly or indirectly from the Sun. Energy moves through ecosystems in a process called energy flow. This flow happens along food chains and food webs. It follows the laws of thermodynamics and moves in one direction only. Energy flows from the Sun to producers like plants, then to consumers like animals.
Plants are the first step in the energy flow. They use sunlight to make food through photosynthesis. This process stores energy in their cells. Plants also release oxygen as a by-product. Animals that eat plants are called herbivores. They are the second step. Herbivores are also called primary consumers. Animals that eat herbivores are called carnivores. Carnivores are secondary consumers. Some carnivores eat other carnivores. These are tertiary consumers. Decomposers like bacteria and fungi break down dead plants and animals. They return nutrients to the soil.
Energy decreases as it moves up the food chain. Only 10% of energy moves to the next level. The rest is lost as heat. This means higher-level consumers get less energy. Food chains cannot have more than five or six levels because energy runs out. Energy flow helps maintain balance in nature. It shows how all living things depend on each other.
A food chain explains who eats whom in an ecosystem. It starts with producers and ends with decomposers. A food web is made of many interconnected food chains. Food webs show how organisms interact. Nutrients move in cycles. The main cycles are oxygen, carbon, nitrogen, and water. Oxygen is used by animals and released by plants. Carbon moves between living things and the air. Nitrogen is fixed by bacteria and returned to the air. Water moves through evaporation, condensation, and precipitation.
Nature stays balanced when biotic and abiotic parts work together. Biodiversity helps maintain this balance. Human activities like pollution and deforestation can disturb it. Disturbances can harm ecosystems. Protecting nature is important to keep the balance. Steps include protecting habitats and reducing pollution. Understanding energy flow and nutrient cycles helps us care for ecosystems.
Energy flow and nutrient cycles are key to life. Plants, animals, and decomposers all play roles in these processes. Food chains and food webs show how energy moves. Nutrient cycles explain how elements like oxygen, carbon, and nitrogen are reused. Balance in nature depends on these interactions. Humans must take action to protect ecosystems for future generations.
Video tutorial
Textbook solutions
Multiple Choice Questions (MCQs)
1. ……………….is the primary source of energy in all ecosystems.
(a) Soil (b) Water (c) Sunlight (d) None of these
Answer: (c) Sunlight
2. Without the transfer of energy there could be no life and no ecosystem.
(a) True (b) False
Answer: (a) True
3. Transfer of energy at trophic levels and linking of trophic levels is called
(a) Food web (b) Food chain (c) Symbiosis (d) None of these
Answer: (b) Food chain
4. Animals that obtain their energy by eating plants only are called
(a) Omnivores (b) Carnivores (c) Herbivores (d) None of these
Answer: (c) Herbivores
Very Short Answer Questions
1. Define food chain.
Answer : A food chain explains which organism eats another organism in the environment. It is a linear sequence of organisms where nutrients and energy is transferred from one organism to the other. It begins with the producer organism, follows the chain and ends with the decomposer organism. The food chain also explains the feeding pattern or relationship between living organisms.
2. What do you understand by food web?
Answer : Several interconnected food chains form a food web. A food web is similar to a food chain but it is comparatively larger than a food chain. Occasionally, a single organism is consumed by many predators or it consumes several other organisms. Because of this, many trophic levels get interconnected and the food chain fails to showcase the flow of energy in the right way. But, the food web is able to show the proper representation of energy flow, as it displays the interactions between different organisms.
3. What is nutrient cycle?
Answer : Nutrient cycling is a cyclic process that encompasses the movement of nutrients from the physical environment to living organisms and back to the environment. Nutrients are present on the earth where they are recycled, transformed into different forms and reutilized.
4. What is hydrological cycle?
Answer : Water is an essential element for life to exist on earth. Water from oceans, lakes, rivers and other reservoirs is continuously converted to vapour by the process of evaporation and transpiration from the surface of plants. Water vapours get condensed and return by precipitation and the cycle continues. The water falling on the ground is absorbed and stored as groundwater.
5. Give a brief description of oxygen cycle.
Answer : Oxygen is essential for life. Aquatic organisms are dependent on oxygen dissolved in water. Atmospheric oxygen is taken up by living organisms in the process of respiration and release carbon dioxide which is used for photosynthesis by plants. Photosynthesis is the main source of oxygen present in the atmosphere. It is required for decomposition of biodegradable waste products.
6. What do you understand by the balance in nature?
Answer : Balance in nature means interaction between biotic and abiotic components in equilibrium. Ecological balance plays a crucial role in an ecosystem. It describes the state in which the various organisms and their habitats interact with each other in a harmonious system. Biodiversity is a key element in maintaining the ecological balance. This delicate balance is based on complex interactions and dependencies between species and their environment. This system is maintained by complex food webs and chains.
Short Answer Questions
1. What do you mean by energy flow?
Answer : Flow of energy that occurs along a food chain is called energy flow. It involves the transfer of energy from one organism to another, primarily through food. This flow is governed by the laws of thermodynamics. It is unidirectional from the Sun to producers and then to consumers, sustaining life.
2. Give two features of the producers in an ecosystem.
Answer : (i) In this stage or level, the sunlight is converted into chemical energy. This energy remains stored in the cells.
(ii) The chemical energy is formed through the process of photosynthesis.
3. Define food web. Give some examples also.
Answer : A food web is similar to a food chain but it is comparatively larger than a food chain. Occasionally, a single organism is consumed by many predators or it consumes several other organisms. Because of this, many trophic levels get interconnected and the food chain fails to showcase the flow of energy in the right way. But, the food web is able to show the proper representation of energy flow, as it displays the interactions between different organisms.
Examples:
(i) Grass → Rats → Hawk
(ii) Grass → Grasshopper → Insects
4. Mention two roles of decomposers in an ecosystem.
Answer : (i) They act as environmental cleaners by decaying dead plants and animals.
(ii) They aid in the recycling of nutrients.
5. What is photosynthesis?
Answer : Photosynthesis is the process in which sunlight is converted into chemical energy. This energy remains stored in the cells. The chemical energy is formed through the process of photosynthesis. The most important by-product of this process is the oxygen which is used by all organisms.
6. What do you understand by loss of energy in trophic levels?
Answer : When energy is transferred from one level to another, only 10% is passed to the next higher trophic level. Remaining 90% is released to the environment. There is a continuous decline in the energy as it transfers from one trophic level another throughout the food chain. It means that longer the food chain, lesser the amount of energy available to the last recipient.
7. Briefly describe the energy flow in first trophic level.
Answer : In this stage or level, the sunlight is converted into chemical energy. This energy remains stored in the cells. The chemical energy is formed through the process of photosynthesis. The most important by-product of this process is the oxygen which is used by all organisms. Plants are the first link of the food web; therefore, they are also called primary producers.
8. Why the flow of energy is important to an ecosystem?
Answer : Energy flow is the phenomenon that is responsible to sustain life on this planet. All the biotic components in this ecosystem need energy for their survival. If the energy flow in an ecosystem is disturbed, then it leads to ecological imbalance. It is vital for all living things in ecosystem to survive and function properly. It helps us to understand who eats whom in nature. More the diversity of organisms more stable the ecosystem is. It shows how all creatures in an ecosystem depend on each other and how changes can affect each other. It helps us to see how human actions are affecting the ecosystem. Understanding the flow of energy in an ecosystem helps us to devise proper conservation techniques to save the ecosystem.
Long Answer Questions
1. Explain the process of energy flow through trophic levels.
Answer: Flow of energy that occurs along a food chain is called energy flow. It involves the transfer of energy from one organism to another, primarily through food. It is unidirectional from the Sun to producers and then to consumers, sustaining life.
First Trophic Level: This is the first stage of energy flow. In this stage or level, the sunlight is converted into chemical energy. This energy remains stored in the cells. The chemical energy is formed through the process of photosynthesis. The most important by-product of this process is the oxygen which is used by all organisms. Plants are the first link of the food web; therefore, they are also called primary producers.
Second Trophic Level: In the second trophic level, many animals and insects feed on the plants. Thus, the energy is transferred from plants to animals eating them. This way the energy is transferred from the first trophic level to the second trophic level. Animals that obtain their energy solely by eating plants are known as herbivores. They are also called the primary consumers because they are the first to consume energy generated by plants or primary producers.
Third Trophic Level: The third trophic level is made by the animals that feed on the herbivores. They are flesh-eating animals and are called carnivores. This way the energy is transferred from the second trophic level to the third trophic level. Animals of this trophic level are called secondary consumers because they are feeding on the herbivores who have already consumed energy from plants.
Fourth Trophic Level: The fourth trophic level is also made up of carnivores. These animals feed on other carnivores. The energy is transferred from the third trophic level to the fourth trophic level. Animals of the fourth trophic level are called the tertiary consumers.
Fifth Trophic Level: The fifth trophic level is made up of decomposers which include microorganisms like bacteria and fungi. They break down the dead and decaying matter into nutrients that can be used again. Decomposition of food, in fact, can take place at other trophic levels also. Thus, they are capable of receiving energy from all types of plants as well as animals. They also supply energy to all the organisms at all levels.
2. No energy transfer is 100% efficient. Discuss.
Answer: When energy is transferred from one level to another, only 10% is passed to the next higher trophic level. Remaining 90% is released to the environment. The primary producers, therefore, receive maximum energy and carnivores at the fourth level receive minimum energy. There is a continuous decline in the energy as it transfers from one trophic level to another throughout the food chain. It means that the longer the food chain, the lesser the amount of energy available to the last recipient. This way the food chain cannot be more than five or six levels. Herbivores, therefore, get more energy than the carnivores.
3. What is food chain? Explain with examples.
Answer: A food chain explains which organism eats another organism in the environment. It is a linear sequence of organisms where nutrients and energy is transferred from one organism to the other. It begins with the producer organism, follows the chain and ends with the decomposer organism. The food chain also explains the feeding pattern or relationship between living organisms. Trophic level refers to the sequential stages in a food chain, starting with producers at the bottom, followed by primary, secondary and tertiary consumers.
Examples of Different Food Chains:
(i) Food chain of a typical Grassland (Terrestrial food chain): Grass → Insects → Frogs → Snakes → Hawk/Otter.
(ii) Forest food chain (Terrestrial food chain): Forest vegetation → Deer → Lion.
(iii) Freshwater food chain (Aquatic food chain): Aquatic plants/phytoplanktons → Small fish → Large fish → Egret.
(iv) Marine (Aquatic) food chain: Bull kelp → Sea-urchin → Gray whale → Orca.
4. What is nutrient cycle? Discuss hydrological cycle in detail.
Answer: Nutrient cycling is a cyclic process that encompasses the movement of nutrients from the physical environment to living organisms and back to the environment. Nutrients are present on the earth where they are recycled, transformed into different forms and reutilized.
Water is an essential element for life to exist on earth. Water from oceans, lakes, rivers and other reservoirs is continuously converted to vapour by the process of evaporation and transpiration from the surface of plants. Water vapours get condensed and return by precipitation and the cycle continues. The water falling on the ground is absorbed and stored as groundwater.
5. Write a detailed note on the ‘balance in nature’.
Answer: Balance in nature means interaction between biotic and abiotic components in equilibrium. Ecological balance plays a crucial role in an ecosystem. It describes the state in which the various organisms and their habitats interact with each other in a harmonious system.
Biodiversity is a key element in maintaining the ecological balance. This delicate balance is based on complex interactions and dependencies between species and their environment. This system is maintained by complex food webs and chains. If this balance is disturbed, whether by human activity or natural events, serious consequences can occur for the entire ecosystem. Disturbances can spread like an echo through the food chains, causing further damage. Pollution, climate change and habitat destruction are just some of the man-made factors that exacerbate these disturbances. Human activities like deforestation or pollution are increasingly endangering this sensitive ecosystem.
Extras
Additional questions and answers
1. What is energy flow?
Answer: Flow of energy that occurs along a food chain is called energy flow. The energy flow of an ecosystem is essential for ecological balance. It involves the transfer of energy from one organism to another, primarily through food.
67. Define a food chain. What are the major components of a food chain?
Answer : A food chain explains which organism eats another organism in the environment. It is a linear sequence of organisms where nutrients and energy is transferred from one organism to the other. It begins with the producer organism, follows the chain, and ends with the decomposer organism. The food chain consists of four major parts, namely: The Sun, which is the initial source of energy providing energy for everything on the planet; Producers, which include all autotrophs such as phytoplankton, cyanobacteria, algae, and green plants; Consumers, which contain almost all living organisms i.e., herbivores, carnivores, parasites, and lastly the scavengers; and Decomposers, which act as environmental cleaners by decaying dead plants and animals and aid in the recycling of nutrients.
Additional MCQs
1. What is the ultimate source of energy for all living organisms?
A. Soil
B. Water
C. Sunlight
D. Air
Answer: C. Sunlight
38. What aspect of a food web makes an ecosystem more sustainable?
A. Linear energy flow
B. Complex interactions
C. Limited connections
D. Fixed trophic levels
Answer: B. Complex interactions
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