Get summaries, questions, answers, solutions, notes, extras, PDF and guides for Chapter 2 Biodiversity for Sustenance of Mankind: NBSE Class 12 Environment (Environmental Education) textbook, which is part of the syllabus of students studying under the Nagaland Board. These solutions, however, should only be treated as references and can be modified/changed.
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Summary
Nature maintains a balance. Living things are connected through food chains and food webs, where food and energy pass between them. As energy moves up each step, or trophic level, some is lost. This means higher levels support fewer individuals. Isaac Newton first explained this balance.
Energy and materials flow continuously. Plants, called producers, make food using sunlight, air, and water. Herbivores eat plants, and carnivores eat other animals; these are consumers. When organisms die, decomposers like bacteria and fungi break them down, returning nutrients to the soil for new plants. This cycle keeps nature balanced. Biodiversity, meaning many different kinds of life, is key to this balance. Human activities, however, can disrupt it. As human population and needs grow, nature faces pressure.
Biodiversity is vital for human survival and well-being. It provides basic needs like food, shelter, clothing, and medicines. Many traditional medicines come from plants and animals. For food security, having diverse crops is important. If only one crop type is grown and it gets a disease, much food can be lost. Wild plant relatives have helped save food supplies.
Biodiversity also gives us wood. Fisheries, rich in diverse water life, provide food globally. Nature offers unseen services too. Species depend on each other. A single tree can be a home, clean air, and hold soil. People enjoy nature’s beauty through parks and wildlife watching.
Cultural and religious values also help protect certain plants and animals. We can choose to save nature now for future use. Genetic variety within species is a resource for better crops and new medicines. Nature also helps control pollution, as some organisms clean air, water, and soil.
Using too many resources creates problems. Overpopulation and rising demands lead to resource limitations, meaning not enough for everyone or for nature to recover. Large projects, mining, and converting natural areas to farms or cities destroy biodiversity-rich places. Pollution also harms life. Forest destruction and habitat damage cause species to disappear. This loss of biodiversity can increase poverty and natural disasters. Taking steps to protect biodiversity is necessary.
Textbook solutions
Short Answer Questions
1. Define the term ‘Trophic Level’.
Answer: The term ‘Trophic Level’ refers to the position occupied by each species in a food chain. Trophic levels are also described as steps or divisions of a food chain and are characterised by the method of obtaining food. The number of trophic levels coincides with the number of species in a food chain.
2. Who has given the concept of balance in nature?
Answer: The concept of balance in nature was given for the first time by Issac Newton, who explained it in terms of thermodynamic laws.
3. What do you understand by interaction between living and non-living components?
Answer: I understand that the interaction between living and non-living components means there is a continuous interaction between the living and non-living matter of the environment. For example, green plants or producers make their own food with the help of the physical environment like sunlight, CO2, and water.
4. Why are herbivores and carnivores grouped under consumers?
Answer: Herbivores and carnivores are grouped under consumers because herbivores and other consumers take food from green plants. Higher-level consumers, in turn, take herbivores and other consumers as their food. This process of obtaining food from other organisms categorizes them as consumers.
5. What is option value?
Answer: Option value means that as biodiversity exists in nature, we always have the option of paying now for the future use of nature. For example, we can establish a national park so that we can use and enjoy it later.
Long Answer Questions
1. How is balance in nature maintained with the help of biotic factors? Explain.
Answer: Nature has its own way to keep balance in itself, and this balance is significantly maintained with the help of biotic factors. There is a link between different species in a community made by the pathway of food chains. In the living world, food and energy are passed between species through food chains and food webs. There is a continuous flow of energy and matter from one trophic level to another. Simultaneously, there is a continuous interaction between the living and non-living matter of the environment. For example, green plants or producers, which are biotic factors, make their own food with the help of the physical environment like sunlight, CO2, and water. Herbivores and other consumers, also biotic factors, take food from green plants. Higher-level consumers, in turn, take herbivores and other consumers as their food. After the death of animals and plants, these are decomposed by bacteria and fungi, which are biotic decomposers, thereby increasing soil fertility. Plants again use these minerals when they grow in soil. This continuous flow of food, minerals, and energy throughout nature, facilitated by these biotic interactions, keeps balance in it. In other words, it can be said that biodiversity itself, which encompasses all biotic factors, maintains a balance in nature.
2. How is aesthetic pleasure related with biodiversity?
Answer: Aesthetic pleasure is closely related to biodiversity. The number of people who visit a natural site is an indication of its aesthetic value. For example, lakhs of people visit Sanjay Gandhi National Park, on the outskirts of Mumbai every year, drawn by its natural beauty. Each species and ecosystem, which are components of biodiversity, provides richness and beauty to life on Earth. Millions of people derive aesthetic pleasure from enjoying activities such as camping, picnics, fishing, wildlife watching, and other recreational activities that are based on nature and its diverse life forms. Therefore, the diversity of life contributes significantly to the aesthetic experiences and enjoyment of people.
3. How is human survival related to biodiversity?
Answer: Human survival is related to biodiversity because biodiversity touches almost every aspect of our life, and its degeneration would mean a threat to the survival and sustenance of mankind. The most important value of biodiversity, particularly in developing countries like India, is that it meets basic survival needs of a vast number of people. Man cannot survive without biodiversity. Some traditional communities even today depend wholly or partially on the surrounding natural resources for their day-to-day needs of shelter, clothing, medicines, fertilisers, etc.
4. Describe the decomposition process in nature.
Answer: The decomposition process in nature occurs after the death of animals and plants. These are decomposed by bacteria and fungi, which increases soil fertility. Plants again use these minerals when they grow in soil. This continuous flow of food, minerals, and energy throughout nature, facilitated by decomposition, helps keep balance in it.
5. How is health and healing dependent on biodiversity?
Answer: Most of the people in developing countries depend on traditional methods for primary health care, most of which is derived from plants and some from animal and mineral sources. Nearly one-fourth of all prescription drugs used in the developed world are based on plants, some of which are indispensable like Aspirin from the plant Filipendula ulmaria and quinine from the bark of cinchona tree. Some medicinal plants and animals and their uses include Rauwolfia for hypertension, Cinchona bark for malaria treatment, Poppy plant as an analgesic, Rosy periwinkle plant as an anti-cancer drug, Penicillin as an antibiotic, and Foxglove plant as a heart stimulant. From animal sources, Bacterium provides antibiotics, Blowfly larva is a wound healer, and Sparge is used for leukaemia cure. Today, medical science is also progressing fast by utilising genetic resources, and vaccines and medicines are being produced by genetic engineering.
6. What do you know about resource limitation?
Answer: Major causes of biodiversity loss can be traced, directly or indirectly to the growing demands leading to resource limitations. A few of the factors responsible for this are overpopulation, growing demands, and unplanned development. The human overpopulation has put pressure on biodiversity. Greater demand for food and land, excessive consumption of minerals and other non-renewable resources, and high overuse and waste of energy have aggravated the problem which ultimately resulted in resource limitation.
Some of the main reasons behind resource limitations are:
- Large-scale development projects have contributed substantially to the loss of biodiversity-rich areas.
- The enormous demand for minerals in a rapidly industrialising economy has resulted in large-scale deforestation for mining purposes.
- Large areas rich in biodiversity have been reduced to small pockets due to their conversion to agricultural land or for construction of roads and housing.
- In the last few decades, changing market forces and the increase in demand for food have prompted farmers to change their traditional agricultural practices.
- Pollution of soil, water, and air affects the functioning of ecosystems and may reduce or eliminate sensitive species. For instance, in India, industrial effluents are destroying coral reefs and other marine life.
- Fresh water fish species are threatened because dams and water withdrawals have radically altered river systems.
Resource limitations can be broadly categorised as biological resource limitation, land resource limitation, water resource limitation, and mineral resource limitation. Biological resource limitation is generally associated with extinction of species, with the main reason behind it being the destruction of forests and degradation of habitat. These bring changes in the availability of food and space for normal growth, breeding habit, and movement in animals, thus posing a great threat to them. Land resource limitation is mostly associated with land use pattern; growing demand and modern agronomic practices along with industrialisation pose a great threat to land. Similarly, excessive use of water and minerals and pollution of water through human activities are also the reasons behind these resource limitations.
Think and Answer
Q. Is there any direct relationship between resource limitation and human activity?
Answer: Yes, there is a direct relationship between resource limitation and human activity. Major causes of biodiversity loss can be traced, directly or indirectly, to the growing demands of humans leading to resource limitations. Factors such as overpopulation, growing demands, and unplanned development are responsible for this. Human overpopulation has put pressure on biodiversity. Greater demand for food and land, excessive consumption of minerals and other non-renewable resources, and high overuse and waste of energy by humans have aggravated the problem, which ultimately resulted in resource limitation. Furthermore, excessive use of water and minerals and pollution of water through human activities are also reasons behind these resource limitations.
Project Work & Activity
Take potted plants and observe the effect of light, humidity and water on them for a month. Prepare a report of the conclusions relating them with ecosystem as a whole.
Answer: Do it yourself. Here are the instructions:
For this project, we need to see how light, humidity, and water affect plants over a month and then write a report about it, connecting our findings to the whole ecosystem. Here’s how you can do it:
1. Get Your Plants and Materials:
- Plants: Get 3 or 4 small potted plants. Try to get plants that are the same type and roughly the same size. This makes it easier to compare them.
- Pots: Make sure they all have drainage holes.
- Soil: Use the same type of soil if you’re repotting, or just use them as they are if already potted.
- Watering Can/Measuring Cup: To give specific amounts of water.
- Notebook & Pen: To write down all your observations.
- Ruler: To measure plant height.
- Camera (phone is fine): To take pictures of your plants.
- Locations: You’ll need places with different light conditions.
- (Optional for humidity): A clear plastic bag (large enough to cover a plant without touching it much) or a spray bottle for misting.
2. Set Up Your Experiment:
Label your plants (e.g., Plant 1, Plant 2, Plant 3, Plant 4). You want to change only one thing (variable) for some plants and keep everything else the same.
- Plant 1: The Control Plant
- Light: Place it in a spot with good, bright, indirect sunlight (like near a window but not scorching sun).
- Water: Water it regularly – when the top inch of soil feels dry. Don’t overwater.
- Humidity: Normal room humidity.
- This plant is your baseline to compare others against.
- Plant 2: Testing Low Light
- Light: Place it in a spot with low light (e.g., a shadier corner of a room, further from the window).
- Water: Water it the same way as Plant 1.
- Humidity: Normal room humidity.
- Plant 3: Testing Less Water
- Light: Place it in a spot with good light, similar to Plant 1.
- Water: Water it less often than Plant 1. For example, if you water Plant 1 twice a week, maybe water this one only once a week, or wait until the soil is very dry.
- Humidity: Normal room humidity.
- Plant 4: Testing Humidity (Optional, can be a bit tricky)
- Light: Place it in a spot with good light, similar to Plant 1.
- Water: Water it the same way as Plant 1.
- Humidity: Try to increase humidity. You can do this by:
- Lightly misting the leaves with water once a day.
- Or, placing the pot on a tray filled with pebbles and a little water (make sure the pot bottom isn’t sitting in the water).
- Or, you could try loosely covering it with a clear plastic bag for some part of the day, making sure there’s some air circulation.
3. Observe and Record (For One Month):
- Check your plants daily or every other day.
- In your notebook, for each plant, record:
- Date of observation.
- Height: Measure from the soil level to the top of the plant.
- Leaves: Count them if possible. Note their color (green, yellow, brown, spots?), are they firm or wilting? Any new leaves?
- Stem: Is it strong or weak?
- Overall appearance: Does it look healthy, droopy, vibrant?
- Soil: Note if it’s dry, moist, or wet before you water.
- Amount of water given (if you’re measuring).
- Take photos of each plant once a week from the same angle if possible. This will help show changes over time.
4. Prepare Your Report:
After one month, gather all your notes and photos. Your report should have these parts:
- Title: Something like “The Effect of Light, Water, and Humidity on Plant Growth and its Relation to Ecosystems.”
- Introduction:
- Briefly state the aim of your project (to observe how light, water, and humidity affect plants).
- Mention why plants are important (e.g., they produce food, oxygen).
- Materials Used:
- List everything you used (plants, pots, soil, ruler, etc.).
- Method/Procedure:
- Describe how you set up your experiment. Explain the conditions for each plant (Plant 1, Plant 2, etc.).
- Explain how often you observed and what you recorded.
- Observations and Results:
- Present your findings. You can use a table to show changes in height, leaf count, etc., for each plant over the month.
- Describe the changes you saw in each plant (e.g., “Plant 2 in low light grew taller but its leaves turned pale,” or “Plant 3 with less water started to wilt.”).
- Include your weekly photos, labeled.
- Discussion/Conclusions:
- Analyze your results: What effect did different light conditions have? What about different watering? And humidity (if you tested it)?
- Compare the growth of Plant 2, 3, (and 4) to Plant 1 (the control).
- Relate to the ecosystem as a whole: This is super important!
- Explain that plants need things like sunlight and water (non-living parts of the ecosystem) to make their food (photosynthesis) and grow.
- Discuss how healthy plants contribute to the balance in nature. For example, they provide food for herbivores, shelter for animals, produce oxygen we breathe, help keep soil in place, and even help clean the air.
- Think about what would happen in a real ecosystem if there was a big change in sunlight (e.g., a forest fire clearing trees, or new tall trees shading smaller ones), or water (e.g., a drought or a flood). How would it affect the plants, and then the animals and the whole environment?
- You can mention that biodiversity (lots of different types of plants and animals) helps keep ecosystems stable. If some plants are affected by a change, others might still survive.
- Difficulties/Limitations (Optional):
- Mention any problems you faced (e.g., it was hard to keep humidity constant).
Extras
Questions and Answers
1. What is the basic source of energy for an ecosystem?
Answer: The basic source of energy for an ecosystem is solar energy.
42. Discuss the relationship between reduced biodiversity and increased poverty and frequency of natural disasters.
Answer: Reduction in biodiversity increases poverty in developing countries. Nowadays, the frequency of natural disasters is increasing due to the imbalance in nature. Thus, we must take concrete steps to save our biodiversity.
MCQs
1. What is the maximum number of species a food chain normally contains?
A. Four
B. Six
C. Eight
D. Ten
Answer: B. Six
46. What does ‘sustenance’ mean?
A. Nourishment
B. Extinction
C. Equilibrium
D. Consumption
Answer: A. Nourishment
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