Short & Long Answer Question - Our Environment

Q1: Define environment?
Ans: The biotic and abiotic factors which surround any living organism are considered its environment. It can be defined as a community of organisms living in a particular place together with the physical elements of that place with which they interact. Such interactions determine the survival, growth and reproduction of organisms.

Q2: What is a food chain?
Ans:

The food chain is the sequence of organisms each of which eats the preceding one. It shows the transfer of energy and nutrients from one organism to another. For example: Grass → Grasshopper → Frog → Snake → Eagle. Producers (plants) form the first link and consumers (herbivores and carnivores) follow.

Q3: Define "biodegradable" and "non-biodegradable" substances. Explain the environmental impact of non-biodegradable waste. Provide examples of each type of waste and their effects on ecosystems.
Ans: Biodegradable substances are materials that can be broken down naturally by biological processes into simpler, non-harmful substances. Examples include food waste, paper, leaves and other organic matter.
Non-biodegradable substances are materials that persist in the environment for long periods and do not break down easily. Examples include many plastics, synthetic fibres, glass, metal and certain chemicals.

Environmental Impact of Non-Biodegradable Waste:
i. Accumulation: Non-biodegradable waste accumulates in the environment, causing visual pollution and blocking drains and waterways.
ii. Soil and Water Contamination: Harmful chemicals from persistent waste can leach into soil and groundwater, reducing soil fertility and polluting water supplies.
iii. Harm To Wildlife: Animals may ingest or become entangled in persistent waste, leading to injury, starvation or death. Marine life is especially vulnerable to plastic pollution.
iv. Microplastics: Large plastic items break down into microplastics that enter food chains and can affect the health of many organisms, including humans.
Examples of Biodegradable and Non-Biodegradable Waste:
Biodegradable: Food scraps, paper, wood and garden waste - these return nutrients to soil when decomposed.
Non-biodegradable: Plastics, synthetic textiles, glass, metal and certain pesticides - these persist and cause pollution, harm wildlife and may enter the food chain.

Q4: What is pollution?
Ans: Pollution is the introduction of substances or energy into the environment that cause adverse changes to air, water, soil or living organisms. Examples include air pollutants from vehicles, chemicals in water, and noise or thermal pollution.

Q5: Explain the effects of human activity on the environment?
Ans: Human activities change the environment in many ways. Some changes are beneficial to people but may harm nature. Examples and effects include:

• Land Clearing: Removing vegetation for agriculture, homes, roads and industry destroys habitats and reduces biodiversity.
• Soil Erosion: Deforestation and over-cultivation remove topsoil, reducing land fertility and increasing runoff.
• Pollution: Emissions from factories and vehicles pollute air and water, harming plants, animals and human health.
• Resource Extraction: Mining and excessive groundwater use deplete resources and can damage ecosystems.
• Urbanisation: Replacing natural areas with cities fragments habitats and alters local climate.
• Conservation Efforts: Positive activities such as protected areas, reforestation and pollution controls can help restore and protect the environment.

Q6: We often observe domestic waste decomposing in the bylanes of residential colonies. Suggest ways to make the residents realise that the improper disposal of their waste is harmful to the environment. 

Ans: To make residents aware that improper waste disposal is harmful, the following measures are useful:
(i) Conduct seminars and workshops explaining health and environmental risks of improper waste disposal.
(ii) Distribute pamphlets, posters and short videos that show simple actions people can take, such as segregation and composting.
(iii) Form an eco-club or residents' committee to organise awareness drives, demonstrations of composting and local clean-up events.

• Improper disposal of waste releases foul odours and harmful gases, making the environment unhygienic.
• Waste washed by rain can reach rivers and lakes, becoming a threat to aquatic life and polluting water bodies.
• Stagnant waste provides breeding sites for mosquitoes and other disease vectors, increasing risk of malaria, dengue and other illnesses.
• Hazardous chemicals in some wastes can enter the soil and harm plants, animals and humans through the food chain.

Q7: What are the after-effects of ozone depletion?
Ans: 

Ozone depletion leads to more ultraviolet (UV-B) radiation reaching the Earth's surface. This can cause:
- Increased skin cancer and sunburn in humans.
- Higher risk of cataracts and other eye damage.
- Suppressed immunity in people and animals.
- Damage to phytoplankton in oceans, affecting the base of many food chains and reducing fish yields.
- Reduced crop productivity and increased damage to terrestrial plants.
For these reasons, ozone depletion is a major environmental concern.

Q8: Why is it necessary to manage our garbage?
Ans: Proper garbage management is essential because it:
- Keeps surroundings clean and reduces the spread of disease.
- Prevents contamination of soil and water.
- Protects wildlife and reduces pests.
- Allows recovery of resources through recycling and composting, reducing pressure on natural resources.

Q9: What happens when higher energy ultraviolet radiations act on the oxygen at the higher level of the atmosphere? 
Ans: When high-energy ultraviolet radiations strike oxygen molecules in the stratosphere, they split O₂ into individual oxygen atoms. These free oxygen atoms are highly reactive and combine with other O₂ molecules to form ozone (O₃). This process helps build the ozone layer that absorbs harmful UV radiation.

Q10: What are the advantages of cloth bags over plastic bags during shopping?
Ans: Cloth bags are better than plastic bags because they:

• Can carry heavier and more items safely.
• Can be reused many times, reducing waste.
• Are made from materials that are biodegradable or easier to recycle.
• Do not cause the same level of pollution as single-use plastic bags.

Q11: Why does following a vegetarian diet help us obtain more energy?

Ans: 

A vegetarian diet helps us obtain more usable energy because we eat directly from plants, which are the primary producers in a food chain. Plants convert sunlight into chemical energy through photosynthesis, so they contain the largest share of the original energy.

According to the 10 percent energy transfer rule, only about 10% of the energy at one trophic level is passed on to the next level. For example, when a herbivore eats a plant it gains only about 10% of the plant's energy; when a carnivore eats that herbivore it gains only about 10% of the herbivore's energy. Each step up the food chain loses most of the energy as heat and metabolic waste.

By eating plants (the first trophic level) we therefore get more of the original solar energy with fewer losses. In contrast, eating animals means consuming energy that has already passed through one or more trophic levels and has been greatly reduced.

Q12:
(a) From the following group of organisms create a food chain which is most advantageous for human beings in terms of energy.
Hawk, Rat, Cereal plant, Goat, Snake, Human being
(b) State the possible disadvantage if the cereal plant is growing in soil rich in pesticides.
(c) Construct a food web using the organisms mentioned above. 

Ans:

(a) A food chain most advantageous for humans in terms of energy is:
Cereal plant → Human being

(b) If the cereal plant grows in soil rich in pesticides, these chemicals are taken up by the plant and enter the bodies of animals and humans that eat the plant. The concentration of such harmful chemicals can increase at higher trophic levels - a process called biological magnification. This can harm non-target species and cause health problems in animals and humans.

(c) Food web using the given organisms:
Cereal plant → Rat → Snake → Hawk
Cereal plant → Goat → Human being
Cereal plant → Human being
Also: Rat → Hawk
This web shows that the cereal plant is eaten by both rat and goat, rats are eaten by snake and hawk, snake is eaten by hawk, and humans may eat goat or cereal directly.

Q13: What is meant by trophic level in a food chain? Construct a terrestrial food chain with trophic levels. The energy flow in a food chain is always unidirectional. Why? 

Ans: A trophic level is any of the successive steps in a food chain where organisms obtain their energy. Each level represents a group of organisms that share the same position in the flow of energy.

Four trophic levels in a terrestrial food chain:
Grass (Producers) → Rabbit (Primary consumer/herbivore) → Wild cat (Secondary consumer) → Tiger (Tertiary consumer)
Energy flow is unidirectional because energy enters as sunlight and is fixed by producers, then passes to consumers. At each transfer a large portion of energy is lost as heat and used for life processes. Energy cannot be recycled back to producers, so it moves in one direction from producers to successive consumers.

Q14: Describe how decomposers facilitate recycling of matter in order to maintain balance in the ecosystem. 

Ans: Decomposers are micro-organisms such as bacteria and fungi that obtain energy by breaking down dead animals and plants. They convert complex organic substances into simple inorganic nutrients (such as mineral salts) that return to the soil. Plants take up these nutrients again, completing the cycle. In this way decomposers recycle matter and help maintain the balance of nutrients in an ecosystem.

Q15: What will happen if we kill all the organisms in one trophic level?

Ans: If all organisms in one trophic level are killed, several consequences follow:

• The population of organisms in the previous trophic level (the level they used as food) will tend to increase due to reduced predation.
• The organisms in the next higher trophic level will lose their food source, causing them to migrate, decline in number or die.
• Such changes produce an ecological imbalance that can lead to collapse of local food chains and loss of biodiversity.

Q16: How is ozone formed in the higher level of the atmosphere? "Damage to ozone layer is a cause of concern". Justify this statement.
Ans: Ozone is formed when high-energy ultraviolet rays from the Sun split oxygen molecules (O₂) into single oxygen atoms (O). These free oxygen atoms then combine with other O₂ molecules to form ozone (O₃). The reaction is:

O + O₂ → O₃ (Ozone)
Ozone depletion is a cause for concern because the ozone layer absorbs much of the Sun's harmful ultraviolet radiation. If the ozone layer is damaged, more UV-B reaches the surface, increasing risks of skin cancer, eye cataracts and immune system suppression in humans. It also harms plants and aquatic organisms at the base of food chains, reducing crop yields and affecting ecosystems. Certain human-made chemicals, such as chlorofluorocarbons (CFCs), accelerate ozone depletion, which is why protecting the ozone layer is important for health and the environment.