Class 7 Science Forests Our Lifeline Worksheets
FAQs on Class 7 Science Forests Our Lifeline Worksheets
1. What are some of the most important 3-mark questions that can be asked from the CBSE Class 7 Science chapter 'Forests: Our Lifeline' in the 2025-26 exam?
For the Class 7 Science exam, some frequently asked 3-mark questions from 'Forests: Our Lifeline' focus on core concepts. Students should prepare for questions such as:
- Explain how forests help in preventing soil erosion and regulating the flow of water.
- Describe the role of decomposers in a forest ecosystem.
- List three important products we obtain from forests, other than wood.
- Explain why forests are often called 'dynamic living entities'.
2. Explain the statement: ‘There is no waste in a forest’. How do decomposers contribute to this natural process?
The statement ‘There is no waste in a forest’ highlights the perfect recycling system of nature. Everything is reused. Decomposers, such as fungi and bacteria, play a crucial role. They break down dead organic matter like fallen leaves, dead animals, and animal waste. This process converts the complex organic substances into simple, nutrient-rich soil called humus. These nutrients are then absorbed by the roots of living plants, completing the cycle. Thus, nothing is wasted; it is simply recycled.
3. Why are forests considered the 'green lungs' of our planet? Explain the process and its importance.
Forests are called 'green lungs' because they perform a function similar to our lungs but on a global scale. Through the process of photosynthesis, plants and trees in the forest absorb carbon dioxide (CO₂) from the atmosphere and release oxygen (O₂), which all living beings need for respiration. This vital process helps to:
- Purify the air by removing harmful CO₂.
- Maintain the balance of oxygen and carbon dioxide in the atmosphere.
- Combat global warming by absorbing a major greenhouse gas.
4. How are plants and animals in a forest interdependent? Illustrate with an example of a simple food chain.
Plants and animals in a forest share a relationship of deep interdependence for survival.
Plants provide:
- Food: Herbivores eat plants to get energy.
- Shelter: Trees and shrubs provide homes for birds, insects, and other animals.
- Oxygen: Released during photosynthesis for animals to breathe.
- Pollination: Insects and birds help in the pollination of flowers, leading to fruit and seed formation.
- Seed Dispersal: Animals eat fruits and disperse seeds to faraway places, helping in the growth of new plants.
- Nutrients: Animal waste and their decomposition add essential nutrients to the soil.
5. What would be the long-term consequences if a large forest area is cleared for building a factory? (HOTS)
Clearing a large forest area, an act known as deforestation, would have severe long-term consequences:
- Climate Change: With fewer trees to absorb CO₂, the amount of this greenhouse gas in the atmosphere would rise, contributing to global warming.
- Soil Erosion and Floods: Tree roots bind the soil. Without them, heavy rain would wash away the topsoil, leading to soil erosion and increasing the risk of flash floods downstream.
- Loss of Biodiversity: Countless species of plants and animals would lose their habitat, leading to a decrease in biodiversity and potential extinction.
- Disruption of Water Cycle: Forests play a key role in the water cycle through transpiration. Their absence would lead to reduced rainfall and could result in droughts in the region.
6. For a 5-mark question, how would you describe the different layers of a forest?
A forest is typically structured in several vertical layers, each with its own unique set of plants and animals. The main layers are:
- Canopy: This is the topmost layer, formed by the crowns of the tallest trees. It receives the most sunlight. Animals like monkeys, eagles, and various birds are found here.
- Understorey: This layer is found beneath the canopy and consists of smaller trees, shrubs, and young trees that are tolerant of shade. Animals like leopards, deer, and various insects inhabit this layer.
- Forest Floor: This is the bottom-most layer, covered with fallen leaves, twigs, and decaying organic matter. It receives very little sunlight. It is home to decomposers like fungi and bacteria, as well as insects, snakes, and small mammals.
7. A student argues that since we get wood and paper from forests, cutting trees is a good activity. How would you counter this argument by explaining other crucial services provided by forests?
While it is true that we get timber and paper from forests, it's a misconception that cutting trees is only beneficial. Forests provide essential ecological services that are far more valuable than just wood. To counter the argument, you should explain that forests also:
- Regulate Climate: They absorb carbon dioxide and influence rainfall patterns.
- Provide Clean Air and Water: They produce oxygen and act as natural filters for water.
- Prevent Natural Disasters: They prevent soil erosion and reduce the impact of floods.
- Are a Source of Other Products: We get many non-timber products like medicines, gums, resins, and honey from forests.
- Support Biodiversity: They are home to millions of species, which are crucial for ecological balance.
8. What are some key terms from the chapter 'Forests: Our Lifeline' that students must know for 1-mark questions?
For objective or 1-mark questions, a strong understanding of key terminology is essential. Important terms from this chapter for the 2025-26 syllabus include:
- Humus: The dark, organic material in soil, formed from decomposed leaves and other plant material.
- Deforestation: The clearing or cutting down of forests on a large scale.
- Canopy: The uppermost layer of a forest, formed by the branches and leaves of the tallest trees.
- Food Web: A system of interlocking and interdependent food chains in an ecosystem.
- Seed Dispersal: The movement or transport of seeds away from the parent plant.
- Regeneration: The natural process of forests growing back after being disturbed or cut down.
