Science STD 7 Chapter 12: Forests: Our Lifeline - Exercises

Animals living in the forest help it grow and regenerate in several ways:

• Animals, especially birds and mammals, help in **seed dispersal** by carrying seeds to new locations.
• Herbivores feed on plants, but in doing so, they also help in the growth of new seedlings by creating space for them.
• Animal droppings provide **nutrients** to the soil, enriching it and helping new plants to grow.
• The decaying remains of dead animals also contribute to the humus in the soil, which helps in the nutrient cycle.

Forests prevent floods by acting as a natural absorber of rainwater. The dense canopy of trees intercepts raindrops, slowing down their fall. The fallen leaves on the forest floor act like a sponge, absorbing a large amount of water. The extensive root systems of trees and other plants bind the soil together, allowing the water to slowly seep into the ground rather than rushing off the surface. This helps in maintaining the groundwater table and prevents soil erosion and flooding.

Decomposers are microorganisms that break down dead plant and animal matter. Two examples of decomposers are **bacteria** and **fungi**. In a forest, decomposers play a crucial role in converting dead organic matter into a dark, nutrient-rich substance called **humus**. This process returns valuable nutrients to the soil, which are then absorbed by the roots of living plants, ensuring the continuous cycle of life in the forest.

Forests play a vital role in maintaining the balance of oxygen and carbon dioxide in the atmosphere. During photosynthesis, plants take in carbon dioxide from the air and release oxygen. This process replenishes the oxygen that is used by animals and humans during respiration. The trees in the forest absorb a large amount of carbon dioxide, thus helping to regulate the levels of these gases and prevent an increase in the Earth's temperature.

There is no waste in a forest because everything is part of a natural cycle. Dead leaves, animal droppings, and the remains of dead animals are broken down by decomposers (fungi and bacteria). This process converts the waste into humus, which is rich in nutrients. These nutrients are then reabsorbed by the plants, and the cycle continues. Thus, waste is recycled and nothing goes unused in a forest ecosystem.

Five products we get from forests are:

1. Timber (wood)
2. Medicinal plants
3. Honey
4. Gums and resins
5. Spices

We should worry about the conditions of forests far from us because they affect the global ecosystem. Forests, regardless of their location, play a crucial role in maintaining the balance of oxygen and carbon dioxide in the atmosphere, influencing the global climate, and supporting the water cycle. Deforestation in a distant country can contribute to climate change and unpredictable weather patterns in our own area. Thus, the health of all forests is interconnected and affects everyone on Earth.

A variety of animals and plants is essential for a healthy and stable forest ecosystem. Different types of plants form a canopy and different layers (understorey), providing a variety of habitats and food sources for different animals. A wider variety of animals, in turn, helps in pollination and seed dispersal, which is crucial for the regeneration of the forest. The interaction between various species in the food chains ensures a balanced and resilient ecosystem where each component depends on the others to survive.

The diagram shows the interdependence of various components in a forest. The arrows would be marked as follows:

• **Clouds** to **Rain** (downward arrow).
• **Plants** take in **Carbon dioxide** (from atmosphere) and release **Oxygen** (to atmosphere).
• **Animals** take in **Oxygen** and release **Carbon dioxide**.
• **Roots** (of plants) absorb water from the **Soil** which is connected to the **Water table**.
• **Rain** goes into the **Soil** and reaches the **Water table**.

[Image of the diagram with the correct labels and arrows]

1. Gum
2. Plywood
3. Sealing wax
4. Kerosene

1. Forests protect the soil from erosion.
2. Plants and animals in a forest are not depedent on one another.
3. Forests influence the climate and water cycle.
4. Soil helps forests to grow and regenerate.

1. sand
2. mushrooms
3. humus
4. wood

Outline: This activity requires you to write a persuasive letter based on what you have learned about forests. The letter would outline the importance of the forest as a natural resource, a source of oxygen, and its role in preventing floods and soil erosion. It would argue that the long-term benefits of the forest outweigh the short-term economic gains of a housing complex, urging the department to reconsider its decision.

Outline: This is an observational project that encourages students to experience a forest firsthand. By following the provided steps, you would learn about the different layers of a forest (canopy, understorey), its diverse plant and animal life, and how to identify species based on their characteristics. The activity helps in building a deeper understanding and appreciation for the complex and dynamic nature of a forest ecosystem.