Tata DAV S.St Chapter 2 solution
A. Tick (✔) the correct option
- Which type of erosion leads to desertification?
✅ (a) soil erosion
Loss of top fertile soil leads to barren land (desertification). - Which one is suitable for restoring soil fertility?
✅ (d) rotation of crops
Different crops restore nutrients in soil. - Which of the following is NOT in favour of multipurpose river valley projects?
✅ (c) large scale displacement of people
This is a disadvantage, not a benefit. - Maintenance of lakes and ponds is essential for—
✅ (b) increasing water table
It helps groundwater recharge. - Which factor is more responsible for quick formation of soil in Rajasthan?
✅ (c) extreme difference in day and night temperature
Temperature variation breaks rocks faster.
B. Fill in the blanks
- Earth’s surface is divided into biotic and abiotic zones.
- To maintain ecological balance, 33% of the land should be under forest.
- Planting of trees is commonly known as afforestation.
- The main source of fresh water is rainfall.
- Earth is known as blue planet due to the presence of water on it.
C. Technical terms / appropriate words
- It is formed by decomposed parts of plants and animals.
👉 Humus - The original rock from which the soil is formed.
👉 Parent rock (Parent material) - It is formed as a result of long continued weathering process of rocks.
👉 Soil - A project which serves various purposes at the same time.
👉 Multipurpose project - The process in which the top layer of the soil is removed by natural and human activities.
👉 Soil erosion
D. Answer the following questions in brief
1. Why is soil considered an important resource? (any three)
Soil is very important for our life.
- It helps in growing crops, which gives us food.
- Many plants and small animals live in soil, so it supports life.
- It is also used for building houses, roads, and other structures.
2. Highlight any three causes of soil erosion
Soil erosion happens when the top layer of soil is removed. Some main causes are:
- Cutting of trees (deforestation), which leaves soil loose.
- Overgrazing by animals, which removes grass cover.
- Heavy rains or floods, which wash away the soil.
3. Explain hydrological cycle with the help of a diagram
The hydrological cycle is the continuous movement of water on Earth.
- The sun heats water and causes evaporation.
- Water vapour cools and forms clouds (condensation).
- Clouds bring rain (precipitation).
- Water collects in rivers, lakes, and oceans (collection).
👉 You can draw a simple diagram showing:
Sun → Evaporation → Clouds → Rain → Rivers/Oceans
4. How does river water get polluted? Explain
River water gets polluted mainly due to human activities.
- Factories release dirty chemicals into rivers.
- People throw garbage and sewage into water.
- Farmers use fertilizers and pesticides, which flow into rivers.
Because of this, water becomes unsafe for drinking and harms aquatic life.
5. Identify any three ecological problems caused by building large dams
Large dams can create many environmental problems:
- Many people are forced to leave their homes (displacement).
- Forests and wildlife are destroyed when large areas are submerged.
- It disturbs the natural flow of rivers, affecting ecosystems.
D. Answer the following questions in brief (Paragraph Format)
1. Why is soil considered an important resource?
Soil is considered one of the most important natural resources because it supports life on Earth in many ways. It is essential for agriculture, as crops grow in soil and provide us with food. Without soil, farming would not be possible. It also acts as a habitat for many small organisms like insects, bacteria, and earthworms, which help maintain ecological balance. In addition, soil is used for construction purposes, such as building houses, roads, and other infrastructure. Thus, soil plays a vital role in sustaining both living organisms and human activities.
2. Highlight any three causes of soil erosion.
Soil erosion is mainly caused by both natural forces and human activities. One major cause is deforestation, where cutting down trees leaves the soil exposed and loose, making it easy to be carried away by wind or water. Another important cause is overgrazing, where animals eat up all the vegetation, leaving the soil bare and unprotected. Heavy rainfall and floods are also significant causes, as they wash away the top fertile layer of soil. These factors together reduce soil fertility and can lead to land degradation.
3. Explain the hydrological cycle with the help of a diagram.
The hydrological cycle, also known as the water cycle, is the continuous movement of water on, above, and below the surface of the Earth. It begins with evaporation, where heat from the sun causes water from oceans, rivers, and lakes to turn into water vapour. This vapour rises into the atmosphere and cools down to form clouds through condensation. When the clouds become heavy, water falls back to the Earth in the form of precipitation such as rain or snow. This water then collects in rivers, lakes, and oceans, and some of it seeps into the ground as groundwater. This continuous cycle maintains the balance of water on Earth.
4. How does river water get polluted? Explain.
River water gets polluted mainly due to various human activities. Industries often discharge untreated chemical waste directly into rivers, which contaminates the water. Domestic sewage and garbage are also dumped into rivers, making the water dirty and unsafe. In addition, the use of chemical fertilizers and pesticides in agriculture leads to runoff during rains, which carries harmful substances into rivers. Religious activities and bathing can also add pollutants to the water. All these factors degrade water quality and harm aquatic life as well as human health.
5. Identify any three ecological problems caused by building large dams.
Although large dams are useful, they also create several ecological problems.
(1) One major issue is the )displacement of people, as many families are forced to leave their homes when large areas are submerged.
(2) Another problem is the destruction of forests and wildlife habitats, which leads to loss of biodiversity.
(3) Dams also disturb the natural flow of rivers, affecting aquatic ecosystems and sediment movement. Over time, this can lead to environmental imbalance and long-term ecological damage.