Class 8 General Science Notes: - Unit-1: Ecology: Solved Exercise (Long Questions and Answers)

(National Book Foundation - New Book/New Syllabus Based on National Curriculum Pakistan 2023-2024 and Onwards)

(Class 8 General Science Notes for 8th Centralized Exam 2023-2024 and onward, FDE, Islamabad)

Click Here for Solved MCQs Unit-1

C. Long questions:

1. Explain the carbon cycle and find the reasons for the gradual increase of carbon dioxide in the atmosphere.

Ans:

CARBON CYCLE:

Carbon is constantly being removed from and released into the environment, in the form of carbon dioxide. The amount of carbon dioxide in the atmosphere is 0.04%. Plants absorb this carbon dioxide to prepare their organic food through the process of photosynthesis. Animals gain carbon in the form of organic compounds when they feed on plants or other animals. The respiration process in both animals and plants releases carbon dioxide back into the environment.

A chemical reaction between substances and oxygen in which CO2, heat, and light are generated, is called a combustion reaction. Animal and plant bodies buried under the earth's crust were converted into fossil fuels like coal, oil, and gas. The combustion of fossil fuels in factories, automobiles, and houses is adding up carbon dioxide in the atmosphere rapidly.

The oxygen cycle is interconnected with the carbon cycle. Oxygen is produced in photosynthesis and carbon dioxide is produced in respiration. Both these processes maintain the level of these gases in range to sustain life.

2. How positive activities of humans can help to restore an ecosystem.

Ans:

POSITIVE IMPACT OF HUMANS ON THE ECOSYSTEM:

A balanced ecosystem ensures that human beings have access to clean air, water, and fertile land for agriculture. To save our planet and diverse ecosystems, a number of steps are being taken.

Reforestation:

Reforestation is the plantation of trees, where already existing forest has been destroyed by some cause. It is very important as trees decrease toxic gases from the surrounding nature. Forests are natural carbon sinks. By removing greenhouse gases from the air planned forests can reduce global warming.

Reforestation is a solution of stopping soil erosion to maintain land quality. Forests support other plants and animal species, thus maintaining the ecosystem.

Afforestation:

Afforestation is a plantation of forest on land where there was no forest before. It is very useful to increase forest land in Pakistan as we have very low forest coverage.

Control of Pollution:

Air and water pollution has badly affected all forms of life. However, many steps are being taken to control pollution which will ultimately help to conserve endangered species.

The shift to clean energy sources will help reduce air pollution and reverse its effect on the environment. The use of wind power stations and solar energy is replacing coal and oil power station. Electrical vehicles are becoming popular day by day.

The protection of clean water resources is a challenge. Water conservation, treatment of sewage from homes and industry, and less use of plastic are key steps to control water pollution. Thus more clean water will be available to keep the ecosystem flourishing.

Conservation of Endangered Species:

Plants and animals maintain the health of an ecosystem. When a species becomes endangered, it is a sign that the ecosystem is out of balance. Government, NGOs, local communities, and individuals work together to contribute towards growing the population of endangered species. The awareness campaign aimed at getting more people involved in conservation work is a very effective way for species conservation.

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