Olympiad Test: Natural Resources And Calamities - 1 - Class 5 MCQ

Humus is a dark-colored, organic substance formed from the decomposition of dead plants and animals. It is rich in nutrients and plays a vital role in improving soil fertility, helping plants to grow. Humus also helps retain moisture in the soil and supports healthy soil structure.

• Gravel is made up of small, loose stones.
• Loam is a type of soil that contains a mixture of sand, silt, and clay.
• Clay is a fine-grained natural material that can become sticky when wet and is often used to make pottery.

Topsoil is indeed the layer that supports plant growth the most. Here's why:

• Topsoil contains the right mix of nutrients, organic matter (humus), and microorganisms needed for plants to grow. This is where most of the roots of plants are found.
• Subsoil and bedrock are typically not as rich in nutrients for plants, making them less suitable for plant growth.

So, the correct answer is B: Topsoil.

• Clayey soil has the highest water-holding capacity because its tiny particles are closely packed, allowing water to stay within the soil for a longer time.
• Loamy soil is a balanced mixture of sand, silt, and clay, and while it holds water well, it doesn't retain as much as clayey soil.
• Sandy soil has larger particles and doesn't hold water as effectively; it drains quickly.

So, clayey soil is the correct choice.

• Humus is the decomposed organic matter in soil. It is rich in nutrients like nitrogen, phosphorus, and potassium, which are essential for plant growth.
• It also improves soil structure, making it easier for plant roots to grow.
• While humus does help with water infiltration and supports microorganisms that can break down pollutants, its primary importance lies in enriching the soil with nutrients, boosting fertility.

• Soil erosion is the process where the top layer of soil, which is rich in nutrients, is carried away by natural forces like wind, water, or human activity.
• This leads to the loss of fertile soil, which can harm agricultural productivity and affect the ecosystem.
• It is a harmful process that reduces the land’s ability to support plant life.

Fossil fuels, like coal, oil, and natural gas, are formed from the remains of plants and animals that lived millions of years ago. They provide energy for cooking, transportation, and electricity, but they take a very long time to form and cannot be replaced quickly.

Terrace farming involves creating steps on hilly or mountainous land, which helps prevent soil erosion by slowing down the flow of water. This method uses land more effectively and protects the soil from being washed away.

• B: Reducing soil erosion by deforestation – Deforestation increases soil erosion, not reduces it.
• C: Reducing soil erosion by water – Terrace farming reduces the harmful effects of water erosion, not promotes it.
• D: Reducing soil erosion by overgrazing – Overgrazing actually increases soil erosion.

A flood occurs when water rises and covers land that is usually dry. Floods can be caused by heavy rain, overflowing rivers, or poor drainage. They can damage crops, homes, and affect people and animals.

Floods can lead to various environmental consequences, including the dispersal of weed species, erosion of soil, and the release of pollutants into waterways, all of which can harm ecosystems.

• A: Dispersal of weed species – Floodwaters can carry weed seeds to new areas, spreading unwanted plant species.
• B: Erosion of soil – Floods can wash away the top layer of soil, causing erosion.
• C: Release of pollutants into waterways – Floods can carry pollutants like chemicals, sewage, and waste into rivers and lakes.

Weather forecasts provide information about expected temperature, rainfall, and wind to help people plan their daily activities. They cannot predict earthquakes, control the weather, or always give exact rainfall amounts.