3. Explain why holes are made in hanging banners and hoardings.
Sketch the cross section of soil and label the various layers,
Why is transport of materials necessary in a plant or in an animal? Explain.
Answers
Answer:
Explanation:
A vertical section through different layers of the soil is called the soil profile. Each layer differs in feel (texture), colour, depth and chemical composition.
These layers are referred to as horizons.
The uppermost horizon is generally dark in colour as it is rich in humus and minerals. The humus makes the soil fertile and provides nutrients to growing plants. This layer is generally soft, porous and can retain more water. It is called the topsoil or the A-horizon.
The next layer has a lesser amount of humus but more of minerals. This layer is generally harder and more compact and is called the B-horizon or the middle layer.
The third layer is the C-horizon, which is made up of small lumps of rocks with cracks and crevices.
Below this layer is the bedrock, which is hard and difficult to dig with a spade.
Answer: ⤵️
Transport of materials is necessary in both plants and animals as every cell needs a regular supply of nutrients and oxygen for releasing energy through respiration. The food that we eat is broken down into smaller components to be absorbed by the cells. The oxygen that we inhale is also transported to all the cells of the body. Our body also requires a constant removal of waste materials such as carbon dioxide. For the transport of all these materials (food, oxygen, and wastes), our body has a specialised transport system. Similarly, in plants, the transport of water and food is accomplished with the help of a complex transport system.
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