Wednesday, 14 October 2015

Class 7 NCERT Science Transportation



The heart has four chambers: two atria and two ventricles. The right atrium receives oxygen-poor blood from the body and pumps it to the right ventricle. The right ventricle pumps the oxygen-poor blood to the lungs. The left atrium receives oxygen-rich blood from the lungs and pumps it to the left ventricle


 
1 - Why is transport of materials necessary in a plant or in an animal? Explain.
Answer: The cells of plants and animals need various substances to carry out important metabolic activities. Further, many waste products are created during these metabolic activities. Transport of materials is necessary to supply the various substances and to remove the waste products.
2 - What will happen if there are no platelets in the blood?
Answer: Clotting is necessary to prevent blood loss. Platelets are responsible for clotting of blood. If there are no platelets, the blood would not clot in case of an injury. This will lead to excess blood loss and finally in death of the person.
3 - What are stomata? Give two functions of stomata.
Answer: The innumerable very small pores on the surface of leaf are called stomata. Transpiration and exchange of gases (carbon dioxide and oxygen) are some of the functions of stomata.
4 - Does transpiration serve any useful function in the plants? Explain.
Answer: Transpiration serves important functions in plants. Transpiration creates the transpiration pull; which is responsible for the rise of water to great heights in tall plants and other trees.
5 - What are the components of blood?
Answer: The main components of blood are: Plasma, Blood Cells and Platelets.
6 - Why is blood needed by all the parts of a body?
Answer: Blood acts as a carrier of various substances. Every part of the body needs certain substances to perform its functions. Additionally, every part creates some waste products. Blood is needed by all parts of the body so that various substances can be supplied to them and waste can be removed from them.
7 - What makes the blood look red?
Answer: Blood is red because of the presence of a pigment; called haemoglobin.
8 - Describe the function of the heart.
Answer: The heart is a pumping organ which pumps the blood. The heart pumps the deoxygenated blood to the lungs; for oxygenation. Moreover, the heart pumps the oxygenated blood to different parts of the body.
9 - Why is it necessary to excrete waste products?
Answer: Waste products can prove lethal if not removed in time. Hence, it is necessary to excrete the waste products.
10 - Draw a diagram of the human excretory system and label the various parts
Answer
 

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