Biology
Give biological explanations for the following:
(i) Education is very important for population control.
(ii) The placenta is an important structure for the development of a foetus.
(iii) All the food chains begin with green plants.
(iv) Plants growing in fertilized soil are often found to wilt if the soil is not adequately watered.
(v) We should not put sharp objects into our ears.
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ICSE 2018
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Answer
(i) If people are literate they will understand the benefits of having a small family, the superstitious and traditional beliefs that a son is essential can be overcome through education, they will be able to realize the importance of spacing and limiting the number of children in the family. They will be more aware and adopt family planning measures.
(ii) The placenta serves as an interface between the mother and the developing foetus, it is through the placenta that the foetus receives its nutrition, and sends out the nitrogenous wastes, exchange of respiratory gases is enabled because of the placenta.
(iii) Green plants are capable of Photosynthesis and Photosynthesis is ultimately the source of energy and food for all living beings. Through Photosynthesis, green plants utilise sunlight as the source of energy to synthesise food. They are the primary producers as they have the maximum amount of energy which is transmitted to higher trophic level in the food chain. For these reasons, all the food chains begin with green plants.
(iv) Fertilisers lead to the soil becoming hypertonic leading to exosmosis taking place and the cells losing their water content, as a result the cells become flaccid and the plant wilts.
(v) Sharp objects can damage eardrum / tympanum leading to deafness.
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