Question 6 Answer

i) An autotroph is an organism that makes its own food.

ii) Commensalism is an association where one partner benefits and the other does not gain from the relationship while mutualism occurs when both organisms benefit from the association  .

b) The process by which plants make their own food is called photosynthesis. This process occurs in two stages, a light and a dark reaction in the chloroplast of plant cells. In the light reaction, energy from the sum is used to split the water molecules into their component hydrogen and oxygen. The oxygen is given off as a gas during this reaction. In the dark reaction, the carbon dioxide which was taken in by the process of diffusion is combined with the hydrogen to make glucose.

c) Place a healthy potted plant in a dark area for 5 days. After the 5 day period, test two leaves for starch. The result should be negative. Fasten a piece of folded black paper around one of the leaves. Be sure not to remove the leaf from the plant. Place the potted plant in a sunny area for 5 days. After the 5day period, remove the paper and test the leaf for starch. The area that was covered by the paper would appear pale and the test result for starch negative.

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