Robin can have a ddt concentration of 444ppm while the ddt concentration of soil is 10 ppm. This happens due to biological magnification.
<u>Explanation:</u>
In biological magnification the concentration of toxic substances at successive trophic levels keeps increasing. Due to biomagnification, what starts out as a small concentration grows while moving to successive trophic levels. DDT is a pesticide which is used to kill pests that affect crops.
DDT used in farms gets deposited in the soil. From the soil it can reach various trophic levels. At each trophic level its concentration keeps increasing.
Robin is a bird that is a secondary consumer and thus belongs to the higher trophic level. Thus even if the DDT concentration is as low as 10ppm in the soil its concentration will keep increasing and can become a high value like 444ppm.
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Statement 3 is the best choice
During a dehydration reaction, two monomer molecules are covalently bonded to each other, with the loss of a water molecule. In this reaction, each monomer contributes part of the water molecule that is released during the reaction. This reaction is repeated as monomers are added to the chain one by one, making a polymer.