Changes in the physical environment, whether (1) occurring or ( induced, have thus contributed to the expansion of some (3) the (4) of new distinct species as populations diverge under different conditions, and the decline–and sometimes the (5) –of some species.

answer: 20 percent

the fish culture has become a developing commercial practice in developing countries which is already prominent in developed countries of the world. the major fish protein demand is being supplemented in developing countries is   fishing to meet the needs of the growing population. therefore, in some developing nations, the percentage of animal protein from fish in the diet can be as high as 20 percent.