3 pts D Question 10 Earth has something like 12,000 times more marine habitat th

Question

3 pts D Question 10 Earth has something like 12,000 times more marine habitat than freshwater habitat (by volume), yet about 50% of all fish species live in freshwater. What probably accounts for the greater tendency of freshwater fish to form new species? O Fish have lived in freshwater for more time. O Freshwater populations are more isolated from each other O Freshwater fish have high mutation rates D Question 11 3 pts The rates of many diseases, such as coronary heart disease (CHD) climb as we age. CHD kills millions of people a year, so it has a significant effect on human survival rates. Twin studies tell us that CHD has a large genetic component, about 40%, why hasn't natural selection weeded out the genes that promote CHD, which lower our lifespan? O selection is a weak evolutionary force in large populations diseases that affect the very old have little effect on reproductive success new mutations in the population keep the genes that cause CHD in the population O

Explanation / Answer

Q 10 Answer-B Hint- Freshwater fishes are separated by geographical barriers.These isolated species lose the ability to breed with different population thus separating into different species.Researches show that most of the marine species which are present now are evolved from freshwater species.This is because older marine species were wiped out by mass extinction.This mass extinction was severe in marine than in freshwater species as marine fishes are connected to each other via oceans.

Q11 Answer C Hint- New Mutations in the population keep the genes that cause CHD because CHD causing genes are important for reproduction.They affect the functions of human reproductive organs.So, natural selection has maintained genetic variation (which results in coronary heart disease) because of its benefits on human fitness rather than its ill effects.Benefits outweighed ill effects.

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