23. If the bacterium Staphylococcus aureus experiences a cost for maintaining on

Question

23. If the bacterium Staphylococcus aureus experiences a cost for maintaining one or more 23. antibiotic-resistance genes, then what should happen in environments from which antibiotics are missing? A) The bacteria should try to make the cost worthwhile by locating, and migrating to, microenvironments where traces of antibiotics are present. B) These genes should continue to be maintained in case the antibiotics ever appear. C) These bacteria should be outcompeted and replaced by bacteria that have lost these genes D) The bacteria should start making and secreting their own antibiotics. 24. Structures as different as human arms, bat wings, and dolphin lippers contain many of the 24 same bones, these bones having developed from very similar embryonic tissues. How do biologists interpret these similarities? A) by proposing that humans, bats, and dolphins share a common ancestor B) by the principle of convergent evolution C) by identifying the bones as being homologous structures D) Three of the statements above are correct. E) Two of the statements above are correct. 25. 25. Which mutation provides a survival advantage? A) a brightly colored fish that attracts predators B) a shrub that loses the ability to make seeds C) a tree that grows shorter than the surrounding trees D) a horse that lacks the ability to digest either grains or grass E) a flower that attracts more bees

Explanation / Answer

23. C

S.aureus experience a cost to achieve antiobiotic resistance. Each organism wants to save their energy. If their is no antibiotic in the environment it will not make the antibiotic resistance protein unnecessirly. Their can be two possiblities

1) either they stop producing antibodies but the antibiotic resistance gene remain present . Over a period of time they will loose the gene.

2) or they continue to make antibodies and waste their energy in it. But that expenditure of energy will not be giving them any survial advantage. As their huge amount of energy is bing wasted they will be growing and multiplying less as compared to the bacteria whic lack these genes.

Most likely these bacteria will be outcompeted and replaced by the bacteria that have lost this antibiotic resistance genes.

24. E

all three structure shows the homology. They are similar structure but have different functions. It shows that they share a common ancestor but in order to adapt in different environment they have acquired different functions. This is an example of divergent evolution.

25. E

a flower that will attract bees has a high chance of pollination. That means it has a high chance of mixing different pollens even if its a cross pollinating. Thus that will allow more variation in its gene pool. High variation allows to survive in high range of environmet condition. Thus provides survival advantage.

Other than E all examples directs the population towards their end of life.

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