nae% had ins of the 1 Over evolutionary time, many cave-dwelling organisms have
ID: 192428 • Letter: N
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nae% had ins of the 1 Over evolutionary time, many cave-dwelling organisms have lost their eyes. Tapeworms selection account for these losses? 21 can natural A) Natural selection accounts for these losses by the principle of use and disuse. B) Under particular circumstances that persisted for long periods, each of these structures presented greater costs than benefits. C) The ancestors of these organisms experienced harmful mutations that forced them to find D) Natural selection cannot account for losses, only for innovations new habitats that these species had not previously used. 22. Anolis lizards with long legs adapted for climbing have been transplanted from an lizards have many large trees to islands with many small plants and no trees. These A) evolved shorter legs adapted for the smaller plants B) evolved even longer legs C) evolved to be able to maneuver less efficiently undergone no evolutionary change evolved to be able to run away from predators more quickly 23._ 23. If the bacterium Staphylococcus aureus experiences a cost for maintaining one or more ich antibiotic-resistance genes, then what should happen in environments from wh 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 contine to be aintained in ca antibioi evr aear 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 same bones, these bones having developed from very similar embryonic tissues. How do biologists interpret these similarities? 24. Structures as different as human arms, bat wings, and dolphin lippers contain many of the 24 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 beesExplanation / Answer
21. Natural slelcetion can account for these losses based on the principles of use and disuse i.e., the answer is A.
Now, as per Lamarck's theory during the course of evolution any organ which had not been used for over many a generation was eventually lost as its presenc eor absence did not make any difference to the organism being living or dead. However, later a number of other theories came up which provided a rationale for Lamarcks' theory. As per these sometimes a regressive mutation in certain gene/s destroys an organ and if nature finds out that the organism is able to survive and multiply even in the functional absnece of that gene, then it will select for the mutation. This will allow the mutation to accumulate for over several generation eventually leading to complete wiping of a particular organ, whose presence or absence does not make any changes.
22. The lizards upon introduction to a new area will undergoe adapatation. SInce they have been transferre dto an area with smaller plants and and no trees comapared to their original habitat. Adaptation to new habitat generally involves several morphological changes. In the present case, since the lizards will now be present more on land rather than tree trunks therefore longer legs will help them in their aboility to grasp and sprint better. Therefore the answer would be B.
23. Antibiotic resistanc ein bacteria is mostly due to the presence of one or more plasmid encoded gene and their maintainence requires sonme energy cost. THerefore, if the bacteria founds an environment where the antibiotics are absent it will soon try to overcome the extra cost/burden of mainting the antibiotic resistant genes by losing the plasmid encoding those genes. This procedure is called plasmid curing. Therefore the answer would be C.
24. Human arms, dolphin flippers, and bat wings are all homologous organs and these three organism share a common ancestor. Therefore, statement A and C are the explanation for the occurence of these organs. And thus option E which says two of the above are correct is the right answer.
These feature are called homologous because they share the same anatomy even though they have evolved to served different purposes. Smae anatomy between organism is only possible if they all generated from one common ancestor. Convergent radiation, on the other hand, is a phenonmenon that leads to development of parts/organs which are functionally similar but anatomically different and such parts are called analogous organs.
25. From the options given above, E willl be the right answer. This is because a mutation which causes the flower to attract more bess (a pollinator) will make sure that large number of pollens are segrated and thus chances of more offsprings icreases. In all the other case no reproductive advantage is provided so survival will be challenged. For example if a shrub cannot make sseds then it will not be able to propagate.
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