Right before it starts to decline (fall)
Should be A the newer layers are usually on top
Answer:
C. a whale's flipper and a cat's leg
Explanation:
Homologous structures are the organs which have same basic anatomical structure but they perform different function based on the type of environment in which the organism is living. Two organisms which have homologous organs indicate that both the organisms are evolutionarily closely related to each other i.e. their ancestry is common. It is basically divergent evolution which is responsible for formation of homologous organs. If two closely related organisms are living in different environment then their organs which basically have same origin will tend to perform different functions as a part of adaptation. In contrast to this, analogous structures are the ones which perform similar function but anatomically they are very different and evolutionarily they are not closely related. Analogous structures are evolved as a result of convergent evolution which is meant for adaptation in a particular environment. So, even if two organisms are not closely related they still develop the structures which perform similar function so as to adapt into a particular environment.
Whales and cats both are mammals so they are closely related to each other but since they live in different environment, their organs which are anatomically similar perform different functions. Flippers in whales help in swimming while cat's leg help in walking. So, option C is correct answer.
All other options are examples of analogous organs.
A bird's wings and a butterfly's wings are perfect example of analogous organs. A bird is a vertebrate while a butterfly is an arthropod so evolutionarily they are very distantly related so their wings are also anatomically very dissimilar but they still perform similar function which help these two organisms in flying. So option A is incorrect. Similarly option D is also incorrect because wasp is an arthropod while dolphin is a vertebrate. Option B is also incorrect because catfish is a vertebrate and bee is an arthropod.
Prokaryotic cells lack a nucleus.
