GENETICS AND EVOLUTION
EVOLUTION
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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In every generation, the length of giraffes’ necks showed variation.
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All giraffes, regardless of neck length, had an equal chance of survival.
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Abundant resources insured that competition among giraffes was limited.
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None of the above
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Detailed explanation-1: -in order for natural selection to have produced the long necks of giraffes, what must have been true about the evolutionary history of giraffes? in order for natural selection to have produced the long necks of giraffes, the length of giraffe’s necks must have showed variation within the species in every generation.
Detailed explanation-2: -Charles Darwin held up giraffes as a prime example of natural selection, his theory that’s often summarized as “survival of the fittest.” Giraffes with comparably longer necks could reach food high up in trees, which gave them an advantage over other animals and members of their own species with shorter necks.
Detailed explanation-3: -There are only seven vertebrae in mammal necks, meaning that the giraffe has vertebrae that are nearly a foot long each! Their cervical (neck) vertebrae have actually just extended in length, instead of adding more bones into the anatomy. This elongation is responsible for the neck becoming so long.
Detailed explanation-4: -According to Lamarck, the giraffe got its long neck because its ancestors stretched theirs to eat leaves that were just out of reach. This stretching of the neck was passed on to their offspring, over generations, until it reached its current length.