With shorter necks, giraffe ancestors could not reach food-containing branches on tall trees. This resulted in the directional selection of giraffes with longer necks.
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Why is choosing a direction necessary? </h3>
It nearly appears obvious that the giraffe's long neck developed as a result of a lack of food in the lower branches of trees. The giraffe has a significant advantage because it is taller than any other mammal and can feed where few others can.
When compared to modern giraffes, the giraffe's ancient predecessors had a shorter neck. The plants that were lying at a higher level were inaccessible to them. Giraffe phenotypes have changed in various ways, and now have long necks to reach vegetation that is higher up. The extreme form is chosen above other features in directional selection. It was decided to choose the long-necked giraffe over the short-necked.
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Answer: Food can be an obvious answer because people will not survive without food so they will die. And death means there will be a decrease on population size. So food can be a limiting factor that is dependent on population size.
Chemosynthesis is the biological conversion of one or more carbon- containing molecules.
Answer/Explanation:
First, initiator protein unwinds a short stretch of the DNA double helix. <u>The length of the DNA double helix about to be copied must be unwound. </u> In addition, the two strands must be separated, much like the two sides of a zipper, by breaking the weak hydrogen bonds that link the paired bases. Once the DNA strands have been unwound, they must be held apart to expose the bases so that new nucleotide partners can hydrogen-bond to them. Then, a protein known as helicase attaches to and breaks apart the hydrogen bonds between the bases on the DNA strands, thereby pulling apart the two strands.
