Question 19 (2 points) The leaves of a tree turn a deeper shade of red each fall depending on the amount of
certain chemicals in that tree. The greater the amount of these chemicals present in
the tree, the more red the leaves will turn. What kind of relationship do the shade of
red and the chemicals in the tree have?
non-related
cyclic
indirect
direct

Our friend Abhijit Patil captured this image via drone from northeastern Vermont on September 29, 2019. He wrote: “The brilliance is back for the season!” Thank you, Abhijit! Click in to find his forecast for autumn color in the area. Image via Abhijit Patil.

Throughout the spring and summer, the deep green color of chlorophyll, which helps plants absorb life-giving sunlight, hides any other colors present in the leaves of trees. The vivid yellows and oranges of fall leaves are there, but hidden. In the fall, trees break down the green pigments and nutrients stored in their leaves. The nutrients are shuttled into the tree’s roots for reuse in the spring. It’s then that the trees take on their autumn hues.

As leaves lose their chlorophyll, other pigments become visible to the human eye, according to Bryan A. Hanson, a professor of chemistry and biochemistry at DePauw University who studies plant pigments. Some tree leaves turn mostly brown, indicating that all pigments are gone.

Explanation:

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in 1859, charles darwin set out his theory of evolution by natural selection as an explanation for adaptation and speciation. he defined natural selection as the "principle by which each slight variation [of a trait], if useful, is preserved".