What ia the result purpose of crossing over during meiosis?

Which excerpt from the land, part 4 best supports the claim that paul is a talented horseback rider? a/“figure that says more than anything else! now, i want to ride that stallion! " b/my daddy shook his head. "paul only rides horses he knows. ” c/? i glanced over at the other rider. the fellow was older than i, and had the weight of a man on him. d/a man out of alabama, man name of ray sutcliffe, told my daddy i was such a good rider, he wanted me to ride some races for him.

Plz ! ive been stuck on this forever

The concept of keystone species is controversial among ecologists because most organisms are highly interdependent. if each of the trophic levels is dependant on all others how can we say one is most important