a prey population consists of individuals with a variety of running speeds. The adaption that allows some of these animals to run fast would be an example of natural selection if it helps them

answer: the blood-brain barrier is a layer of specialized membranes and cell processes designed to keep undesirable substances from passing from the bloodstream into the precious tissues of the brain. while the blood-brain barrier does keep most bad things out of the central nervous system, it is not impermeable.

explanation:

for  example, forests have higher evapotranspiration than other ecosystems,  such  as grasslands, because of their deeper roots and greater leaf area. thus forests have a net moistening effect on the atmosphere and become a moisture source for downwind ecosystems.

all matter is made up of atoms

in any element all atoms are the same

elements in a compound are always in a constant ratio: apex