For an ecological study, you monitor herbivore-plant interactions in a rainforest and notice that mammalian herbivores avoid the leaves of a particular species of plant. However, a number of tiny herbivorous insect generalists that feed by piercing individual plant cells with their mouthparts appear capable of completing their entire life cycle feeding on this same species. You hypothesize that in this species the chemical defenses are: a. stored in the cytoplasm of epidermal leaf cells. b. stored in the vacuole in an inactive form and are activated by enzymes in the cytoplasm. c. contained in a latex stored in vascular canals. d. non-existent.

1) gene flow

- it is described as the transfer of genes from one population to another population so that frequency of gene is increased.

-a zebra migrates to join a different herd of zebras.

2) natural selection

- a mechanism of evolutionary change in which individuals with advantageous traits survive and reproduce whereas the others ( those that can not adapt) eliminate from the population.

-competition for sunlight leads to taller trees.

3) mutation

- permanent change in the nucleotide sequence of dna ( genetic material) that could have harmful or useful consequences.

-the dna of a snake changes to make its venom stronger.

4) genetic drift - it is a random phenomenon ( that occurs by chance such as fire) that results in change in the gene frequency in a small population.    

-a grassfire randomly sweeps through a population of buffalo and kills most of the animals.

explanation:

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: