in high elevation forests n Pennsylvania, ecologists have noticed a serious decline in certain tree species. Some scientists propose that increased soil acidity might be the cause. Whats the phenomenon? A. Mercury contamination B. Decreased in pH caused by climate change C. Acid rain, which is caused by SO2 from combustion mixed with atmospheric water vapor D. Ozone depletion

I would choose answer B.

Explanation:

Acid rain is caused by combustion chemicals mixing with water vapor in the atmosphere. It normally results in high amounts of acid in the soil, and surrounding bodies of water.

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: oof wait

explanation: