In a meadow where earthworms live in the soil, the ph gradually decreases from the optimum range into the zone of stress. what is the most likely effect on the earthworm population? a. the size of the earthworm population increases, but otherwise the population is unchanged. b. the size of the earthworm population decreases, but otherwise the population is unchanged. c. earthworms that tolerate high ph become more common in the population. d. earthworms that tolerate low ph become more common in the population.

ANSWER: D, earthworms that tolerate high pH become more common in the population.

REASONING: This is a result of natural selection.  Natural selection is a process in which organisms that are better adapted to their environment will likely survive and reproduce more than those less adapted to their environment.

Option D

Explanation:

When the pH of the soil changed from the optimum level to the stress level then only the stress tolerant earthworm would be left in the soil.

The earthworm that can tolerate the low pH will be common in the coming generation of the earthworm because only fittest will survive and reproduce.

Due to this reason the low pH tolerant population of the earthworm will be common.

So, the correct answer is option D

blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium of the heart. as the ventricle contracts, blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs where it is oxygenated.