According to the endosymbiotic theory how did mitochondria evolve?

the correct answer is:

a population changes in response to a change in the environment.

meiosis is the first to occur after the nuclei of opposite of opposite mating types fuse

request for reexamination

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.