Which of the following is a true statement concerning genetic variation?

a. It must be present in a population before natural selection can act upon the population.

b. It tends to be reduced by the processes involved when diploid organisms produce gametes.

c. It is created by the direct action of natural selection.

d. A population that has a higher average heterozygosity has less genetic variation than one with a lower average heterozygosity.

e. It arises in response to changes in the environment.

Archeologists have discovered three sites showing conclusive evidence for the mastery of fire in tanzania, from a period slightly after the time that homo habilis was present in africa. these sites clearly were founded by homo erectus, the descendent species of homo habilis that migrated north, out of africa and into asia. homo erectus was known to have mastered fire, from ample evidence at sites in asia. there is no reason to attribute mastery of fire to homo ergaster, the descendent species of homo habilis that remained in africa.which of the following is an assumption on which the argument depends? (a) before their migration, homo erectus occupied african territory as far south as tanzania.(b) the strain of migration provided the selective pressure motivating homo erectus‘ mastery of fire.(c) homo ergaster would not have derived as much benefit from the mastery of fire as did homo erectus.(d) homo ergaster inherited all cultural knowledge from homo habilis, a species that did not have mastery of fire.(e) homo ergaster did not occupy regions as far south as tanzania until well after the time of these three sites.

Compare and contrast your sells take in oxygen, water, and food. what is one waste product that leaves your cells?

What property of water provides for appropriate sugar, salt, and amino acid levels to be present and carried in the blood of animals to be delivered to cells