Which of the following best describes the biological role of the lac operon? a) it prevents other sugars from being metabolized until all available lactose has been used. b) it ensures that a cell dedicates resources to the production of enzymes involved in lactose metabolism only when lactose is available in the environment. c) it ensures that a cell produces enzymes involved in lactose metabolism in a constitutive manner. d) it ensures that bacterial cells produce lactose only when no other food sources are available.

The terrestrial planets are characterized by having a a.) silicate core b.) iron-rich silicate core c.) iron-rich metallic core d.) none of these

Humans are believed to have evolved in coastal regions in east africa. the region had an abundant supply of fish for early humanoids to eat. when scientists analyze the fads gene they see an interesting pattern. people whose families have lived in this area of east africa for generation show a high level of diversity in alleles for the fads gene. conversely, people whose families had migrated inland a moderate distance from sources of fish showed a much lower diversity for fads gene alleles. additionally, the fads alleles found in people whose family has lived inland for generation are almost all gene alleles which produce fads proteins with a high level of function and activity. how do anthropologists explain this?

What are some of the immune functions of the lymphatic system? a. cleaning red blood cells from the blood and creating lymph fluids b.transporting lymph to the tissues and creating lymph fluids c.removing infectious agents and making white blood cells d.making red blood cells and removing infectious agents