Cnidaria and flatworms exchange gases and remove wastes by way of their:
A) open circulatory systems. B) closed circulatory systems. C) gastrovascular cavities. D) moist skin surfaces. E) respiratory and excretory systems.

Select the correct answer. which term do biologists use to describe the average number of individuals of a species per unit area? a. carrying capacity b. population density c. minimal viable population d. survivability curve

What is the next step in the process after a substrate enters the active site of an enzyme

What is required in the genotype of an individual to show a recessive trait? a. two recessive alleles b. at least one recessive allele c. no recessive alleles