Even though it is the phenotype that is exposed to a particular environment, the genotype frequencies of a population can change over time. explain.

The genotype is responsible for the variability of phenotypes in a population. However, natural selection pressures choose which phenotype is best adapted to the environment. These ones are able to pass their genes to the next generations. Natural selection, therefore, continually weeds out recessive genes from a population. This way, the genotype frequencies change depending on changes in the environment. Additionally, mutations in the genotype could change the frequency of alleles in a population.

parasites can detrimentally affect their host, but also must not allow their host to die before they can complete their life cycle. some parasites have complex life cycles with many different hosts, and have had to find ways of persisting in many different environments during the change from one host to another. ectoparasites live outside the body of the host, and can more easily  disperse, but are  more exposed to predators, parasites, parasitoids. endoparasites live inside the body of the host, and are therefore protected from the outside environment. but they can be  attacked by the host's immune system. they have therefore developed  mechanisms for dispersal such as  complex life cycles.