In a cross between two heterozygous individuals (eg. rr x rr), the expected phenotypic ratio of the offspring would be a) 1: 2: 2: 1. b) 1: 2: 1. c) 1: 1. d) 3: 1.

In a cross between two heterozygous individuals (eg. Rr X Rr), the expected phenotypic ratio of the offspring would be 3:1.

Reason:

When we cross Rr X Rr

we get

RR Rr Rr rr

Since R is dominant over r, the individuals with genotype RR and Rr will have the dominant phenotype. This implies that 3 offsprings will have dominant phenotype and 1 offspring (rr) will have recessive phenotype.

Thus the phenotypic ratio will be 3:1.

The image for the Punnett cross displaying this cross is attached for a better understanding of how the cross is made.

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.