Final answer:
The term describing the situation where a litter can have different fathers is 'heteropaternity.' Polyandry, where one female mates with many males, is related to heteropaternity. Monogamous relationships and population variation are additional concepts related to genetic diversity and mating systems.
Step-by-step explanation:
The phenomenon where animals within a litter of cats (or dogs) can have different fathers is known as heteropaternity. This occurs due to the fact that a female cat or dog can mate with multiple males during a single estrous cycle, leading to fertilization by different males' sperm. The term polyandry refers to a mating system where one female mates with many males, which is related to the concept of heteropaternity in that a single female may receive genetic material from multiple males.
By contrast, a monogamous relationship, where one male mates with one female, can provide advantages such as paternal assistance with protecting and feeding offspring, which can enhance the survival chances of the offspring. In the context of how mating systems affect genetic diversity, population variation such as different fur colors and patterns in domestic dogs, or the distribution of genotypes like in Mendel's pea plants, provides examples of how genetic material can combine in various ways. These examples illustrate the concepts of genetic variation and population variation through sexual reproduction.