Many animals have life cycle stages that differ from one another morphologically. In some animals, the larval form is a dispersal stage; in other animals, the adults are more likely to disperse than are larvae. In several groups of organisms, asexual reproduction without fission leads to coloniality.

Question 1

In a multicellular organism, every cell has the same genotype, and the cells are all physiologically interconnected and interdependent to form one functioning organism. In a colonial species, the individuals are more loosely integrated with one another, and individuals that make up a colony may also be able to exist independently of one another. In some cases, different individuals in a colony have different genotypes, although some colonies may be composed of clonally duplicated organisms that function as an integrated whole. Every individual in a colony is typically multicellular, unlike the single cells in a multicellular individual.

Question 2

Typically the characteristics of an animal in one life stage are beneficial under certain conditions but detrimental under others. A change that improves one characteristic, such as a thicker shell for protection against predation, usually comes at a cost of some kind, such as less mobility. In a life cycle, an animal may evolve to produce more eggs, but that usually comes at a cost of the investment of resources in each egg, which leads to lower survivorship of the average offspring. For this reason, there are limits on the changes that can occur in the evolution of life cycles.