Question

with the help of an example of host parasite relationship explain the concept of co-evolution.

Answer 1

The growth of interest recently in co-evolution of hosts and their parasites arises partly from the hope that a better understanding of the processes involved should provide new insights into disease control in agriculture. Unfortunately, examination of natural systems makes it immediately clear that they are often complex and that the host-parasite interaction may be obscured by many other interactions with different organisms and with physical factors that all affect evolution. For example, though it may be generally true that parasites are deleterious to their hosts in natural systems, this may not always be the case. There is evidence that some parasites are directly beneficial to their hosts: others may be cryptically so.

Furthermore, although processes such as density-dependent and frequency-dependent selection are considered to be important in host parasite co-evolution, there is little direct evidence for such effects. The role of gene-for-gene interactions and the effects of “unnecessary” virulence genes are also poorly understood.

The principal reason for our lack of understanding of host-parasite co-evolution is that there have been no large-scale analyses of natural ecosystems that have been repeated at regular intervals to follow the dynamics of the host and parasite genotypes under selection.

(Hope that helps)

Answer 2

Answer:

The term co-evolution is used to describe cases where two or more species affect each other's evolution in a mutually dependent manner . Each party in a co-evolutionary relationship exerts selective pressures on the other, thereby affecting each other's evolution. Co-evolution functions by reciprocal selective pressures on two or more species, analogous to an arms race in an attempt to out-compete each other.The host-parasite relationship is one of the most classic examples of co-evolution. Co-evolution of hosts and parasites involves the reciprocal evolutionary change that occurs specifically between these classic antagonists, and is predicted to be ubiquitous, given the intimate relationships that parasites share with their hosts and the strong selective pressures that each can exert on each other.

This co-evolution is driven by the reciprocal evolution of host resistance that inhibits parasite establishment or survival within the host and parasite infectivity. This antagonistic co-evolution between resistance and infectivity traits may lead to either increased or decreased host or parasite fitness.