I'm confused on why mutation-selection balance is responsible for this: looking at the host-parasite co-evolution graph attached and it shows how host genotypes decline in frequency when they are common and increase when they are rare.

Polio has a basic reproduction number (R) = 5. The vaccine is very good; in fact, polio vaccine is 99% effective when two follow up booster shots are given. What proportion of a population needs to be vaccinated in order for herd immunity to be effective? Be sure to enter your answer as a decimal, not as a percentage.

66)Parasites are organisms that make a living at the expense of another organism called a host. In populations of hosts and parasites, not all the possible parasite genotypes can successfully infect all the possible host genotypes. The most successful parasite genotypes (i.e. those with the highest fitness) are those that can exploit the most common host genotypes. As a result, the most common host genotypes suffer a decline in fitness. Meanwhile, rare host genotypes are relatively unaffected by parasites and thus enjoy a higher fitness which causes them to become more common. As a host genotype becomes more common, it also becomes a bigger target for parasites and eventually experience a decline in fitness. This is a case of Stabilizing selection   Negative frequency dependent selection   Disruptive selection   Purifying selection   Heterozygote advantage

1) A mathematical (differential equation) representation for a metapopulation can be written as dp/dt = cp(1- p) - ep where p is the proportion of patches occupied at time t, c is the rate of patch colonization, and e is the rate of patch extinction.  The term on the left hand side is the ‘rate of change in the proportion of patches occupied.’  The first term on the right hand side of the equation provides the effective gain in patch occupancy as a function of p due to the colonization process, and the term in parentheses represents the fraction of patches not currently occupied.  The second right hand side term provides the effective loss of patch occupancy due to the (local) extinction process. a) Look at the term for the colonization process. How would you modify this term if you wanted to capture the idea that habitat loss destroyed (i.e., made uninhabitable) a proportion D from the patches that are available for colonization ? b) What value of D guarantees complete extinction of…