A species of hummingbird feeds on nectar of a particular plant whose flowers form a long, skinny cup. Beak length is a heritable trait that varies among individual hummingbirds. The birds' beaks must be long enough to reach the nectar, but longer beaks are also heavier and make flying more costly in terms of energy. a. Which mode of selection is this hummingbird species experiencing? b. How does this mode of selection affect the mean and standard deviation over time?

Consider a gene with two alleles, C and M. The table below describes fitness for different genotypes in two populations.   Fitness   CC CM MM Population 1 1.0 1.0 0.6 Population 2 0.9 0.9 1.0  Assume that both populations begin with frequencies of 0.5 for each allele, population size is infinite, and there is no migration between populations. Which of the following statements is true based on the information you have on these populations?

In a species of beetle, the size and color of the wings are controlled by two distinct genes. There are two alleles for the size gene: the big allele makes wings large, and the small allele makes them smaller. There are two alleles for the color gene: red and yellow. You are able to estimate the frequency of the four haplotypes from a museum collection from 60 years ago. You also estimate haplotype frequencies in the present day. The data are shown in the table below. Museum (60 ya) Present day big/red 0.69 0.5452 big/yellow 0.00 0.1448 small/red 0.09 0.2348 small/yellow 0.22 0.0752 A) What is linkage disequilibrium (LD) between the size and color loci in the museum collection? What is LD in the present day? B) Assuming one generation per year, what is the recombination fraction between the size and color loci?

Threatened species often have small, isolated populations where mating between relatives occurs. Let's assume one of these threatened species has a disease controlled by a gene that has two alleles A and a. Only individuals with two copies of the "a" allele have the disease and die before reproducing.  Question:  What are the effects of inbreeding on the frequency of the "a" allele, and the frequency of the disease in the population?

A. What does it mean if an allele is “fixed”?  B. Explain one reason why EVEN if an allele is undergoing strong positive selection it may not become fixed in the population.

Calculate selection for the following scenario. In a population of prairie dogs living on a prairie, prairie dogs with genotype AA have 9 offspring per year on average, those with genotype Aa have 5 offspring per year on average, and those with genotype aa have 8 offspring on average. Round selection to the nearest hundredth, report selection as a value ranging from "0.00" to "1.00" • Selection on genotype Aa: • Selection on genotype AA: • Selection on genotype aa: Which genotype has the highest fitness? Fill in the blank with homozygous dominant, heterozygous, or homozygous recessive

You are studying a population of mulberry plants. The average mulberry produces 55 leaves, but an insect herbivore preferentially kills plants with more leaves, and therefore the remaining population has an average of 35 leaves after the insects kill certain plants due to the herbivory. The heritability of leaf number is 0.75. What is the response to the selection imposed by the insect herbivores?    a. -10 leaves   b. -20 leaves   c. -15 leaves   d. -5 leaves