During a study session about evolution, one of your fellow students remarks, "The giraffe stretched its neck while reaching for higher leaves; its offspring inherited longer necks as a result." Based on your knowledge of natural selection and adaptation, which statement is most likely to be helpful in correcting this student's misconception? a) Char 5. acteristics acquired during an organism's life are generally not passed on through b) c) d) genes. Spontaneous mutations can result in the appearance of new traits. Only favorable adaptations have survival value. Disuse of an organ may lead to its eventual disappearance. 6. Which of the following is not an example of genetic variation? a) The gene for detecting odors is duplicated several hundred times in humans Flowers of pea plants are purple or white due to allelic differences b) c) Caterpillars that are raised on a diet of oak flowers resemble the flowers; while caterpillars raised on a diet of oak leaves resemble oak twigs Cancer cells multiply at a very fast rate compared to normal cells d) In the Hardy-Weinberg equation, what does the variable 2pq represent? 7. Frequency of recessive allele b) Frequency of the dominant allele c) Frequency of the homozygous recessive individuals d) Frequency of the heterozygous individuals In a Hardy-Weinberg population with two alleles, A and o, that are in equilibrium, the frequency of the allele a is 0.8. What is the frequency of individuals that are homozygous dominant? a) 0.32 b) 0.04 c) 0.64 d) 0.2 8. 9. What is the founder effect? a) b) c) A selection of the best-suited traits for the environment A series of chance events that change allele frequency When a few individuals become isolated from a larger population, and their gene pool differs from that source population A sudden change in the environment that reduces the size of the population d)

Natural selection dictates that all living organisms undergo some form of change in the DNA sequence (mutation), however these changes are often random and can be either neutral, deleterious or beneficial. If a random mutation confers a selective advantage (beneficial) i.e. an organism with a mutation becomes better than others in its environment, that mutation will be carried onto future generations. This happens because the organism with the new mutation will be able to thrive in its environment (adapt) increasing its chances of reproduction. Therefore, “spontaneous mutations can result in the appearance of new traits”.

Genetic variation is simply differences in the genomic DNA of individuals. These differences may arise due to mutations, genetic exchange or even genetic recombination. For example, in a family you have a mother and a father with particular genetic backgrounds. If they have a child that child will have genes from both parents. Then they decide to have another child. That child will also have genes from both parents. However, these children will look different (even in the case of identical twins) because random genes from the parent mix. Genetic variation can be measured at both individual and population levels. In this question gene duplication does not show variation, but suggests similarity of genes.

The Hardy-Weinberg law/principle states that two alleles which are in equilibrium will have constant genotype and allele frequencies granted that no evolutionary pressure on this alleles is present. Therefore, to calculate the frequencies of these alleles one must consider this:

First alleles are different forms of genes. For example a person has two alleles for the color of their eyes, one from their mom and the other from their dad. Both of these are genes for eye color.

Secondly, alleles can be Homozygous dominant AA, Heterozygous Aa, or Homozygous recessive aa.

Lastly, the Hardy-Weinberg frequencies for each of these under random mating are calculated as:

f(A)=p or f(AA)=p^2

f(a)=q or f(aa)=p^2

f(Aa)=2pq

To calculate the frequency of individuals that have the AA genotype:

p+q=1

p+0.8=1

p=1-0.8

p=0.2

Therefore,

f(AA)=p^2

f(AA)=(0.2)^2

f(AA)=0.04

Often in nature populations experience challenges in their environments that may reduce population sizes. For example if a few group of people decide to migrate from a highly populated area to a new, uninhabited piece of land and they begin to reproduce and populate that area, that group is the founder population. This population will have low genetic variation compared to the larger population. The founder effect is when the genetic variation in a population is reduced because of the separation of a small group from the larger (genetically variable) population.