Microevolution and Popular Genetics (ALA week 11)

Directional

one extreme/one end of the phenotype spectrum

Disruptive

balancing

Stabilizing

against both extremes and for the phenotype(s) in the middle of the spectrum (to keep heterozygotes in the population)

Longer gill rakers function better for capturing open water prey, shorter gill rakers function better for capturing shallow water prey. Which type of selection is most likely to be found in a large lake (open water in the middle and shallow around the sides) with a high density of these fish? Why?

Disruptive selection because it’s has advantages for both sides.

In the Hard-Weinberg equation, Allele frequencies are

p and q

In the Hardy-Weinberg equation, genotype frequencies are

p² is a homozygote, q² is a homozygote and 2pq is a heterozygote

The percentage of carriers of the cystic fibrosis allele in the US is approximately 2%

genotype

Approximately 1 in 2500 babies in the US is born with cystic fibrosis

phenotype

The number of new mutations for achondroplasia, a dominant genetic disorder, is approximately 5×10-5

allele

South American anteaters are mammals that eat only ants. They have many traits that help them catch and eat ants efficiently. Firstly, anteaters have remarkably large claws that allow them to easily rip open ant hills.  They feed by sticking their tongue into tunnels in the ant hills. Their entire head and mouth is adapted for catching ants. Their tongues are 24 inches long and covered with sticky saliva.  Anteaters cannot open their mouth, and do not have teeth. Even the stomachs of anteaters are unique: unlike most mammals, anteaters do not secrete acid in their stomachs. None is needed.  Ants naturally contain formic acid; ants eaten by anteaters digest in their own acid. Biologists have concluded that anteaters evolved all of these unique traits from ancestors that looked similar to rats.

Which of the following statements is the best description of how long tongues likely evolved in anteaters?

individuals with the shortest tongues were not as good at catching ants and starved

Anteaters likely evolved long claws from ancestors that had shorter claws. Think about the first anteater to have claws as long as modern anteaters.  Why did this individual have such long claws?

the anteater was lucky a genetic accident gave it long claws

An ancestor of modern anteaters has a tongue that is only half as long as modern anteaters. Because her tongue is relative short, she has to work hard to extend her tongue far enough inside ant hills to catch ants. How will these efforts affect the tongues of her offspring?

Her efforts will not affect the tongues of her offspring

Modern anteaters do not have teeth, but their ancestors did. Which of the following is the best description of what caused anteaters to lose their teeth?

anteaters without teeth had more young than anteaters with teeth

Natural selection acts on genetic variation. In sexually reproducing organisms with a long generation times, what processes accounts for individual variation? 

mutations, random fertilization, crossing over, independent assortment

Indicate which of the Hardy–Weinberg conditions is being violated in the following example: Some moths on a tree are easier to see due to their lighter color and therefore are eaten by predators more often.

no selection

Indicate which of the Hardy–Weinberg conditions is being violated in this example: Due to global warming, a river has dried up, allowing two different rabbit populations to mate with one another, whereas they were isolated before.

no gene flow

What is a population bottleneck?

an event that drastically reduces the size of a population

List three possible causes of a bottleneck

environmental disaster, hunting of a species to the point of extinction, habitat destruction