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17.1 Genes and Variation

Questions Answers

1. In your own words, explain what the following phrase means: “Natural selection acts directly on phenotype, not genotype” Natural selection is more focused on the characteristics of the animal, not the alleles.
2. Explain the relationship between gene pools and allele frequencies. Gene pools is all the genes in a species, including the alleles.  Allele frequencies is how many times an allele shows up in a gene pool.  
3. People usually think that mutations are bad, but that isn’t usually the case. Explain what a mutation is, and how common they are. A mutation is an unexpected change in chromosomes within a cell.  Since it is any change, it can be good bad or neither.  It can improve an organism to help it survive, or be a different colour which could be any of them.  It could make them less noticeable, more noticeable, or stay the same.
4. There are lots of forms of genetic recombination. In your own terms, explain what genetic recombination is, and why you think it is important for the fitness of a species. It is when the gametes of the parents combine to make a new diploid cell.  The gametes don’t have to be the exact same as the parents since chromosomes move independently.   It is important because to evolve, survive, and live to reproduction, species need to have variation to pick out the strongest of the group.
5. i. Compare and contrast single-gene traits and polygenic traits

ii. Without having any information about the genotype, how can you tell whether a trait you are studying is single-gene or polygenic?

  1. Single gene traits are controlled by a single gene, whereas polygenic traits are controlled by more than two genes.  
  2. You can tell because single gene traits are with/without.  Polygenic can have different possibilities.


17.2 Evolution as Genetic Change in Populations

Questions Answers

1. Explain the following statement in your own words: “An adaptation is any genetic trait that increases an organism’s chance of passing on its alleles” It means that adaptations help species survive and reach the reproductive age.
2. Explain how natural selection leads to changes in allele frequencies in single gene traits. Feel free to use an example to explain your answer. If an adaptation of a single gene trait is successful, then it will become more frequent.
3. Explain and give an ORIGINAL example (not from the book) of each of the following:

i. Directional Selection

ii. Stabilizing Selection

iii. Disruptive Selection

  1. It is when one type of feature is more effective than another feature, so the average amount of one type increases.  When one colour is the most effective for survival, and other colours dies out.
  2. When things that are average survive the best, they will become more common and balance out.  The average colour in a species became the most prevalent.
  3. It creates two distinct phenotypes in a species.  Like two different colour in a species that survive equally as good.
4. When natural selection is not acting on a trait, you might see evidence of genetic drift.

i. What is genetic drift?

ii. Why is it more likely to occur in small populations?

iii. What is the relationship between genetic drift and the bottleneck effect?

  1. Genetic drift is a random change in allele frequency.
  2. Because in small populations there are less variables and it can happen more quickly.
  3. The relation between the two is that they both are strange or sudden changes in gene pools
5. How might the founder effect explain some of the variety seen in Darwin’s finches? IT explains it because when the finches migrated to the islands, the gene pool was a bit different, and it lead to changes in the phenotype.
6. What is genetic equilibrium? Why is it unlikely that one might find genetic equilibrium in a wild population? It is when a species is not changing, and allele frequencies are not changing.  It is unlikely because the environment is always changing.
7. The Hardy-Weinburg principle is a good way to make predictions about allele frequencies at a given moment, but is not beneficial for making predictions about the future in a wild population. Why not? It does not take into account predation.


17.3 The Process of Speciation

Questions Answers

1. What is speciation? Why is reproductive isolation so important to the process of speciation? It is when the same species gets seperated, and evolves into its own species different from the original.  It is important because it won’t happen without it.
2i. Compare and contrast behavioral, geographic and temporal isolation. What do they have in common? How are they different?

ii. The females in a particular species of frog go into estrus (become reproductively receptive) during the third week of April. A mutation occurs where some females begin estrus during the first week of April, and others during the first week of May. Both of these times are better than the third week of April, because they are during times of low predator activity. Therefore, the population begins to develop two separate mating periods, and over time, there are no more frogs in estrus during the third week of April anymore.

What type of isolation is this?

iii. What do you think will happen over time to the species of frogs described above? Be specific

  1. All of them are types of isolation between a species, however they all are different types, since some deal with mentality, area, or reproduction.
  2. This is Temporal isolation because there is a difference in mating times inside the species.
  3. Since the two groups of frogs have different estrus times, they will evolve into two different species.  
3. In 3-5 sentences, summarize the current theory of how Darwin’s finches came to populate the Galapagos Islands. A founding species went to the Galapagos.  Since there are many different islands, geographic isolation went down, and they phenotype changed, turning into its own species.  Then, the gene pool for each population became accustomed to the new changed.

17.4 Molecular Evolution

Questions Answers

1. What is the relationship between molecular clocks and mutations? Molecular clocks use mutations as a way to tell when species start to grow away from each other.
2. A particular protein, McHughin, has a mutation rate of one mutation per 500,000 years. Humans and chimpanzees both produce this protein. When you compare the gene for McHughin, you will find 26 nucleotide differences. According to this molecular clock, how long ago did the common ancestor between humans and chimpanzees exist? 6-7 million years ago.
3. How might a duplicate gene lead to a new trait in a species? New copies of a gene may undergo mutations and adaptations that change the purpose.  Since it changes, it can change the phenotype to accommodate.
4. What is “evo-devo”? This isn’t a hugely important vocabulary term, but it’s too cool of a word to not include a question about. It is  field of study around the EVOlution of embryo DEVelOpment.
5. What is a hox gene? Do your best to explain in your own terms. Feel free to use an example They are a group of related genes that control the bodily plan along the spine of an embryo.  

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