BIOL 1070 Lecture Notes - Lecture 3: Genetic Drift, Gene Flow, Glochidium

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18 Jan 2017

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Genetic variation: different dna level in organisms of the same population or species. Alleles: different versions of the same gene. Mutation, natural selection, genetic drift and gene flow can cause genetic variation. Mutations do not occur in a specific order and are not always beneficial. Gene flow: movement of genes among populations. Genetic drift: evolution by chance due to sampling error: dramatic genetic drift: Bottleneck: evolution by chance due to random event (ex: tornado) Natural selection: action of an organism adapting to its surroundings. Sexual selection: type of natural selection demonstrating preference to characteristics of one sex. Artificial selection: process in which two organisms with the desired trait reproduce. ****example diagrams!! (percentage of each species before after) Two talented basketball players, one 7"7 and one 5"3, both good at the game for different reasons. Sample of males and females comparing height. First requirement of speciation: gene isolation, therefore; no gene flow. Gene must be isolated to reproduce effectively.

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Q1. What is the founder effect?

Sampling error that occurs during the establishment of a newpopulation by a small number of migrants.

Strong natural selection acting on the founders of a newpopulation because the environment they are now living in is sodifferent from the environment they came from.

A phenomenon named after William Founder, who observed that toppredators generally have low genetic diversity.

Rapid population growth following a bottleneck.

Q2. The effects of genetic drift are more pronounced in largerpopulations.

True

False

Q3. Inbreeding tends to increase the proportion of homozygousindividuals in a population (i.e. individuals that have two copiesof the same allele).

True

False

Q4. The effective size of a population is:

The size of an idealized randomly-mating population that is notunder selection and has the same heterozygosity as the actualpopulation.

The size of an idealized randomly-mating population that has thesame heterozygosity as the actual population, but does not loseheterozygosity over time.

The size of an idealized randomly-mating population losinghomozygosity at the same rate as the actual population.

The size of an idealized randomly-mating population losingheterozygosity at the same rate as the actual population.

Q5. Which of the following tends to reduce the effective size ofa population?

Check all that apply:

Increasing the population size.

A biased sex ratio.

Non-random mating.

Q6. If gametes from a gene pool combine randomly to make only asmall number of zygotes, the allele frequencies among the zygotesmay be different than they were in the gene pool because:

The effects of natural selection are more pronounced in smallpopulations.

The effects of genetic drift over several generations are morepronounced with small numbers of gametes.

The effects of differences in frequencies for different allelesare more pronounced with small numbers of zygotes.

The effects of sampling error are more pronounced with smallsamples.

Q7. Genetic drift is different from natural selectionbecause:

In natural selection allele frequencies change because somealleles confer higher fitness, whereas in genetic drift allelefrequencies change because of chance sampling error.

Natural selection acts primarily in large populations, whereasgenetic drift acts primarily in small ones.

Natural selection is a mechanism of evolution, whereas geneticdrift is an outcome of evolution.

Natural selection tends to cause rapid evolution, whereasgenetic drift tends to cause slow evolution.

Q8. Imagine a population evolving by genetic drift in which thefrequency of allele K is 0.65. What is the probability that at somepoint in the future allele K will drift to a frequency of 1?

Q9. A dwindling population of 1000 frogs occupies an isolatedwatershed in Costa Rica. To help preserve the species, scientistscaught 20 frogs to start a new population in a nearby watershed.This species has a gene that affects eye shape. The 1000-memberwild population has two alleles for this gene: R and r, withfrequencies 0.7 and 0.3, respectively. What will be the allelefrequencies of R and r in the 20-member founder population?

The frequencies will be 0.7 for R and 0.3 for r.

The frequencies will be 1.0 for R and 0 for r.

The expected frequencies are 0.7 for R and 0.3 for r. The actualfrequencies could be different.

The founder populations's allele frequencies will necessarily bedifferent than the source population's frequencies.

Q10. For a population containing 90 females and 10 males, whatis the effective population size, N_e ?

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Question 5

Which of the following is FALSE:

Natural selection has foresight, and can mold organisms in accordance with environments in the far future. This is why organisms have a good "fit" to their environments long after they have arisen through speciation.

Selection is an undirected process that can only ever work with the materials at hand.

Human beings have foresight because they possess brains that can think about possible outcomes and the consequences of actions. This is different to a process like natural selection.

The fact that natural selection has no foresight does not mean that it is incapable of producing beings that have foresight.

Question 6

The wings of bats, birds and flying insects are examples of:

Convergently evolved traits (at least in terms of their basic functionality).

Homologous traits.

Plesiomorphies.

None of the above.

Question 7

The effect of a trait depends on the environment because:

Organisms decide to change their behavior every so often to evade predators.

It is only ever in the context of an environment that these traits can exist, and whether they assist the organism or inhibit it will depend on the particularities of that environment in which it must interact.

Sexual selection will not tolerate wasteful and extravagant displays.

The environment is changing too fast for the organism to keep up with in terms of its conscious appreciation of it, so it must rely on its traits to do the work.

Question 8

Which of the following is TRUE:

Natural selection is not random; mutation is random; speciation is necessarily driven by natural selection.

Natural selection is not random; mutation is random; speciation is not necessarily driven by natural selection.

Natural selection is random; drift is random; speciation is not necessarily driven by natural selection.

Natural selection is not random; mutation is random; speciation must occur through the evolution of pre-zygotic barriers to mating.

Question 9

Heritability is:

The same as inheritance.

Another way of stating the degree to which a trait is genetic (for example, you could say that the color of your skin is "80 percent genetic and 20 percent environmental")

The proportion of variance of a trait in a population that is attributable to genetic variance in that population.

Present in populations, but not necessary for evolution by natural selection.

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44.Why donât similar genotypes always produce the same phenotype?

A. Parent alter their phenotype and pass on this phenotype to progeny

B. Phenotype is the product of many environmental influences

C. Genetic variations of ADH enzyme produce the same phenotype

D. Animals display different phenotypes dependent on diet, not genotype

46.Which of the following attributes has the least effect on the contribution an individual makes to the gene pool of the next generation?

A. spas of mating privileges

B. more efficient at obtaining food

C. produces more offspring

D. camouflage from predators

47.âUntil the agricultural evolution 10,000 years ago, people used to live in small populations with little gene flow between them. That is the best situation for rapid evolution.â said Sewall Wright. one of the founders of population genetics. This conclusion on gene flow conflicts with Hardy Weinberg equilibrium, which states that no gene flow means

A. natural selection

B. no evolution

C. no random mating

D. no genetic drift

58 Larval flies (maggots) express the Ubx gene in all of their segments, and thereby lack appendages. If this same gene continued to be expressed throughout subsequent developmental stages, except in the head region, and if the result was a fit, sexually mature organism that still strongly resembled a maggot, this would be an example of

A. homochrony

B. exaptation

C. paedomorphosis.

D. adaptive radiation

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BIOL 1070 Lecture Notes - Lecture 3: Genetic Drift, Gene Flow, Glochidium

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