BIO SCI 97 Lecture 20: Lecture 20 Notes

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pinkhornet528

22 Dec 2018

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Heritability was developed to help measure the proportion of phenotypic variation that is due to genetic variation. It is a measure of the degree to which genetic differences contribute to the phenotypic variation of a trait. Heritability values are accurate only for the environment and population in which they are measured. Heritability for a given trait in a population can change. High heritability does not preclude environmental factors. Narrow sense (h^2) estimates the proportion of phenotypic variation that is due to. Broad sense heritability (h^2) - estimates the proportion of phenotypic variation that is additive genetic variation ( = va/ vp) due to total genetic variation (=vg/vp) Both expressed as proportions ranging in magnitude from 0 - 1. 0. Heritability is very difficult to measure accurately in human populations, but phenotypic variation in twins can provide some insight. For mz twins, vp = ve (phenotypic variance = environmental variance) Monozygotic twins - identical twin that share 100% of their alleles.

Related Questions

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.

jadelocust741

CAN YOU PLEASE ANSWER 2 AND 3 :) THANK YOU

QUESTION 1 Use the information below to answer questions 1-3. Northern burrowing bugs feed on small arthropods that they search for under the bark of trees. These bugs vary considerably in the width of the pronotum; male bugs show greater variability than do females. Using light traps, you collect all of the bugs in the area, sort them by sex, and measure their pronotum width. By using a male-specific genetic markers you are able to determine which male is the father of each male offspring. The males do not associate with the females after they have mated; therefore any resemblance between males and their offspring is due only to geneticsânot environment. The phenotypic variance of the males is 175.2, while the phenotypic variance of the offspring is somewhat lessâ146.1. The covariance in snout length between males and their offspring is 14.6. What is the heritability of pronotum width?

a) 0.083 b) 0.100 c) 0.167 d) 0.335 e) 0.500

QUESTION 2 Northern burrowing bugs shelter from cold weather in deep crevices in tree bark. Bugs who do not find shelter will not survive sever cold weather. During your study, a period of subfreezing temperatures caused all bugs that were not small enough to tunnel into crevices in the bark to die. Because of this, only those bugs with a pronotum width that averaged 12 mm narrower than the population mean to survive. Relative to the original population, how much will pronotum width differ in the next generation (young born after the severe cold period)?

a) 2.0 mm b) 3.0 mm c) 6.0 mm d) 12.0 mm e) You do not have enough data to tell

QUESTION 3 In Question 2, what type of selection is operating on pronotum width?

a) directional selection for a wider pronotum b) directional selection for a narrower pronotum c) stabilizing selection d) disruptive selection

orchidgoat535

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 ?

chocolateplatypus914

BIO SCI 97 Lecture 20: Lecture 20 Notes

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