Organic Evolution Exam 3

complex adaptations

coexpressed traits that experience selection for a common function

Blueprint for making spores

Dna damage induces Sda which represses KinA

Up regulation by energy

Bacteria can survive harsh conditions by making spores

Hox genes are regulatory network of developmental genes in

a. fungi

b. plants

c. animals

d. bacteria

c. animals

promiscuous proteins

capable of carrying out functions other than their primary task, likely to take on new functions if duplicated

paraog

homologous gene that arises by gene duplication

gene recruitment

co-option of a particular gene or network for a totally different function as a result of a mutation

novel traits can evolve

when genes are expressed in a new developmental context

when duplication occurs and proteins are co opted into other functions

Question: In what way is gene recruitment involved in the evolution of aerobic citrate metabolism in E. coli?

A. Gene recruitment was not involved.

B. The citT gene was mutated to encode a promiscuous protein.

C. A duplicated citT gene came under the control of the rnk promoter.

D. A 2933-bp segment including the citT gene and the rnk promoter was duplicated and inserted next to the original segment.

C. A duplicated citT gene came under the control of the rnk promoter.

Molecular basis of citrate metabolism elucidated

normally citrate metabolism is only expressed w no oxygen

normally rnk expressed in presence of oxygen

now citT expressed in presence of oxygen

Venom delivery in venomous snakes requires

A. venom glands.

B. hollow teeth called fangs.

C. muscles around venom glands.

D. all of the above.

D. all of the above.

Regulatory mutation led to production of defensin gene in the mouth

pancreas to mouth(venom gland)

The genes recruited for venom production

a. evolved independently in each lineage of venomous snakes.

b. evolved in the ancestor of snakes.

c. evolved in the ancestor of snakes and their closest living relatives.

d. evolved in the ancestor of snakes and mammals.

c. evolved in the ancestor of snakes and their closest living relatives.

Based on the homology of Hox genes in humans, mice and flies, what can we deduce?

A. Hox genes are likely a result of convergent evolution.

B. Hox genes likely evolved after the two lineages diverged from a common ancestor.

C. The common ancestor of flies and mammals already had a set of Hox genes that controlled development.

D. The common ancestor of flies and mammals could not share a homology in developmental genes because the lineages are separated by nearly 570 million years

C. The common ancestor of flies and mammals already had a set of Hox genes that controlled development.

Hox genes are part of a conserved “genetic toolkit” among animals

A common ancestor in early animal evolution passed this gene set to animals now as diverse as flies and mammoths

orthologs

homologous genes seperated

Expression of Alx4 and Hoxd13 in fishes and tetrapods drives limb differences

Alx doesn’t extend beyond the wrist

How do bat forelimbs differ from their mammalian counterparts?

A. They have elongated digits.

B. They have an extra elongated digit.

C. They have extra limb bones evolved from a different ancestor.

D. There is no difference in bat forelimbs compared to their mammalian counterparts.

A. They have elongated digits.

Change in expression of Bmp2

Expression differences in a single gene – Bmp2 – give rise to limb elongation

Changes in the expression of developmental genes can dramatically alter phenotypes

– Turning fins into limbs.

– Turning ordinary mammal limbs into bat wings.

Opsin evolution

evolved the ability to capture photons and the early animals with these opsins could now sense light

Crystallins evolved through gene recruitment

When a gene is co- opted for a new function (but maintains its original) as a result of a mutation.

recent hypothesis for evolution of the vertebrae eye

The condition that occurs when a mutation that causes beneficial effects for one trait also causes detrimental effects on other traits is

A. pleiotropy.

B. positive selection.

C. negative selection.

D. antagonistic pleiotropy.

D. antagonistic pleiotropy.

Antagonistic pleiotropy

Single gene affects expression of many traits

mutations may have positive effects for one trait but negative effects for another trait

Law of physics

atmospheric O2 concentrations constrain insect size

Parallel evolution is

A. the independent evolution of two lineages into a similar form.

B. the independent evolution of similar traits, starting from a similar ancestral condition.

C. the process in which the genealogy of any pair of homologous alleles merges in a common ancestor.

D. a condition that occurs when the growth and development of traits in different lineages result from underlying genetic mechanisms that are inherited from a common ancestor.

B. the independent evolution of similar traits, starting from a similar ancestral condition.

Convergent evolution

Independent evolution leading to similar traits in two different lineages

– Result of similar selection pressures

parallel evolution

Independent evolution of similar traits in multiple lineages, all starting from a similar ancestral condition

– Cavefish species

– Three-spined stickleback

deep homology

When growth and development of traits in different lineages result from underlying mechanisms inherited from a common ancestor

• Is the fly eye homologous to the mouse eye, or is it

convergent?

• Both, depending on the level of development

examined

patterns of diversification

divergent evolution, convergent evolution, parallel evolution, coevolution

The difference in beak size between offspring of finches that survived the drought on Daphne Major and the population average before the drought is

a. the response to selection (R).

b. the selection differential (S).

c. heritability (H2).

d. heritability (h2).

e. the mutation rate (μ).

a. the response to selection (R).

What is beak size evolution

severe drought resulted in only harder woody seeds

result: larger beaked birds are favored

evolutionary response to selection equation

R=h²xS

broad sense heritability h² equation

proportion of total phenotypic variance of a trait that is attributable to genetic differences among individuals

phenotypic variance

vp=vg+ve, environment + gene

broad sense heritability in terms of vg and vp

vg/vp or (va+vd+vi)/vp

narrow sense heritability equation

The proportion of phenotypic variance explained by the additive effects of alleles:

h²=va/vp

how to estimate heritability

mean of offspring from 2 specific parents

slope=heritability on graph

significance of peter and rosemary grant’s findings

They have demonstrated how very rapid changes in body and beak size in response to changes in the food supply are driven by natural selection.

selection differential equation

S=mean of reproducing individuals-mean of original population

true or false: high heritability results in larger change

true

stabilizing selection

mean selected, variance decreases

directional selection

mean shifts, variance decreases

disruptive selection

mean stays or two selected, variance increases

Question: Which statement describes the evolutionary history of winter-brown

snowshoe hares in Washington?

A. Their entire genome suggests they are in a clade with black- tailed jackrabbits and acquired the Agouti gene from winter- white hares.

B. They have a mutation for winter-brown fur that occurred in theAgouti gene of a winter-white hare and persisted where it increased fitness.

C. They descended from winter-white hares and acquired the Agouti allele for winter-brown fur from random matings with black-tailed jackrabbits.

D. They are infertile hybrids produced by matings between winter-white hares and black-tailed jackrabbits, which contribute the Agouti allele.

B. They have a mutation for winter-brown fur that occurred in theAgouti gene of a winter-white hare and persisted where it increased fitness.

which type of heritablity did the grant’s measure

narrow-sense heritability

Natural selection can lead to variations across habitats or environments.

Atlantic and Gulf Coast mice both evolved white fur, but the specific mutations responsible are different.

• The effect of natural selection can change in response to climate change.

• Alleles can spread rapidly in populations via hybridization.

predators vs parastitoids

More than one agent of selection can act on a trait

• Such agents can drive selection in two different directions at the same time

stabilizing selection on gall size

Intermediate size (stabilizing selection) results because:

1. Woodpecker eat larger galls

(directional selection for smaller galls).

2. Parasitoids are more effective at infecting smaller galls

(directional selection for larger galls).

If a population of gallflies occurred in an area where birds were present but parasitoid wasps were absent, which type of selection is most likely to affect gall size?

a. stabilizing

b. negative frequency-dependent

c. directional

d. disruptive

c. directional

Parallel evolution

the independent development of similar traits, forms, or behaviors in closely related, distinct lineages, usually when adapting to similar ecological niches

Question: Why do three-spined stickleback fish with low-Eda alleles have an advantage in freshwater over sticklebacks with high-Eda alleles? They have fewer predators in lakes.

A. Low-Eda fish stop growing at smaller body sizes, which allows them to survive with less armor.

B. Low-Eda fish use their available energy to grow faster and add body mass instead of armor.

C. Low-Eda fish can grow heavier armor to defend against the predators in freshwater.

D. Low-Eda fish can produce both large bodies and heavy armor when food is abundant.

B. Low-Eda fish use their available energy to grow faster and add body mass instead of armor.

Low-Eda allele favored in freshwater populations

• Production of armor is energetically costly.

– Little predation pressure means the cost may outweigh the benefit.

• Low-Eda allele present at low frequency in marine environment

– Favored when introduced to freshwater.

Humans as agents of selection

domesticated many plants and animals

many variations of both have been produced by artificial selection

Question: Why have so many species of weeds become resistant to glyphosate?

A. Glyphosate persists in the environment for a long time.

B. Many farmers used glyphosate as their only herbicide for years.

C. Glyphosate only targeted weeds and did not affect any crop plants.

D. Plants repeatedly sprayed with glyphosate develop tolerance for it

B. Many farmers used glyphosate as their only herbicide for years.

The graph below shows the effect of hunting imposed on horn length in bighorn sheep populations. What type of selection does it show?

a. stabilizing

b. negative frequency-dependent

c. directional

d. disruptive

c. directional