HINT FOR NEXT TIME: Look for a type of selection where female choice results in highly ornamented males.
Result of intrasexual selection
Great! Competition between members of one sex for access to the other is intrasexual selection.
HINT FOR NEXT TIME: Intrasexual selection often creates huge differences in size between males and females, as well as highly aggressive male behavior.
Result of artificial selection.
Good work! All of these plants varieties resulted from artificial selection.
HINT FOR NEXT TIME: Artificial selection is when breeders select specific traits, creating modified populations with characteristics of benefits to humans.
Result of natural selection
Fantastic! Selection for camouflage created the fantastic form of the leaf insect.
HINT FOR NEXT TIME: Camouflage results from natural selection
[q json=”true” hotspot_user_interaction=”label_prompt” dataset_id=”Evolution Click-On Challenge Dataset|c403d46f13550″ question_number=”2″] Types of selection: Which one is which?
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Directional selection
Terrific. “A” is directional selection.
HINT FOR NEXT TIME: Look for a type of selection against one extreme, pushing the population toward the other extreme.
Stabilizing selection
Thumbs up! “B” is stabilizing selection.
HINT FOR NEXT TIME: Look for a type of selection that selects against the extremes, and for the mean.
Disruptive selection
Superb! “C” is disruptive selection.
HINT FOR NEXT TIME: Disruptive selection is against the mean, pushing the population toward both extremes.
Finches with larger beaks are able to get food by cracking open larger seeds.
Outstanding. That’s directional selection, shown at “A.”
HINT FOR NEXT TIME: This would be directional selection. Look for a type of selection against one extreme, pushing the population toward the other extreme.
In a shoreline habitat, flies with long wings are blown out to sea. Flies with short wings can’t escape predators. What’s the result?
Nice! The result will be stabilizing selection.
HINT FOR NEXT TIME: in this scenario, you’re eliminating both extremes, and selecting for the mean. That’s stabilizing selection. Which scenario looks like that?
The ground where a population of mice lives in either light sand or dark rock. The result would be…
Superb! The result would be disruptive selection (“C”)
HINT FOR NEXT TIME: Look for Disruptive selection. That is selection against the mean, pushing the population toward both extremes.
[q json=”true” hotspot_user_interaction=”label_prompt” dataset_id=”Evolution Click-On Challenge Dataset|4c930df3f51af” question_number=”4″] Genetic drift and other population genetics phenomena.
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Explains low genetic diversity in Cheetahs and Northern Elephant seals.
Yes! Population bottlenecks reduce genetic diversity
HINT FOR NEXT TIME: Think of a metaphor when only only a small proportion of a population’s gene pool would be able to pass through some catastrophic effect, drastically reducing genetic diversity.
When a small number of individuals leaves a large parent population, random sampling can change allele frequencies in the new population.
Way to go! That’s the founder effect.
HINT FOR NEXT TIME: This is a kind of genetic drift associated with creating new populations. Who creates a new population?
Even when an allele is harmful, it might be in higher than expected frequency if it’s beneficial in certain genotypes.
Very nice! That’s what heterozygote advantage is all about.
HINT FOR NEXT TIME: This is why the sickle cell allele is in relatively high frequency.
[q json=”true” hotspot_user_interaction=”label_prompt” dataset_id=”Evolution Click-On Challenge Dataset|11806403811212″ question_number=”5″] Vertebrate phylogeny. Traits are in red. Circled letters are ancestral species.
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The shared, derived trait of the lizard, alligator, robin, rat, and gorilla clade.
Yes! It’s claws or nails.
HINT FOR NEXT TIME. Start by identifying the clade. Then find the common ancestor. Then find the trait that this ancestor possessed which was passed on to the entire clade.
The outgroup for the clade of all species with a vertebral column.
Way to go! It’s the hagfish.
HINT FOR NEXT TIME: Find the clade that includes all the organisms with a vertebral column. Which organism is outside this clade?
The common ancestor of lizards, alligators, and robins.
That’s right. It’s “E.”
HINT FOR NEXT TIME: Find the lizard, alligator, and robin lineages. Go back in time until all three lineages come together.
The robin’s closest relative.
Superb! It’s the alligator.
HINT FOR NEXT TIME: Find the taxon with whom the Robin shares the most recent common ancestor.
An ancestral trait for the clade with lungs and four limbs.
Nice job! It’s a vertebral column.
HINT FOR NEXT TIME: Find a trait that all of the taxa with lungs and four-limbs share, but which is also present in a more inclusive clade with a more distant common ancestor.
The shared derived trait the rat and gorilla clade.
Great work. It’s fur and mammary glands.
HINT FOR NEXT TIME: Find a trait that’s only shared by rats and gorillas.
Symbolically represents the frequency of heterozygotes.
Fantastic! It’s 2pq.
HINT FOR NEXT TIME: heterozygotes have both the recessive and the dominant allele (both p and q). What could represent such a genotype?
Symbolically represents the frequency of homozygous recessives
Exactly. It’s q2.
HINT FOR NEXT TIME: If “q” represents the recessive allele, what could represent a homozygous recessive (who inherited two copies of q)?
Symbolically represents the frequency of homozygous dominants.
Excellent! It’s p2.
HINT FOR NEXT TIME: If “p” represents the recessive allele, what could represent a homozygous dominant (who inherited two copies of p)?
Symbolically represents the frequency of the recessive allele?
Yes, it’s q.
HINT FOR NEXT TIME: If “q2” represents the frequency of homozygous recessive individuals, what could represent the frequency of the recessive allele?
Symbolically represents the frequency of the dominant allele.
Nice! It’s “p.”
HINT FOR NEXT TIME: If “p2” represents the frequency of homozygous dominant individuals, what could represent the frequency of the dominant allele?
[q json=”true” hotspot_user_interaction=”label_prompt” dataset_id=”Evolution Click-On Challenge Dataset|10e0647265d634″ question_number=”7″] Allopatric speciation model. Colored circles represent individuals with similar genotypes. For questions about stages, use the left column.
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The letter that represents gene flow
Yes! Letter “a” represents gene flow.
HINT FOR NEXT TIME: Before speciation can happen, gene flow has to stop. What process does the geographic barrier at “B” prevent?
The letter that represents the appearance of a geographic barrier.
Way to go! It’s “B.”
HINT FOR NEXT TIME: Find something that blocks gene flow between the Western and Eastern populations.
The stage where variant types start to emerge
Thumbs up! It’s stage 2.
HINT FOR NEXT TIME: Use the left column for stages. Notice the differences between the populations at stage 1, stage 2, and stage 3.
The stage where the geographic barrier has been removed.
That’s right. It’s stage 4.
HINT FOR NEXT TIME: Use the left column for stages. There’s no geographic barrier in stage 1, but there is in stages 2 and 3. When does it disappear?
The image that indicates that the new species are in contact.
Nice. It’s the area in stage 4 where “e” and “f” are in contact.
HINT FOR NEXT TIME. Where do you see “e” and “f” in contact.”
The stage or image where the Western and Eastern populations have evolved into new species, but are still divided by a geographic barrier.
Nice going. It’s stage 3.
HINT FOR NEXT TIME: In what stage have the divided populations changed into two forms with different genotypes?