Part A
Which of the following statements apply to the variation in
human skin color?
Select all that apply.
Select all that apply.
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Human skin color variation is primarily determined by the type and amount of melanin pigment in the skin. |
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Human skin color variation likely evolved in response to differences in the intensity of sunlight around the world. |
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Human skin color variation evolved recently in hominid evolution, once some populations of our human ancestors migrated out of Africa. |
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The color of human skin and the skin of our closest primate relative exhibits a similar range in variability. |
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Variability in human skin color can be explained by the activity of a single gene. |
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Part B
Which of the following statements accurately describes melanin's
function?
Which of the following statements accurately describes melanin's
function?
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The more melanin an individual has in his or her skin cells, the more likely he or she is to get mutations in DNA. |
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Everyone has the same type of melanin, but the amount varies from person to person. |
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Lighter skin has less of the dark-brown eumelanin that protects cells from UV damage. |
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Melanin is a molecule that distinguishes humans from their primate relatives. |
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Part C
Darker skin is more prevalent in high-UV areas. Dr. Nina
Jablonski proposed a hypothesis to explain the selective pressure
for darker skin in these environments. On what evidence did she
base this hypothesis?
Darker skin is more prevalent in high-UV areas. Dr. Nina
Jablonski proposed a hypothesis to explain the selective pressure
for darker skin in these environments. On what evidence did she
base this hypothesis?
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the melanin in darkly pigmented skin protects DNA from UV radiation, and UV radiation can cause skin cancer |
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she discovered that people of African descent have less folate circulating in their blood and that folate is important for human reproduction |
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people of African descent all have the same version of the MC1R gene, indicating that this gene was under selection |
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the melanin in darkly pigmented skin protects circulating folate from being destroyed by UV radiation, and folate is important in human reproduction |
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Part D
Human populations in low-UV environments tend to have more
lightly pigmented skin. One explanation is that the selective
pressure for dark skin decreases as UV intensity decreases. At the
same time there is selection for lighter skin to absorb more UV
radiation, which is needed for vitamin D production.
What evidence supports the vitamin D hypothesis for the evolution
of lighter skin tones?
Human populations in low-UV environments tend to have more
lightly pigmented skin. One explanation is that the selective
pressure for dark skin decreases as UV intensity decreases. At the
same time there is selection for lighter skin to absorb more UV
radiation, which is needed for vitamin D production.
What evidence supports the vitamin D hypothesis for the evolution
of lighter skin tones?
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lightly pigmented people cannot synthesize vitamin D in high-UV environments, such as equatorial Africa |
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lightly pigmented people tend to be at higher risk of vitamin D deficiency |
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red hair and light skin are typical of people of northern European descent |
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indigenous peoples living at high latitudes have darker skin, but they eat foods rich in vitamin D |
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Part E
Based on the risk factors discussed in the video, which of the
following groups would be most likely to develop the bone disease
rickets?
Based on the risk factors discussed in the video, which of the
following groups would be most likely to develop the bone disease
rickets?
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children born to parents with dark skin living far from the equator |
| adults with dark skin who live close to the equator |
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children born to parents with light skin living close to the equator |
| adults with light skin who live far from the equator |
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Part F
In what way does natural selection depend on the specific
environment in which an organism lives?
In what way does natural selection depend on the specific
environment in which an organism lives?
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when the environment changes, traits that were beneficial to an organism may become harmful and vice versa. |
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natural selection is random, and the direction of the selective pressure cannot be predicted based on the environment. |
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when an organism enters a new environment, it evolves all of the traits it needs to survive there |
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natural selection produces traits that are always either helpful or harmful, regardless of the environment. |
Answer
Part A
Human skin color variation
is primarily determined by the type and amount of melanin pigment
in the skin.
Explanation: The amount of
melanin present pigment present determines the colour of the skin.
more melanin pigment the more dark they are.
Human skin color variation
likely evolved in response to differences in the intensity of
sunlight around the world.
Explanation: It is developed
due to differential exposure of human to varied environment during
the migration.
Human skin color variation
evolved recently in hominid evolution, once some populations of our
human ancestors migrated out of Africa.
Hence, the above statements
are true.
