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? the melanin in darkly pigmented skin protects circulating folate from being destroyed by uv radiation, and folate is important in human reproduction the melanin in darkly pigmented skin protects dna from uv radiation, and uv radiation can cause skin cancer people of african descent all have the same version of the mc1r gene, indicating that this gene was under selection she discovered that people of african descent have less folate circulating in their blood and that folate is important for human reproduction

The answer is; the melanin in darkly pigmented skin protects DNA from UV radiation, and UV radiation can cause skin cancer

In Africa, due to its equatorial latitude location, receives direct sunlight at more or less 90 degrees most of the year. These highly concentrated rays increase the UV radiation exposure  that can cause damage to cell DNA. Selection pressure, therefore, favored individuals with high melanin concentrations that protect against UV. Therefore population evolved towards high melanin densities in the skin.

9.9 years

a = p(1 + rt) . . account balance after time t at rate r starting with principal p

3000 = 2500(1 + 0.0202t) . . filling in the given numbers

1.2 = 1 + 0.0202t . . divide by 2500

0.2 = 0.0202t . . . subtract 1

0.2/0.0202 = t ≈ 9.901

it will take about 9.9 years for the account balance to reach $3000.

when the displaced particles are perpendicular to the direction the wave travels, is called a transverse wave, whereas in longitudinal wave the displace practices are parallel to the direction of the wave.

in the given image:

first image shows - longitudinal wave

second image shows - transverse wave

third image shows - longitudinal wave

fourth image shows - longitudinal wave