Answer:
Nobody can help you with this without an image. You built something and we need to be able to see it to reply.
Explanation:
Answer:
two
At the beginning of the S stage, each chromosome is composed of one coiled DNA double helix molecule, which is called a chromatid. At the end of this stage, each chromosome has two identical DNA double helix molecules, and therefore is composed of two sister chromatids.
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.
The blood pressure in the arteries are fast paced so the arteries would need to be strong in order to manage while the blood pressure in the vains are much slower so the are not really strong builded
hope this helped
