Sickle cell anemia is a disease that affects the shape of red blood cells in individuals who have two copies of the sickle cell allele. Individuals with one copy, called carriers, do not exhibit sickle cell anemia but are resistant to the disease malaria, which is spread by mosquitoes. The top map shows where malaria is common, while the bottom map shows regions where the sickle cell allele is most prevalent. Which of the following statements might account for the prevalence of the sickle cell allele in the areas shown?
a
Sickle cell is a polygenic trait, so it must be present on many chromosomes.
b
The allele is advantageous in cold areas uninhabited by mosquitoes.
c
Sickle cell is caused by chromosomal nondisjunction.
d
The allele is advantageous in tropical areas where the risk of malaria is the greatest.

primary succession occurs in essentially lifeless areas regions in which the soil is incapable of sustaining life as a result of such factors as lava flows, newly formed sand dunes, or rocks left from a retreating glacier. secondary succession occurs

it has to be understood that the sea water contains a huge amount of sodium and chlorine ions and if they enter the cell of the atlantic cod fish, the cell will shrivel and the fish will die. to avoid such a condition, the fish uses active transport for the purpose of removing the ions against the gradient.

explanation:

the atlantic cod is not a maritime osmoconformer. its native application of salts is less than that of the seawater it lives in. it is continually falling water from the gills to the ocean via osmosis.

countering that, the fish is going to be swallowing seawater. but since its internal collection of salts is lower than seawater, the fish will want to go free of excess salt, and since that's going upon a gradient, then active transport, requiring energy, must be used to pump out the salt. much marine fish use the organs to filter out the salt and these fish discharge very straight urine.

the answer is a) cell division.

hope this !

the answers are as following:

1. c. double helix, nucleosome, coil, supercoil, chromosome

2. b. g2 phase, preparation for mitosis

3. d. interphase consists of the g1, s, and g2 phases

4. c. metaphase

5. a. chromosomes are duplicated before cell division so that each new daughter cell has a complete set