<span>They have very stable outer electron shells</span>
No, the sickle-cell anemia allele won't be eliminated by natural selection.
Sickle-cell anemia trait is controlled by a single gene and the allele (S) for sickle-cell anemia is a harmful autosomal recessive.
It is caused by a mutation in the normal allele (A) for hemoglobin (a protein on red blood cells).
Heterozygotes (AS) with the sickle-cell allele are resistant to malaria, a deadly tropical disease. It is common in many African populations.
In these areas, (S) carriers have been naturally selected, because their red blood cells, containing some abnormal hemoglobin, tend to be in sickle shape when they are infected by the malarial parasite.
Therefore, they are more likely to survive and reproduce. This keeps the S allele in the gene pool.
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Answer:Transpiration
Explanation: water cycle is the continuous movement of water on the Earth to ensure the availability of water.water is a universal solvent that is essential for the survival of living things.water cycle ensure that clean water is available.plants require water which is gotten from the soil.water is lost from the leaves of trees through transpiration.transpiration may also occur through the lenticels and stomata of stems.
the movement of water through the plant is called transpiration pull.this is responsible for the pull of water into the leaves.it increases the absorption of minerals from the soil and also cools the plant.
This water vapour that transpire from the plant,is condense as clouds, which then falls to the Earth as rain and the water cycle continue
Answer:
Innate immunity is a non-specific immune system which provides defence against any pathogenic microorganism in early stages. It includes physical barrier such as skin, chemical barriers such as saliva, tears, et cetera, phagocytic cells such as macrophages, et cetera.
Acquired immune system is the one which develops after exposure to pathogen or antigen. It is highly specific in nature. It includes B-lymphocytes and T-lymphocytes. It includes the production of antibodies.
Vaccines are used to develop acquired immunity in people. The process is termed as vaccination or immunisation. Heat-killed or weakened pathogen or antigen is inserted into a person after which a person develops antibodies and memory cells against that pathogen or disease. So, the immune system acts more vigorously against that pathogen in secondary infection.
Thus, a person becomes immunised.
the answer is yess hope it is
