Answer:
Variability was seen as imperfection, so natural selection could only eliminate the inferior and imperfect, not giving rise to new things, new species.
:
The answer is stabilizing selection.
<span>Sickle-cell anemia is a recessive disorder caused by the presence of two recessive alleles "s", so genotype is "ss". This disorder is characterized by sickle hemoglobin. In an area with malaria, heterozygous individuals "Ss" (with one dominant allele and one recessive allele) have an advantage. These individuals will have both normal and sickle hemoglobin. But pathogen that causes malaria affect only normal hemoglobin, so heterozygous individuals will have half of the hemoglobin resistant to the pathogen and those individuals are resistant to malaria.</span>
Stabilizing selection favors heterozygotes Ss, disruptive selection favors dominant (SS) and recessive (ss) homozygotes, while directional selection favors dominant (SS) or recessive (ss) homozygote. Since in this example, people with genotype Ss (heterozygotes) are in advantage, then this is an example of stabilizing selection.
.5 of a micrometer in width
2 micrometers in length
Answer: Adaptive immunity
Explanation:
The adaptive immunity is also known as acquired immunity. It is a sub system of the overall immunity.
It can defined as the immunity which is not present in the body when we are born. It develops in the body when it is exposed to the pathogens no matter it is natural or artificial.
The acquired immunity can develop in the body and makes the body susceptible to infections and develops prevention for the next time when the body will be exposed for the next time.
