Stimulus is something that causes a psychological response. It can be internal or external. The stimulus is the contact with the hot pan. It is an external stimulus. Sense organs, such as the sensory receptors in the skin are sensitive to external stimulus. The quickly pull of your hand is a reflex action.
The contact causes a nerve impulse that will travel to the spinal cord via the sensory neurons.<span>To respond to the stimulus of the reflex arc, the muscle needs to contract to pull the hand quickly away from the hot pan.</span>
Answer: Ribose is synthesized from glucose and other monosaccharide molecules in living cells by a process known as pentose phosphate pathway. The pentose phosphate pathway is a series of chemical reactions taking place in the cytosol of cells.
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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The variety of traits a species has best defines genetic diversity.
Answer:
True.
Explanation:
As we know, the plasma membrane of the cells is semi-impermeable, that is, it only allows the passage of some molecules in sizes and specific burning nature. Although the Na + and Cl- molecules are very small, they are polar, electrically charged molecules. These molecules are not well seen by the membrane, which does not allow them to pass into the intracellular medium.
