B. mass extinctions happen when populations crash due to overpopulation while background extinctions are more likely to result from disease.
The answer is <span>geographic isolation.</span>
<span>When a new species form by geographic isolation, it is called
geographical speciation or allopatric speciation. Geographical isolation is a physical separation which prevents gene
flow between distinct populations (on the island and on continent). The island populations will eventually diverge from a single species that migrated to the island. The members of the populations, which once belonged to the same species, will
no longer be able to mate and produce offspring. Eventually, the formation
of new species will occur, for example kangaroos, koala, and wombats, form that one species.</span>
Answer:
A. Natural killer (NK) cells are activated in response to interferons or macrophage and Major histocompatibility complex (MHC) and allows direct apoptosis of virus.
Viruses can invade NK cells by inhibiting MHC from reaching the cell surface. Using stimulating the inhibitory receptors and disrupting the activating receptors, viruses can avoid NK cells. MHC act as a ligand of inhibitory receptor, and when bind with inhibitory receptor allows damage to NK cells.
So, if i would be a virus i will use inhibitory receptors stimulation to avoid NK cells.
B. Bacteria are killed by phagocytic immune cell macrophages by engulfing them.
Bacteria avoid macrophages by escaping from phagosome before the lysosome fuses as lysosomal chemical kill the bacteria and some bacteria prevent acidification of the phagosome.
C. Parasites can avoid macrophages by modulating the host's cell cytoskeleton to block proper phagocytosis.
D. Bacteria can avoid dendritic cells by avoiding lysosomal degradation and prevent antigen presentation on MHC molecules that will modulate the entrance to DCs.
E. B cells are responsible for producing antibodies. Activation of B-cell depends on positive and negative signals transmitted through the B-cell receptor (BCR), so genetic polymorphisms and mutations affects the positive and negative signals. If mutation is done showing negative signal, B cell will not the activate and no antibodies will produce.
Answer: I don’t know how to comment but thanks for the answer on my recent question
Explanation:
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Answer:
The antibodies mistakenly identify the cells as foreign material.
