Answer:
A callus is a hardening of skin, keratin is the protein which is abundant in callus. Skin is a protective layer against a external environment. Outer layer of skin consist of keratin which is also found in hair. Callus is the accumulation of dead cells result due to friction and pressure exerts on the part in which they are present. The keratin component (keratinocytes) remains undifferentiated in these dead cells which causes hardening in callus.
Answer:
They produce or process nutrients in the digestive tracts of humans and other animals.
Explanation:
Answer is A. A population becomes separated by environmental factors into two groups that do not reproduce with one another.
When a population of a species become geographically separated then gene flow between them stops. Over a period of time, the population may become genetically different in response to the natural selection due to different environments. Selection and genetic drift will act differently on these two separated populations. This will results into two separate species. This type of speciation is called allopatric speciation.
I think the correct answer among the choices listed above is option B. The process that creates specialized cells like blood cells, nerve cells, or bone cells, is called differentiation. It is a process where generic embryonic cells become specialized cells.
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-Payshence xoxo