The difference in concentration between solutions on either side of a cell membrane is a concentration gradient.
In the field of biology, a concentration gradient can be described as a difference in the concentration of molecules inside and outside of a cell. It is due to concentration gradient that molecules move into and out of a cell through the cell membrane.
Some molecules move from an area of higher concentration gradient to an area of lower concentration along the concentration gradient. Diffusion is an example of such a process.
On the other hand, some molecules move from an area of lower concentration to an area of higher concentration against the concentration gradient. Active transport is an example of such a process.
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A constant is something that is kept the same throughout the course of a experiment. So I would guess C) because they are not doing anything special. If it’s not C then it is A. :)
Answer: (B) Pre-zygotic; post-zygotic.
Explanation:
Prezygotic isolation occurs before fertilization of eggs. It occurs between the two sex gametes and deter sexual reproduction between different species.
However, individuals are considered to be diverge on the phylogeny tree and different species, when they cannot reproduce.
Mechanisms of prezygotic isolation include habitat isolation, gamete isolation, mechanical isolation, behavioral isolation, and mating seasons.
Whereas, postzygotic isolation prevents the formation of fertile offspring. This phenomenon leads to production of an hybrid offspring from different species and this is a form of speciation in nature.
Mechanisms of postzygotic isolation include hybrid inviability, hybrid breakdown, and hybrid sterility.
<span>They bind messenger RNA and transfer RNA to synthesize polypeptides and proteins.</span>
