<span>Repeated and prolonged episodes of stress can cause a state of exhaustion within the immune system which can ultimately cause infection.</span>
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.
This statement is true. To be more specific, the calcium ions bind to the troponin, which are attached to the protein tropomyosin. The tropomyosin then to shifts to expose the actin filaments to which myosin heads need to bind to produce contraction.
Come into existence and develop
