The correct answer is it decreases genetic diversity only by reducing population size.
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The great explanation for this is a bottleneck effect, which is an extreme example of genetic drift. The bottleneck effect occurs when the size of a population is reduced due to a catastrophe. When it happens, only a small, random number of individuals survive the event and pass through the bottleneck. Thus, the genetic composition of the random survivors is now the genetic composition of the entire population which means that the genetic diversity is reduced.</span>
While giving birth to her infant during labor, the safest and the most effective pushing technique taught to a woman during contractions is grasping knees, head elevated and breathing out.
During labor, it is very important for the mother to keep breathing. If she holds her breath, it will put pressure on the vena cava and lead to a reduction in the blood return. The head is kept elevated and the back is rounded which aids the abdominal muscles to help the uterus to push the baby out. Grasping the knees also helps in pushing and encouraging the movement of the infant outside the body.
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4 is true with question you asked
They are both important because mechanical has to do with physical - cause mechanical means physical, so chewing your mouth is physical (you break your food into smaller pieces physically). And then chemical digestion is when food and saliva mix together. They happen when breaking down food into nutrients - enzymes. Enzymes are important for that process, because they make a nutrient.
Hope this helps!!