Hi there!
A prezygotic isolating mechanism is a mechanism that causes something to happen, not allowing the organisms to breed before fertilization. I'll explain each one for you.
A - That is postzygotic because the organisms were not stopped before fertilization. The result is a sterile organism.
B - Again, that is postzygotic because the organism was produced.
C - This is prezygotic! The sperm dying shows that something is in action to prevent fertilization, meaning that it cannot happen.
D - Fertilization was successful, so it is postzygotic.
ANSWER:
C - the sperm dies when it reaches the female tract
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Answer: Spinal cord.
Explanation:
The spinal cord of the central nervous system helps to move off quickly as a part of the reflex response. Jill stepped on a tack and suddenly he realizes that he should quickly move his legs out of the tack.
The pain is not stimulated until the signals reaches from the receptor to the brain. The formation of the reflex arc ensures that the amount of potential tissue damaged is less.
It forces the body to move quickly from the place that is causing damage.Example: Moving the leg up involuntarily when stepped on pin.
This occurs because the sensory neurons connects to the motor neurons within the spinal cord.This leads to the contraction of bones and muscles.
Hence, the correct option is spinal cord.
<span>Growth harmones are released from pitutary gland in to the blood stream. This harmone promotes growth in children till they grow upto 15-18 years. Then this harmone stops. The excess secretion of this harmone leads to over height that is Gigantism. the dificiency of growth harmones are leads to shortness i.e. dwarfinism. The growth harmones secretes equally in both boys and girls. It secretes in hypothalamus of the brain</span>
Answer:
D. The presence of aquaporins (proteins that form water channels in the membrane) should speed up the process of osmosis.
Explanation:
Water moves in the cells through osmosis which means water moves from its higher concentration to lower concentration. In many animals and plants, water channels are also present which is called aquaporins which allow the water to move through it in and out of cell more quickly.
The rate of diffusion by channel proteins is higher than simple diffusion therefore the aquaporins speed up the process of osmosis. No ATP is required to transport the water through aquaporin channel proteins.
