In
cell-cell contact , signals pass through a cell junction from one cell to adjacent cells.
Membrane-bound signals bind to receptors on adjacent cells in the process of
paracrine signalling.
An example of
autocrine signalling is when cells release signals that affect themselves and nearby target cells.
In
synaptic signalling cells release signals that affect nearby target cells. Cells release signals that travel long distances to affect target cells during
endocrine signalling.
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Answer:
b. It allows gas exchange while preventing water loss
Explanation:
Amniotic eggs are the feature of land animals such as reptiles, birds, mammals, etc. The amniotic eggs have four extra-embryonic membranes. This semipermeable protective shell allows the exchange of respiratory gases but does not support the transport of water out of the egg.
The ability to maintain the water inside the egg while permitting gaseous exchange is the specific feature of amniotic eggs and allowed diversification of land animals in the land habitats.
Answer:A
Explanation:
The meaning of evolution-the process by which different kinds of living organisms are thought to have developed and diversified from earlier forms during the history of the earth.
So, B is incorrect since it is talking of the present. C, shows the growing of hair, but has no answer to evolution, since it does not show an organism growing from the past to present. D, shows evolution of land but no “living organism”
In conclusion, the best answer is A.
Answer:
The main factor that causes vasoconstriction is the high concentration calcium inside muscle cells.
Explanation:
When the vessels suffer vasoconstriction, the blood supply is decreased and in this way the heat of the body is maintained. The way this happens is because the blood can no longer reach the surface and therefore decreases outward heat radiation. The main factor that causes vasoconstriction is the high concentration calcium inside muscle cells. There are several factors that cause vasoconstriction, internal or external. Environment is one of the external factors, and what happens to the penguins' feet is an example for it, since they are trying to preserve body heat to survive.
