Answer: the correct option is : highly developed cell- cell communication.
Explanation: In complex multicellular organisms, cell - cell communication also known as cell signalling is part of any communication process that leads basic activities of cells and coordinates multiple cell functions.
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The principle of diffusion consists in the movement of substances through a membrane from a zone with high concentration, to a zone with low concentration, until the concentration is equal on both sides of the membrane.
An example of diffusion is the process that happens when we breathe. Two substances in the body that will move based on the principles of diffusion are Carbon Dioxide and Oxygen. Carbon Dioxide will move from the bloodstream to the alveoli, and Oxygen will move from the alveoli to the bloodstream.
interdependance can be defined as dependance upon each other...
Answer:
The correct answer is: geography and UV radiation.
Explanation:
Skin variation occurred thanks to evolution, and was driven as a consequence of the geographical location of different populations of humans.
The humans that lived in hot and sunny places, closer to the equator, where much more exposed to the sun's ultraviolet radiation. In order to survive the amount of UV lights that they were exposed to, new humans in those regions were being born with a darker skin tone, which was rich in melanin (a brown pigment that protects us from the sun radiation).
Contrary to these humans that lived in the tropical areas, the humans that populated the areas that were closer to the poles, developed much lighter skin as a result of lower amounts of melanin in their skin. Since sun exposure in the poles is very limited, humans needed to receive as much as they could for the production of Vitamin D, and thus, their skins got lighter and less protected.
