They are said to be “denser” than air. what happens is that light slows down when it passes from the less dense air into the denser glass of water. this slowing down the ray of light also causes the ray of light to change directions. it is the change in the speed of the light that causes refraction.
A high biodiversity tally may indicate that some of its organisms may be able to survive drastic environmental changes. If there weren't at least a few organisms that contribute to biodiversity, most of the biotic Earth would be gone by now.
For example, woolly mammoths were unable to adapt to the up-and-coming warmth of the poles. Because they lacked biodiversity among their species, all of them died out and weren't able to adapt to the heat.
I hope I helped!
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