Answer:
The water molecules in ice are considerably far apart as compared to cold water of 4 degrees centigrade and below. This, therefore, makes ice less dense than water at these temperatures (because they are fewer water molecules in ice per unit volume). This is why ice floats on cold water below 4 degrees centigrade. Ice, being a bad conductor of heat, shields the water below an ice sheet from excessive heat loss to the atmosphere. This is why water remains liquid below an ice sheet protecting the marine life below from complete freezing.
Where's the evolution?
The physics of light affects not just how blue water looks to us, but how the animals living in the world's oceans, lakes, and rivers are able to find food and each other — and this, in turn, can impact their evolution. Natural selection favors traits that perform well in local environmental conditions. Many fish species, for example, have evolved vision that is specifically tuned to see well in the sort of light available where they live. But even beyond simple adaptation, the physics of light can lead to speciation. In fact, biologists recently demonstrated that the light penetrating to different depths of Africa's Lake Victoria seems to have played a role in promoting a massive evolutionary radiation. More than 500 species of often brightly colored cichlid fish have evolved there in just a few hundred thousand years!
Answer:
The amount of light they receive.
Explanation:
In an experiment, the independent variable is the part of the experiment that the experimenter changes. In this experiment, the only thing that's different for each of the plants is the amount of light they receive. Everything else is the same - the same amount of soil, same amount of water, same pots, and so on.
