2) explain the properties of water that allow an insect to walk on water 3) when a lake freezes, how does the density of water prevent all of the living organisms in the lake from freezing as well ?

Cohesion known as water attraction to other water molecules is one of the major properties of water. liquid water has surface tension. this allows for insects such as water striders to walk on water. question number 3 the answer is because ice is less dense then liquid water because the water molecules for a new large structure as they cool down. of course Lakes freeze a course from top down even though the coldest areas are at the bottom. cold water begins to rises when it begins to freeze it accumulates at the top with a sheet of ice. the ice provides some insulation for the water below so that there is typically a significant portion of water under the ice sheet unless it's extraordinary really cold for a very very very very long time. if a lake froze from the bottom up they would more than likely freeze completely

The answer your looking for is a food chain grid. it describes how nature can support itself and survival of the fittest comes into play..

Lipid because of the high percentage of carbon to carbon bonds, which store more energy than other bonds.