I think its because when your upside down, your not breathing right. So its a way of trying to breathe correctly.
The term that can be used to describe evolution by natural selection is SCIENTIFIC THEORY.
Theory means "the best explanation so far."
Scientific theory is a work in progress. It is a well-substantiated explanation of some aspect of the natural world that is acquired through the scientific method, and repeatedly confirmed through observation and experimentation.
The answer is D unrestricted whaling could lead to their extinction.
Hydrogen bonds are classified as weak because they are formed fast, but they also break easily under normal biological conditions.
Weak bonds can be easily broken, but this is extremely important because they are in bold in biological systems. For example, they help to decide and stabilize the shapes of water molecules.
Each layer of earth has a different density the more in you go with the layers the more density is going to show up.
Crust-2.2g/cm^3
Upper mantle-3.4g/cm^3
Lower mantle-4.4g/cm^3
Outer core-9.9g/cm^3
Inner core-12.8g/cm^3
Hope I helped in something, Sorry if I didn't gave it my best shot:)