The five main characteristics are foot region, hard exoskeleton, bilateral symmetry, left and right limbs and a segmented body.
In my opinion, <u>natural gas</u> is a source that will be most common in the future. Considering that natural gas is a fossil fuel that is used as a source of energy for heating, cooking, and electricity generation. It is also used in stoves, ovens, clothes dryers, lighting fixtures and other appliances that are used and needed in everyday life. Imagine a life without natural gas. We wouldn't be able to heat our homes, cook our food, etc.
The fact that they can breed but cannot produce fertile offspring shows that they are different species. T<span>hey may have different characteristics which means they cannot breed </span>successfully, too.
I hope this helps! :-)
xo Leafling