Not everything is used when it comes to food but everything is used with energy in the body!
Elliptical galaxies. I hope thats correct.
1. formaldehyde
2. paradichlorobenzene
3. tobacco smoke
4. toronto smog
5. pesticides
I believe the answer is comparative anatomy. It is the study of the similarities and differences in the structures of different species. Similar body parts may be homologies or analogies, such that both provide evidence of evolution. Similarities in embryos are evidence of common ancestry. For example all vertebrates embryos have gill slits and tails.
Over a liter of water is reabsorbed by the colon