What substance must plants produce in order to make lipids?

Many animals cannot sweat to maintain a stable body temperature. what is one other way animals can cool down?

Where can you find prokaryotic and eukaryotic cells?

How can a geological time scale best be reconstructed? a) comparing vestigial structures in living species b) comparing homologous structures in living species c) examining homologous structures in fossil remains d) examining the written records of scientists from past cultures