Some now extinct organisms had traits that were intermediary between other major groups of species. ... Living things on Earth are fundamentally similar in their chemical compositions and in the way their basic structures develop. ... These segments of DNA are chemically coded instructions for developing proteins by linking together specific amino acids in particular sequences. The many types of proteins in living things are made of only twenty kinds of amino acids. ...

• Word Count: 1026
• Approx Pages: 4
• Grade Level: Undergraduate