DNA – n. short for deoxyribonucleic acid; a substance that carries genetic information in the cells of plants and animals

ecologist – n. someone who studies the relationships between groups of living things and their environments

endangered – adj. threatened; used to describe an animal or plant that has become very rare and that could die out completely

extinction – n. the situation that results when something such as a plant or animal species dies out completely

phase – n. a part or step in a process; part of a series of related events or actions