a characteristic of an organism that allows it to survive more effectively in a particular environment.

a situation that exists in nature when two or more different species require the same environmental resource such as food and shelter to survive.

no longer living, describes a species that has completely died off.

the remains or impressions of plants and animals which lived on the Earth in the past and are now preserved in rocks.

the process in nature by which organisms that are vest adapted to their environment tend to survive and reproduce while those less adapted tend to die off, also called "survival of the fittest".

a scientist who uses fossils to study organisms that lived in ancient times.

addition of harmful particles and gases into the air.

a term that describes how changes in one aspect of the environment can cause changes in another aspect of the environment; a relationship in which plants and animals depend on one another for survival.

addition of harmful materials into the soil

any harmful material released into the environment. Some pollutants may be compounds that are naturally found in the environment but are released in excess amounts.

general term for the addition of harmful compounds or materials into the environment. Includes air, land, and water.

release of harmful compounds into water. This includes ground water.