1. Animals are systems of activities that are adapted to environment. 2. Animals become adapted to the environment by transformation, selective survival, migration. 3. Each habitat limits the patterns of systems of activities that may result from reactions within it. The type of adaptation is set by the environment. 4. Though animals possess considerable power of adjustment to changes in environment, there is no evidence that they became adapted as species to slow changes due to physiographic succession. They do respond to rhythmical daily, monthly, and seasonal changes in an adaptive way. Animals appear to become most specialized, or adapted to particular environments, when conditions are most stable. 5. Environment permits and directs evolution, but does not appear to cause it by forcing the acquirement of new characters.