1. Species have the ability to produce more offspring than is necessary to replace themselves (superfecundity)
2. There is a finite pool of resources that is smaller than necessary to allow all offspring to survive
3. Natural populations are of constant size (over the long term)
4. Individuals within a species vary in many characteristics
5. Much of that variation is heritable

Darwin's inferences

1. Individuals compete (or otherwise struggle with each other) for limited resources
2. Only some individuals survive to reproduce
   • those that more successfully obtain resources are more successful
3. Over many generations, a population will consist of the most successful kinds of individuals