What are Darwin's 4 tenets of Natural Selection?

I believe they are:

1) Traits Vary

-traits vary from one population of a species to the next.

2) Traits are inheritable

-offspring can inherit traits from their parents.

3) Overproduction of Offspring

-when the population is bigger than the environment can support.

4) Competition for resources

- overproduction of offspring will result in a lack of resources/food for organisms, creating competition for them.