Overproduction
Most species produce more offspring than can survive.
Competition
Since living space and food are limited, organisms must compete for the necessities.
Variation
Differences between individuals in a population.
Adaptations
Any kind of inherited trait that improves an organism's chances of survival.
Natural selection
The environment selects organisms with optimal traits to be the parents of the next generation.
Speciation
Over many generations, favorable adaptations accumulate and may result in a new species.