Darwin's proposed mechanism for evolution is natural selection. Natural selection allows species to respond to their surroundings through time, or to become progressively excellently-suited. Natural selection is environmentally based and involves established heritable variation within a population.
They lead to changes in species over time:
- Darwin suggested species will evolve over time, new species originate from pre-existing species, and all species share a common ancestor with each other.
- In this framework each organism has its own special set of heritable i.e genetic variations from the common ancestor that have slowly developed over very longer periods of time.
- Parroted branching activities that isolate new species from a common ancestor create a multi-level tree that connects all living organisms.