Evolution and Natural Selection Review Sheet Name:__________________________________
What is the definition of evolution?
Evolution is the change of traits in a population over many years/generations that usually results
in the population being more fit for the environment.
What is the definition of natural selection?
The process by which organisms of a species with different traits are competing to survive and
reproduce. Certain traits are successful for an organism and that organism gets to survive and
reproduce making more of the population have that trait until they all do.
How is natural selection linked to evolution?
Natural selection makes evolution happen.
What makes a trait an adaptation?
If the trait helps an organism survive and reproduce in the ecosystem, it’s an adaptation.
Are adaptations random or chosen by the organism? (i.e. can organisms change themselves
willingly to better fit their environment?)
Organisms don’t get to choose what traits they have – the environment picks which organisms
survive based on their traits. The traits the environment gets to pick from are random.
How do certain traits become more common in a population?
Adaptations appear more frequently because organisms with those traits survive and reproduce
more often than organisms without that trait.
Explain how fossils help show changes in a species over time.
Fossils show us organisms that are similar to other organisms alive today. We know they are
related because they have many of the same features. However, we can see that they have
changed over time because of the different traits they have gained – usually allowing it to survive
better in the environment.
Explain Darwin’s 4 steps for natural selection and how it connects to evolution. Include a
diagram to aid in your understanding of how the concepts connect to one another. (Think
about the tortoises, the finches, and the crickets).
Step 1 – Overproduction: organisms are gonna die.
Step 2a – Variation: organisms have all sorts of differences in their traits
Step 2b – Competition: Organisms are trying not to die from starvation, predators, etc…
Step 3 – Selection: Organisms with good traits win the competition and have babies
Step 4 – Evolution: With more organisms with specific traits surviving and reproducing makes the
whole population have that trait!