Natural selection could not occur without 25. ___________ and acts on a(n) 26. ___________. A trait that makes a species better suited to survive in its environment is called a (n) 27. ___________. A species is a group of organisms that have unique features and cannot 28. ___________ with other organisms. All the evolutionary evidence including fossils points to organisms having a(n) 29 ___________ Having a lot of different species living in a habitat is called 30. __________.