Darwin’s Ideas

Inherited Variation In talking with farmers, Darwin found that different animals had different traits. Some cows produced a lot of milk; others produced more meat Farmers had bred vegetables into many different strains

Artificial Selection The process by which humans breed animals and plants for traits that are desirable.

Evolution by Natural Selection Three Main Ideas The Struggle for Existence Survival of the Fittest Descent with Modification

The Struggle for Existence There is not enough resources to support all organisms that are born All species need to compete to get food, living space and other resources.

Survival of the Fittest The organisms that are best suited for their environment will survive and produce offspring. Fitness- the ability to survive and reproduce in an environment.

Survival of the Fittest Adaptation- Any inherited characteristic that increases an organism’s chance of survival. Brainstorm: What are some adaptations of local animals to our environment?

Survival of the Fittest Natural Selection- The process by which organisms become more fit to their environment over time.

Descent with Modification Species that exist today have descended from previous species that have changed over time. Common Descent – all species were derived from common ancestors.

Evidence of Evolution- 1800’s Fossil Record Geographic Distribution of Living Species Homologous Body Structures Similarities in Embryology

Fossil Record As scientists found more fossils Realized the earth was older than previously thought Life was more diverse than previously thought Found intermediate species that showed evolution between one species and the next

Geographic Distribution Animals in different continents had different common ancestors so different species evolved. The similarities were due to living in similar environments

Homologous Structures Structures in animals that develop from the same embryonic tissues but have different mature forms. Vestigial Organs- traces of homologous structures that don’t serve a known purpose Appendix Tailbone

Brainstorm: How has each of the bones shown above changed from animal to animal?

Similarities in Embryology Early embryos of many animals with backbones look similar, although differences occur.

Who am I? On the next slides, I will show you different embryos. You need to decide which of the animals you are looking at.

Am I a bat, cat or human?

Results:

Am I a chicken, a fish, a human, a rabbit, a salamander, or a turtle?

Results: