1. Evolution and natural selection

2. Question 6

3. Evolution Evolution is change over time.
The Theory of Evolution explains how living things descended (come from) from earlier organisms
A scientific theory is NOT just a belief, it is a well-supported tested explanation.
Lots of Evidence Supports Evolution
Fossils
Similarities in DNA and protein
Similarities in Body Structure
Similarities in Early Development Pg

4. Who?
Charles Darwin AND Alfred Wallace are credited with developing the Theory of Evolution. Pg

5. Charles Darwin Father of Evolution
Proposed a mechanism for evolution, natural selection
Darwin went on a 5-year trip around the world on the ship, the HMS Beagle
As the ship’s naturalist, he made observations of organisms in South America and the Galapagos Islands
Wrote a book, “Origin of the Species”

7. Darwin’s Finches

8. Alfred Wallace - Discoveries
Founder of biogeography
“Wallace Line”: imaginary line separating Asia and Australia

9. Evidence for Evolution: Fossils
Fossils provide a look into the past
Scientists can trace how a species have changed.
Fossils show that an Eohippus has 4 toes on its hooves. A modern day horse has one toe on its hooves.

10. Evidence for Evolution: Early Development
Similarities among embryos in development allow scientist to infer evolutionary relationships.
Animals that are more closely related are more similar in development.

11. Evidence for Evolution: Similarities in body Structure
Homologous Structures
traits that are similar in different species because the species share a common ancestor.
Ie. Arm, fin and wing may have evolved from the forelimb of a common vertebrate.

14. Natural Selection
Natural Selection: Organisms that are best adapted to an environment survive and reproduce more than others

15. Darwin’s Theory of Natural Selection occurs in four steps:
Overproduction
Variation
Competition
Selection

16. 1. Overproduction
Each species produces more offspring that can survive

17. 2. Variation
Each individual has a different combination of inherited traits.
Adaptation: an inherited trait that increases an organism’s chances of survival

18. What adaptations do you see?

19. What adaptations do you see?

20. Why is Variation Important?
Variation is important because the environment changes.
The more variation within a species, the more likely it will survive
EX: If everyone is the same, they are all vulnerable to the same environmental changes or diseases

21. 3. Competition
Individuals COMPETE for limited resources and the ones that survive will pass on their traits.
Natural selection occurs through “Survival of the fittest”
Fitness: the ability to survive and reproduce
Not all individuals survive to adulthood

22. 4. Selection
The individuals with the best traits / adaptations will survive and pass on their genes to their offspring
Natural selection acts on the phenotype (physical appearance), not the genotype (genetic makeup)

23. Individuals with traits that are not well suited to their environment either die or leave few offspring.
Evolution occurs when good traits build up in a population over many generations and bad traits are eliminated by the death of the individuals.