1. Darwin & Natural Selection

2. Learning Goals Define "Evolution" & "Natural Selection".
Describe the 4 steps of Natural Selection, giving an example of each.
Explain the importance of "Variation".
Does Natural Selection act on an organism phenotype or genotype? Explain!
List the 5 evidences that support the Theory of Evolution.

3. Theory of Evolution Evolution: The process of change over time
Specifically, a change in the frequency of a gene or allele in a population over time

4. 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”

6. Darwin’s Finches

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

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

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

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

11. What adaptations do you see?

12. What adaptations do you see?

13. Why is Variation 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
The more variation of types of species in an habitat, the more likely at least some will survive
EX: Dinosaurs replaced by mammals

15. 3. Competition Individuals COMPETE for limited resources:
Food, water, space, mates
Natural selection occurs through “Survival of the fittest”
Fitness: the ability to survive and reproduce
Not all individuals survive to adulthood

16. 4. Selection
The individuals with the best traits / adaptations will survive and have the opportunity to pass on it’s traits to offspring.
Natural selection acts on the phenotype (physical appearance), not the genotype (genetic makeup)
Ex: When a predator finds its prey, it is due to the prey’s physical characteristics, like color or slow speed, not the alleles (BB, Bb)

17. 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.

18. Peppered Moth A
Which moth will the bird catch? B

19. Descent with Modification
Descent with Modification – each living species has descended, with changes, from other species over time.
Common Descent – all living organisms are related to one another

21. Evidence for Evolution:
Fossil Record
Homologous Body Structures
Vestigial Organs
Embryology
Biochemical Evidence

22. The Fossil Record
Fossils: a record of the history of life on Earth

23. Archaeopteryx
Missing link between reptiles and birds

25. Homologous Body Structures
Homologous Body Structures: similar anatomy in different types of animals because of common ancestor

27. Vestigial Organs
Vestigial Organs: “leftover” traces of evolution that serve no purpose

29. Embryology
Embryology: embryos of all vertebrates are very similar early on

31. Biochemical Evidence
Biochemistry: DNA with more similar sequences suggest species are more closely related
EX: Humans and chimpanzees share more than 98% of identical DNA sequences

33. Coral Snake (Poisonous)
Milk Snake (Not poisonous)

40. Stick Mantid

41. Flower Mantid