Class notes on Darwin, Natural Selection, and Evolution

1. Darwin & NaturalDarwin & Natural
SelectionSelection

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

3. Theory of EvolutionTheory 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 DarwinCharles Darwin
 Father of Evolution
 Proposed a mechanism for
evolution, natural selectionnatural 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, “Wrote a book, “Origin of the SpeciesOrigin of the Species””

6. Darwin’s Finches

7. Natural SelectionNatural 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 parts:
 Overproduction
 Variation
 Selection
 Adaptation

9. 1. Overproduction1. Overproduction
 Each species produces more
offspring than can survive

10. 2. Variation2. Variation
 Each individual has a
unique combination
of inherited traits.
 These natural
differences are
called variations

12. Why is Variation Important?
 Because the environment
changes.
 The more variationvariation withinwithin aa
speciesspecies, the more likely it will
survivesurvive
 EX: If everyone is the same, they
are all vulnerable to the same
environmental changes or diseases
 The more variation ofvariation of types oftypes of
speciesspecies in an habitat, the more

13. Which community has a betterWhich community has a better
chance of surviving a naturalchance of surviving a natural
disaster?disaster?
Community ACommunity A Community BCommunity B

14. 3. Selection3. Selection
 Individuals COMPETE for limited
resources:
 Food, water, space, mates
 Natural selection occurs through
“Survival of the fittestSurvival of the fittest”
 FitnessFitness: the ability to survive and
reproduce-the advantageous trait will
be passed to the next generations
 Not all individuals survive to

15. 4. Adaptation4. Adaptation
 The individuals with the bestbest
traits / adaptations will survivetraits / adaptations will survive
and have the opportunity to passand have the opportunity to pass
on it’s traitson it’s traits to offspring.
Adaptation:Adaptation: an inherited trait that increases an
organism’s chances of survival

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

17. What adaptations do you see?

18. What adaptations do you see?

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

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

25. The Fossil RecordThe Fossil Record
 FossilsFossils: a record of the history of
life on Earth

26. Archaeopteryx
 Missing link between
reptiles and birds

28. HomologousHomologous (Common)(Common) Body StructuresBody Structures
 HomologousHomologous
Body StructuresBody Structures:
similar anatomy
in different
types of animals
because of
common
ancestor

30. Vestigial OrgansVestigial Organs
 Vestigial Organs: “leftover” traces of
evolution that serve no purpose

32. EmbryologyEmbryology
 EmbryologyEmbryology: embryos of all
vertebrates are very similar early
on

34. Biochemical EvidenceBiochemical Evidence
 BiochemistryBiochemistry: DNA with more
similar sequences suggest
species are more closely related
 EX: Humans and chimpanzees share
more than 98% of identical DNA
sequences

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

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

44. Stick Mantid

45. Flower Mantid