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1. Evolution

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 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”

5. Voyage of the Beagle

6. Voyage of Beagle
 Dates: February 12th, 1831
 Captain: Charles Darwin
 Ship: H.M.S. Beagle
 Destination: Voyage around the world.
 Findings: evidence to propose a
revolutionary hypothesis about how life
changes over time

8. Video on Darwin
https://youtu.be/6GNUlZhE_jE -Darwin
https://youtu.be/ZbITQ0dqxCQ
Galapagos Island
https://youtu.be/XOiUZ3ycZwU
Theory

9. Patterns of Diversity
Darwin visited Argentina and Australia
which had similar grassland ecosystems.
those grasslands were inhabited by very
different animals.
neither Argentina nor Australia was home to the
sorts of animals that lived in European
grasslands.

10. Patterns of Diversity
 Darwin posed challenging questions.
 Why were there no rabbits in Australia, despite
the presence of habitats that seemed perfect for
them?
 Why were there no kangaroos in England?

11. Patterns of Diversity
Darwin collected the preserved remains
of ancient organisms, called fossils.
Some of those fossils resembled
organisms that were still alive today.

12. The Galapagos Island

13. The Galapagos Island
 Darwin was fascinated in particular by the
land tortoises and marine iguanas in the
Galápagos.
 Giant tortoises varied in predictable ways
from one island to another.
 The shape of a tortoise's shell could be used
to identify which island a particular tortoise
inhabited.

14. Animals found in the Galapagos
Land Tortoises
Darwin Finches
Marine Iguanas

15. Darwin’s Finches

16. The Journey Home
Darwin Observed that characteristics of
many plants and animals vary greatly
among the islands.
Hypothesis: Separate species may
have arose from an original ancestor

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

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

20. 1. Overproduction
 Each species produces more
offspring that can survive

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

22. 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

23. Which community has a better chance
of surviving a natural disaster?
Community A Community B

24. 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

25. 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)

26.  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.

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

28. 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

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

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

32. Archaeopteryx
 Missing link between
reptiles and birds

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

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

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

40. 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

41. Summary of Darwin’s Theory
Individuals in nature differ from one another
Organisms in nature produce more offspring
than can survive, and many of those who do
not survive do not reproduce.
Individuals best suited for the environment
survive and reproduce most successful
Species change over time

42. Jean Baptist Lamarck 1800’s

43. Lamarck’s Theory of Evolution
 Tendency toward Perfection(Giraffe necks)
 Use and Disuse –
 If a body part were used, it got stronger
 If body part NOT used, it deteriorated
 Inheritance of Acquired Traits-
 acquired changes were passed to offspring

44.  Lamarck’s Theory of
Evolution:
 Giraffes all had SHORT necks
originally
 Giraffe’s Necks got LONGER
from stretching for food
 “Acquired” trait (long necks)
then passed to offspring
 Giraffe population became long-
necked

45. Lamarck’s Mistakes
 Was he correct??
 NO!
 Traits are passed down from one generation to
the next by GENES, not by an individual’s life
experiences or activities
 Lamarck did NOT know how traits were
inherited (Traits are passed through genes)
 Genes Are NOT Changed By Activities In Life
 Change Through Mutation Occurs Before An
Organism Is Born