Evolution and population genetics presentation

lamarck's theory and darwin's theory discussed, population genetics, gene pool, rate of evolution, gradualism

1. Evolution

2. Darwin’s Theory of
Natural Selection
MAIN IDEA: Charles Darwin
developed a theory of evolution based
on natural selection.

3. Why was Darwin’s work
controversial?

4. Evolution vs. Creationism
Creationism – belief that God
created all living things to be unique
Evolution – theory that organisms
have changed over time.

5. Until the 1800s
People thought the same types of
organisms on earth were always in
existence
This changed when scientists found
fossils of organisms no longer on
earth

6. What made Darwin question
previous assumptions on how
different organisms came to be?

7. Scientists observed…
Fossil evidence
Many different species
Variations (differences) within
species

8. Change in Thought
Scientists began to wonder how and
why these changes took place
2 biologists believed organisms
changed in response to their
environments:
French Jean Baptiste Lamarck
British Charles Darwin

9. Lamarck’s Theory
1809 – Lamarck proposed his theory
of evolution
Theory based on 2 hypotheses:
Organisms develop traits by the use
and disuse of body parts
Acquired characteristics – passed from
parents to offspring

10. According to Lamarck, why do
giraffes have long necks?

11. Lamarck’s giraffe example(Don’t
Copy)
Lamarck assumed giraffes had short necks
originally and ate grass
Grass died due to climate change
Giraffes ate leaves off trees
As giraffes stretched necks, necks grew
Giraffe’s acquired long necks – passed to
future generations
Scientists questioned this theory…

12. Charles Darwin
Born in 1809
Age 22, went on voyage on HMS Beagle
(British ship) as a naturalist
Mapping expedition of S. America and
S. Pacific

13. Darwin’s Thoughts (Don’t Copy)
Charles Lyell’s book influenced Darwin -
Lyell said Earth was millions of years old
Observed fossils of marine animals on
mountains, etc
Observed changing earth: earthquakes,
volcanoes, etc; saw change in the land
Thought organisms would have to adapt to
these changes

14. Darwin’s Studies
Observed thousands of different
species
Took careful notes
Collected specimens
Studies fossils

15. Galapagos Islands (Don’t Copy)
Off coast of Ecuador
Observed MANY different species
Many similar to those on coast of S.
America
Observed tortoises, iguanas, finches, etc
with slight differences on different islands
Ex: different beaks of finches

16. Help from Gould (Don’t Copy)
John Gould, another British naturalist
Concluded finches were different
species, and were not on mainland of S.
America
Darwin though species changed after
reaching islands

17. DO NOW
What is the difference between natural
selection and artificial selection?
What is the difference between natural
selection and evolution?

18. Artificial vs. Natural Selection
Artificial - breeding for desired traits
Natural – naturally “desired” traits are
bred more often – causes gradual change
in species over time (evolution)

19. Darwin’s Theory
Published book: On the Origin of Species
by Means of Natural Selection with help
from another scientist, Alfred Russel
Wallace
Theory based on 4 main ideas:
Variations
Inheritance of traits
Overproduction
Survival of the fittest

20. Variations
Variations (differences) occur among
members of the same species
Ex: different breeds of dogs, horses, cats,
etc.
Inheritance of Variations
Traits are inherited

21. Overproduction
Organisms produce more organisms than
can survive and reproduce
This ensures that some offspring will
survive to reproduce
Ex: fish, insects, frogs, etc.

22. Survival of the Fittest
Organisms with traits that are better for
adapting survive to reproduce
Pass on these useful traits
Natural selection – environment
determines which variations will be
selected

23. Peppered Moth Example
(DON’T COPY)
Early 1800s, England
Peppered moths were mostly light gray;
few were white, few were black
(variations)
Gray blended with tree trunks – birds
didn’t see or eat them, so they survived,
but black ones were eaten

24. Peppered Moth Cont’d
(DON’T COPY)
Industrial Revolution – many factories
built
Black soot on trees
Which moths were NOW more likely to
survive?

25. Do Now
Once, many years ago, horses were the size
of cats. Now, they are obviously much
bigger. How would Lamarck explain this
change? How would Darwin explain it?

26. Evidence of Evolution
Fossils
Anatomy
Embryos
Molecules
Biogeography

27. Fossil Evidence
Show extinct species
Show relationships between current and
ancient organisms
Show intermediate species – those in
between ancient and modern species
Difference in traits – derived vs.
ancestral

28. Anatomical Evidence
Similar structures found in closely related
species; have common ancestor
Diverse vertebrates have similar limb
structures, but may not have same function
–homologous
Vestigial structures – structures not
currently used by organism; evidence of an
organism’s evolutionary past Ex: hind
limbs of dolphins/whales

29. Homologous Structures

30. Homologous vs. Analogous
Remember, homologous – similar
STRUCTURE
Analogous – structures with similar
FUNCTIONS, but different
structures/origins
Ex: bat’s wing and bird’s wing -
analogous

32. Evidence in Embryos
Pattern of meiosis (gametes)  fertilization
 mitosis (adults)
All vertebrate embryos have homologous
structures that may not be in adults:
Tails (most adults keep their tails!)
Limb buds – become limbs
Vertebrates have a common ancestor

34. Molecular Evidence
DNA:
Basic genetic code for each species
Ex: humans all have same basic genetic
code
Species that are similar have many
similarities in their DNA
Species with a more distant ancestor have
more differences in DNA

35. Molecular Evidence
Proteins:
Because of similar DNA, organisms of
the same species have the same basic
proteins
Similar species – similar amino acid
sequences in their proteins

36. Biogeography
Study of distribution of organisms on
earth
Similar environments lead to similar
adaptations in organisms, even if far
apart

37. Adaptations
Traits that allow for survival
Fitness – way to measure how effective
traits are
Examples of adaptations:
Camouflage
Mimicry

38. Remember that…
Not all traits evolve slowly; Ex: bacteria
Not all traits increase fitness
Mutations can be a source of new traits

39. Evolution and Genetics

40. Population
Members of same species living in same
area
All genes in a population = gene pool

41. Population Genetics
Allele frequency – percent of certain alleles
(gene types) in a population’s gene pool
Ex: all homozygous red flowers have a 100%
frequency for red alleles
Usually remains stable in a population

42. Changes in the Gene Pool
Changes can occur in the gene pool, which
could cause evolution
Kinds or percentages of genes can change
4 things cause these changes
Natural selection
Mutation
Migration
isolation

43. 4 Factors Change the Gene Pool
1. Natural selection
Well-adapted organisms survive to reproduce
Pass on genes to next generation, increasing
the gene frequency

44. 4 Factors Change the Gene Pool
2. Mutation
•Adds a new gene to the gene pool
•Can cause small, immediate change, or go
undetected for generations
•Can be helpful, harmful, or neutral

45. 4 Factors Change the Gene Pool
3. Migration
•Movement of organisms into or out of a
population
•Causes gene flow – movement of genes in
or out of populations

46. 4 Factors Change the Gene Pool
4. Isolation
Organisms become separate from other
organisms (geographic isolation)
Caused by physical barriers, natural disasters,
etc
Causes speciation
Causes reproductive isolation between the
now separate species

47. Create
With your group, pick any species, and
create a scenario as to how it may evolve
based on your assigned factor. Base your
predictions on facts about the species.
Describe and/or draw your predictions,
and then present to the class!

48. The Rate of Evolution

49. Gradualism
Evolution through slow change
Believed to be true by Darwin and many
other scientists
Fossil evidence supports this

50. Punctuated Equilibrium
Species remain unchanged for thousands
of years, then suddenly undergo rapid
changes
Fossil evidence of trilobites – unchanged
for millions of years, then suddenly died
off