evolution and natural selection

1. Ch. 19 terms
 Evolution
 Paleontology
 Catastrophism
 Gradualism
 Uniformitarianism
 Endemic species
 Natural selection
 Artificial selection
 Population
 Homologous
structures
 Vestigial organs
 Molecular
homologies
 Biogeography

2. Essential Questions
Please answer Essential Question #1 in
this box now.
Essential Questions My initial answer My best answer
What is biological evolution?
What is natural selection?
What are some observations
from nature that can be
explained by natural
selection?
How do evolution and
natural selection lead to
biodiversity?

3. Descent with Modification
Ch. 19

4. Evolution
 Change - over time - in
the genetic makeup of a
population
 Over time, enough
changes may accumulate
in a population for it to be
considered a separate
distinct species

5. A Little History
Lesson
 Georges Cuvier
(1769-1832)
pioneered the field
of paleontology – the
study of ancient life
Observed that older
fossils in the strata
were more different
from today’s species
that younger fossils
Proponent of the idea of
catastrophism - a local
catastrophe like a flood
wiped out species, and
neighboring species
moved in to take their
place

6. A Little History
Lesson
James Hutton (1726 - 1797)
 Advocated gradualism - big changes in
the environment can be the result of lots of
little changes over a long period of time
 The forces shaping the earth today are still
at work
 Rivers carving valleys, for example

7. A Little History Lesson
Charles Lyell (1797 - 1875)
 Advocated uniformitarianism -
the idea that geologic processes
have not changed over time –
i.e. they are still at work

8. A Little History
Lesson
Jean-Baptiste de
Lamark (1744-1829)
 The only one before
Darwin to propose an
idea for HOW species
change
 2 ideas:
 Use & disuse - used
parts get stronger,
disused parts weaker
 Acquired
characteristics passed
on to offspring
 stronger traits passed
on

10. Hutton - 1726-1797 Lamark - 1744-1829 Cuvier - 1769-1832 Lyell
- 1797-1875
 Darwin (1809 - 1882)
Liked to collect birds and
bugs
Dad sent him to med
school at 16
He hated it - He had to
watch surgeries done without
anesthetic
Left after watching a
horrible surgery done on a
small child without anesthesia

11.  Enrolled at Cambridge to
become a clergyman
 Graduated 10th in his class
 Heard about evolution there
 Heard lectures by James
Audubon about bird
adaptations
 It was clear to scientists that
living things were related &
adapted to their environments

12. The Beagle
 Darwin invited to work aboard the SS Beagle in 1831
(he was 22)
 The crew surveyed the unmapped coast of South
America
 Darwin studied the plants & animals
 Noticed the fossils in SA more similar to current SA species
than to fossils in Europe
 Noticed geologic differences
 Major earthquake hit Chile and he observed the coast rise several
feet
 These observations challenged the idea of a young, unchanging Earth

13. The Galapagos
Islands
Geologically young
Lots of unusual animals there
Many species found only on 1 island
(endemic - found no where else in the
world)
Each species uniquely adapted to the
conditions (food sources) of its island

14. Some of the species Darwin observed

15. Darwin focused on the organisms
adaptations
Saw that environmental conditions and
adaptations related

16. The
environment
changes
Living things
are well
adapted to
their
environments

19. Quick Think
Describe some of the ideas
and experiences that
influenced Charles Darwin

21. The Origin of Species
 By the 1840s Darwin’s book ready for
publication, but he didn’t publish
 In 1858 Alfred Russell Wallace (1823-1913)
sent his manuscript to Darwin for review
 It contained nearly the same ideas as Darwin’s
 Darwin published first and was given credit for
the theory of evolution by natural selection
 Within 10 years, most biologists accepted the
ideas
 The book was well written and very logical and had
tons of evidence
Super awesome book
about Wallace

22. The Origin of Species
2 main ideas:
 All species are descendents of earlier, now extinct
species
 Natural selection is the mechanism for evolution

23. Essential Questions My initial answer My best answer
What is biological evolution?
What is natural selection?
What are some observations
from nature that can be
explained by natural
selection?
How do evolution and
natural selection lead to
biodiversity?
Essential Questions
Please refine your answer to number 1 and
answer Essential Questions 2 here now

24. Natural Selection
Individuals with favorable traits leave
more offspring than those without
Eventually results in evolutionary
adaptation - an accumulation of traits
that increase the chances of survival –
this is Darwin’s idea of descent with
modification

25. Darwin’s
Logic
Observation 1 -
populations will increase
exponentially if all offspring
survive and reproduce
Observation 2 -
populations tend to remain
stable in size
Observation 3 - resources
are limited

26. Conclusion
The struggle for resources and the natural
overproduction of offspring means that
some offspring do not survive to reproduce,
thus not passing on their traits to the next
generation

27. Darwin’s Logic
Observation 4 - there is
variation among members
of a population
Observation 5 - these
variations are often
inherited from the parents

28. Conclusion
 Individuals that have inherited favorable traits
for their environment are more likely to survive
and have offspring
 The differential survival and reproduction of
members of a population leads to gradual
changes in the genetic makeup of a population
accumulated over many generations

29. Artificial Selection also influenced
Darwin’s thinking
The selection & breeding of individuals
that have desired traits
 Crop plants
 Livestock
 Pets
Do not
resemble their
wild ancestors
anymore

30. The Main Points of Natural Selection
1. Natural selection is the differential success in
survival & reproduction of individuals in a
population
2. Over time, natural selection increases the
adaptations found in a population
3. When the environment changes, natural
selection may result in new adaptations that
may lead to new species

31. Essential Questions My initial answer My best answer
What is biological evolution?
What is natural selection?
What are some observations
from nature that can be
explained by natural
selection?
How do evolution and
natural selection lead to
biodiversity?
Essential Questions
Please refine your answer to Essential
Questions 2 & try question 3 now

32. 3 important points
1. Individuals are selected,
POPULATIONS evolve
2. Natural selection acts only
on heritable traits
3. Favorable adaptations in
one environment may not
be favorable in another -
natural selection is always
at work
Population – a
group of
interbreeding
individuals who live
in a particular place
at a particular time

33. Misconceptions
1. Survival of the fittest = survival of the
strongest
2. Evolution is not a “grand plan” that will
lead to perfectly adapted species

34. Darwin’s Theory Explains many
Observations
Helps explain why
different species
have related parts
with different
functions
Homology -
similar characters
resulting from
common ancestry
Homologous structures

35. Darwin’s Theory Explains many
Observations
Embryos - all vert. embryos have tail
and throat pouches - they develop into
different structures in different species

36. Darwin’s Theory Explains many
Observations
Vestigial Organs - structures of little
to no importance to the organism; the
remnants of the organism’s ancestors

37. Darwin’s Theory Explains many
Observations
Genetic
similarity among
organisms –
molecular
homologies

38. Biogeography The geographic
distribution of species
Closely related species
tend to be found in the
same geographic
region
Similar niches in
different places will be
occupied by very
different species
 These species may be
similar looking though

39. Quick Think
Please refine question 3 and answer
Essential Question number 4 here
now
Essential Questions My initial answer My best answer
What is biological evolution?
What is natural selection?
What are some observations
from nature that can be
explained by natural
selection?
How do evolution and
natural selection lead to
biodiversity?

40. The Importance of the Theory of
Evolution
 In science, there is no such thing
as “just a theory”
 The theory of evolution is a good
theory because:
 It explains tons of direct
observations and data
 The process of natural selection
can be tested
 It is broad and allows scientists to
make new predictions
 It is constantly being tested and
refined

41. Quick Think
Please refine Essential Question
number 4 here now
Essential Questions My initial answer My best answer
What is biological evolution?
What is natural selection?
What are some observations
from nature that can be
explained by natural
selection?
How do evolution and
natural selection lead to
biodiversity?