History and fundamental Evolution theory

2. Change is Constant!

3. Fixity of Species ??

4. Photo credit: Dennis Sandgathe
Extinct Species?
4

6. Variation within species

7. Incredible
Biological
Variation

8. John Ray
(1627–1705)
Species
concept
and Genus

9. Linnaeus
(1707–1778)
Taxonomy and
Binomial
Nomenclature
Kingdom
Phylum
Class
Order
Family
Genus
Species

10. George Buffon
(1707–1788)
“Species adapt slightly
to new conditions.”
François-Hubert Drouais
Vestigial organs and limbs

11. Lamarck
(1744–1829)
“Inheritance of
acquired characteristics”

12. Evidence
for
Evolution

13. Charles Darwin
(1809–1882)

14. Voyage of the HMS Beagle 1832–1836

15. 15
Geographic correlation between the
fossil record and living organisms
Megatherium:
extinct species
of sloth
Three-toed sloth
of Central and
South America

16. 16
Glyptodon:
an extinct relative
of the armadillo
Armadillo

17. Galápagos
Islands

18. Galápagos Finches

19. Galápagos Tortoises

20. 2.2 Natural Selection Theory

21. Evolution is
not a theory
It is a
demonstrable
fact

22. The theory of
Photo credit: GorillazFanAdam
Natural Selection

23. 6 Fundamental Premises of Natural Selection
1. More offspring are produced by a species than can be
supported by naturally available food sources.

24. Thomas Malthus
(1766–1834)
1798
An Essay on the
Principles of
Population
“Animal populations tend to
increase exponentially while
food supplies tend to
remain stable.”

25. 2020
me
most
of you
World population
400 BC to 2050 AD
in billions

26. 2. Within any one species there exists a significant
amount of biological/genetic variability.

27. 3. Individuals with advantageous traits will have an edge over
other members of their species in terms of their ability to
survive longer.

29. 4. Those individuals with traits that will increase their chance
of living longer are more likely to reach the age at which
they will begin reproducing and so are more likely to
contribute offspring to subsequent generations ...
… and therefore, those traits that gave these individuals
this advantage will be passed on to their offspring giving
them the same advantage.

30. 5. Those traits that are advantageous under current
environmental conditions will tend to be passed on.

31. An individual’s reproductive success is generally dictated
by their reproductive potential or fitness: products of their
ability to adapt (or not) to specific environmental conditions.

32. 6. Over long periods of time, accumulated changes within a
species will eventually result in new species. This is called
speciation.
Plains bison
Bison bison bison
Wood bison
Bison bison athabascae
Starting with subspecies …
32
Genus species subspecies Genus species subspecies

33. European bison
Bison bonasus
North American bison
Bison bison
… eventually separate species
Genus species Genus species

34. … eventually different genera (plural of genus)
Bison
North America
Bison bison
Aurochs
Eurasia
Bos primigenius
34
The process of speciation is often aided
by geographic isolation.

35. 35
Example: Trinidad Guppies Upstream
habitats
Downstream habitats

36. Other Fundamental Components
of the Evolutionary Process
1. Of the inherent variability in
traits in a species:
36
Most represents neither potential
advantage or disadvantage to
their survival so are not subject
to Natural Selection …
…they are Neutral Traits.
… and this depends almost entirely on the environment they face.
Of the variability, a very small percentage has the potential to be
disadvantageous, and a very small percentage has the potential to
be advantageous …

37. 2. Natural selection only acts on the variation that already exists
in a species.
37
Now that`s what
I`m talkin aboot!
Natural selection selects from what’s already there.
Natural selection does not grant organisms what they “need”.

38. A common misconception about evolution is that it is moving in a
specific, purposeful direction.
38

39. 3. Natural selection can only act on genetic variability.
39

40. 40

41. 4. Natural selection can only play a role in the
selection of traits that affect the reproductive
success of an individual.
41

42. But …
What about female
menopause in humans?
42
Grandmother Hypothesis

43. Microevolution
Micro- vs. Macro-evolution
Chimpanzee Bonobo
Eastern Gray FoxWestern Gray Fox

44. Macroevolution
44

45. Traditional view: species spread into a variety of environments
and, either through geographic barriers or just sheer distance,
different populations fail to continue to interbreed and so very
slowly and gradually diverge into new species as they adapt to
the new conditions they face.
How Does Speciation Actually Occur?
Phyletic Gradualism
45

46. The Fossil Record
… an obvious lack of
intermediate forms 46

47. Punctuated Equilibrium
47

48. 48
1,000,000 years ago500,000 years ago

49. Replacement Evolution
desertification?
parent species goes extinct
A B
vs Divergent Evolution
Also called Anagenesis and quite rare.
Occurs when all members of species
are together in a contained environment
– caves for example:

50. Divergent Evolution
Both species
continue to exist
A B
Also called Cladogenesis.
It results from species occurring as separate populations that
can be subject to different selective pressures and is the most
common way that evolution occurs.