Evolution%20Lectures%202005

1

• Evolution Lectures 2005
• Modified 2008
• M.Elizabeth

2
Evolutionary Evidence

• Comparative anatomy - living things are
  constructed along the same lines
• Taxonomy - life is hierarchical (tree of life)
• Geology - Earth is ancient, fossils record
  evolution, small changes can have big effects
• Biogeography - same environment yields different
  organisms

3
Definition Evolution

• 'Evolution' is a description of AND an
  explanation of the history of species - their
  origins, how they change, survive, become
  extinct.
• So evolution concerns BOTH a historical account
  of life on earth AND an attempt to explain how
  observed changes have happened.
• Defined as the slow change of organisms over time
  and a change in the frequency of certain alleles
  in the population.

4
Overview of Lecture

• Evidence that evolution has occurred
• Comparative anatomy
• Taxonomy
• Geology and fossils
• Biogeography

• How does evolution occur?
• Malthus and natural selection
• How does perfection arise?
• How does novelty arise?

5
A changing world view (200-300 years ago)
Earth is young In the 17th century Archbishop
James Ussher used the Bible to date the origin of
the earth as 4004 B.C. (Vice-chancellor of
Cambridge refined this to the morning of Sunday,
October 23rd, 4004 B.C.) Fixity of
species Species are permanent, natural kinds.
They do not change. A fixed plan of
creation. Design Living things seem designed
for a purpose, and a design implies a designer
6
A changing world view
Earth is ancient Approximately 4,500,000,000
years old (radioactive isotopes) Species
evolve Living things are constantly changing,
new species arise and others go extinct The
history of life is contingent Adaptation Fit
between organisms and their environment is due to
natural selection (blind watchmaker) Organisms
are often imperfectly created
7
Darwins place in science
8
Unity

• How we are the same and yet different

9
All living organisms contain four macromolecules

• carbohydrates
• lipids
• proteins
• nucleic acids

10
Life is constructed on a similar plan
Human and chimpanzee facial expressions
11
Life is constructed on a similar plan
homologous structures.
12
Vestigial organs
The eye bulbs of blind, cave-dwelling creatures,
such as the grotto salamander (Typhlotriton
spelaeus).
The anthers and pollen of asexual dandelions.
13
Vestigial organs in humans
Appendix
Nictating membrane in eye
14
What is Embryology?

• Embryology is the study development of the
  embryo.
• An embryo is the young animal undergoing
  development within the egg or womb.
• Embryology is used to illustrate common ancestry
  because there are similarities between organisms'
  embryological development.

15
Hind limbs in whales
Whale embryo
Fossil whale
Modern whale
16
Human embryo at 5 weeks
17
Similarities during embryonic development
18
7 properties of life

1. Ordered structure
2. Reproduction
3. Growth and development
4. Energy utilization
5. Response to environment
6. Homeostasis
7. Evolutionary adaptation

19
(No Transcript)
20
What is evolution?
Decent with modification
21
What is evolution?
Low High
Trait value
We can redefine evolution as a change over
time
22
(No Transcript)
23
Causes of Evolution
There are 5 causes The accidental toolkit

• Natural selection
• Genetic drift
• Mutation
• Gene flow
• Nonrandom mating

24
Causes of Evolution
1. Natural Selection
There are 3 important points
25
Causes of Evolution
1. Natural Selection
There are 3 important points

• Variation

• Differential success

• Inheritance

Over time there will be mainly white individuals
26
Causes of Evolution
1. Natural Selection
Differences in reproductive success
Fitness
- relative contribution to the next generation
survival access to mates breeding
success
27
Causes of Evolution
1. Natural Selection
Example the peppered moth
28
Causes of Evolution
1. Natural Selection
Example of the industrial melanism of the
peppered moth
black form
1800 1900
2000
29
Causes of Evolution
2. Genetic Drift
Random changes in the frequency of traits to
chance factors
Occurs under 2 conditions founder effect
bottleneck
effect
30
Causes of Evolution
2. Genetic Drift
Founder effect - when a new population is a small
sample of a large population
31
Causes of Evolution
2. Genetic Drift
Bottleneck effect - when only a small fraction of
the population survives that is no longer
representative
32
Causes of Evolution
2. Genetic Drift
Bottleneck effect - when only a small fraction of
the population survives that is no longer
representative
Example Lions living in the Ngorogoro
100
After crash
50
Number of lions
COMMON
1960 1975 1990
33
Causes of Evolution
3. Mutation
Changes in an organisms DNA
34
Causes of Evolution
4. Gene Flow
Changes due to movement from one place to another
35
Causes of Evolution
5. Nonrandom Mating
Individuals with particular traits are more
likely to mate Sexual Selection
36
Causes of Evolution
5. Nonrandom Mating
Boys fight - inter-sexual competition
The winner will mate
37
Causes of Evolution
5. Nonrandom Mating
Boys look fetching - intra-sexual competition
The male with the best ornament will be chosen
38
(No Transcript)
39
Does Evolution lead to Perfection
Does the ability to perform improve? - ADAPTATION
40
Does Evolution lead to Perfection
How do we know there is an ADAPTATION?

Foraging efficiency
Bill size
Adaptation happens only by selection, all other
changes are like a lottery
41
Does Evolution lead to Perfection
The course of evolution depends on
42
The Tale of the Monkey
43
The Tale of the Monkey
Natural Selection Edits Variation
44
Evolution is not the work of a designer, but the
work of a tinkerer.
Variation is the fuel of evolution - next
45
Natural Selection
If variation of a trait within a population
has a genetic basis,
and some variants have greater survival and
reproduction,
then, over time, the favored trait will
predominate in the population.
46

• Requirements

• C Variation in a trait
• within a population.
• (Giraffe's necks)

• C More individuals are
• born each generation
• than can survive the
• "Struggle for Existence"

47

• C Giraffes with longer
• necks get better food,
• have more babies
• (have an advantage in
• the struggle for existence)

• C Longer necks beget
• longer necks
• (variation is heritable)

48
Results Over time, average neck length
increases
49
Under other conditions, over longer periods of
time, new species form (e.g. the Okapi)
50
Evolution as a result of chance events (e.g.
Dinosaurs!)
51
Role of chance in evolution Extinctions
52
Catastrophic Event

• Cretaceous-Tertiary (K?T) transition
• Dinosaurs disappear instantaneously 65 myr ago
• Meteorite event
• Luis and Walter Alvarez transition rich in
  iridium (Ir), like in meteorites
• High K?T Ir the same around the world
• High abundances of osmium, gold and platinum
• Shocked quartz formed at high temperature and
  pressure
• Spherical rock droplets molten rock solidifies
  in air
• Soot (some sites) widespread fires
• 200 km crater in Yucatán peninsula 10 km
  meteorite

53
Mass Extinctions Methods

• 108 hydrogen bombs
• Tidal wave up most of low-lying North America
• Forest fires worldwide ? harsh winter ? plants
  die ? lack of food
• Acid rain ? kill life in the oceans too
• 99 of all living died, 75 of all species became
  extinct

54
Colonization of Land

• Microbes
• Hard to know when colonization occurred
• Easy to find water and UV protection on land
• Larger organisms
• Remained in the oceans longer, particularly
  animals
• Need to draw water from the soil but energy from
  sunlight
• Plant colonization of land began 475 myr ago

55

• Ozone
• Main UV protection, but history even more
  uncertain than that of oxygen
• Algae
• DNA plants evolved from algae
• Algae ? plants in small pools during periods of
  dryness?
• Carboniferous period
• Animals followed plants to land within 75 myr
• Large forests 360 myr ago ? coal

56
(No Transcript)
57
(No Transcript)
58
(No Transcript)
59
(No Transcript)
60
Other Mass Extinctions

• Multiple mass extinctions
• At least 5 big ones
• Many smaller ones
• Event like K?T every 100 myr
• Old seafloor craters would be gone by now
• Nearby supernova explosions also every 100 myr
• Magnetic reversals every few myr remove
  cosmic-ray protection of the magnetosphere
• Evolution
• Catastrophes create opportunities, not just
  disaster
• May have more effect than gradual evolution

61
(No Transcript)
62
Continuing Impact Threat

• Impact objects
• Meteor small (lt1 cm), 25 million per day, burn
  in atmosphere
• Fireball (not UFO) medium (10 cm ? 1 m), explode
  in the atmosphere
• Meteorite large (gt few m), vaporizes solid rock,
  leaving a crater
• Tunguska meteorite (1908) lt30 m, energy of
  several atomic bombs, sound heard round the
  globe, no crater (comet?)
• Future
• Probability declines rapidly with size
• Currently able to detect threat, but not divert it

63
Colonization of Land

• Microbes
• Hard to know when colonization occurred
• Easy to find water and UV protection on land
• Larger organisms
• Remained in the oceans longer, particularly
  animals
• Need to draw water from the soil but energy from
  sunlight
• Plant colonization of land began 475 myr ago
• Ozone
• Main UV protection, but history even more
  uncertain than that of oxygen
• Algae
• DNA plants evolved from algae
• Algae ? plants in small pools during periods of
  dryness?
• Carboniferous period
• Animals followed plants to land within 75 myr
• Large forests 360 myr ago ? coal

64
K?T Event

• Cretaceous-Tertiary (K?T) transition
• Dinosaurs disappear instantaneously 65 myr ago
• Meteorite event
• Luis and Walter Alvarez transition rich in
  iridium (Ir), like in meteorites
• High K?T Ir the same around the world
• High abundances of osmium, gold and platinum
• Shocked quartz formed at high temperature and
  pressure
• Spherical rock droplets molten rock solidifies
  in air
• Soot (some sites) widespread fires
• 200 km crater in Yucatán peninsula 10 km
  meteorite
• Mass extinction
• 108 hydrogen bombs
• Tidal wave up most of low-lying North America
• Forest fires worldwide ? harsh winter ? plants
  die ? lack of food
• Acid rain ? kill life in the oceans too
• 99 of all living died, 75 of all species became
  extinct

65
(No Transcript)
66
(No Transcript)
67
(No Transcript)
68
(No Transcript)
69
Other Mass Extinctions

• Multiple mass extinctions
• At least 5 big ones
• Many smaller ones
• Event like K?T every 100 myr
• Old seafloor craters would be gone by now
• Nearby supernova explosions also every 100 myr
• Magnetic reversals every few myr remove
  cosmic-ray protection of the magnetosphere
• Evolution
• Catastrophes create opportunities, not just
  disaster
• May have more effect than gradual evolution

70
(No Transcript)
71
Continuing Impact Threat

• Impact objects
• Meteor small (lt1 cm), 25 million per day, burn
  in atmosphere
• Fireball (not UFO) medium (10 cm ? 1 m), explode
  in the atmosphere
• Meteorite large (gt few m), vaporizes solid rock,
  leaving a crater
• Tunguska meteorite (1908) lt30 m, energy of
  several atomic bombs, sound heard round the
  globe, no crater (comet?)
• Future
• Probability declines rapidly with size
• Currently able to detect threat, but not divert it

72
(No Transcript)
73
Moth Camouflage - Selection
74
Genetic Drift Bottleneck Founder Effect
75
(No Transcript)
76
Bottleneck
77
Founder Effect
78
(No Transcript)
79
Phylogeny and Molecular Evolution

• The history of the genes can provide us with
  information about the structure and function, and
  significance of a gene or family of genes
• We can also use the reconstructed history to test
  hypotheses about evolution itself
• Rates of change
• The degree of change
• Implications of change, etc
• We can then pose and test hypotheses about the
  evolution of phenomena unrelated to the genes
• Evolution of flight in insects
• Evolution of humans
• Evolution of disease

80
Assumptions made by phylogenetic methods

• The sequences are correct
• The sequence are homologous
• Each position is homologous
• The sampling of taxa or genes is sufficient to
  resolve the problem of interest
• Sequence variation is representative of the
  broader group of interest
• Sequence variation contains sufficient
  phylogenetic signal (as opposed to noise) to
  resolve the problem of interest
• Each position in the sequence evolved
  independently