Title: Evolution%20Lectures%202005
1- Evolution Lectures 2005
- Modified 2008
- M.Elizabeth
2Evolutionary 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
3Definition 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.
4Overview 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?
5A 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
6A 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
7Darwins place in science
8Unity
- How we are the same and yet different
9All living organisms contain four macromolecules
- carbohydrates
- lipids
- proteins
- nucleic acids
10Life is constructed on a similar plan
Human and chimpanzee facial expressions
11Life is constructed on a similar plan
homologous structures.
12Vestigial organs
The eye bulbs of blind, cave-dwelling creatures,
such as the grotto salamander (Typhlotriton
spelaeus).
The anthers and pollen of asexual dandelions.
13Vestigial organs in humans
Appendix
Nictating membrane in eye
14What 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.
15Hind limbs in whales
Whale embryo
Fossil whale
Modern whale
16Human embryo at 5 weeks
17Similarities during embryonic development
187 properties of life
- Ordered structure
- Reproduction
- Growth and development
- Energy utilization
- Response to environment
- Homeostasis
- Evolutionary adaptation
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20What is evolution?
Decent with modification
21What is evolution?
Low High
Trait value
We can redefine evolution as a change over
time
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23Causes of Evolution
There are 5 causes The accidental toolkit
- Natural selection
- Genetic drift
- Mutation
- Gene flow
- Nonrandom mating
24Causes of Evolution
1. Natural Selection
There are 3 important points
25Causes of Evolution
1. Natural Selection
There are 3 important points
Over time there will be mainly white individuals
26Causes of Evolution
1. Natural Selection
Differences in reproductive success
Fitness
- relative contribution to the next generation
survival access to mates breeding
success
27Causes of Evolution
1. Natural Selection
Example the peppered moth
28Causes of Evolution
1. Natural Selection
Example of the industrial melanism of the
peppered moth
black form
1800 1900
2000
29Causes of Evolution
2. Genetic Drift
Random changes in the frequency of traits to
chance factors
Occurs under 2 conditions founder effect
bottleneck
effect
30Causes of Evolution
2. Genetic Drift
Founder effect - when a new population is a small
sample of a large population
31Causes of Evolution
2. Genetic Drift
Bottleneck effect - when only a small fraction of
the population survives that is no longer
representative
32Causes 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
33Causes of Evolution
3. Mutation
Changes in an organisms DNA
34Causes of Evolution
4. Gene Flow
Changes due to movement from one place to another
35Causes of Evolution
5. Nonrandom Mating
Individuals with particular traits are more
likely to mate Sexual Selection
36Causes of Evolution
5. Nonrandom Mating
Boys fight - inter-sexual competition
The winner will mate
37Causes of Evolution
5. Nonrandom Mating
Boys look fetching - intra-sexual competition
The male with the best ornament will be chosen
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39Does Evolution lead to Perfection
Does the ability to perform improve? - ADAPTATION
40Does 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
41Does Evolution lead to Perfection
The course of evolution depends on
42The Tale of the Monkey
43The Tale of the Monkey
Natural Selection Edits Variation
44Evolution is not the work of a designer, but the
work of a tinkerer.
Variation is the fuel of evolution - next
45Natural 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- 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)
48Results Over time, average neck length
increases
49Under other conditions, over longer periods of
time, new species form (e.g. the Okapi)
50Evolution as a result of chance events (e.g.
Dinosaurs!)
51Role of chance in evolution Extinctions
52Catastrophic 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
53Mass 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
54Colonization 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
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60Other 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
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62Continuing 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
63Colonization 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
64K?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
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69Other 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)
71Continuing 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
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73Moth Camouflage - Selection
74Genetic Drift Bottleneck Founder Effect
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76Bottleneck
77Founder Effect
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79Phylogeny 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
80Assumptions 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