evolution. evidence supporting evolution fossil record shows change over time anatomical record...
TRANSCRIPT
Evolution
Evidence supporting evolutionFossil record
shows change over timeAnatomical record
comparing body structureshomology & vestigial structuresembryology & development
Molecular recordcomparing protein & DNA sequences
Artificial selectionhuman caused evolution
Fossils help decipher life’s history
LaetoliHyracotherium
Layers of rock contain fossils new layers cover older ones
creates a record over timefossils show evidence for past life
over a long period of time
Fossils tell a story…
the Earth is old
Life is old
Life on Earth has changed
Evolution of birdsToday’s organisms descended from ancestral species
Fossil of Archaeopteryxlived about 150 myalinks reptiles & birds
Land Mammal
?
?
?
?
Where are the
intermediate
fossils?Where are the
intermediate
fossils?
Ocean Mammal
Complete seriesof transitional
fossils
Whale evolution
Vestigial organsHind leg bones on whale fossils
Why would whales have pelvis & leg bones if they were always sea creatures?
Dolphin embryo
Hind limb buds
Evolution from sea to land• 2006 fossil discovery of early tetrapod
o 4 limbs• Missing link from sea to land animals
ichthyostega
Anatomical record
Animals with different structures on the surface
But when you look under the skin…
It tells an evolutionary story of common ancestors
Compare the bones
Homologous Structures
But don’t be fooled by these…
• Analogous structures• look similar on the outside• Same function• different structure & development
on the inside• different origin• no evolutionary relationship
Solving a similar problem with a similar solution
Analogous structures• Dolphins: aquatic mammal• Fish: aquatic vertebrate
• both adapted to life in the sea
• not closely related
Convergent evolution3 groups with wings
Does this mean they have a recent common ancestor?
Flight evolved 3 separate times — evolving similar solutions to similar “problems”
Convergent evolution led to mimicry
• Why do these pairs look so similar?
Monarch malepoisonous
Viceroy maleedible
Comparative embryology
Development of embryo tells an evolutionary story similar structures during development
Molecular record
100 20 30 40 50 60 70 80 90 100 110 120
LampreyFrogBirdDogMacaqueHuman
328 45 67 125
Comparing DNA & protein structureeveryone uses the same genetic code!
DNA
compare common genescompare common proteins
number of amino acids different from human hemoglobin
Building “family” treesClosely related species are branches on the tree — coming from a common ancestor
Evolution: the source of Earth’s biodiversity
• Biological evolution: genetic change in populations of organisms across generations–Natural selection:
reproductive fitness
Understanding evolution is vital• to understand how organisms adapt
to their environment and change over time.
• It is needed for ecology, a central component of environmental science.– Relevant for agricultural,
medicine, pesticide resistance, environmental health
Genetic variation• Genes of better-adapted individuals will be more
prevalent than those of less well-adapted individuals in future generations.
• Adaptive trait (adaptation): a trait (characteristic) that promotes reproductive success
• Mutations: accidental changes in DNA that may be passed on to the next generation– Non-lethal mutations provide the genetic variation on
which natural selection acts.
• Sexual reproduction, which involves recombination (the mixing of parental genes), also leads to variation.
–functioningfunctioning: beaks in honeycreepers
Evidence of natural selection is everywhere
• How do we know natural selection can change a population?– we can recreate a similar process– “evolution by human selection”
Artificial selection
“descendants” of wild mustard“descendants” of wild mustard
Artificial selectionHumans create the change over timeHumans create the change over time
“descendants” of the wolf“descendants” of the wolf
Artificial selection
Artificial Selection gone bad!Unexpected consequences of artificial selection
Pesticide resistance
Antibiotic resistance
Insecticide resistance
Spray the field, but…• insecticide didn’t
kill all individuals- variation
• resistant survivors reproduce
• resistance is inherited
• insecticide becomes less & less effective
Evolution generates biodiversity
• Biological diversity (biodiversity): an area’s sum total of all organisms –The diversity of species
–Their genes
–Their populations
–Their communities
Evolution: A Preview
Adaptation of a population to a new environment – may lead to a new species
Darwin’s Observations
More offspring than needed
Population size is about the same
Individuals differ
Some variation is inherited
Evolution: A Preview
Adaptation of a population to a new environment – may lead to a new species
Darwin’s Observations
More offspring than needed
Population size is about the same
Individuals differ
Some variation is inherited
You won’t see this unless you are prepared to see itYou won’t see this unless you are prepared to see it
Expeditions
Alfred Wallace
Brazil Malay Peninsula 8 years 125,000 animal specimens
Access to remote places to make biodiversity collections
Age of the Earth
Uniformitarians
Present mechanisms hold for the past
Erosion & uplifting = mountains
Catastrophists
A few violent events occur suddenly
Age of the Earth
Uniformitarians
Earth must be old
Catastrophists
Earth can be young
Not an evolutionary question
(Bishop Usher: “October 22, 4004 BC” )
Malthus & Population
popu
latio
nsi
ze
time
Tendency to rise beyond numbers that can be supported by the environment
Reduced by disease, war
1776-1834
Evolutionary Questions
Do species change?
If so, how?
Evolution: Change through timeEvolution: Change through time
Jean-Baptist Lamarck
Variability within species
Trend of increasing complexity in species
Outstanding Naturalist
Observations
Lamarck’s Theory of Evolution
Species change in response to a changed environment
Species can change by “use”
Changes are passed on
Theory of Acquired Characteristics
Published in 1809
Lamarck’s GiraffeOriginal short necked ancestor
Keeps stretching neck to reach leaves higher up on tree
and stretching
and stretching until neck becomes progressively longer
Darwin’s Giraffe
Original group exhibits variation in neck length
Natural selection favors longer necks: better chance to get higher leaves.
Favored character passed on to next generation
After many, many generations the group is still variable, but shows a general increase in neck length
Lamarck’s Contributions to the Development of Evolutionary Theory
Lamarck’s Contributions to the Development of Evolutionary Theory
• Presented evidence that fossils were the remains of extinct animals.
• Occurrence of fossils suggested to Lamarck that profound changes had taken place during the history of life on earth.
• Proposed the hypothesis of evolution by the inheritance of acquired characteristics.
Lamarck’s Theory of Evolution
Lamarck had good data
It is good common sense
But it isn’t right
Theories in Lamarck’s time
If data support your theory, and
You can’t think of an alternative theory
Your theory must be right
Theories Today
Poor theories are not discarded
A poor theory can only be replaced by a better one
A subtle but important difference
Darwin (1809-1882)
But … Darwin relied on his own observations
Ground work for the acceptance of evolution already done
Many of the main ideas already known
Darwin: Accomplishment
Age 27: 5 year voyage completed
Age 30: good travel book written
Middle age: natural history expert
Age 50: “Origins” published
Lifetime = 20 books, 80 papers
Darwin: Attributes
Gifted experimentalist
Equivalent of a “millionaire”
Quiet & modest lifestyle
Darwin: Attributes
Tremendous energy
Gift of simplicity
Courageous
Wrote so that the common person could read his works
Darwin: Chronology
College, but “sporting set”
Active naturalist, collector
Beagle as companion to Fitzroy
Gone for 5 years
Darwin
South America = no rabbits
But animals therewere similar to rabbits
“Why no rabbits?”
Ancestors had to get there or they must have originated there
European Rabbit: Oryctolagus cuniculus
Mara:Mara:Dolichotis patagonumDolichotis patagonumMara:Mara:Dolichotis patagonumDolichotis patagonum
Darwin
Struck by similarities between the types of animals(Europe vs. South America)
Found evidence of change in collections of fossils
Returned to EnglandMarried, ill health
Darwin
London
Species in Darwin’s Time
What is a species?
Each species created as a unique entity
Species characteristics do not change
SpeciesVariability?
Rock Dove
Artificial Selection
I liked breeding pigeons!
Darwin's Ideas
1837: Outline of ideas
1842: Full set of notes
1844: Book length manuscript
But he didn’t publish this ...
Why Did Darwin Wait?
160 pages not enough?
Another book, “Vestiges of the History of Creation”
1856: Nagged by Lyell (geologist)
1857: Wrote to Wallace (to get some facts)
Alfred Russel WallaceAlfred Russel Wallace
1823 - 19131823 - 1913
Wallace
12 pages – same basic conclusion as Darwin12 pages – same basic conclusion as Darwin
1858: Wrote sketch of his theory of evolution
Sent to Darwin to be published
Darwin
Linnean Society Presentation
5 page summary of events
Previous Darwin letter
Wallace’s 12 page letter
Result?
No notice
Darwin produced book by 1859
All copies sold on the first day
10 years later: most scientists believe Darwin’s theory
Darwin’s Natural Selection
A few serious challenges
Ideas languished
Mid-20th century revival
Why so long?Needed a mechanism: modern genetics
Darwin’s Observations & Conclusions
O1: Organisms produce more offspring than are needed for replacement
O2: Population size stays about the same
C1: There is competition for survival
Darwin’s Observations & Conclusions
O3: Natural resources are limited
C2: Most adapted individuals leave more offspring (= natural selection)
Darwin’s Observations & Conclusions
O4: Within a population, individuals exhibit variation in their characteristics
O5: Some variation is inherited (genetic)
Darwin’s Observations & Conclusions
C3: Some organisms exhibit heritable characteristics that make them more likely to survive and produce offspring .
Evolution by Natural Selection
Variability in the population
Changed environment
Isolation of the population
Time
Result: adaptation leading to a new species
Genetic ChangeGenetic Change
Evolution Variabilityin the
population
Transport to a different
environment
Isolation & time
Adapted to windAdapted to calm & shade
Genetic Variation in Giraffe Population
Giraffokeryx (extinct- giraffe ancestor 27 mya)
Genetic Variation in Giraffe Population
Giraffes
The HMS BeagleThe HMS Beagle
Galapagos
Galapagos
Galapagos Tortoises
Galapagos Tortoises
Blue footed boobieBlue footed boobie
Sea LionsSea Lions
Marine IguanasMarine Iguanas
Land IguanasLand Iguanas
MockingbirdsMockingbirds
Long-tailed
Hood
FinchesFinches
Medium ground finch
Cactus finch
Darwin’s FinchesDarwin’s Finches
DARWIN’S FIVE THEORIES OF EVOLUTION
1. Perpetual Change2. Common Descent3. Multiplication of Species4. Gradualism5. Natural Selection
Perpetual Change
The universe is not constant nor recently created nor perpetually cycling but rather is steadily changing and that organisms are transformed in time.
Horse Evolution
Common Descent
Every group of organisms descended from a common ancestor and all groups of organisms, including animals, plants, and microorganisms, ultimately go back to a single origin of life on earth.
Bears
Carnivores
Amniotes
Multiplication of Species
Species multiply either by splitting into daughter species or by “budding,” that is by establishment of geographically isolated founder populations that evolve into new species.
Foxes
Arctic fox Grey fox
Speciation produces new types of organisms
• Allopatric speciation: species formation due to physical separation of populations– Can be separated by glaciers, rivers,
mountains, etc. – Over time, each population
accumulates different mutations– Populations can no longer interbreed– The main mode of species creation
Model for Allopatric
Speciation
• Selection of certain traits that enhance reproductive success (fitness)
• Only the organisms best adapted to their environment tend to survive
Natural Selection
Extinction• Extinction: the disappearance of a
species from Earth– Average time a species spends on earth: 1–
10 million years
The number of species in existence = speciation - extinction
What Contributed to Extinction in Hawaiian Birds and other fauna?
• Hunting
• Disease (mosquitoes)
• Habitat loss
• Invasive species:– Rat, mongoose, ungulates, plants
Some species are more vulnerable to extinction
• Extinction occurs when the environment changes too rapidly for natural selection to work.
• Many factors can cause extinction:– Climate change– Changing sea levels– Arrival of new, harmful species– Severe weather (i.e., droughts)– Specialized species and small populations very
susceptible to extinction– Usually have small populations (i.e., golden toad)
Endemic species: a species only exists in a certain area
Very susceptible to extinctionUsually have small populations (i.e., golden toad)
Okapi
Earth has had several mass extinctions
• Mass extinction events: 5 events in Earth’s history that killed off massive numbers of species at once– 50-95% of all species went extinct at
one time• Humans are causing the sixth mass
extinction event.– Population growth– Development– Resource depletion
Questions
1. A simple definition of "evolution" is:
2. Lamarck's explanation of species changes:
3. An example of a homologous structure is:
4. An example of an analogous structure is:
5. Cabbage, corn, dogs and pigeons are an example of:
Questions
6. A theory that is wrong:
7. One of Darwin's notable non-scientific contributions was:
8. Darwin took quite a while to publish his ideas about evolution because:
9. Species evolution by natural selection, according to Darwin, requires that: