Evolution

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: