Download - Evidence and Evolution
EVOLUTION:WHERE'S THE EVIDENCE?
Examples of evidence from:• The fossil record• Living populations• The DNA record
www.christs.cam.ac.uk/darwin200
EVIDENCE & EVOLUTION
What’s the evidence that evolution by natural selection happens?
There’s lots! Too much to catalogue here…
But we can discuss the sorts of evidence scientists have.
Evidence supporting natural selection comes from many sources, including:• the fossil record• observations of living populations• the DNA record
EVIDENCE & EVOLUTION
THE FOSSIL RECORD
Its very difficult to become a fossil
EVIDENCE & EVOLUTION
THE FOSSIL RECORD
Its very difficult to become a fossil
EVIDENCE & EVOLUTION
THE FOSSIL RECORD
Its very difficult to become a fossil
EVIDENCE & EVOLUTION
THE FOSSIL RECORD
Its very difficult to become a fossil
EVIDENCE & EVOLUTION
THE FOSSIL RECORD
Its very difficult to become a fossil
EVIDENCE & EVOLUTION
THE FOSSIL RECORD
Its very difficult to become a fossil
EVIDENCE & EVOLUTION
THE FOSSIL RECORD
Its very difficult to become a fossil
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EVIDENCE & EVOLUTION
THE FOSSIL RECORD
Its very difficult to become a fossil
Despite this the fossil record provides lots of evidence for evolution:• the earliest fossils appear in rocks 1-2 billion years old• the earliest fossil animals appear in rocks about 650 million years old• the fossil record contains many examples of intermediates between groups
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TRANSITIONAL FOSSILS: example 1 – from fish to tetrapods
Tetrapods share ancestry with lobe-finned fish.
EVIDENCE & EVOLUTION
coelocanth
salamander
TRANSITIONAL FOSSILS: example 1 – from fish to tetrapods
Tetrapods share ancestry with lobe-finned fish.
EVIDENCE & EVOLUTION
coelocanth
salamander
Acanthostega
TRANSITIONAL FOSSILS: example 1 – from fish to tetrapods
Tetrapods share ancestry with lobe-finned fish.
EVIDENCE & EVOLUTION
coelocanth
salamander
Tiktaalik
Acanthostega
TRANSITIONAL FOSSILS: example 1 – from fish to tetrapods
Tetrapods share ancestry with lobe-finned fish.
EVIDENCE & EVOLUTION
coelocanth
salamander
Tiktaalik
Ichthyostega
Acanthostega
EVIDENCE & EVOLUTION
TRANSITIONAL FOSSILS: example 1 – from dinosaurs to birds
Birds are living descendents of dinosaurs.
Coelophysis
EVIDENCE & EVOLUTION
TRANSITIONAL FOSSILS: example 1 – from dinosaurs to birds
Birds are living descendents of dinosaurs.
Coelophysis
Archeopteryx
EVIDENCE & EVOLUTION
TRANSITIONAL FOSSILS: example 1 – from dinosaurs to birds
Birds are living descendents of dinosaurs.
Coelophysis
Archeopteryx
Caudipteryx
EVIDENCE & EVOLUTION
TRANSITIONAL FOSSILS: example 1 – from dinosaurs to birds
Birds are living descendents of dinosaurs.
Coelophysis
Archeopteryx
Caudipteryx
Confuciusornis
EVIDENCE & EVOLUTION
LIVING POPULATIONS
Evolution is often thought to be very slow, too slow to observe within a human lifetime.
This isn’t true! We have a number of examples of evolution caught in action.
EVIDENCE & EVOLUTION
LIVING POPULATIONS
Evolution is often thought to be very slow, too slow to observe within a human lifetime.
This isn’t true! We have a number of examples of evolution caught in action.
MICROEVOLUTION
Microevolution is evolutionary changes within a population. - changes in allele frequencies- often has a small but significant phenotypic effect
Over many generations microevolution can ‘sum up’ to produce large changes.- it is the engine of evolution!
EVIDENCE & EVOLUTION
MICROEVOLUTION: example 1 – Darwin’s finches
The Galapagos Islands are home to 13 species of finches.
They are more closely related to each other than to any other species.
They are descended from a finch species that migrated to the islands from South America.
EVIDENCE & EVOLUTION
MICROEVOLUTION: example 1 – Darwin’s finches
The Galapagos Islands are home to 13 species of finches.
They are more closely related to each other than to any other species.
They are descended from a finch species that migrated to the islands from South America.
Since arriving on the island the finches have:- Specialised- Diverged
They now occupy different niches, each species feeding in a different way.
EVIDENCE & EVOLUTION
MICROEVOLUTION: example 1 – Darwin’s finches
Scientists have been studying the ground finches on one island called Daphne for 40 years.
There are 3 ground finches: a large, medium and small specieswhich specialise on large, medium and small seeds.with different sized beaks to match – big seeds need big beaks to crack open
EVIDENCE & EVOLUTION
MICROEVOLUTION: example 1 – Darwin’s finches
Scientists have been studying the ground finches on one island called Daphne for 40 years.
There are 3 ground finches: a large, medium and small specieswhich specialise on large, medium and small seeds.with different sized beaks to match – big seeds need big beaks to crack open
The researchers observed the finches during a drought:• plants struggled with water shortage• they produced fewer seeds
• the finches quickly ate all the small seeds• only large, tough seeds were left
• only the birds with the largest beaks could find food• the smaller-beaked birds starved
EVIDENCE & EVOLUTION
MICROEVOLUTION: example 1 – Darwin’s finches
Scientists have been studying the ground finches on one island called Daphne for 40 years.
There are 3 ground finches: a large, medium and small specieswhich specialise on large, medium and small seeds.with different sized beaks to match – big seeds need big beaks to crack open
The researchers observed the finches during a drought:• plants struggled with water shortage• they produced fewer seeds
• the finches quickly ate all the small seeds• only large, tough seeds were left
• only the birds with the largest beaks could find food• the smaller-beaked birds starved
the average beak size of the large ground finch increased by 1mm in one season – >10% increase!
EVIDENCE & EVOLUTION
MICROEVOLUTION: example 1 – melanism in peppered moths
Melanism is the occurrence of both a dark and light form of a species.
The peppered moth is a famous example.
The peppered moth (Biston betularia) has a few forms, one is:- typica - speckled white- carbonaria – black
They are found in woods in Britain, they are active at night and predated on by birds during the day when they are at rest on branches.
During the industrial revolution soot covered the lichen on tree trunks, the typica form was more easy for birds to spot & the carbonaria arose and increased in frequency.By 1895, 98% of Mancunian population were black.
EVIDENCE & EVOLUTIONMICROEVOLUTION: example 1 – melanism in peppered moths
A biologist called Kettlewell performed experiments to show that birds ate more typica than carbonaria in the 1950s.
The Clean Air Act was introduced in the 1950s, trees regained their former appearance. The typical form 6% to 30% by 1984 and continues to increase.
EVIDENCE & EVOLUTIONMICROEVOLUTION: example 1 – melanism in peppered moths
A biologist called Kettlewell performed experiments to show that birds ate more typica than carbonaria in the 1950s.
The Clean Air Act was introduced in the 1950s, trees regained their former appearance. The typical form 6% to 30% by 1984 and continues to increase.
This became a text book case of evolution in action.
However anti-evolutionists attacked the evidence.
Mike Majerus at Cambridge University responded by re-doing Kettlewell’s experiments – his hypothesis was that Carbonaria would decrease in frequency.
carbonaria
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2001 2002 2003 2004 2005 2006 2007
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EVIDENCE & EVOLUTIONMICROEVOLUTION: example 1 – melanism in peppered moths
A biologist called Kettlewell performed experiments to show that birds ate more typica than carbonaria in the 1950s.
The Clean Air Act was introduced in the 1950s, trees regained their former appearance. The typical form 6% to 30% by 1984 and continues to increase.
This became a text book case of evolution in action.
However anti-evolutionists attacked the evidence.
Mike Majerus at Cambridge University responded by re-doing Kettlewell’s experiments – his hypothesis was that Carbonaria would decrease in frequency.
carbonaria
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
2001 2002 2003 2004 2005 2006 2007
Year
Series1
That’s what he found! He tested each claim made by the critics and found no support for any of them: melanism in the peppered moth was confirmed as an example of microevolution
EVIDENCE & EVOLUTION
DNA
DNA is a molecule that carries instructions on how to build an organism.
It encodes information to build and express proteins:
DNA
messenger RNA
Protein
It is passed on from parent to offspring.Mutations in an organism’s DNA produce phenotypic changes – which natural selection then works one
EVIDENCE & EVOLUTION
THE DNA RECORD
All living organisms use DNA as their genetic information. As it is passed through generations the DNA sequence evolves.
We can sequence homologous stretches of DNA from different species and use them to test for relatedness.
EVIDENCE & EVOLUTION
THE DNA RECORD
All living organisms use DNA as their genetic information. As it is passed through generations the DNA sequence evolves.
We can sequence homologous stretches of DNA from different species and use them to test for relatedness.
We can also see that these same stretches of DNA often have conserved functions.
For example the HOX genes control the development of the body axis in animals.
HOX gene expression in mice.. … and humans
EVIDENCE & EVOLUTION
THE DNA RECORD
All living organisms use DNA as their genetic information. As it is passed through generations the DNA sequence evolves.
We can sequence homologous stretches of DNA from different species and use them to test for relatedness.
We can also see that these same stretches of DNA often have conserved functions.
For example the HOX genes control the development of the body axis in animals.
HOX gene expression in mice.. … and humans
DNA evolves through common descent& is acted upon by natural selection
EVIDENCE & EVOLUTION
THE DNA RECORD
Changes in DNA cause changes in development –acted upon by natural selection
For example: three-spine sticklebacks
EVIDENCE & EVOLUTION
THE DNA RECORD
Changes in DNA cause changes in development –acted upon by natural selection
For example: three-spine sticklebacks
Mutations in the gene Pitx1 affect the development of pelvic spines.
Pelvic spines are a defence against predation by fish.
Loss of the spines are thought to help the fish escape crustacean predators living on the water bed.
CONCLUSIONS: THE EVIDENCE FOR EVOLUTION
-Evidence from the fossil record
- Evidence from living populations
- Evidence from the DNA record
- Heritable changes in DNA affecting development fitness
www.christs.cam.ac.uk/darwin200
EVIDENCE & EVOLUTION
For more information on these examples and for more examples visit:
CONCLUSIONS: THE EVIDENCE FOR EVOLUTION
-Evidence from the fossil record
- Evidence from living populations
- Evidence from the DNA record
- Heritable changes in DNA affecting development fitness
www.christs.cam.ac.uk/darwin200
EVIDENCE & EVOLUTION
For more information on these examples and for more examples visit:
CONCLUSIONS: THE EVIDENCE FOR EVOLUTION
-Evidence from the fossil record
- Evidence from living populations
- Evidence from the DNA record
- Heritable changes in DNA affecting development fitness
www.christs.cam.ac.uk/darwin200
EVIDENCE & EVOLUTION
For more information on these examples and for more examples visit:
CONCLUSIONS: THE EVIDENCE FOR EVOLUTION
-Evidence from the fossil record
- Evidence from living populations
- Evidence from the DNA record
- Heritable changes in DNA affecting development fitness
www.christs.cam.ac.uk/darwin200
EVIDENCE & EVOLUTION
For more information on these examples and for more examples visit:
CONCLUSIONS: THE EVIDENCE FOR EVOLUTION
-Evidence from the fossil record
- Evidence from living populations
- Evidence from the DNA record
- Heritable changes in DNA affecting development fitness
www.christs.cam.ac.uk/darwin200
EVIDENCE & EVOLUTION
For more information on these examples and for more examples visit: