Download Evolution : The Evidence

EVOLUTION
The evidence
© 2016 Paul Billiet ODWS
Systematics
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Jardins des Plantes Paris
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© 2016 Paul Billiet ODWS
Collections of animals
and plants in museums
from 17th century
Need for systematic
classification
Carl Linneus (1735)
The binomial
classification
To “put order into God’s
creation”
Binomial system
Homo sapiens
Genus
Capital case
© 2016 Paul Billiet ODWS
Species
Small case
Levels of hierarchy
Taxon
Domain
Kingdom
Phylum
Class
Based on relatedness (phylogeny) but artificial
Order
Family
Genus
Species
© 2016 Paul Billiet ODWS
Some biological basis
Comparative Anatomy
Classification  comparisons of shape and
form  comparative anatomy
 Comparative anatomists noticed that different
species have the same structures used for
different functions (e.g. the pentadactyl limb
of terrestrial vertebrates)
 These are called homologous structures.
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© 2016 Paul Billiet ODWS
The pendadactyl limb
Lizard
Frog
Bat
© 2016 Paul Billiet ODWS
Human
Comparative Embryology
Early embryos of
animals show similar
features
Revealing a common
ancestry
Their similarity
diverges as they
develop (Von Baer)
More distantly related
species diverge
earlier
© 2016 Paul Billiet ODWS
Vertebrate embryos Ernst Haeckel 1892
Comparative biochemistry
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Protein molecules the bottom line in studying
the phenotypes of organisms
Similarities and differences in the amino acid
sequences of the same molecule
(e.g. haemoglobin) taken from different species
produce a phylogeny
The phylogeny revealed by studying protein
structure ≈ phylogeny of comparative anatomy
and embryology but with a much finer resolution.
© 2016 Paul Billiet ODWS
Molecular genetics
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Comparison of the base sequences of
variable regions of DNA taken from different
organisms
In particular mitochondrial DNA
The genotype is being analysed
Rates of mutations are assumed to be
constant
The analysis of DNA provides a molecular
clock against which the geological clock can
be compared.
© 2016 Paul Billiet ODWS
Phylogenetics
Classification led to phylogeny: the study of
related groups as revealed by systematic
classification
 Closely related organisms are more similar
than distantly related organisms
 Currently the systematic analysis of
relatedness uses a technique called
cladistics.
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© 2016 Paul Billiet ODWS
Cladogram for the birds
Archeopteryx
reversed first toe, fewer
than 26 tail vertebrae
Velociraptor
halfmoon-shaped
wrist bone
Modern birds
no teeth,
horny beak
Allosaurus
three fingered hand
Coelophysis
three functional toes
and hollow bones
Titanosurus
Node
Other
dinosaurs
© 2016 Paul Billiet ODWS
PALAEONTOLOGY
The study of
fossils
© 2016 Paul Billiet ODWS
The formation of fossils
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Fossils are generally of rock
that has replaced the
preserved organism or its
traces
Usually occurs when the
organism is covered quickly
so it is preserved
Sediment, forming
sedimentary rock, is then laid
down
Petrifaction follows.
© 2016 Paul Billiet ODWS
The formation of fossils
Not all fossils are petrified
 Some are preserved by:
dehydration (mummified),
in ice,
in peat bogs,
in tar beds
trapped in amber.
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© 2016 Paul Billiet ODWS
http://www.fossilmall.com/EDCOPE_Enterprises/amber/a046/A046A.jpg
Fossil DNA
The current limit for
fossil DNA appears to
be about 100 000 years
old
 Oxygen and water
damage the molecule
with time.
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© 2016 Paul Billiet ODWS
http://www.amazon.com/Jurassic-Park-Michael-Crichton/dp/0345370775
Finding fossils
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Fossils are only formed under certain conditions and
then have to be uncovered
Natural erosion exposes the deeper, older layers
containing the fossils
Gorges, quarries, caves and desert areas
Fossilisation is rare
Fossil discovery is even rarer
The fossil record is very incomplete
Gaps in the record
Restricted distribution of many species
Palaeontologists can improve their chances by searching
systematically in places where fossils are likely to be
found.
© 2016 Paul Billiet ODWS
Common ancestors &
missing links
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Evolution from a common
ancestor, would explain their
common features
Fossils found close to the
origin of a common ancestor
These are called missing
links
(e.g. Archaeopteryx a fossil
dinosaur with bird-like
features)
© 2016 Paul Billiet ODWS
Archaeopteryx
Artificial selection
Domestic pig
Wild boar
9000 years
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Evolution on a very short time scale.
© 2016 Paul Billiet ODWS
The Neolithic Revolution
Sami herding
reindeer
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The origins of domestication began about
10 000 years ago
Animals that naturally form herds were probably
followed by nomads and gradually domesticated
Selective breeding followed.
© 2016 Paul Billiet ODWS
Selecting characters
Higher production (more offspring, faster
growth)
 Higher quality produce
 Material of a specific quality (white fleece)
 Less aggressive behaviour
 Climatic tolerance
 Eventually, disease resistance.
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© 2016 Paul Billiet ODWS