Download EVIDENCE FOR EVOLUTION

Scientific evidence to support the Theory of
Evolution by Natural Selection
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FOSSILS – are the
mineralized remains or
traces (tracks,
imprints) of animals,
plants or other
organisms
THE FOSSIL RECORD –
fossils found in rock
strata that show a
sequence or history of
life on Earth
Trilobite fossil found in
Burgess Shale
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The Burgess Shale is a
middle Cambrian site
(~540 MYA)
One of the few places
in the world where
difficult-to-preserve
soft-bodied organisms
of our past were
preserved
Some of the fossils found here are
now long extinct and are unlike
anything presently existing
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Fossils found in young
layers of rock (ie closer to
the surface) tend to be
more similar to present day
organisms
Fossils appear in
chronological order (oldest
ancestors in deepest layers
Not all organisms appear in
the fossil record at the
same time – ie fish are the
oldest vertebrates – then in
subsequent layers
amphibians, reptiles,
mammals and birds
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Transitional fossils are
fossils that show
intermediary links
between groups of
organisms
They can provide a link
between the past and
present
Archaeopteryx – a transitional fossil
because of its characteristics of
both reptiles (dinosaurs) and birds
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Example: Basilosaurus
and Dorudon were
ancient whales with
tiny hind limbs – living
entirely in water
Ambulocetus – a more
recent ancestor, had
heavier leg bones and
lived in both water and
on land
- The tiktaalik was an ancient tetrapod
- It was thought to have descended
from lobe-finned fishes
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They lived in oxygen-poor water
- used their lobe fins to live partly on
land-possibly gave rise to amphibians
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Darwin and Wallace
observed that many
species evolve in one
location and spread
out to other areas
Darwin found 14
different species of
finch – he theorized
all evolved from one
common ancestral
finch
ADAPTIVE RADIATION –
Diversification of a
common ancestral species
into a variety of species
Close environments (ie
desert & forest in South
America) have more
related species than
geographically separate
but environmentally
similar locations (ie –
desert in S.America,
desert in Australia)
-left: cactus from S.America
-right: cactus from Australia
Animals found in
islands often
resemble animals
found on closest
islands –
suggesting
animals have
evolved to suit
new environment
Example: lizards
off NW coast of
Africa (canary
islands are similar
to lizards in West
Africa
Top: Canary Island lizard
Bottom: West African lizard
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Fossils of the same
species can be found
on the coastline of
neighbouring
continents
Example: Cynognathus
has been found in
Africa and S.America
At one time, all
continents were joined
(Pangea – 250 MYA)
-a depiction of the Earth 250 MYA
– continents were joined together
-distribution of ancient
organisms
Cynognathus crateronotus
Vertebrate forelimbs
can be used for many
different functions:
 Flying (birds, bats)
 Swimming (whales)
 Brachiation (monkeys)
 Running (horses, dogs)
HOWEVER: they ALL contain the
same set of bones organized in
similar ways – WHY?
Homologous structures are similar
in structure but often differ in
function
Homologous structures provide
evidence for a common ancestor
amongst all vertebrates
Analogous Structures
Structures that evolve
separately to perform a similar
function are analogous. The
wings of birds, bats, and
insects, for example, have
different embryological origins
but are all designed for flight.
•Bird:
feathers
•Bat: skin
•Butterfly: chitin
Vestigial structures
are thought to have
had a purpose at
one time in our
ancestry, but no
longer have a
specific function
(eg) human appendix
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“c” indicates the
Underdeveloped hind legs
Of the baleen whale
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The muscles connected to
the ear of a human do not
develop enough to have the
same mobility as those of
the monkey
The embryos of
different vertebrates
show similar stages of
embryonic
development
 Neck pouches – in
humans become ears &
throat
- in fish become gills
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- Similarities among embryos
point to a common ancestor
Can you tell which
embryo is which?
A – cat
B – cow
C - horse
D - human
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Many organisms share
similar cellular
components such as:
Proteins – long chains
of amino acids used for
building & repair
Enzymes – made from
proteins – they control
many biochemical
reactions in the cell
DNA – genetic material
found in the nucleus
The DNA of chimpanzees &
humans is ~ 98% identical
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Hemoglobin—the oxygen-transport
protein that gives blood its red color—got
its start at about the time life originated
on earth, nearly four billion years ago.
Now it is almost ubiquitous, appearing in
the cells of plants, animals and even
bacteria, and a study of this protein
affords scientists a rare glimpse back as
well as forward in time. A look at the
ancestral hemoglobins indicates that
newly arising proteins co-opt the
chemistry of older ones and gain new
functions through structural alterations.
But these studies have revealed an
additional way to modify function.
Scientists are coming to the realization
that changes in a protein's regulation—
the when and how of its expression—can
also give rise to functional differences.
The surprise, says the author, is that
these regulatory changes outpace
structural ones—an important lesson for
students of molecular evolution and a
possible indicator of where protein
evolution will go in the future.
http://adsabs.harvard.edu/abs/1999A
mSci..87.....H
hemoglobin (found in
RBCs) is used to bond to O2
Above:hominid evolution