The Missing Loonie Riddle
Sources of Evidence for
Evolution
1.Fossil Evidence
2.Biogeography Evidence
3.Anatomy Evidence
4.Embryology Evidence
5.DNA Evidence
1. Fossil Evidence
• As new rock is formed,
the older rock layers
become deposited under
the new rock layers.
• Creates a geological time
scale
• In each of the layers
of rock, different
fossils can be found
according to major
extinction events.
• Comparing fossils at
various depths, one
can compare fossil
records
Fossil Records: In Summary
• Fossils found in young layers of rock (closer to
the surface) are similar to species alive today
than the one’s found in older (deeper) layers of
rock.
• Fossils appear in chronological order in rock
layers.
Transitional Fossils
• Transitional Fossils – a fossil that shows the
intermediary links between two groups of
organisms with slight different features.
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Transitional Fossils – Evidence of
Evolution
Transitional Fossils
• The modern day whale evolved from an aquatic
species Dorudon which contained a hind limb.
• Dorudon evolved from terrestrial species which
had a function for the hind limbs.
Fossil evidence suggests that modern
toothed whales evolved from a terrestrial
ancestor.
Modern toothed whale
Dorudon and Basilosaurus – (not shown)
Rodhocetus kasrani – had small hindlimbs
Ambulocetus natans – likely walked on land
Pakicetus attocki – lived on land
Whale Evolution Summarized
2. Biogeography
The study of the past and present
geographical distribution of organisms
Geographical Distribution
• Geographically close environments are
more likely to be populated by related
species than locations that are
geographically separate but
environmentally similar.
• Species found on islands often closely
resemble species found on the nearest
islands and continents.
Closely Related But Different
Features
• Animals that are found in
areas close to one another
are often closely related.
• They may however have
different features due to
environmental differences.
• E.g. Darwin’s Finches
Distantly Related But Similar
Features
• If two species live far away from one another
but live in similar environments they are likely
to have similar features.
– Environment puts selective pressure for a species to
adapt to the environment.
– Evolved from different ancestors
Geographical Distribution - Fossils
• Fossils of the same species can be found
on the coastlines of neighbouring
continents.
– Due to the fact that the world was once
Pangaea.
• Closely related species are almost never
found in exactly the same location or
habitat.
– Due to competition
3. Anatomy Evidence
• Homologous structures – structures that have
similar structural elements and origin but may
have a different function
• Analogous structures – structures of organisms
that do not have a common evolutionary origin
but perform similar functions.
Analogous Structures
• The camera type eye in vertebrates (e.g.
humans) and mollusks (e.g. octopus) evolved
separately but function in a similar way.
• Vestigial structures – are remnants of
structures that may have had important
functions in ancestral species but have no
clear function in some modern descendants.
Vestigial Features in Humans
4. Embryology
• The study of early, pre-birth stages of an
organism’s development
Embryology Developed
• Embryos of closely related organisms
often have similar stages in development.
– All vertebrates at some point of development
possess gill pouches (eventually develops
into the chin and other skull bone
structures).
– All vertebrate animals have tails during
development (some will continue to develop
their tails while others do not)
5. DNA Evidence
• If two species have similar patterns in their DNA,
these DNA sequences must have been inherited
from a common ancestor.
Homework/In-class Questions
• # 1, 3, 5, 8-12 (page 340)