Transcript Evidence for Evolution

Evidence of Evolution
Evidence of Common Ancestry
(Element 1)
1. Biogeography:
Geographical distribution of species.
• Studying distribution of species in terms of their
geography and history (where they live now or
lived historically)
• E.g. Ratites, tree ferns – Gondwanaland
• Studies make use of present distribution, rock
layers, pollen record, fossils as evidence.
2. Fossil Record:
Fossils and the order in which they
appear in layers of sedimentary
rock (strongest evidence).
• Fossil record is now remarkably complete
with many species well studied. It has
been discovered on average that a
species lasts for 5-10 million years. Most
change in the gene pool occurs early on in
a species’ population, then they tend to
stay stable until extinction occurs.
3. Comparative Anatomy
• Parts of animals or plants are compared to
show similarities and differences.
Homologous structures
Structures that may have
very different form and
function may have an
underlying similarity,
resulting from a common
ancestry.
E.g. Mammal limbs
Check out
http://evolution.berkeley.edu/evolibrary/
article/0_0_0/homology_01
Analogous structures
Have the same function but a different
ancestry.
• Vestigial organs – Organs that have
become reduced or lost their function.
4. Embryology:
Study of structures that appear during embryonic
development. The early embryo stages of vertebrates
(fish, reptiles, amphibians, birds, mammals) are all
similar even though the adults are very different.
• The more similarities
there are chemically the
closer the organisms are
thought to be.
• Geneticists study
percentage similarity
between DNA sequences
of species.
• Cytochrome-C is a
protein involved in cell
respiration. Scientists
have compared the
sequence of amino acids
in many different species
for this protein.
5. Molecular Biology:
DNA and proteins
• Species that have
more similar patterns
of amino acids are
more closely related.
Number amino acids
in Cytochrome-C
sequence different to
humans
Chimps
0
Dog
13
Duck
17
Horse
17
Kangaroo
12
Moth
36
Penguin
18
Rabbit
12
Rhesus monkey
1
Tuna
31
turtle
19