Transcript Evidence for Evolution Notes

Recap on Evolution
What is the Theory of Evolution?
• Evolution is defined as change over time.
• One of the earliest theories of evolution was put forward
by Darwin.
• He studied physical differences in finches on the
Galapagos Islands.
• From his studies he discovered the theory of Natural
Selection which favors some adaptations.
• Organisms not favored can become extinct.
• Natural selection works off of competition for resources
and adaptations that help animals survive in an
environment.
Evidence for Evolution
Fossils (Palentology)
• The study of fossils
• Fossils show us what organisms looked
like a long time ago
• We know how old they are– Relative dating: what layer of rock the fossil is
found in
How are fossils evidence?
• If modern species looked exactly the same
as fossils, then it would show that nothing
has changed but they do not look the
same.
• Extinctions: species were not “fit” for the
environment any more
Comparative anatomy
• Anatomy is the study of the body parts of
an organism
• Homologous structures: structures in
different species that are similar but have
evolved to be different because they are
used differently
• Vestigial structures: structures that no
longer serve a purpose in modern
organisms
• Divergent evolution: when one species
evolves into two or more
– Adaptive radiation: when one species evolves
into many
• Convergent evolution: when two unrelated
organisms have similar structures because
of their environment
How is anatomy evidence?
• If a group of organisms have similar
structures, we know they had a common
ancestor
Embryology
• Embryology is the study of embryos and
how they are similar
• During the first few hours and days of
development, all animals start out looking
the same because they all use the same
genes to get started.
How is embryology evidence?
• If the organisms are using the same genes
to create the same structures, it shows
that they were at one time the same
organism and that they share a common
ancestor
DNA and the universal code
• DNA is the genetic molecule for every
organism on earth
• All organisms use A, T, G, and C which is
called the universal code
• DNA makes proteins out of 20 amino acids
• Mutations cause changes to DNA
sequences and amino acid sequences
How is DNA evidence?
• If all organisms use the same code (DNA),
then they all started out as one organism
(3.5 billion year ago)
• Mutations have caused changes to some
organisms and other changes to other
organisms
• The more similar the DNA (or protein) is
between two species, the more recently
they were related to each other
Population genetics
• Population genetics is a fusion of Darwin’s
ideas with genetics
• Speciation is the creation of a new species
• Speciation can occur by:
– Mutations
– Gene flow
– Genetic drift
– Selective mating
– Natural selection due to environmental
changes
How is population genetics evidence?
• When speciation occurs, changes are
made to the gene pool which cause
different populations to be different
• If there are enough differences, they
become isolated from each other and they
are considered different species
• Types of isolation
– Mechanical
– Seasonal
– Habitat
- Geographic
- Behavioral
• Types of selection
– Disruptive
– Stabilizing
– Directional