Download Homology– Evidence of a Common Ancestor

Evidence
for
Evolution
Evidence for Evolution
•Homology
•Convergent evolution
•Vestigial structures
•Selective Breeding
•Fossils
•Embryology
•DNA
•All of these evobots used the same red pieces that were
present in their ancestor but not in earlier generations.
•We can see the steps
between the reptile jaw
and the human ear–
they use what appear to
be the same bones.
•When we see very similar
parts in many living things,
we gain evidence of their
common ancestor and its
characteristics.
•This is especially true
when similar parts have
different functions
Convergent Evolution
•Most evolution appears to be divergent– those closest to
the ancestral state are the most similar and organisms
become more different as they evolve.
•This is not always the case. Sometimes, organisms come
up with similar solutions to the same environmental
problems.
Convergent Evolution
Convergent Evolution
•Most evolution is Divergent (species with
similar traits have a common ancestor)
•According to Natural Selection, species
evolve traits that help them survive in an
environment.
•Sometimes, the requirements to survive in
an environment are so strong that several
VERY DIFFERENT SPECIES evolve traits
that function in similar ways. This is
convergent evolution.
•Structures that are no longer
useful, such as our appendix,, or
the fingers on a whale are
vestigial structures. They are
evidence that these creatures
evolved from other creatures that
used these structures.
Kakapo
(New Zealand)
Kiwi
(New Zealand)
Cassowary
(New Giunea)
Spine Structure
and tailbone
Body Hair and Goosebumps
•We humans have been selecting
characteristics of pets and domesticated
plants and animals for thousands of
years. In many cases, we have
dramatically changed how species look
and behave.
•In some ways, animals do this too both
through sexual selection and natural
selection itself.
Cows are bred for
beef or milk
production
(Video).
Corn has been selectively
bred for 600 to 10000 years by
people in North America.
Peacock Colors
Bowerbird Nests
In many animal species,
females choose males that
win competitions with other
males. Alleles that help them
win these competitions are
then selected for.
Pollinators “select” flowers that are more appealing. Bees
tend to select blue and purple flowers whereas humming
birds prefer red.
Fishes “select”
the angler fish
with the most
attractive lure-- by getting
eaten by them!
Any prey species,
inadvertently
selects
characteristics in a
predator that allows
the predator to
catch and eat them.
•There are fossils of many creatures
that no longer exist today. They often
show intermediate forms between
species that exist today and their
ancestors.
•We also see that fossils deeper in the
earth only show simpler creatures with
more advanced life forms closer to the
surface.
•Embryos of some animals show
traits that are not present in adults
such as gills and tails in humans.
These are evidence that these traits
were found in our ancestors.
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If you look at the DNA of living creatures you
can see the similarities.
Many sections of DNA are don’t code foe
anything at all. These sections are similar to
working or useful sections in other creatures.
Even in human DNA, you can see the broken
parts of code that were important in an
organism long ago
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Pseudogenes are sections
of chromosomes that
resemble functioning genes
in related creatures, but lack
start codons (or promoters)
and are never translate into
proteins.
For example, genes for gills
may be present in mammals,
but in a non-functional,
mutated, broken form.
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Humans and other chimps split from dogs long
before they spit from each other.
We would expect to see more genetic
similarities between chimps and humans than
either would have with dogs.
We would ALSO expect humans and chimps to
show similar difference from chimps, and they
do.
Evidence for Evolution
•Homology
•Convergent evolution
•Vestigial structures
•Selective Breeding
•Old Earth
•Embryology
•Fossils
•DNA