Transcript Direct Evidence for Evolution

Direct Evidence for Evolution
• Fossil Record
• Paleontologists have collected millions of fossils that make up the fossil record
• The fossil record is incomplete as many organisms die and vanish without
leaving a trace
• Does give a relatively clear picture of change.
• Ex. Evolution of the Horse
Direct Evidence for Evolution
• Fossils
• Preserved remains or traces of an
organism that lived in the past.
• Fossils are formed when
organisms die and are buried in
sediment. Eventually the
sediment builds up and hardens
to become sedimentary rock.
Direct Evidence for Evolution
• Fossil Record
• Shows major changes in Earth’s climate and geography
• i.e. Fossil shark teeth found in Arizona, indicating it was once covered by a
sea
Fossils can be absolute
dated using radioactive
decay of nearby flows
They can be relative
dated using nearby clues
Indirect Evidence for Evolution
 Homologous Structures
 Modified body parts with different
functions that developed from the same
ancestral parts
 Embryological Relationships
 Structural similarities between species
during embryonic development
 i.e. Gill slits in humans
Indirect Evidence for Evolution
 Vestigial Structures
 Structures in the body of organisms
that seem to serve no useful purpose
at all
 May have had a function in ancestral
forms
 Eg. human tailbones, the appendix
 Muscles that move our ears
 Whale hip bones
Indirect Evidence for Evolution
• Comparative biochemistry
• All organisms have similarities in their biochemistry
• All life uses DNA, ATP, Carbon
• The more closely two species are related, the closer the similarities
between their genes
• Humans share: 98% of our genes with chimpanzees; 65% with chickens; 60% with
bananas; 7% with bacteria
The Patterns of Evolution
Divergent Evolution
• Reproductive Isolation often results in Divergent evolution
• The process by which one species gives rise to two or more new species,
whose traits become more and more different, but who share a common,
structural ancestor
• Produces homologous structures
• Different function, but same origin
Convergent Evolution
• The process by which two or more different species evolve to
become structurally similar
• Species must have similar niches
• Ex. shark and dolphin
• Produces analogous structures
• Similar function, but different origin
Parallel Evolution
• The process where two different species follow similar evolutionary
paths
• Species must have similar niches
• Ex. Timber wolf and Tasmanian wolf
• Sleek, hunters, etc…
Co-evolution
• When two or more species influence each
other's evolution.
• It is most often invoked to explain co-adaptations
between species.
• Ex:
Parasites and Hosts
(antagonistic coevolution)
• can lead to evolutionary 'arms races‘
• Ex:
Insects and Flowering Plants
(mutualistic coevolution)
Living Fossils
• Some organisms have changed very
little over the past million years
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E.g. Ginko biloba (270 MYA)
Hagfish (300 MYA)
Red Panda (10 MYA)
Pelicans (30 MYA)
Crocodiles (83.5 MYA)