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Evolution
{ Evidence revisited
Fossils
Fossils:
• Document patterns of evolution
• Provide physical evidence of changes in various
groups of organisms
• Show that present day organisms are different
than those of long ago
• Show that extinctions have occurred
Biogeography
Biogeography= The scientific study of the
geographic distribution of species
Continental drift= The slow movement of
Earth’s continents over time
Example: Island species
•Island species are more like the species of
the nearest mainland, even if the
environment is quite different, rather than
like other distant islands with similar
environments.
Homology
Homology= similarity resulting from common
ancestry
Homologous structures derive from a common
ancestor, but may have evolved to perform
different functions
They are so similar that it would be very unlikely
that they could have developed independently in
each species.
Example: Skeletal homologies-forelimbs
Figure 19.16
Humerus
Radius
Ulna
Carpals
Metacarpals
Phalanges
Human
© 2014 Pearson Education, Inc.
Cat
Whale
Bat
Vestigial structures- a type of homologous structure.
Structures or remnants of structures that no longer serve a
function in an organism, but did in its ancestors
Can give clues, especially in the fossil record, of the
progression of evolutionary
changes
Examples:
• Tail bones
• Hip bones in whales
• Many human structures
Analogous structures= similar features that
occur because of convergent evolution. They
have the same function, but organisms do not
share a common ancestor
Convergent evolution= the independent
evolution of similar features in different lineages
Examples• Jointed legs in mammals and insectslocomotion
Direct observation =
“evolution in action”
Examples:
• Lactose intolerance
• MRSA- methicillin resistant Staph. aureus
• Nylon eating bacteria
Others you might want to explore
• MDR TB- multi drug resistant tuberculosis
• Soapberry bugs
Four modes of natural selection.
1. Directional selection
2. Disruptive selection
3. Stabilizing selection
4. Sexual selection
Homework: Due THURSDAY 12/10
• Define each
• Give an example of each