Transcript Mechanisms & Applications of Evolution

Mechanisms & Applications
of Evolution
Mechanisms of Evolution
(how it happens)
1. Natural Selection (“survival of the fittest”)
The development of the natural selection
theory:
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1700s- Lamark was the first person to state that
organisms change over time, and that new
organisms are modified descendants of older
organisms (with is theory of acquired traits)
Natural Selection
• 1800s- Charles Darwin sailed on the H.M.S. Beagle
and gathered data from organisms (fossils, finches,
etc.)
• From this data, Darwin inferred that all species had
descended from one or a few original types of life.
• Darwin also concluded that the way
species/organisms change over time was by natural
selection
Natural Selection
The process of natural selection:
• There must be variation in the traits of a population.
(This variation is caused by organisms having
different genes.)
• There must be environmental pressures that favor
one variation of the trait over the other.
• Organisms with the better traits will survive better
and longer, reproduce, and pass those good traits on
to their offspring.
• The result will be a population better suited for the
environment.
Natural Selection
Mechanisms of Evolution
2. Geographic Isolation
– Organisms of a population can become isolated
from one another by a geographic barrier
– If they are no longer able to reproduce, they
may become two separate species.
– The formation of a new species is called
speciation.
Applications of Natural Selection
(Why is this important to us now?)
1. Antibiotic-resistant bacteria (ex. MRSA)
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Bacteria reproduce and mutate at a very high rate.
Some bacteria’s DNA has mutated to be resistant
to many known antibiotics.
When the resistant bacteria reproduce, they pass
this ability onto their offspring.
Bacteria can also pass the resistance to other
bacteria through conjugation (bacteria’s sexual
reproduction).
Applications of Natural Selection
• To help prevent the development of antibiotic
resistant bacteria,
– Don’t overuse antibiotics (they DO NOT kill viruses!)
– Use a variety of antibiotics (not just the same one over and
over again)
– Finish the whole dose of antibiotics
• Bacteria are also becoming resistant to cleaners!!!
(Don’t overuse antibacterial soaps and cleansers.)
Applications of Natural Selection
MRSA infections, if severe, can cause “flesh eating disease”.
Applications of Natural Selection
2. Pesticide-resistant insects
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Same mechanisms as above.
To help prevent this,
– Don’t overuse pesticides (or don’t use them at all!)
– Raise/buy organic food
– Use biocontrols (such as lady bugs)
Applications of Natural Selection
Convergent Evolution
• Organisms from different ancestors develop
similar characteristics
Different organisms
that look similar
Ancestor A
Ancestor B
http://cas.bellarmine.edu/tietjen/Evolution/convergent_evolution_examples.htm
Divergent Evolution
• Organisms with a common ancestor develop
different characteristics (adapted to their
environments)
Organism A
Organism B
Common Ancestor
Coevolution
• Two organisms that live closely together
both adapt to changes in the other organism
– Ex.: giant hawk moth and Madagascar orchid
– Ex.: bats and cactus flowers