Mechanisms & Applications of Evolution

Mechanisms of Evolution(how it happens)

1. Natural Selection (“survival of the fittest”)

The development of the natural selection theory:

• 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)• 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• 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

Ancestor A Ancestor B

Different organisms that look similar

http://cas.bellarmine.edu/tietjen/Evolution/convergent_evolution_examples.htm

Divergent Evolution

• Organisms with a common ancestor develop different characteristics (adapted to their environments)

Common Ancestor

Organism A Organism B

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