TYPES OF EVOLUTIONAND MECHANISM FOR

CHANGE

Chemical Evolution

Where did all the elements essential for life come from? How did they form into complex organisms?

Chemical evolution refers to the formation of complex ORGANIC molecules from simple inorganic molecules through chemical reactions.

This takes place in Earth’s oceans and lasts for less than a billion years

Miller and Urey Experiment

In the 1950’s two scientists recreated the POSSIBLE conditions in Earth’s atmosphere.

This experiment showed the evolution of organic molecules

These scientists went even further showing how amino acids are formed

Why are amino acids so important? More recently, meteorites have been found

containing amino acids, meaning these compounds are found throughout space. This obviously raises questions regarding the Miller and Urey experiment

Organic Evolution

This is the evolution Darwin is referring to in his work Origin of Species

Organic evolution is the evolution of species or groups of organisms.

The combination of chemical and organic evolution helps explain the steps to the formation of aerobic heterotrophs and photosynthetic autotrophs

It is believed that the first organisms were heterotrophs that produced CO2 as a by product of their metabolic processes

This gave rise to photosynthetic autotrophs, now there is OXYGEN in the atmosphere.

Many of the anaerobic heterotrophs die, but those that survived were able to perform aerobic respiration

These aerobic autotrophs and heterotrophs become the dominant species on Earth

DARWIN AND ORGANIC EVOLUTION

Natural Selection – “Survival of the Fittest”

The process by which organisms best suited to the environment survive, reproduce, and pass their genes to the next generation.

Fitness -(1) Survive Longer, (2) Reproduce More (3) Pass on traits to next generation

Occurs in populations, not in individuals

How does evolution occur through natural selection?

1. Organisms produce more offspring than can survive.

2. Genetic Variation - Individual organisms in a population have slight variations or adaptations.

3. Individuals struggle to survive, those with adaptations best suited to the environment are more likely to survive.

4. Survivors pass on genes for the adaptations to their offspring.

5. Gradually, the population changes or evolves.

Puncuated Equilibrium

Remember the theories of catastrophism and gradualism combine to form uniformitarianism

Punctuated Equilibriumpredicts that a lot of evolutionary change

takes place in short periods of time tied to speciation events

This is especially true for allopatric speciation which is when a new species forms due to geographic isolation

Examples of Natural Selection

Beetles living on brown tree bark are either brown or green.

Predator (bird) can more easily see green beetles and will catch them more often than brown.

Brown beetles live longer and produce more offspring, to whom they pass the gene for brown.

Darwin’s Finches

13 different species of finches on the Galapagos Islands

Each species has a beak that is best adapted for a certain kind of food that is found on the different islands

Natural selection is an “editing” process, not a creating one

If the environment changes and there is not a suitable phenotype to survive in the new environment then the species will go extinct.

There is no amount of “trying” that can help you evolve.

Nature simply “selects” the greatest physical traits to survive in different environments and those are passed on.

Also, what is beneficial in one environment may not be beneficial in another.

Note

Blue Footed Booby

Marine iguana

Swallowtail Gull

Finch

Hawkfish

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