The Man with the Plan

Voyage of the Beagle

• Charles Darwin was born on Feb. 12th, 1809.• Fortunate to be on the crew for the H.M.S.

Beagle in 1831.• Set sail around the world and recorded his

observations of plant and animal life.

The Questions

• Is there some type of process that leads to such a variety of ways of living and reproducing?

• Why have so many species disappeared?• Why are so many living species suited so well

for their environment?

How is a polar bear adapted to its extremely cold climate?

white greasy fur repels water and acts as camouflage

thick fur and body fat insulate from the cold

large, wide feet spread the body’s weight and act as good paddles and snow shoes

Other adaptations that polar bears have evolved to cope with conditions in the harsh polar environment include:

small ears and small body surface area to volume ratio reduces heat loss

eyes have brown irises to reduce the glare from the Sun’s reflection

black skin is a good absorber of heat

The Galapagos Islands

• Characteristics of certain animals varied based on what island they inhabited.

• These characteristics were established as adaptations.– Inherited characteristic that increase an

organism’s chance of survival and reproduction.

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Galápagos finches

Darwin thought all the finches could have evolved from one type of finch that came from the mainland.

Some finches had strong and claw-like beaks, suitable for crushing seeds.

Other finches had thin and delicate beaks, suitable for picking insects from holes in the ground.

In the Galápagos, Darwin noticed that different islands had different types of finches, with different types of beak.

Natural variation meant that some finches had slightly different beaks. These finches would have been able to eat different types of food and avoid competition. They wouldtherefore have survived and passed on their genes.

Artificial Selection

Artificial Selection

Artificial Selection

Inherited Variation• Darwin observed that variation exists among

organisms.– Breeders used heritable variation for better crops and

livestock.• Artificial Selection

– Nature provides variation, humans select the variation they find useful.

• These variations can be passed from parent to offspring.

• At the time of his publication Darwin had no understanding of genetics.

The Big Idea

• Does this idea apply to nature?• An idea of natural selection as the process by

which evolution occurs?• Struggle for existence.

– Intra and interspecific competition.– Those best suited for their environment can catch

prey and avoid being caught. Cheetah video?

Natural Selection

• Process where organisms with certain inherited characteristics (adaptations) are more likely to survive and reproduce than are organisms with other characteristics.– This process is not guided by increased complexity.– Organisms can not “want” a specific adaptation.

Fierce Competition

Survival of the Fittest

• Biological Fitness– Ability of an individual to survive and reproduce in

its environment.– How many offspring you have is a measure of your

fitness.

Evolution

• Describe our class’s current understanding of evolutionary theory.

Natural Selection

MECHANISM FOR EVOLUTION•Organisms differ and some of this variation is heritable.•Some of these variances result in great reproductive potential (increased fitness).•Resources are limiting.•Some organisms survive and reproduce to pass their heritable traits to their offspring.

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• Darwin proposed that over long periods, natural selection produces organisms that have different structures, establish different niches or occupy different habitats.

• He called this idea DESCENT WITH MODIFICATION

Natural Selection Game

• http://phet.colorado.edu/en/simulation/natural-selection