Notes: Evolution & Natural Selection

Charles Darwin His father was a wealthy doctor and wanted Charles to become a doctor. At age 16, he went to Medical School. In 1827, his father sent him to become a priest. In 1831, a friend asked him to go on a ocean trip as an unpaid naturalist.

HMS Beagle The purpose of the trip was to draw accurate maps of the region. Darwin was to collect specimens and document the plant and animal life.

Darwin’s original beliefs Divine creation - each species was created by God, unchanging and existing as it was originally created. However, on the voyage, his beliefs began to change when he got to the Galapagos Islands.

Darwin’s Finches The finches showed convincing evidence that species evolve.

Darwin was struck by the fact that the animals of the Galapagos Islands resembled those of the nearby coast of South America. Darwin hypothesized that ancestors of the Galapagos Islands must have migrated to the island and changed after they arrived.

Darwin published his book in 1844: On the Origin of Species by Means of Natural Selection.

Darwin’s Theory of Natural Selection 1.There is variation within any species 2.All organisms tend to over-reproduce 3.There is a struggle for survival 4.The fittest survive 5.The environment determines who is the fittest

1. Variation exists within every population 1. Ladybugs have different spots

2. Zebras all have different stripes 1. Variation exists within every population

2. All species tend to produce more offspring than they can support 3. Frog eggs 1. Turtle eggs 2. Insect eggs 4. Baby mice

3. There is a Struggle for Survival 1.To eat 2.To drink 3.Territory 4.To mate

4. The fittest will survive

1. Weak or strong woman? 2. Healthy or sick horse?

5. Nature (the environment) will determine which organism is the fittest to Survive 1. long neck giraffes survive over short neck giraffes.

Evidence of Natural Selection in our lifetime The Peppered Moth in England Before the industrial revolution After the industrial revolution

Explanation for the peppered moth There was variation in the moth population to begin with, some were black and some were white. This variation was due to random mutations.

Before the industrial revolution, the bark of the tree bark was white in color. The white moths then were easily camouflaged, survived, and reproduced. Black moths were rare.

After the industrial revolution, the trees became covered in soot/pollution from all of the factories and the trees turned black. Now the black moth were easily camouflaged, survived, and reproduced. White moths were rare.

How does the peppered moth illustrate natural selection? There was variation in the population to begin with (some white, some black). Moths tend to over-reproduce. Therefore there is a struggle for survival. The fittest (those that were camouflaged the best) survived. The environment determined which moths were the most fit.

Natural Selection may lead to Speciation Speciation - the evolution of a new species

The process of speciation ßGeographic Isolation - when two populations become isolated by a geographic barrier. Geographic Isolation

ßReproductive Isolation - Sometimes when populations have been separated for a long, long time, they become so different that they can no longer breed and produced fertile offspring. Same species now, but may become two different ones.

1. Horse and Donkey = Mule Mule is infertile (can’t have babies) mule horse donkey

Lion and Tiger = Liger Liger is infertile (can’t have babies)

2. The Kaibab and Abert Squirrels Became reproductively isolated by huge mountains

3. Wood and Leopard Frogs Leopard frogsWood frogs Seem to be the same species, but they breed at different times of the year.

ßSpeciation - When two populations become so different that they can no longer breed and produce fertile offspring. They are then considered two separate species.