Evolution and Natural Selection

• Nature encourages no looseness, pardons no errors�- Ralph Waldo Emerson

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• I have called this principle, by which each slight variation, if useful, is preserved, by the term Natural Selection. �- Charles Darwin, The Origin of Species

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Charles Darwin

• In 1859, he published his famous work Origin of Species after a five year journey on the HMS Beagle. During his journey, he studied animals and plants. It was 20 years before he published his book. He spoke of pigeons, dogs, beetles, and other forms of life. However, he barely mentions MAN…only saying “light will be thrown on his origin in the future.” Obviously, his book was instantly controversial and remains so to this day.

And this is not me!

Darwin's Theory

Darwin’s theory has 4 parts.

1. Organisms have changed over time, and the ones living today are different from those that lived in the past. Furthermore, many organisms that once lived are now extinct. The world is not constant, but changing. The fossil record provided ample evidence for this view.

Darwin’s Theory

2. All organisms are derived from common ancestors by a process of branching. Over time, populations split into different species, which are related because they are descended from a common ancestor.

Darwin’s theory

3. Change is gradual and slow, taking place over a long time (thousands to millions of years).

Darwin’s theory

4.The mechanism of evolutionary change was called Natural Selection.

Scientists have described roughly 400,000 species of beetles, and it's estimated that there are potentially between 1 and 2 million beetle species in total, making beetles the most species-rich order of insects.

Natural Selection

The process takes many generations

• 1st - If all the offspring that organisms can produce were to survive and reproduce, they would soon overrun the earth. Organisms have more offspring than can survive.
• 2nd - Organisms within a population differ from each other and those best suited will live to reproduce (give examples of variation).
• 3rd – Offspring tend to be like their parents, including their adaptations , and the best adapted are more likely to reproduce….

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Natural Selection

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4th – There must be a struggle to survive and reproduce…”SURVIVAL OF THE FITTEST”.

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Darwin did not exist during the time of Genetics, but we now know that traits are determined by genes. Good genes tend to be passed to offspring more than poor genes.

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Also not known was the idea of Mutation

Review Video

Arrow back to beginning…organism slightly different

Form = Function

Coevolution

The process by which two or more interacting species evolve together, each changing as a result of changes in the other . It occurs, for example, between predators and prey and between insects and the flowers that they pollinate.

Yucca Moth and Yucca plant.

Buff-tailed sicklebill

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Garter snake and rough-skinned newt

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Wherever these deadly rough-skinned newts co-resided with garter snakes, the local snake populations would evolve impressive resistance against tetrodotoxin. And that prompted the newts to create even more of the toxin, which is 10,000 times deadlier than cyanide.

Punctuated Equilibrium

(Ignore this for notes for 2025)

In Punctuated Equilibrium, change comes in spurts. There is a period of very little change, and then one or a few huge changes occur, often through mutations in the genes of a few individuals. 

Gradualism is selection and variation that happens more gradually.. Change is slow, constant, and consistent.

Mutations

• A mutation is a permanent change in a gene (or more precisely in the DNA of the gene).

Mutations

• Most mutations are silent (cause no real change) or neutral (cause a change that doesn't make any real difference)
• (color of cat paws)

• Of the rest, most are harmful (at least in the organism's current circumstances),

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• but a small percentage may even provide an advantage.
• (Beak shape)

Selective Breeding

Humans speeding up evolution by choosing organisms to breed that have desired traits.

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Domestication of Silver Foxes