Evolution

I may have some pretty wimpy arms, but surely you believe I existed. Right?

Of course you believe I existed! Scientists have fossilized bones of my buddies and me! But you’ve never seen me running through your back-yard. That’s because life on Earth has changed. That change in organisms found on the Earth over time is called evolution. wimpy arms

Most scientists don’t disagree that life on earth has changed. What is still being debated is how and why things have changed on Earth. This is why we call it a theory of evolution. It’s our best explanation of how and why life has changed.

So From a Scientific Standpoint How Did We Get To The Theory of Evolution?

Jean Baptiste de Lamarck Many people talked about the idea that life on Earth changes The first person to propose a reasonable theory for how and why life changes was Lamarck.

Lamarck Idea #1 The inheritance of acquired traits. How did the giraffe get his long neck? A giraffe stretches his neck up to reach the last leaves available on the highest branches. Eventually, its neck gets just a bit longer. He passes that on to the next generation. Over time giraffes’ necks grow gradually longer.

Cave Dwelling Eyeless Organisms Use and disuse of organs If parts were useful and needed, then they would be modified to help If parts were not needed, then they were lost Lamarck was no dummy.: Correct: changes were related to the interaction of the organism with its environment Didn’t Know: that we can only form structures as our DNA allows us to Lamarck Idea #2 Cave Dwelling Eyeless Organisms

Charles Darwin Provided an acceptable mechanism for evolution organisms change by means of “natural selection” Let’s look into Natural Selection! Charles Darwin

Natural Selection Organisms of the same species are still a little different – look at our class! Some variations have more of an advantage then others The ones with the “better” variation are more likely to survive --- nature selects them. Because they survive, they reproduce in greater numbers than the others.

Beetles!

What Lead Darwin to the Idea of Natural Selection?

Voyage of the Beagle, 1831-1836

Darwin is already famous before he ever gets home because of the amazing catalog of specimens he identified and named during his travels! Darwin Already Famous!

So What Did Darwin Observe?

Darwin found ocean fossils in the high Andes (over 2 miles up)? Earth must have changed a lot over time. Maybe it’s really, really old!

A typical land iguana of South America A typical land iguana of South America. Could this be the ancestor of the marine iguana of the Galapagos?

The Galapagos Finches (13 different species) Why do each of these finches have a different sized beak?

What observation did Darwin make about these tortoises? VS.

Why would having a long neck be an advantage on an island with less water?

So Darwin Observed and noted all of these examples of natural selection, but was apprehensive about publishing it until…

Alfred Russell Wallace Wallace independently came up with an almost identical set of ideas to Darwin’s Knowing that Darwin was working on his own theory of evolution, in 1858 Wallace sent his ideas to Darwin. This was Darwin’s final prod to get him to publish his work Wallace never resented that Darwin – what a great guy!

Darwin’s world-changing book, published in 1859.

One of a host of negative cartoons Darwin’s life became much more difficult after the publishing of The Origin of Species

Down House, Darwin’s home Darwin lived as a recluse the rest of his life in this house outside of London

So Are You Ready For Darwin’s Theory? Because it’s super important so you’d best get ready

Darwin’s Theory of Evolution 1) All organisms produce way more offspring than can possibly survive. 2) Populations tend to stay at a relatively constant number. 3) There are limited resources in the environment. 4) These factors lead to a struggle for survival 5) All populations have great variation within the species. 6) Those with a better set of variations survive better in the environment. 7) Those that survive reproduce and thus pass on their variations in greater numbers.

Change In Darwin’s Theory Gradualism: all organisms change very slowly over long periods of time (gradually) Punctuated equilibrium: long periods of little or no change will be “punctuated” by periods of very rapid change after a key mutation.

The Story of the Peppered Moth