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Natural Selection- Chapter 22
Transcript of Natural Selection- Chapter 22
Evolution: An Introduction
The processes happening on Earth now are similar to those that happened in the past
"Principles of Geology": VERY OLD Earth
Science Does Not Happen In A Vacuum
Darwin didn't freestyle evolution from nothing
Thinking about life was pretty standard scientific faire for the 19th century
Had life always existed as it does now? Was it always changing?
How old was the Earth (Bible: ~7,ooo years old)
What's up with all these fossils?
Rock takes a long time to form!
What's the deal with that?
Does God get tired of some organisms?
Isn't God perfect?
Populations would like to grow forever, but....
Jean-Baptiste de Lamarck
1. Life Evolves!
2. Inheritance of
3. Use and Disuse!
(Only the first bit is right, just ask this guy!)
Why don't we see any trilobites at the beach?
Bonsai Tree babies are regular size!
Compared to what actually goes on, this seems quaint!
This Was The Thought Stew That Darwin Worked In!
Darwin: Brief Biography
A remarkably unspectacular young life
Comfortable family wealth
Notoriously undecided about a job
Med-school, parsonage, naturalist, whatever...
Family connections got him a gig as the captain's companion on the
Circumnavigation of the globe!
5 years (22-27)!
Became the ship's naturalist
Read, collected, wrote & thought!
The Galapagos Islands
An important stop for Darwin
Weird, unique animals
The "A-ha!" Moment:
"The natural history of these islands is eminently curious, and well deserves attention. Most of the organic productions are aboriginal creations, found nowhere else; there is even a difference between the inhabitants of the different islands; yet all show a marked relationship with those of America, though separated from that continent by an open space of ocean, between 500 and 600 miles in width. ...Hence, both in space and time, we seem to be brought somewhere near to that great fact—that mystery of mysteries—the first appearance of new beings on this earth."
There are 12 species of Galapagos Finch
Different beak structure driven by different feeding behavior
All share a common immigrant finch ancestor
The only example of natural selection in the "
Origin of Species
All 1 species
Different shell shapes due to different cactus plants on different islands
The only swimming lizard in the world!
Darwin came home....
...published his journal...
...married his cousin...
...had ten children...
...buried three of them...
...did a lot of other work...
...and didn't publish his theory FOR 20 YEARS!
He received a paper from a young naturalist asking for his thoughts on a new theory
The same theory he had developed 20 years earlier
He wrote a quick paper
Both papers were published simultaneously
And Darwin wrote a book
Probably the most important one ever in the biological sciences
Introducing a whole new idea about how life evolves
Alfred Russel Wallace
(1809 - 1892)
How it Works:
Common Ancestry of Life:
among individuals (observation)
for limited resources (inference)
4. Successful competitors survive, reproduce, & pass on their traits (observation)
of offspring (Malthus)
5. Repeat 1-4 every generation over millions of years (Lyell)...
...& life will
to the environment
Reaction to the Theory
Competition for limited resources!
About those finches...
Most babies won't grow up!
No two are quite the same!
It's the "Struggle for Existence!"
The selective pressure of the Galapagos environment has driven the evolution of the finches
Beaks are very important for birds
The environment determines fitness!
Any birds that survive pass on their beak traits to their offspring
Repeat for millions of years
Darwin provided a lot of examples of "artificial selection"
Just like natural selection, but "fitness" is determined by human needs/wants
Big changes can happen very fast
Life will always adapt if it can
Spraying of pesticides kills all of the pests who aren't resistant
The resistant survivors reproduce...
...resistance increases (leading to more spraying, more resistance...)
Similar mechanisms drive the evolution of:
antibiotic resistance in bacteria
antiviral resistance in viruses
150 years later, we have a mountain of examples of natural selection in action
In the modern age, the focus has been on quantifying the effects of natural selection on the characteristics of a population
Take home message: Natural Selection is universal!
The effect of food type on the length of the beak of the soapberry bug:
A fundamental conclusion of
The pattern of evolution of life on Earth
If we accept that life evolves, logic suggests that all of life should share a common ancestor
This is supported by all evidence scientists have found
I think it is the most amazing thing ever determined about life on Earth
Public reaction was mixed
Certain religious perspectives can't reconcile evolution with their modes of thinking
These are not mainstream religious beliefs
For whatever reason, it's a particular issue in the U.S.
Scientifically, evolution is the unifying principle of all other fields of biological study
Natural selection (and other modes of evolution) are as close to biological "laws" as anything going
"Nothing in Biology makes sense except in the light of evolution"
Almost entirely, issues with evolution are due to misunderstandings about the Theory:
“if we came from apes how come were not hairy and have a big mouth and did we end up looking like we do know and besides there isnt any serious proof of apes they showd a video saying an ape waswondering around in the forest that thing looked exactly like a costume that i had saw at a store know one ever cought an ape”
-From a post on the internet
Two Facts, Both Explained by Common Ancestry:
Similarity in skeleton's of 5 great Ape species
Similarity between fossils and modern organisms
The only illustration in "Origin" 1st ed:
Another tree by Ernst Haekel
A modern tree (informed by DNA analysis):
The ultimate tree (DNA again)
What did people think about life on Earth 200 years ago?
How do organisms evolve?
Explain the development of evolutionary theory, the contributions of all people discussed in this presentation, and the evidence that they based their contributions on.
Describe the process of natural selection and give at least three examples of how it can lead to changes in a species.
Compare natural selection with artificial selection.
Explain why the criticisms of evolution discussed in this presentation are the product of faulty reasoning.