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Natural Selection- Chapter 22

Image Credits: Biology (Campbell) 9th edition, copyright Pearson 2011, & The Internet.

Sara Mitchell

on 12 January 2015

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Transcript of Natural Selection- Chapter 22

Make sure you can
Evolution: An Introduction
Brief History
Natural Selection
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?
Flood remnants?
Rock takes a long time to form!
Georges Cuvier
What's the deal with that?
Does God get tired of some organisms?
Isn't God perfect?
Charles Lyell
Thomas Malthus
Populations would like to grow forever, but....
Jean-Baptiste de Lamarck
1. Life Evolves!
2. Inheritance of
Acquired Characteristics!
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
HMS Beagle

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
Giant Tortoises!
All 1 species

Different shell shapes due to different cactus plants on different islands
Marine Iguanas!
The only swimming lizard in the world!

Algae eaters
And Then....
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

Uh Oh...

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)
Some Examples
of offspring (Malthus)
5. Repeat 1-4 every generation over millions of years (Lyell)...

...& life will
to the environment
Reaction to the Theory
Big Question
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
Artificial Selection
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
Pesticide Resistance
Modern Science
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
Natural Selection
Tree Thinking
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"
-Theodosius Dobzhansky
"Sara's Law":
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
Darwin's Notes:
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?
Any Questions?
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.
Full transcript