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Evolution 1: Introduction

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Sarah Blechacz

on 2 February 2016

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Transcript of Evolution 1: Introduction

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Evolution: An Introduction
Brief History
Natural Selection
Science Does Not Happen In A Vaccuum
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!
Came up with the idea of
Uniformatarianism
:
The process happening on Earth now are similar to those that happened in the past

"Principles of Geology": VERY OLD Earth
Georges Cuvier
Thoughts:
Extinction:
What's the deal with that?
Why do some organisms seem to vanish off the earth?
Charles Lyell
Thomas Malthus
Populations would like to grow forever, but....
...Why?
Jean Baptiste Lamarck
1. Life Evolves!
2. Inheritance of
Acquired Characteristics
!
3. Use and Disuse!
How come I don't see any trilobites at the beach?
Is this how life has come to be?
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
Medschool, Parsonage, Naturalist, Whatever.

Family connections got him a gig as the captains companion on the
HMS Beagle
.

Circumnavigation of the globe!
5 years (22-27)!
Became the ships naturalist.

Read, Collected, Wrote & Thought!
The Galapagos Islands
An important stop for Darwin.
Weird, unique animals.
The "A-ha!" Moment.
He saw things like...
Finches!
There are 12 species of Galapagos Finch.

Different beak structure driven by different feeding behavior.

All share a common imigrant finch ancestor

The only example of natural selection in the "
Origin of Species
"
Giant Tortoises!
All 1 species, but he found 14 or so sub-species (kind of like different races). Each of these have 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 four children...
...buried one of them...
...did a lot of other work...


...and didn't publish his theory FOR 20 YEARS!
Until...
He recieved 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 on Biology.

Introducing a whole new idea about how life evolves
Alfred Russel Wallace
(February 12th 1809 - April 19th 1892)
How it Works:
Common Ancestry of Life:
2.
Variation
among individuals
3.
Competition
for Limited Resources
4. Successful competitors survive, reproduce, & pass on their traits
Some Examples
1.
Overproduction
of Offspring (Malthus)
5. Repeat steps 1-4 every generation over millions of years (Lyell)...





...& life will
adapt
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!"
FITNESS!!!
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
If we accept that life evolves, logic suggests that all of life should share a common ancestor.
This is supported by all evidence we have found.
I suggest it is the most amazing thing ever determined about life on Earth.
"
Tree Thinking
"
The pattern of evolution of life on Earth.
Public reaction was mixed.
Some extreme religious perspectives can't reconcile evolution with their modes of thinking.

For whatever reason, it's still a particular problem in the US.
Scientifically, Evolution is the unifying principle of all other fields of Biological study.
"Nothing in Biology makes sense except in the light of evolution"
-Theodosius Dobzhansky
Almost entirely, issues with evolution are due to misunderstandings about the Theory
2 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.
3.5 till infinity...
Thought:
Full transcript