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Evolution. The unifying theme of biology. Bellringer. Make these 3 columns and jot down a few ideas. The Ins and Outs. Evolution does argue…. Evolution does not argue…. That all species are related and came from one ancestral species

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The unifying theme of biology


Make these 3 columns and jot down a few ideas

The ins and outs
The Ins and Outs

Evolution does argue…

Evolution does not argue…

  • That all species are related and came from one ancestral species

  • That species change over millions of years and can become new species or split into separate species

  • That the earth is much older than biblical accounts

  • That there is no God or creator

  • That we evolved from monkeys or that monkeys should each evolve into humans

  • That animals should give birth to brand new species overnight

Evolution does not address
Evolution Does not Address

  • How life began

  • Morality

  • Whether species are “better” or “higher order”

  • The meaning of life or significance of “being human”

There is very little scientific debate
There is very little scientific debate

  • Scientists debate the details of evolution but there is overwhelming consensus that evolution does occur

  • There is a lot ofevidence

But evolution is a theory
But evolution is a theory…

  • A “theory” in science is a well-supported argument that matches all experimental evidence and is widely accepted – like gravity

  • Scientists never say we “prove” or we “know”. We say “the data suggests or supports”

The first person to suggest evolution was
The First Person to Suggest Evolution was…

  • NOT Charles Darwin, but

  • Jean Baptiste Lamarck revived a theory that existed for thousands of years

  • Suggested species change over time and can become new species

  • BUT he had no evidence, and his hypothesis did not properly explain how evolution could occur

Charles darwin
Charles Darwin

  • Proposed a well-thought out, coherent, well-researched hypothesis

  • Was scared to publish for many years- in fact a man named Alfred Wallace published at the same time

  • But Darwin’s version was more complete so he gets all the credit

2 main parts to the theory
2 Main Parts to the Theory

Descent with Modification

Natural Selection

  • Species change over long periods of time

  • Enough differences accumulate that new species form

  • All species came from one common ancestor (this was a bit of a leap of faith on his part)

  • This is more of the theoretical part

  • The environment causes populations to change over time

Natural selection
Natural Selection

  • Individuals compete for resources and mates

  • Certain genes cause some individuals to outcompete others

  • That means these genes become more common and less favorable genes become less common or disappear

  • Over long periods of time these favorable genes accumulate and the population will be very different than its ancestors

Natural selection1
Natural Selection

  • Traits that help individuals survive and reproduce become more common

  • Incredibly complex traits come about after millions to billions of years of small changes



What is advantageous depends on the environment
What is Advantageous Depends on the Environment

  • White moths were common in London before industrial evolution

  • After- soot covers most of the city and black moths become common

Some of the evidence
Some of The Evidence

  • Biogeography

  • Homology

  • Fossils

  • DNA/Protein analysis


  • Animals are closely related to those around them

  • Similar looking animals from other continents are NOT related


  • The order in which you find fossils in the soil matches expected evolutionary history

    • Ancient fish Ancient Amphibians Ancient reptiles ancient mammsls

  • Intermediate species have been found

    • i.e. fish with legs


  • The anatomy of species that we believe share ancestors are similar

  • Bat wings are much, much more similar to a human arm than to a bat wing

Leftover structures
Leftover Structures

  • Many organisms have structures they don’t use from their ancestors

  • Whales and snakes have leg bones

  • Human appendix?

  • Ear point in humans

More homology
More Homology

  • The development of closely related animals is very similar

  • Humans still have gills and a tail early on in development

Dna evidence
DNA Evidence

  • The newest, strongest and most complete evidence for evolution

Evidence of common descent
Evidence of Common Descent

  • Some genes have been conserved in all living things

  • All living things use DNA and have some similar processes in common (i.e. DNA mRNA protein)

Dna evidence for relationships
DNA Evidence for Relationships

  • Closely related species share more genes

  • But there are differences where mutations have occurred

Dna also provides a mechanism
DNA Also Provides a Mechanism

  • We know that mutations in the DNA do occur (Darwin didn’t know this)

  • So new genes come about or new combinations of genes come about

  • If they are advantageous, they become common (i.e. wings)

  • If they are not they disappear

Classifying species
Classifying Species

  • Attempt to figure out when they diverged or split from a common ancestor

  • Use a variety of sources of evidence – look at DNA, proteins, fossils, where they live etc.

  • Fewer differences = more closely related

  • The advent of DNA technologies has VASTLY changed how we view the tree of life

  • Fungi are more closely related to animals than to plants!