EVOLUTIONThe unifying theme of biology

BELLRINGERMake these 3 columns and jot down a few

ideasFirst thing you think of when you hear “evolution”

What do you know about evolution?

What questions do you have about evolution?

THE INS AND OUTS

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 argue… Evolution does not argue…

EVOLUTION DOES NOT ADDRESSHow life beganMoralityWhether species are “better” or

“higher order”The meaning of life or

significance of “being human”

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 of evidence

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…

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 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

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

Descent with Modification 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 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

EXAMPLEhttp://www.youtube.com/watch?v=iraaygtYSYk&feature=related

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 EVIDENCEBiogeographyHomologyFossilsDNA/Protein analysis

BIOGEOGRAPHYAnimals are

closely related to those around them

Similar looking animals from other continents are NOT related

FOSSILS 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

HOMOLOGY 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

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

Whales and snakes have leg bones

Human appendix? Ear point in

humans

MORE HOMOLOGYThe

development of closely related animals is very similar

Humans still have gills and a tail early on in development

DNA EVIDENCEThe newest, strongest and most complete evidence for evolution

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 RELATIONSHIPSClosely related species share more genes

But there are differences where mutations have occurred

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 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!