Sources of Genetic Variation & Evolution

3 main sources of genetic variation

1. Mutations› Point mutation, inversion, deletion,

translocation, addition, etc.› Aneuploidy & polyploidy

2. Gene flow› Genes move from one population to another as

individuals emigrate & immigrate

3. Sexual Reproduction› Meiosis creates unique gametes› Random fertilization further increases

variation

Genetic Variation & Evolution

A population must have genetic variation in order to evolve› Comes from the 3 sources listed earlier

Natural selection acts on the variation in a population› Evolution is a result of natural selection!

Natural Selection The environment selects individuals with

the traits most helpful to survive & reproduce more than others in the population› Helpful traits are called adaptations› This increases the frequency of the helpful

alleles in the population in the next generation Over time this can cause large changes in

the population & can lead to new species› The large changes are what we call evolution

Misunderstandings About Evolution

Myth 1: Evolution is Linear or Directional

While amusing to watch, the Simpsons video illustrates a common myth about evolution. › Evolution isn't linear!

Organisms aren't striving to become anything…

More Misunderstandings

› This is also related to the misunderstanding that evolution follows a linear path...that everything is trying to be human.   NOT TRUE!

There are many kinds of primates, each adapted to its own environment, just like there are many kinds of felines

Why are there still monkeys if humans evolved from monkeys?

This picture is flawed, but commonly used to illustrate human evolution.

None of these cats will evolve into a lion.

Myth 2:  Scientists regularly debate whether evolution occurs.

The only place debate occurs is in social settings, and is philosophical in nature.  › If any debate occurs among biologists, its often regarding

specifics - such as timing, or what animal is related to what, or when did a creature evolve and what is its origins.    

As a THEORY, evolution is supported by a large body of evidence and is used to EXPLAIN new observations.  

Biologists would consider it a waste of time to debate this.

Myth 3: A person cannot believe in God and in evolution.  There are many scientists who have religious beliefs. One

does not necessarily preclude the other.   

To say that the two are incompatible is grossly unfair to both scientists and people of faith. 

Remember, "strong" and "weak" are relative.  › Organisms do not have to

be strong to survive. 

Read this story about wimpy cuttlefish who pretend to be females:

"Cuttlefish Wimps.."

Myth 4: Evolution encourages the strong to destroy the weak.  

Other ResourcesPBS Evolution - many resources covering the topic - videos, articles, activities and more

Darwin's Dangerous Idea - 1st in a 7 part series on evolution; begins with Darwin's voyage on the Beagle and how he established the Theory of Evolution by Natural Selection

Nova:  Intelligent Design on Trial  - A recent covering of a trial in Dover, Delaware, where the school board tried to establish "intelligent design" as part of its science curriculum.

The Panda's Thumb - news archives about evolution and society, focuses on debunking "creation science" and "intelligent design"