What is Evolution?In biology, evolution is the change in the inherited

traits (a.k.a. genes/alleles, genotypes/phenotypes) of species (or populations of a species) over time.

Throughout this unit, you will see that three main processes determine the rate of evolution:1) variation within a species (i.e. the fact that no one is

an identical clone to another person)2) reproduction: the method of reproduction and the

rate at which a species reproduces will affect how fast it evolves.

3) selection: whether natural selection or sexual selection, you will see that those best suited to their particular environment will pass on their genes more frequently.

Evolution by Natural SelectionThe most famous

explanation of evolution was made by Charles Darwin, who stated that those organisms best suited to their environment will be more successful at passing on their traits to the next generation.

This he called Evolution by Natural Selection.

Darwin’s InfluencesCharles Darwin did not foresee himself

getting into the field of evolutionary biology.He wanted to be a doctor like his father, but

he could not stand the sight of blood and the savagery of surgery.

He then wanted to be a minister, but he did not want to study. He preferred riding and shooting to studying.

He eventually became interested in biology through his fascination with such exciting animals as barnacles, beetles and pigeons.

Darwin’s InfluencesHe changed his path at college and took more

biology courses as he developed a great love of taxonomy (yes, the classification stuff we did last unit) and studied intensely under the tutelage of botany professor John Stevens Henslow.

Henslow recommended Darwin for work as an unpaid naturalist on a voyage around the world upon the HMS Beagle, under captain Robert Fitzroy.

As you will see, this journey not only changed Darwin’s life, but also the face of biology forever…

But that is for Next Lecture…Now, we will look at some of the people whose

prior work shaped and influenced Darwin’s thinking and lead him towards his theory of evolution by natural selection.

Pre-Darwinian TimesAristotle (circa 400 BCE)He believed in the Scala

Natura (Scale of Nature).All living things were

arranged on a scale of increasing complexity with humans at the top.

He felt all species were perfectly adapted to their environment and there was no evolution/change.

Pre-Darwinian TimesNatural Theology

(~1700s)This was the church’s

plan to study nature to discover God’s plan (the secret of Life).

It was thought that since each species was made by God, by discovering, classifying and naming all God’s creatures, man would get closer to the divine plan.

Written in the 1700s

Pre-Darwinian TimesCarolus Linnaeus

(1707-1778)He came up with the

binomial nomenclature system of taxonomy we use today in which each species gets a scientific name based on its genus and species.

Ornithorhynchus anatinus

Darwinian TimesGeorges Cuvier

(1768-1832)He was a

paleontologist.He found that rocks

deeper in the Earth had much different fossils than anything that was walking around during his life time.

Darwinian TimesHe did not believe in evolution. He believed in

catastrophism.Catastrophism is the belief that each strata of rock

contained different fossils because it was associated with a catastrophic event (i.e. the flood in Genesis)

The Earth was a place where catastrophes happened and different animals emerged afterwards.

Darwinian TimesJames Hutton (1726-

1797)Introduced

gradualism.Gradualism states

that geological changes are slow and gradual and take long periods of time.

Darwinian TimesCharles Lyell (1797-1875)Famed geologist whose

book, Principles of Geology, Darwin took with him on the HMS Beagle.

He brought up the idea of uniformitarianism.

Uniformitarianism states that geologic processes have not changed throughout earth’s history.

That means that volcanoes, sedimentation, etc., that we observe today have occurred since the beginning of time.

Why are these dead guys important???

There theories kept stretching the time that Earth was formed further and further back in time, which conflicted with religious teachings, but made more sense scientifically.

The ChurchPrevious to these men,

Irish Archbishop James Ussher stated that from biblical study he had found out the precise day the Earth was formed.

The night before October 23rd, 4004 B.C.

Cuvier, Hutton and Lyell pretty much sank the Church’s theory.

Darwinian Times Jean Baptiste Lamarck (1744-1829)

He placed fossils in an evolutionary context and published a theory of evolution in 1809. 

His theory used two common ideas of his time:

1) Use and disuse - parts of the body used on a regular basis become larger and stronger; those not used deteriorate.

                                  2)  Inheritance of these acquired characteristics (I.e.,

the modifications) are passed onto the offspring.                        

Lamarck’s theory was based on observations of fossils, but gave no mechanism for evolution.  However, he set the stage for Darwin… and your homework and our next lecture.