EVOLUTION

What is the theory of Evolution?

Is there any evidence to support it?

What did Darwin find?

Early theories (pre-1700’s)

Before Darwin, nature was seen as not

changing but as having originated through

spontaneous generation.

Carolus Linnaeus was the first one to try to

classify life (1735, placed us with

primates)

1700’s

An understanding of the age of the Earth develops

through geology.

The Earth has been and is still gradually changing.

Inheritance of acquired traits (use and disuse).

ex. Baby giraffes are born with long necks because

their parents stretched their necks to reach leaves

(Jean-Baptiste Lamarck, 1801)

Misconception

Genetics and the Passing on of

Traits

Living organisms pass on their traits to

their offspring.

Today’s species came about through

gradual change.

What drove that change?

SURVIVAL/SEX!!!!

Darwin and the Voyage of the

Beagle

December, 1831’s, Charles Darwin, a naturalist in his 20’s began a 5-year journey around the world on a ship called HMS Beagle

Darwin’s role was to

observe, record, and

collect specimens of

rocks, minerals, plants, and animals

Darwin collected 1000’s of specimens and shipped them to England, mainly from South America and a chain of volcanic islands called Galapagos

He did not realize what he was seeing until years later (ex. didn’t catalogue the finches very well, ate turtles that would later support his theories, etc.)

Darwin spent the next 20 yrs analyzing his findings in light of artificial selection (ex. breeding of pigeons, breeding of dogs, etc.)

Darwin’s Finches

Arrival

Success

Competition

Diversity &

Opportunity

Radiation

How does evolution really work?

http://www.pbs.org/wgbh/evolution/educators/teachstuds/svideos.html

Perhaps a single ancestral species

transported from nearby land might give

rise to a number of similar but distinct new

species.

Hawaiian honeycreeper

What Darwin Observed

1) Homologous and

Analogous Features

Homologous features:

different functions, but

similar structure

(flippers, hands,

wings)

Analogous features: similar functions, but

different structure (wings of birds and

bees)

Darwin’s conclusion: organisms with

homologous features likely shared a more

recent ancestor, while those with

analogous features do not!

2) Vestigial Features:

non-functional

structures that are

homologous to fully

functioning structures

in closely related

species.

Example: whales have

pelvic bones that do

not attach to legs

Similarities in Early

Development

(tailbones)

Goosebumps

Darwin’s conclusion:

these ‘leftover’

features must have

once had a use!

3) Artificial Selection

Selecting offspring with desirable traits as

breeding stock for succeeding generations

Example: corn with higher oil content

Darwin’s conclusion: if people could alter the

appearance and behaviour of species through

artificial selection, then the environment could

have a similar selective effect on wild species!

4) The Struggle for Survival

Plants and animals produce more offspring

than are able to survive

Favourable variations would tend to be

preserved, unfavourable ones would be

destroyed.

INTENSE COMPETITION!!!!!

Natural Selection as the Cause of Evolution

- called “natural selection” because it happens on

its own

1. Genetic Variation

- there are many varieties of alleles

- caused by random mutations

- can be passed onto offsprings (inherited variation)

2. Overproduction of Offsprings

- organisms make too many offsprings

3. Struggle for existence

- competition for limited resources

4. Differential survival and reproduction

- only organisms that have certain characteristics will survive to reproduce

- non-random, caused by the environment: amount of food, competition (ex. Darwin’s finches)

PBS Evolution: The Evolutionary Arms

Race (12 min)

Sideways Sharks Up & Down

Dolphins

• Wiggles work

• Limbs for

leverage

• Upright &

under

• Stepping &

Striding

• Arching &

Aquatic

All of this takes a LOOOOOOONG time