studied medicine at studied medicine at Edinburgh University Edinburgh University (1825-1827) where the (1825-1827) where the

sight of blood and sight of blood and surgery without surgery without

anesthetics repulsed himanesthetics repulsed him

studied to become a studied to become a clergyman at Cambridge clergyman at Cambridge University (1827-1831)University (1827-1831)

born in Shrewsbury, born in Shrewsbury, England, in 1809England, in 1809

After Cambridge, Charles was recommended After Cambridge, Charles was recommended for a surveying trip on the for a surveying trip on the HMS BeagleHMS Beagle..

Darwin sailed around the world on the Darwin sailed around the world on the BeagleBeagle for 5 years, working as a naturalist. for 5 years, working as a naturalist.

Darwin made many Darwin made many observations and observations and

collected evidence collected evidence on his voyage that on his voyage that led to his theory led to his theory

about the way life about the way life changes.changes.

At the time Darwin made At the time Darwin made his trip, the majority of his trip, the majority of

people believed the Earth people believed the Earth and all of its forms of life and all of its forms of life had been created only a had been created only a few thousand years in few thousand years in

the past.the past.

People also believed in People also believed in fixity of speciesfixity of species;; in other in other words, species never changedwords, species never changed..

After careful After careful observation and observation and

study of new study of new scientific scientific

discoveries, discoveries, Darwin began to Darwin began to think otherwise.think otherwise.

People also believed that the Earth had not People also believed that the Earth had not changed during those few thousand yearschanged during those few thousand years..

The first dinosaur to be described scientifically was Megalosaurus by William Buckland in 1824.

Darwin was influenced Darwin was influenced by geologist James by geologist James

Hutton’s writings that Hutton’s writings that described geologic described geologic

forces he thought had forces he thought had changed and were still changed and were still

changing the earth.changing the earth.

Hutton proposed that Hutton proposed that the Earth had to be the Earth had to be

much more than a few much more than a few thousand years old.thousand years old.

The Father of GeologyThe Father of Geology

Darwin was also Darwin was also influenced by influenced by

geologist Charles geologist Charles Lyell who wrote Lyell who wrote

Principia GeologicaPrincipia Geologica..

Lyell’s book proposed Lyell’s book proposed that tremendous that tremendous

geologic processes geologic processes had shaped the Earth had shaped the Earth

such as seen in such as seen in volcanoes active in volcanoes active in

the present.the present.

On the voyage, On the voyage, Darwin noticed Darwin noticed

that everywhere he that everywhere he went, the animals went, the animals

and plants differed and plants differed vastly.vastly.

Patterns in the species Patterns in the species suggested that the suggested that the

species had changed species had changed over time and had given over time and had given rise to new and different rise to new and different

species.species.

The Galapagos The Galapagos Islands lie 500 miles Islands lie 500 miles west of Ecuador in west of Ecuador in the Pacific Ocean, the Pacific Ocean,

directly on the directly on the equator.equator.

Many of Darwin’s Many of Darwin’s conclusions were conclusions were

based on based on observations of observations of wildlife in the wildlife in the

Galapagos Islands.Galapagos Islands.

“Galapagos” means turtle.

What it must have been like to be Darwin…

Darwin noticed on Darwin noticed on these islands, these islands,

there were several there were several types of finches.types of finches.

In particular, In particular, Darwin observed Darwin observed something odd something odd

about the about the finches: they all finches: they all

looked like a looked like a bird he had seen bird he had seen

on the South on the South American American continent.continent.

Darwin wondered if the birds and other Darwin wondered if the birds and other animals had been animals had been createdcreated to match their to match their

environment, why didn’t these birds look like environment, why didn’t these birds look like the birds of the African continent, since the the birds of the African continent, since the

environments of both the Galapagos and environments of both the Galapagos and Africa were similar.Africa were similar.

Darwin guessed that Darwin guessed that some of the birds some of the birds

from South America from South America migrated to the migrated to the

Galapagos.Galapagos.

Once on the islands, Once on the islands, the birds must have the birds must have

changed over the changed over the years.years.

This would explain the numerous species of This would explain the numerous species of birds present.birds present.

woodpecker finch

cactus finch

large ground finch

Darwin called this…Darwin called this…

oror

(change in species over time)(change in species over time)

Darwin concluded:Darwin concluded:

Each species has descended, with changes, Each species has descended, with changes, from other species over time.from other species over time.

Descent With ModificationsDescent With Modifications

Malthus was a British Malthus was a British social scientist who social scientist who

proposed theories on proposed theories on factors controlling factors controlling population growth:population growth:

People have more children than are People have more children than are able to survive.able to survive.

There are built-in population checks: There are built-in population checks: disease, famine, and war.disease, famine, and war.

Darwin based his theory Darwin based his theory on his own observations on his own observations

and the writings of and the writings of Thomas Malthus.Thomas Malthus.

Darwin extended these Darwin extended these principles to biology, which principles to biology, which

helped him form his theory of…helped him form his theory of…

……or Survival of the Fittest.or Survival of the Fittest.

Natural selection was the Natural selection was the mechanism by which mechanism by which Darwin proposed that Darwin proposed that evolution took place. evolution took place.

Darwin published his Darwin published his theory in the booktheory in the book

Five basic components ofFive basic components of

1. All species have genetic variation.1. All species have genetic variation.

Every species is different, Every species is different, even within itself.even within itself.

Variation is caused by Variation is caused by mutations and meiosis.mutations and meiosis.

2. 2. Organisms produce more offspring than Organisms produce more offspring than can survivecan survive. Many that survive do not . Many that survive do not produce offspring. produce offspring.

The female green sea turtle lays a clutch of about The female green sea turtle lays a clutch of about 110 eggs. She may lay several clutches.110 eggs. She may lay several clutches.

It is likely that It is likely that less than 1%less than 1% of the hatchlings will ever of the hatchlings will ever reach sexual maturity.reach sexual maturity.

3. 3. Since more organisms are produced than Since more organisms are produced than can survive, there is can survive, there is competitioncompetition (struggle for (struggle for existence)existence)..

Competition exists WITHIN and AMONG species.Competition exists WITHIN and AMONG species.

foodfoodWithin and Among Species for

And Within a Species for

waterwater

matesmates

sheltershelter spacespace

The constant struggle for survival is affected by short-term natural disasters. (drought, fires, floods, snowstorms, hurricanes, and tornadoes)

The constant struggle for survival is also affected by long-term changes in the environment. (ice ages, biome shifts, etc)

4. 4. Survival of the fittestSurvival of the fittest Some organisms Some organisms are more suited to their environment as a are more suited to their environment as a result of variations in the species.result of variations in the species.

Fitness: the ability of an individual to the ability of an individual to survive and reproduce in its specific survive and reproduce in its specific environment. Fitness is a result of adaptations. environment. Fitness is a result of adaptations.

He who spreads the most genes wins!He who spreads the most genes wins!1st

Individuals that are fit to their environment Individuals that are fit to their environment survive and leave more offspring than those survive and leave more offspring than those who aren’t.who aren’t.

5. 5. Descent with modificationDescent with modification: : Living species Living species today are descended with modifications from today are descended with modifications from common ancestral species that lived in the common ancestral species that lived in the past.past.

Over time, genes for less Over time, genes for less favored characteristics will be favored characteristics will be eliminated from the gene pool.eliminated from the gene pool.

Example: giraffes and their Example: giraffes and their increasingly longer necks.increasingly longer necks.

Characteristics of fit individuals Characteristics of fit individuals increase in a population over time.increase in a population over time.

Natural Selection: Survival of the FittestNatural Selection: Survival of the Fittest

the variation exists first.the variation exists first.

An An adaptationadaptation is any inherited characteristic is any inherited characteristic (a genetic variation) that can increase an (a genetic variation) that can increase an organism’s chance of survival.organism’s chance of survival.

the environment changes.the environment changes.

a variation may give an advantage a variation may give an advantage to survive environmental change.to survive environmental change.

An organism does not change An organism does not change because of need or desire to because of need or desire to survive. The organism either survive. The organism either already has the variation that already has the variation that enables it to survive or it dies.enables it to survive or it dies.

As the environment changes, organisms must As the environment changes, organisms must have variations that allow them to survive have variations that allow them to survive (adapt) to those changes or die(adapt) to those changes or die

If an entire population of If an entire population of a species cannot adapt, a species cannot adapt, that species becomes that species becomes extinct.extinct.

There have been at least 5 MASS extinctions There have been at least 5 MASS extinctions during Earth’s history where a huge % of the during Earth’s history where a huge % of the living species were destroyedliving species were destroyed

At least one of At least one of these has been these has been

attributed to attributed to meteor impact and meteor impact and

it’s it’s consequences.consequences.

It is estimated that It is estimated that 1/5 or more of the world’s 1/5 or more of the world’s speciesspecies will become extinctwill become extinct if the rainforests if the rainforests are destroyed.are destroyed.

Many scientists Many scientists say that the say that the

earth is earth is currently currently

experiencing a experiencing a mass extinction mass extinction

crisis.crisis.

• What do you think biodiversity is?• ANSWER: the variation of life forms in an

ecosystem• How do you think biodiversity would be

affected by mass extinction?• ANSWER: biodiversity would decrease

significantly

Life Variation

If we are in a period of mass extinction . . . If we are in a period of mass extinction . . . What animals will your grandchildren be able What animals will your grandchildren be able to see in the wild?to see in the wild?

Visit the World Wildlife Fund website for more information

on endangered species.

Photos by MartinHarveyWorld WildlifeFund International

Davis, Donald E. “Meteor Impact”. (Also public domain from NASA.) No date. Online image with permission. Dinosaurs and Their Extinction. June 10, 2004. <http://www.donaldedavis.com/PARTS/DDDINOS.html>

“Snow Alaska”. No date. Online image. Public Domain. Mineral Management Service. June 10, 2004. GeekPhilospher.com <http://geekphilosopher.com/bkg/snowAlaskaIce.htm>

“Clearcut in Cameroon Rainforest”. No date. Online image. June 11, 2004. Earth Crash Earth Spirit. <http://www.eces.org/archive/gallery/forestsgfx/forests39.shtml>

Harvey, Martin. No date. Online image. World Wildlife Fund. June 11, 2004. <http://www.panda.org>

“Allosaur”. No date. Online image. Public Domain. Dinosaur National Monument. National Park Service. June 10, 2004. http://www.nps.gov/dino/index.htm