Darwin and Darwin and Natural SelectionNatural Selection

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 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)

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

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

After Cambridge, After Cambridge, Charles was Charles was

recommended for a recommended for a surveying trip on the surveying trip on the

HMS Beagle.HMS Beagle.

After Cambridge, After Cambridge, Charles was Charles was

recommended for a recommended for a surveying trip on the surveying trip on the

HMS Beagle.HMS Beagle.

He sailed aboard the He sailed aboard the BeagleBeagle for 5 years, for 5 years,

working as a naturalist.working as a naturalist.

He sailed aboard the He sailed aboard the BeagleBeagle for 5 years, for 5 years,

working as a naturalist.working as a naturalist.

This voyage lasted from 1831 to 1836. This voyage lasted from 1831 to 1836. This voyage lasted from 1831 to 1836. This voyage lasted from 1831 to 1836.

The The BeagleBeagle sailed around the world. sailed around the world. The The BeagleBeagle sailed around the world. sailed around the world.

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.

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..

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.

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..

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.

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.

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.

James HuttonJames Hutton

The Father of GeologyThe Father of Geology

James HuttonJames Hutton

The Father of GeologyThe Father of Geology

Darwin was also Darwin was also influenced by influenced by

geologist geologist Charles Charles LyellLyell who wrote who wrote

Principia GeologicaPrincipia Geologica..

Darwin was also Darwin was also influenced by influenced by

geologist geologist Charles Charles LyellLyell who wrote 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.

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.

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.

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.

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.

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.

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

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

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.

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 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.

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.

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.

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…Darwin called this…Darwin called this…

orororor

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

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 ModificationsDescent With ModificationsDescent With Modifications

Malthus was a British Malthus was a British social scientist who made social scientist who made these observations about these observations about

humans:humans:

Malthus was a British Malthus was a British social scientist who made social scientist who made these observations about these observations about

humans:humans:

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

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.

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 MalthusThomas Malthus..

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 MalthusThomas 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…

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

Darwin published his ideas in the book

On The Origin of Species by Means of

Natural Selection, or the Preservation of

Favoured Races in the Struggle for Life

Five basic components ofFive basic components ofFive basic components ofFive basic components of

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

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

Look around you…are Look around you…are you all the same?you all the same?

Look around you…are Look around you…are you all the same?you all the same?

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

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

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.

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

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

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

foodfoodfoodfood

Within and Among Species for

And Within a Species for

waterwaterwaterwater

matesmatesmatesmates

sheltersheltersheltershelter spacespacespacespace

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 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)

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

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

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!He who spreads the most genes wins!He who spreads the most genes wins!1st1st

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.

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. Decent with modificationDecent with modification: : Living species today Living species today are descended with modifications from common are descended with modifications from common ancestral species that lived in the past.ancestral species that lived in the past.

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

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.

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.

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

the variation exists first.the variation exists first.the variation exists first.the variation exists first.

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

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

the environment changes.the environment changes.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.

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

An organism does An organism does notnot change 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.

An organism does An organism does notnot change 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.

Species

• A group of organisms that are closely related and naturally mate to produce fertile offspring.

Speciation• The process by which new species form.

– Separate populations of a single species often live in different environments

– In each environment, natural selection acts on populations

– If environments different enough, separate populations can become dissimilar

Different genes favor survival in different habitats

– As two groups become more different over time, they may be unable to breed= new species

Speciation

• What keeps new species separate?

• Reproductive Isolation- two populations of the same species do not mate with each other- can be due to…– Geographic isolation– Temporal isolation– Physical differences– Hybrid sterility

Ex. Garter snakes- some live in water, some are terrestrial

Ex. Courtship behaviors

Ex. Eastern spotted skunk (late winter) and western spotted skunk (late summer)

Ex. Differences in blossoms attract different pollinators

Ex. Gametes of red and purple sea urchins are unable to fuse

Ex. Hybrid salamanders do not complete development, those that do develop are frail

Ex. Donkey + horse = mule- sterile

Ex. Even if the first generation of hybrids is viable and robust, subsequent generations are weak or sterile- rice

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

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.

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.

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.

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.

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.

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?

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