Darwin’s Idea for Darwin’s Idea for Natural Selection Natural Selection

By Kristi SchrammBy Kristi Schramm

Open your books to page 378Open your books to page 378

Read “Publication of ‘On the origin of Read “Publication of ‘On the origin of Species”Species”– Summarize in 3-4 sentencesSummarize in 3-4 sentences

Read ‘Inherited Variation and Artificial Read ‘Inherited Variation and Artificial Selection’Selection’– Summarize in 3-4 sentencesSummarize in 3-4 sentences

Darwin’s Influences Darwin’s Influences

Darwin studied many scientific theories of Darwin studied many scientific theories of his time his time

Scientists that influenced Darwin’s later Scientists that influenced Darwin’s later theories include Hutton, Lyell, Lamarck and theories include Hutton, Lyell, Lamarck and Malthus Malthus

James Hutton and Charles LyellJames Hutton and Charles Lyell

Theory: Theory: The earth is many millions of The earth is many millions of years old and that the same processes years old and that the same processes that shaped the earth millions of years that shaped the earth millions of years ago are the same as todayago are the same as today

Made Darwin wonder: Made Darwin wonder: – If the Earth could change over time, might If the Earth could change over time, might

life change over time?life change over time?– This change would only be possible if the earth This change would only be possible if the earth

was extremely oldwas extremely old

Jean-Baptiste LamarckJean-Baptiste Lamarck

Noticed that animals were “adapt” to their Noticed that animals were “adapt” to their environmentenvironment

Theory: Theory: Acquired Characteristics: the use or Acquired Characteristics: the use or disuse of a body part during it’s lifetime would disuse of a body part during it’s lifetime would effect how traits were passed onto the effect how traits were passed onto the offspring. offspring.

Made Darwin wonder: Made Darwin wonder: – How did parents pass on their traits (inheritance)How did parents pass on their traits (inheritance)– Why are organisms so well adapted to their Why are organisms so well adapted to their

environment?environment?

Thomas MalthusThomas Malthus

Observation: Babies are being born more Observation: Babies are being born more than people are dying. than people are dying.

Theory: Theory: if the human population if the human population continued to grow unchecked, eventually continued to grow unchecked, eventually there would not be enough food or living there would not be enough food or living space for everyone. space for everyone.

Influenced Darwin: Influenced Darwin: Organisms give birth Organisms give birth to many more offspring than can survive to many more offspring than can survive and reproduceand reproduce

Write these questions in the Write these questions in the Cornell Notes section (on the left)Cornell Notes section (on the left) What did Darwin observe in the What did Darwin observe in the

Galapagos Islands?Galapagos Islands?

When did Darwin publish his ideas?When did Darwin publish his ideas?

What is Artificial Selection?What is Artificial Selection?

Darwin Presents His CaseDarwin Presents His Case Darwin studies his Darwin studies his

specimens from the specimens from the Galapagos Galapagos

The wrens, warblers, and The wrens, warblers, and blackbirds he thought he blackbirds he thought he found were all actually found were all actually finches! finches!

Darwin Presents His CaseDarwin Presents His Case

After 25 years of mulling over his theories, After 25 years of mulling over his theories, Darwin receives a document from Alfred Darwin receives a document from Alfred Wallace summarizing the exact theory Wallace summarizing the exact theory Darwin came up withDarwin came up with

Darwin Presents His CaseDarwin Presents His Case Published his book in 1859Published his book in 1859 Artificial Selection: Humans breed the Artificial Selection: Humans breed the

species with the most desired variations to species with the most desired variations to enhance the desired trait. enhance the desired trait.

Ex: Dog BreedingEx: Dog Breeding

Darwin’s Theory of Evolution by Darwin’s Theory of Evolution by Natural SelectionNatural Selection

Natural Selection is a process that allows Natural Selection is a process that allows the evolution of species over timethe evolution of species over time

Darwin stated that three things must be true Darwin stated that three things must be true for natural selection to occur:for natural selection to occur:

– Struggle for ExistenceStruggle for Existence

– Survival of the FittestSurvival of the Fittest

– Descent with modificationDescent with modification

Struggle for Existence Struggle for Existence Based on Malthus’s work populations Based on Malthus’s work populations

Darwin’s theory states that there must be a Darwin’s theory states that there must be a struggle for existence. struggle for existence.

Not all offspring Not all offspring can survive can survive because, there because, there is competition is competition for food, living for food, living space and other space and other necessities of necessities of life.life.

Survival of the FittestSurvival of the Fittest Fitness= ability to survive and successfully Fitness= ability to survive and successfully

reproducereproduce Higher fitness is a result of organisms that Higher fitness is a result of organisms that

have characteristics that help them better have characteristics that help them better survive in their environment. survive in their environment. (These (These characteristics are called adaptations)characteristics are called adaptations)

Organisms with more beneficial Organisms with more beneficial characteristics (phenotypes) will survive characteristics (phenotypes) will survive better. better.

Descent with ModificationDescent with Modification

Species today look different from Species today look different from species long ago (fossil record)species long ago (fossil record)

Natural selection will act on phenotypic Natural selection will act on phenotypic variations that allow organisms that occupy variations that allow organisms that occupy different niches. By occupying a different different niches. By occupying a different niche some of the variation is an adaptation niche some of the variation is an adaptation to one niche, while a different variation could to one niche, while a different variation could be an adaptation to another niche. be an adaptation to another niche.

Variation in beak type made the birds more suited for different niches.

Implies that all species are related to one Implies that all species are related to one another (common descent)another (common descent)

Each living species has descended with Each living species has descended with changes from other species changes from other species – How do you think these changes arose?How do you think these changes arose?

MutationsMutations

Descent with ModificationDescent with Modification

Evidence of EvolutionEvidence of Evolution

Darwin argued that life on earth has been Darwin argued that life on earth has been evolving for millions of years. evolving for millions of years.

The Fossil RecordThe Fossil Record Geographic Distribution of Living SpeciesGeographic Distribution of Living Species Homologous Body StructuresHomologous Body Structures Similarities in Early Development Similarities in Early Development

The Fossil RecordThe Fossil Record

Showed that:Showed that:

– There have been countless species There have been countless species that have lived on earth but no longer that have lived on earth but no longer live on earth todaylive on earth today

– Layers of rocks with fossils (ancient Layers of rocks with fossils (ancient life) demonstrated that thousands, or life) demonstrated that thousands, or even millions of years were needed to even millions of years were needed to create thiscreate this

The Fossil RecordThe Fossil Record

Geographic Distribution of Living Geographic Distribution of Living SpeciesSpecies Animals that are related to Animals that are related to

each other showed ‘decent each other showed ‘decent with modification.’ with modification.’ Organisms had Organisms had modifications that varied modifications that varied based on the environment based on the environment they lived inthey lived in

Animals that were not Animals that were not related each other looked related each other looked similar if they were from similar if they were from similar environments. similar environments.

Beaver Muskrat

Capybara

Geographic Distribution of Living Geographic Distribution of Living SpeciesSpecies

Desert Fox Koala Dingo

Example: Based on what they look like: Which two animals do you think are more closely related to one another?

Geographic Distribution of Living SpeciesGeographic Distribution of Living Species

Desert Fox Dingo

•Are not related to each other even though they look more alike.

•Evolutionists say they look alike because they live in the same kind of environment so over time they adapted in similar ways

Homologous StructuresHomologous Structures

Arms, wings, legs, and flippers all have Arms, wings, legs, and flippers all have very similar bonesvery similar bones

Darwin believed this was evidence that all Darwin believed this was evidence that all species were original descended from one species were original descended from one common ancestor. common ancestor.

Similarities in Early Development Similarities in Early Development

Looking at the embryonic development of organisms Darwin noticed some similarities that other scientists also noticed.