Darwin’s Theory of Darwin’s Theory of EvolutionEvolution

The History of EvolutionThe History of Evolution• Evolution is defined as change over timeEvolution is defined as change over time

• The theory that all organisms on Earth are The theory that all organisms on Earth are related by common ancestry and that they related by common ancestry and that they have changed over time (adapted) mostly have changed over time (adapted) mostly because of natural selection.because of natural selection.

• Charles Darwin is one of the most famous Charles Darwin is one of the most famous scientists associated with the theory of scientists associated with the theory of evolutionevolution

Darwin’s voyageDarwin’s voyage

Darwin’s interestDarwin’s interest• Darwin’s observations and research played Darwin’s observations and research played

an important role in the development of the an important role in the development of the theory of evolution that is still widely theory of evolution that is still widely accepted todayaccepted today

• During his voyage on the U.S.S. Beagle, he During his voyage on the U.S.S. Beagle, he would would collect specimens from the different collect specimens from the different areasareas he visited he visited

• He was fascinated to see the He was fascinated to see the varietyvariety in the in the different plants and animals that he studieddifferent plants and animals that he studied

He did notice one He did notice one similarity:similarity:

All of the organisms he observed All of the organisms he observed were well suited (well matched) to were well suited (well matched) to

their environmenttheir environment

Beaks of finchesBeaks of finches

• The finches beaks have The finches beaks have adaptedadapted and and naturally naturally selected forselected for over time based on what they eat over time based on what they eat

AdaptationAdaptation• An adaptation is any inherited characteristic

that increases an organisms chance for survival

• Adaptations can be physical or behavioral and can be passed from generation to generation

• The process of becoming better suited to the environment

Different types of adaptations:Different types of adaptations:

• Genetic adaptation – always genetically controlled (ex: 5 fingers, giraffe’s neck)

Different types of adaptations:Different types of adaptations:• Physiological adaptation – change in the

reactions; can be genetic or not (ex: acclimation to altitude or climate, coat

color change during seasons)

Different types of adaptations:Different types of adaptations:

• Behavioral adaptation – change in behavior; can be genetic or not (ex:

chimps using sticks to catch termites, bears eating garbage)

Survival of the fittestSurvival of the fittest• The The abilityability of an individual of an individual to survive and to survive and

reproduce is called fitnessreproduce is called fitness

• Adaptations that help an animal become Adaptations that help an animal become more fit to survive and reproduce more more fit to survive and reproduce more successfully are commonly selectedsuccessfully are commonly selected

• This is known as This is known as survival of the fittestsurvival of the fittest

Survival of the fittest is Survival of the fittest is also known as natural also known as natural

selectionselection

Over time, natural selection will Over time, natural selection will change the characteristics of a change the characteristics of a

population, population, increasing the fitness of that increasing the fitness of that

populationpopulation

Proof? You want proof?Proof? You want proof?• Evidence of evolution through adaptation Evidence of evolution through adaptation

and natural selection can be found in:and natural selection can be found in:

– the fossil recordthe fossil record

– Geographical distribution (different animals evolve Geographical distribution (different animals evolve similarly because of the same environmental factors)similarly because of the same environmental factors)

– Homologous structuresHomologous structures

– Similarities in early development of embryosSimilarities in early development of embryos

Fossil RecordFossil Record

Fossil Fossil RecordRecord

Geographical DistributionGeographical Distribution

Geographical DistributionGeographical Distribution

Homologous structuresHomologous structures

Homologous structuresHomologous structures

Development of embryosDevelopment of embryos

Development of embryosDevelopment of embryos

TODAY…• Evolution is widely accepted by the scientific

community• Theories are constantly changing based on new

evidence (mitochondrial DNA/rapid evolution…)• Evolution is still occurring• Many species are becoming extinct because they

cannot evolve as fast as humans are changing the environment.

• Humans are “meddling” with evolution through artificial selection (fruit, dogs…)