Natural Selection - Natural Selection - EvolutionEvolution

What is it?What is it?

Charles Darwin (1859)Charles Darwin (1859) HMS BeagleHMS Beagle Galapagos IslandsGalapagos Islands Studied Anatomy Studied Anatomy

of Finchesof Finches

Charles DarwinCharles Darwin

After Charles Darwin graduated from college, he served After Charles Darwin graduated from college, he served as as naturalistnaturalist on a ship called the HMS on a ship called the HMS BeagleBeagle. During a . During a voyage around the world, Darwin collected thousands of voyage around the world, Darwin collected thousands of plant and animal samples.plant and animal samples.

Darwin’s FinchesDarwin’s Finches

Darwin noticed that the finches of the Galápagos Islands Darwin noticed that the finches of the Galápagos Islands were a little different from the finches in Ecuador. And were a little different from the finches in Ecuador. And the finches on each island differed from the finches on the finches on each island differed from the finches on the other islandsthe other islands

Darwin’s thinkingDarwin’s thinking

• Ideas About BreedingIdeas About Breeding The process in which The process in which humans select which plants or animals to humans select which plants or animals to reproduce based on certain desired traits is called reproduce based on certain desired traits is called selective breeding. selective breeding.

• Ideas About Population Ideas About Population Only a limited number Only a limited number of individuals survive to reproduce. Thus, there is of individuals survive to reproduce. Thus, there is something special about the offspring of the something special about the offspring of the survivors.survivors.

Competition for matesCompetition for mates

Many species have so much competition for Many species have so much competition for mates that interesting adaptations result. For mates that interesting adaptations result. For example, the females of many bird species example, the females of many bird species prefer to mate with males that have colorful prefer to mate with males that have colorful feathersfeathers..

Sometimes, drastic changes that can form a new Sometimes, drastic changes that can form a new species take place. The formation of a new species take place. The formation of a new species as a result of evolution is called species as a result of evolution is called speciation.speciation.

Influences on DarwinInfluences on Darwin

Thomas Malthus: wrote a book stating that Thomas Malthus: wrote a book stating that humans have the potential to reproduce humans have the potential to reproduce rapidly, eventually overrunning the food rapidly, eventually overrunning the food supplysupply

This led Darwin to realize that all species This led Darwin to realize that all species can reproduce rapidly, those who survive can reproduce rapidly, those who survive must pass on traits to their offspring to must pass on traits to their offspring to help them survivehelp them survive

Darwin’s theory of Darwin’s theory of natural selectionnatural selection

• What Is Natural Selection? What Is Natural Selection? Darwin proposed the theory Darwin proposed the theory that evolution happens through a process that he called that evolution happens through a process that he called natural selection.natural selection. Individuals that are better adapted to Individuals that are better adapted to their environment survive and reproduce more successfully their environment survive and reproduce more successfully than less well adapted individuals.than less well adapted individuals.

• Genetics and Evolution Genetics and Evolution Today, scientists have found Today, scientists have found most of the evidence that Darwin lacked. They know that most of the evidence that Darwin lacked. They know that variation happens as a result of differences in genes. variation happens as a result of differences in genes.

What evidence is there?What evidence is there?

In order for natural selection, or any In order for natural selection, or any other theory of evolution to be other theory of evolution to be accurate, there needs to be some accurate, there needs to be some physical evidence supporting it. physical evidence supporting it. Following are some clues scientists Following are some clues scientists have used to piece together the have used to piece together the history of living things on Earth.history of living things on Earth.

FossilsFossils

Cuvier—Extinction Cuvier—Extinction existed existed

Shape and PurposeShape and Purpose

What are fossils?What are fossils?

•The remains or imprints of once-living The remains or imprints of once-living organisms found in layers of rock called organisms found in layers of rock called fossils.fossils.

•By studying fossils, scientists have made a By studying fossils, scientists have made a timeline of life known as the timeline of life known as the fossil recordfossil record. . The fossil record organizes fossils by their The fossil record organizes fossils by their estimated ages and physical similarities.estimated ages and physical similarities.

AnatomyAnatomy

Homologous Homologous StructuresStructures– Same, but Same, but

different different functionfunction

Analogous Analogous StructuresStructures

Same function, Same function, but different but different structurestructure

Anatomy 2Anatomy 2

Vestigial StructuresVestigial Structures– No longer No longer

needed/usedneeded/used

BiochemistryBiochemistry

Study DNAStudy DNA Genetic Genetic

TechnologyTechnology– RFLP’sRFLP’s– Gel ElectrophoresisGel Electrophoresis

Comparative EmbryologyComparative Embryology

Study Embryos of Study Embryos of Different Different OrganismsOrganisms

AdaptationsAdaptations

What is it?What is it?

Who displays it?Who displays it?

Why does it happen? Why does it happen?

MimicryMimicry a superficial resemblance of one organism to another or to natural a superficial resemblance of one organism to another or to natural

objects among which it lives that secures it a selective advantage objects among which it lives that secures it a selective advantage (as protection from predation) (as protection from predation)

CamouflageCamouflage

ResistanceResistance

Mostly bacteria and Mostly bacteria and virusesviruses

Changes in PopulationsChanges in Populations

• Adaptation to HuntingAdaptation to Hunting People hunt elephants for their People hunt elephants for their tusks. As a result, fewer of the elephants that have tusks tusks. As a result, fewer of the elephants that have tusks survive to reproduce, and more of the tuskless elephants survive to reproduce, and more of the tuskless elephants survive.survive.

• Insecticide Resistance Insecticide Resistance A few insects in a population A few insects in a population may be naturally resistant to a chemical insecticide. These may be naturally resistant to a chemical insecticide. These insects pass their resistance trait to their offspring, and an insects pass their resistance trait to their offspring, and an insect population gradually becomes resistant to the insect population gradually becomes resistant to the insecticide.insecticide.