Darwin Presents His Darwin Presents His Case Case

Section 15-3Section 15-3This section explains the concepts of This section explains the concepts of artificial selection, natural selection, artificial selection, natural selection,

and fitness. It also describes evidence and fitness. It also describes evidence for evolution.for evolution.

Publication of Publication of On the Origin On the Origin of Speciesof Species Is the following sentence true or false?Is the following sentence true or false?

• When Darwin returned to England, When Darwin returned to England, he rushed to publish his thoughts he rushed to publish his thoughts about evolution.about evolution.

• FalseFalse

Publication of Publication of On the On the Origin of SpeciesOrigin of SpeciesThe naturalist whose essay gave The naturalist whose essay gave

Darwin an incentive to publish his Darwin an incentive to publish his own work was.own work was.

• Alfred Russel WallaceAlfred Russel Wallace

Publication of Publication of On the On the Origin of SpeciesOrigin of Species• Circle the letter of each sentence that is Circle the letter of each sentence that is

true about Darwin’s book, true about Darwin’s book, On the OriginOn the Originof Species.of Species.

• It contained evidence for evolution.It contained evidence for evolution.

• It described natural selection.It described natural selection.

Inherited Variation and Inherited Variation and Artificial Selection Artificial Selection • Differences among individuals of a Differences among individuals of a

species are referred to as __________.species are referred to as __________.

• variationvariation

Inherited Variation and Inherited Variation and Artificial SelectionArtificial Selection Is the following sentence true or false?Is the following sentence true or false?

Genetic variation is found only in wild Genetic variation is found only in wild organisms in nature.organisms in nature.

falsefalse

Inherited Variation and Inherited Variation and Artificial SelectionArtificial SelectionCircle the letter of each sentence that is true Circle the letter of each sentence that is true

about artificial selection.about artificial selection.

• It is also called selective breeding.It is also called selective breeding.• It occurs when humans select natural It occurs when humans select natural

variations they find useful.variations they find useful.

• It produces organisms that look very It produces organisms that look very different from their ancestors.different from their ancestors.

Evolution by Natural Evolution by Natural SelectionSelection What was Darwin’s greatest What was Darwin’s greatest

contribution? contribution? • His greatest contribution was His greatest contribution was

developing a scientific hypothesis to developing a scientific hypothesis to explain how evolution occurs.explain how evolution occurs.

Evolution by Natural Evolution by Natural SelectionSelectionWhat does the phrase What does the phrase struggle for struggle for

existence existence mean?mean?• It means that members of each It means that members of each

species compete regularly to obtain species compete regularly to obtain food, living space, and other food, living space, and other necessities of life.necessities of life.

Evolution by Natural Evolution by Natural SelectionSelection

• FFitness - The ability of an individual to itness - The ability of an individual to survive and reproduce in its specific survive and reproduce in its specific environmentenvironment

• Adaptation - Any inherited characteristic that Adaptation - Any inherited characteristic that increases an organism’s chance of survivalincreases an organism’s chance of survival

• NNatural selection - Survival of the fittestatural selection - Survival of the fittest

Darwin’s Theory of Darwin’s Theory of EvolutionEvolution Is the following sentence true or false? Is the following sentence true or false? • Adaptations can be physical Adaptations can be physical

characteristics but not more complex characteristics but not more complex features such as behavior.features such as behavior.

• FalseFalse

Darwin’s Theory of Darwin’s Theory of EvolutionEvolution Explain what Darwin meant by the Explain what Darwin meant by the

phrase phrase survival of the fittestsurvival of the fittest. . Individuals that are better suited to their Individuals that are better suited to their environment survive and reproduce environment survive and reproduce most successfully.most successfully.

Darwin’s Theory of Darwin’s Theory of EvolutionEvolution Circle the letter of each sentence that Circle the letter of each sentence that

is true about natural selection.is true about natural selection.

• It selects traits that increase fitness.It selects traits that increase fitness.

• It takes place without human control.It takes place without human control.

Darwin’s Theory of Darwin’s Theory of EvolutionEvolution• The principle that living species The principle that living species

descend, with changes, from other descend, with changes, from other species over time is referred to species over time is referred to as_______ .as_______ .

• Descent with modificationDescent with modification

Darwin’s Theory of Darwin’s Theory of EvolutionEvolution• The principle that all species were The principle that all species were

derived from common ancestors is derived from common ancestors is known asknown as________.________.

• Common DescentCommon Descent

Evidence of Evolution Evidence of Evolution Is the following sentence true or false? Is the following sentence true or false?

• Darwin argued that living things have Darwin argued that living things have beenbeenevolving on Earth for thousands of evolving on Earth for thousands of years.years.

• falsefalse

Complete the concept map.Complete the concept map.

How do fossils that formed in How do fossils that formed in different rock layers provide different rock layers provide evidence of evolution?evidence of evolution?

• They document the fact that life on They document the fact that life on Earth has changed over time.Earth has changed over time.

• Circle the letter of the way Darwin Circle the letter of the way Darwin explained the distribution of finch explained the distribution of finch species on the Galápagos Islands.species on the Galápagos Islands.

• They had descended with They had descended with modification from a common modification from a common mainland ancestor.mainland ancestor.

How did Darwin explain the How did Darwin explain the existence of similar but unrelated existence of similar but unrelated species?species?

• Darwin thought that such species Darwin thought that such species evolved features in common because evolved features in common because they were exposed to similar they were exposed to similar pressures of natural selection.pressures of natural selection.

• Structures that have different mature Structures that have different mature forms but develop from the same forms but develop from the same embryonic tissues are called .embryonic tissues are called .

• HOMOLOGOUS STRUCTURESHOMOLOGOUS STRUCTURES

Is the following sentence true or false? Is the following sentence true or false? • Homologous structures provide strong Homologous structures provide strong

evidence that all four-limbed evidence that all four-limbed vertebrates have descended, with vertebrates have descended, with modifications, from common ancestors.modifications, from common ancestors.

• TRUETRUE

• Organs that are so reduced in size Organs that are so reduced in size that they are just vestiges, or that they are just vestiges, or traces, of homologous organs in traces, of homologous organs in other species are called .other species are called .

• VESTIGAL ORGANSVESTIGAL ORGANS

Summary of Darwin’s Summary of Darwin’s TheoryTheory• Circle the letter of each idea that is part of Circle the letter of each idea that is part of

Darwin’s theory of evolution.Darwin’s theory of evolution.

• There is variation in nature.There is variation in nature.

• Fewer organisms are produced than can Fewer organisms are produced than can survive.survive.

• Species change over time.Species change over time.

Summary of Darwin’s Summary of Darwin’s TheoryTheoryAccording to Darwin’s theory, what According to Darwin’s theory, what

happens to individuals whose happens to individuals whose characteristics are not well suited to characteristics are not well suited to their environment? their environment?

• Such individuals die or leave fewer Such individuals die or leave fewer offspring.offspring.

Summary of Darwin’s Summary of Darwin’s TheoryTheory Darwin believed that all organisms on Darwin believed that all organisms on

Earth are united into a single tree of Earth are united into a single tree of life bylife by

• Descent with modificationDescent with modification

Evolutionary Theory Since Evolutionary Theory Since Darwin Darwin What is the status of Darwin’s What is the status of Darwin’s

hypotheses today? hypotheses today?

• They have been confirmed andThey have been confirmed andexpanded by scientific advances in expanded by scientific advances in biology, geology, and physicsbiology, geology, and physics