Ch. 15 Darwin’s Theory of Evolution. Ch. 15 Outline 15-1: The Puzzle of Life’s Diversity –The Voyage of the Beagle –Darwin’s Observations –The Journey

Ch. 15 Darwin’s Theory of Ch. 15 Darwin’s Theory of EvolutionEvolution

Ch. 15 OutlineCh. 15 Outline

15-1: The Puzzle of Life’s Diversity15-1: The Puzzle of Life’s Diversity– The Voyage of the The Voyage of the BeagleBeagle– Darwin’s ObservationsDarwin’s Observations– The Journey HomeThe Journey Home

Ch. 15 OutlineCh. 15 Outline

15-2: Ideas that Shaped Darwin’s Thinking15-2: Ideas that Shaped Darwin’s Thinking– An Ancient, Changing EarthAn Ancient, Changing Earth– Lamarck’s Evolution HypothesesLamarck’s Evolution Hypotheses– Population GrowthPopulation Growth

15-3: Darwin Presents His Case15-3: Darwin Presents His Case– Publication of Publication of On the Origin of SpeciesOn the Origin of Species– Inherited Variation and Artificial SelectionInherited Variation and Artificial Selection– Evolution by Natural SelectionEvolution by Natural Selection– Evidence of EvolutionEvidence of Evolution– Summary of Darwin’s TheorySummary of Darwin’s Theory– Strengths and Weaknesses of Evolutionary TheoryStrengths and Weaknesses of Evolutionary Theory

The Puzzle of Life’s DiversityThe Puzzle of Life’s Diversity

EvolutionEvolution: The process by which species : The process by which species change over timechange over time

Theory:Theory: Well-supported testable Well-supported testable explanation. It explains a phenomena.explanation. It explains a phenomena.

Voyage of the BeagleVoyage of the Beagle

Charles DarwinCharles Darwin– From EnglandFrom England– Joined the crew of the H.M.S. Beagle as the Joined the crew of the H.M.S. Beagle as the

ship’s naturalistship’s naturalist– 5 year trip around the world5 year trip around the world– Darwin collected specimens at each stopDarwin collected specimens at each stop

Voyage of the Voyage of the BeagleBeagle

Voyage of the BeagleVoyage of the Beagle

Darwin made numerous observations and Darwin made numerous observations and collected evidence that led him to propose collected evidence that led him to propose a hypothesis about the way life changes a hypothesis about the way life changes over time.over time.– This hypothesis is now called the theory of This hypothesis is now called the theory of

evolution.evolution.

Darwin’s ObservationDarwin’s Observation

Patterns of diversityPatterns of diversity– Many plants and animals seemed well suited Many plants and animals seemed well suited

to their environmentto their environment– Organisms survived and reproduced in many Organisms survived and reproduced in many

different waysdifferent ways– Not all organisms lived everywhereNot all organisms lived everywhere

Darwin’s ObservationDarwin’s Observation

Living Organisms and FossilsLiving Organisms and Fossils

Darwin collected fossilsDarwin collected fossils– Fossil:Fossil: Preserved Remains of ancient Preserved Remains of ancient

organismsorganisms

Some fossils didn’t resemble any living Some fossils didn’t resemble any living organismsorganisms

Darwin’s ObservationsDarwin’s Observations

The Galapagos IslandsThe Galapagos Islands– Off the west coast of South AmericaOff the west coast of South America– The Location that most influenced DarwinThe Location that most influenced Darwin– Each Island had a different climate and Each Island had a different climate and

different organismsdifferent organisms– Noticed the birds had different shaped beaks Noticed the birds had different shaped beaks

on each island and tortoises had different on each island and tortoises had different shaped shellsshaped shells

Darwin’s FinchesDarwin’s Finches

The Journey HomeThe Journey Home

After returning back to England, Darwin After returning back to England, Darwin wondered if the birds he collected all wondered if the birds he collected all belonged to the same species at some belonged to the same species at some timetime

An Ancient, Changing EarthAn Ancient, Changing Earth

James Hutton and Charles LyellJames Hutton and Charles Lyell– Developed the theory that the earth is very old. This Developed the theory that the earth is very old. This

idea was contrary to what people thought at the time.idea was contrary to what people thought at the time.

Hutton and Geological Change:Hutton and Geological Change:– Hutton was a geologist. He proposed that layers of Hutton was a geologist. He proposed that layers of

rock form very slowly and others are pushed up from rock form very slowly and others are pushed up from the sea floor to form mountains. (This takes a the sea floor to form mountains. (This takes a longlong time)time)

Lyell’s Principles of GeologyLyell’s Principles of Geology

Lyell believed that the same processes that Lyell believed that the same processes that changed the Earth in the past still operate in the changed the Earth in the past still operate in the present.present.

Darwin was influenced by Hutton and Lyell’s Darwin was influenced by Hutton and Lyell’s work. He reasoned, if the Earth can change work. He reasoned, if the Earth can change over time (earthquakes, volcanoes) maybe life over time (earthquakes, volcanoes) maybe life can change too!can change too!

Lamarck’s Evolution HypothesesLamarck’s Evolution Hypotheses

Before Darwin’s work, Jean-Baptiste Before Darwin’s work, Jean-Baptiste Lamarck observed that life changes and Lamarck observed that life changes and the species descend from other species.the species descend from other species.


Lamarck had two ideas:Lamarck had two ideas:1.1. Organisms can alter their bodies by “use Organisms can alter their bodies by “use

and disuse”and disuse”Use: Use a structure and it will changeUse: Use a structure and it will changeDisuse: Structures not used will disappearDisuse: Structures not used will disappear

2.2. Acquired characteristics can be inherited.Acquired characteristics can be inherited.If you increase your muscle mass your children If you increase your muscle mass your children will inherit your big muscleswill inherit your big muscles


Although Lamarck’s ideas were incorrect, Although Lamarck’s ideas were incorrect, he was one of the first ones to realize that he was one of the first ones to realize that organisms are adapted to their organisms are adapted to their environments and propose a theory of environments and propose a theory of evolution.evolution.

Use and DisuseUse and Disuse

Population GrowthPopulation Growth

Another influence of Darwin was Thomas Another influence of Darwin was Thomas Malthus. This scientist published a book Malthus. This scientist published a book in which he stated that babies were being in which he stated that babies were being born faster than people were dying.born faster than people were dying.– Sooner or later food and living space will run Sooner or later food and living space will run

out.out.

Population GrowthPopulation Growth

Darwin thought this applied to plants and Darwin thought this applied to plants and other animals even more because humans other animals even more because humans usually only have one offspring at a time.usually only have one offspring at a time.– So why wasn’t the Earth completely covered So why wasn’t the Earth completely covered

in maple trees (for example)? Why were in maple trees (for example)? Why were some surviving and others not?some surviving and others not?

Darwin Presents His CaseDarwin Presents His Case

After Darwin returned to England in 1836, he After Darwin returned to England in 1836, he continued to study his specimens. He continued to study his specimens. He discovered that the birds from the Galapagos discovered that the birds from the Galapagos were all finches, not wrens, warblers and were all finches, not wrens, warblers and blackbirds like he thought (found nowhere else blackbirds like he thought (found nowhere else in the world). The same was true for the in the world). The same was true for the tortoisestortoises– All the species All the species resembledresembled ones on the South America ones on the South America

mainland, but they were a different species.mainland, but they were a different species.

Darwin Presents his CaseDarwin Presents his Case

Over 20 years later, Darwin published all his Over 20 years later, Darwin published all his findings in a book called, findings in a book called, On the Origin of On the Origin of SpeciesSpecies. He didn’t publish it earlier because it . He didn’t publish it earlier because it went against the common beliefs about went against the common beliefs about organisms. organisms.

Not only did Darwin propose the theory of Not only did Darwin propose the theory of evolution, he also proposed a mechanism by evolution, he also proposed a mechanism by which it happens:which it happens:– Natural SelectionNatural Selection

Evolution by Natural SelectionEvolution by Natural Selection

Darwin realized the organisms competed Darwin realized the organisms competed for resources for resources (struggle for existence)(struggle for existence). . He noted that organisms better suited to He noted that organisms better suited to their environment (ex. Run faster, hide their environment (ex. Run faster, hide from predators) survived to reproduce and from predators) survived to reproduce and pass on their genes.pass on their genes.


FitnessFitness: The ability of an animal to survive : The ability of an animal to survive and reproduceand reproduce

Adaptation: Adaptation: an inherited characteristic an inherited characteristic that increases an organism’s chance of that increases an organism’s chance of survivalsurvival


Successful adaptations, Darwin Successful adaptations, Darwin concluded, enable organisms to survive concluded, enable organisms to survive and reproduce.and reproduce.– Types of adaptationsTypes of adaptations

StructuresStructures

Physiological processesPhysiological processes

BehaviorBehavior

Evolution of Natural SelectionEvolution of Natural Selection

Survival of the fittest: Survival of the fittest: individuals that are individuals that are better suited for their environment survive and better suited for their environment survive and reproduce most successfully. (Natural Selection)reproduce most successfully. (Natural Selection)

Over time, natural selection results in changes in Over time, natural selection results in changes in the inherited characteristics of a population. the inherited characteristics of a population. These changes increases a species’ fitness in its These changes increases a species’ fitness in its environment.environment.

Evolution of Natural SelectionEvolution of Natural Selection

Darwin proposed that over long periods of time, Darwin proposed that over long periods of time, natural selection produces organisms that have natural selection produces organisms that have different structures. Species today look different different structures. Species today look different than their ancestorsthan their ancestors

Descent with ModificationDescent with Modification: Each living species : Each living species has descended, with changes from other has descended, with changes from other species over time.species over time.

Evidence of EvolutionEvidence of Evolution

Fossil RecordFossil Record

Geographic Distribution of Living SpeciesGeographic Distribution of Living Species

Homologous Body StructuresHomologous Body Structures

EmbryologyEmbryology

Evidence of EvolutionEvidence of Evolution

Fossil record-More Coming in Ch. 16Fossil record-More Coming in Ch. 16

Geographic Distribution of Living SpeciesGeographic Distribution of Living Species– Similar organisms found in different places on EarthSimilar organisms found in different places on Earth– Ex: Darwin’s FinchesEx: Darwin’s Finches– Organisms under the same “pressures” had similar Organisms under the same “pressures” had similar

adaptationsadaptations

Homologous Body StructuresHomologous Body Structures

Structures that have different mature forms but Structures that have different mature forms but develop from the same embryonic tissuesdevelop from the same embryonic tissues– Ex. Wings and armsEx. Wings and arms– Help Scientist determine common ancestorsHelp Scientist determine common ancestors– Not all homologous structures serve important Not all homologous structures serve important

functionsfunctions

Vestigial OrgansVestigial Organs: Organs reduced in size : Organs reduced in size (Traces of homologous organs in other species)(Traces of homologous organs in other species)– Have little or no functionHave little or no function

Homologous StructuresHomologous Structures

Turtle Alligator Bird Mammal

Ancient lobe-finned fish

EmbryologyEmbryology

Organisms that have similar Organisms that have similar developmental stages as embryos are developmental stages as embryos are more closely related to each other.more closely related to each other.

Summary of Darwin’s Theory Summary of Darwin’s Theory

1.1. Individual organisms differ, and some of this variation Individual organisms differ, and some of this variation is inheritableis inheritable

2.2. Organisms produced more offspring that can survive Organisms produced more offspring that can survive and there is competition for limited resourcesand there is competition for limited resources

3.3. Individuals best suited survive and reproduce. Others Individuals best suited survive and reproduce. Others die or leave fewer offspring. This process of natural die or leave fewer offspring. This process of natural selection causes species to change over time.selection causes species to change over time.

4.4. Species alive today are descended with modifications.Species alive today are descended with modifications.

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Ch. 15 Darwin’s Theory of Evolution. Ch. 15 Outline 15-1: The Puzzle of Life’s Diversity –The Voyage of the Beagle –Darwin’s Observations –The Journey