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Charles Darwin the Naturalist

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Voyage of the BeagleCharles DarwinBorn Feb. 12, 1809Joined Crew of HMS Beagle, 1831Naturalist5 Year Voyage around worldAvid Collector of Flora & FaunaAstounded By Variety of Life

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A reconstruction of the HMS Beagle sailing off Patagonia.

Darwin’s Voyage of Discovery

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Darwin Left England in 1831

Darwin returned 5 years later in 1836

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HMS Beagle’s Voyage

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The Galapagos IslandsSmall Group of Islands 1000 km West of South America

Very Different ClimatesAnimals On Islands Unique

TortoisesIguanasFinches

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The Galapagos IslandsVolcanic islands off the coast of South AmericaIsland species varied from mainland species & from island-to-island speciesEach island had long or short neck tortoises

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The Galapagos IslandsFinches on the islands resembled a mainland finchMore types of finches appeared on the islands where the available food

was different (seeds, nuts, berries, insects…)Finches had different types of beaks adapted to their type of food

gathering

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Darwin’s Observations & Conclusions

The Struggle for Existence

Who was Darwin video clip

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Voyage of the Beagle

During His Travels, Darwin Made Numerous Observations And Collected Evidence That Led Him To Propose A Revolutionary Hypothesis About The Way Life Changes Over Time

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Darwin’s ObservationsPatterns of Diversity were shownUnique Adaptations in organismsSpecies Not Evenly Distributed

Australia, Kangaroos, but No RabbitsS. America, Llamas

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Darwin’s Observations

Both Living Organisms & Fossils collected

Fossils included:TrilobitesGiant Ground Sloth of South America

This species NO longer existed.What had happened to them?

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Evidence for Evolution – The Fossil Record

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Definition

•Evolution is the slow , gradual change in a population of organisms over time

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Darwin’s Observations

Left unchecked, the number of organisms of each species will increase exponentially, generation to generation

In nature, populations tend to remain stable in size

Environmental resources are limited

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Darwin’s Conclusion

• Production of more individuals than can be supported by the environment leads to a struggle for existence among individuals

• Only a fraction of offspring survive each generation

• Survival of the Fittest

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Darwin’s Observations•Individuals of a population vary extensively in their characteristics with no two individuals being exactly alike.•Much of this variation between individuals is inheritable.

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Darwin’s Conclusion

•Individuals who inherit characteristics most fit for their environment are likely to leave more offspring than less fit individuals•Called Natural Selection

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•The unequal ability of individuals to survive and reproduceleads to a gradual change in a population, with favorable characteristics accumulating over generations (natural selection)•New species evolve

Darwin’s Theory of Evolution

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Ideas That Shaped Darwin’s Thinking

Thomas Malthus

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Population GrowthThomas Malthus, 1798EconomistObserved Babies Being Born Faster Than

People Were DyingPopulation size limited by resources such as

the Food Supply

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The Struggle for ExistenceMalthus’ Influence:

High Birth Rates & Limited Resources Would Force Life & Death Competition

Each Species Struggles For:FoodLiving SpaceMates

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Population Growth

Malthus Reasoned That If The Human Population Continued To Grow Unchecked, Sooner or Later There Would Be Insufficient Living Space & Food For EveryoneDeath Rate Will Increase To Balance Population size & Food Supply

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Population GrowthDarwin Realized Malthus’s Principles Were Visible In NaturePlants & Animals Produce Far More Offspring Than Can Be Supported

Most DieIf They Didn’t – Earth Would Be Overrun

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Darwin’s Theory of Evolution

Organisms Change Over Time

How do we know evolution happens video clip

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Natural Selection

Driving force for evolutionDuring the struggle for resources, strongest survive & reproduceIdea that at least some of the differencesbetween individuals, which impact their survival and fertility, are inheritable

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Evolution of pesticide

resistance in response to

selection

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Evolution By Natural Selection Concepts

The Struggle for Existence (compete for food, mates, space, water, etc.)

Survival of the Fittest (strongest able to survive and reproduce)

Descent with Modification (new species arise from common ancestor replacing less fit species)

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Survival of the FittestFitness

Ability of an Individual To Survive & ReproduceAdaptation

Inherited Characteristic That Increases an Organisms Chance for Survival

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Survival of the FittestAdaptations Can Be:

PhysicalSpeed, Camouflage, Claws, Quills, etc.

BehavioralSolitary, Herds, Packs, Activity, etc.

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Survival of the FittestFitness Is Central To The Process Of EvolutionIndividuals With Low Fitness

DieProduce Few Offspring

Survival of the FittestAKA Natural Selection

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Survival of the FittestKey Concept

Over Time, Natural Selection Results In Changes In The Inherited Characteristics Of A Population. These Changes Increase A Species Fitness In Its Environment

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Natural SelectionCannot Be Seen DirectlyIt Can Only Be Observed As Changes In A

Population Over Many Successive GenerationsRadiationFossil Record

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Descent With ModificationTakes Place Over Long Periods of TimeNatural Selection Can Be Observed As Changes

InBody StructuresEcological NichesHabitats

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Theory of Evolution Today

Supporting Evidence

Did humans evolve video clip

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Evolutionary Time Scales

Macroevolution: Long time scale events that

create and destroy species.

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Microevolution:Short time scale

events (generation-to-generation) that

change the genotypes and phenotypes of populations

Evolutionary Time Scales

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Evidence of EvolutionKey Concept

Darwin Argued That Living Things Have Been Evolving On Earth For Millions of Years. Evidence For This Process Could Be Found In:

The Fossil RecordThe Geographical Distribution of

Living SpeciesHomologous Structures of Living

Organisms

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Fossil RecordEarth is Billions of Years OldFossils In Different Layers of Rock

(sedimentary Rock Strata) Showed Evidence Of Gradual Change Over Time

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Geographic Distribution of Living Species

Different Animals On Different Continents But Similar Adaptations To Shared Environments

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Homologous Body StructuresScientists Noticed Animals With Backbones

(Vertebrates) Had Similar Bone StructureMay Differ In Form or FunctionLimb Bones Develop In Similar Patterns

Arms, Wings, Legs, Flippers

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Homologous Structures (BONES in the FORELIMBS) shows Similarities in mammals.

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Review

Why does evolution matter now video clip

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Darwin's Theory

1.Individual Organisms In Nature Differ From One Another. Some Of This Variation Is Inherited2.Organisms In Nature Produce More Offspring Than Can Survive, And Many Of These Offspring Do No Reproduce

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Darwin's Theory

3.Because More Organisms Are Produced Than Can Survive, Members Of Each Species Must Compete For Limited Resources4.Because Each Organism Is Unique, Each Has Different Advantages & Disadvantages In The Struggle For Existence

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Darwin's Theory

5.Individuals Best Suited To Their Environment Survive & Reproduce Successfully – Passing Their Traits To Their Offspring.6.Species Change Over Time. Over Long Periods, Natural Selection Causes Changes That May Eventually Lead To New Species

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Darwin's Theory

7.Species Alive Today Have Descended With Modifications From Species That Lived In The Past8.All Organisms On Earth Are United Into A Single Tree Of Life By Common Descent