Natural Selection Definition Evolution is the slow gradual
- Slides: 47
Natural Selection
Definition • Evolution is the slow , gradual change in a population of organisms over time copyright cmassengale 2
Evolutionary Timeline copyright cmassengale 3
Early Ideas On Earth’s Organisms • Linnaeus – 1 st to group similar organisms and assign them Latin names • Two word name (Genus species) • Known as Binomial nomenclature copyright cmassengale 4
Catastrophism • Idea proposed by George Cuvier • Studied fossil in sedimentary rock strata of Paris • Found some species completely disappeared in more recent layers • Stated that species disappear due to a catastrophic event of the earth’s crust (volcano, earthquake…) copyright cmassengale 5
Hutton’s Theory of Geological Change • James Hutton, 1795, Scottish geologist • Studied invertebrate fossils in Paris Museum • Described The Geological Forces That Have Changed Life on Earth Over Millions of Years (erosion, earthquakes, volcanoes…) copyright cmassengale 6
Charles Lyell • Proposed theory of Uniformintarianism • Geological processes at uniform rates building & wearing down Earth’s crust • Proposed that the Earth was millions of years instead of a few thousand years old • Published the Principles of Geology copyright cmassengale 7
Principles of Geology • Darwin read this before the Beagle set sail • Explained Geological Processes That Shaped The Earth • Helped Darwin Understand Sea Shells In The Andes Mountains At 12, 000+ Feet o Expanded Earth’s Age copyright cmassengale 8
Lamarck’s Theory of Evolution • Jean-Baptiste Lamarck, 1809 • One Of First Scientists To Understand That Change Occurs Over Time • Stated that Changes Are Adaptations To Environment acquired in an organism’s lifetime • Said acquired changes were passed to offspring copyright cmassengale 9
Lamarck’s Mistakes • Lamarck did NOT know how traits were inherited (Traits are passed through genes) • Genes Are NOT Changed By Activities In Life • Change Through Mutation Occurs Before An Organism Is Born copyright cmassengale 10
Charles Darwin the Naturalist copyright cmassengale 11
Voyage of the Beagle Charles Darwin • Born Feb. 12, 1809 • Joined Crew of HMS Beagle, 1831 • Naturalist • 5 Year Voyage around world • Avid Collector of Flora & Fauna • Astounded By Variety of Life copyright cmassengale 12
Darwin Left England in 1831 Darwin returned 5 years later in 1836 copyright cmassengale 13
The Galapagos Islands • Volcanic islands off the coast of South America • Island species varied from mainland species & from island-toisland species • Each island had long or short neck tortoises copyright cmassengale 14
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* Beak shapes and sizes were based on their food source. copyright cmassengale 16
Darwin’s Observations • Patterns of Diversity • Unique Adaptations by organisms • Species Not Evenly Distributed • Australia, Kangaroos, but No Rabbits • S. America, Llamas copyright cmassengale 17
Darwin’s Observations n. Both Living Organisms & Fossils collected n. Fossils included: • Trilobites • Giant Ground Sloth of South America This species NO longer existed. What had happened to them? copyright cmassengale 18
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 copyright cmassengale 19
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. copyright cmassengale 20
• 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 copyright cmassengale 21
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 copyright cmassengale 22
Darwin’s Theory of Evolution • The unequal ability of individuals to survive and reproduce leads to a gradual change in a population, with favorable characteristics accumulating over generations (natural selection) • copyright Newcmassengale species evolve 23
Thomas Malthus Ideas That Shaped Darwin’s Thinking 24 copyr ight cmas senga
Population Growth • Thomas Malthus, 1798 • Economist • Observed Babies Being Born Faster Than People Were Dying • Population size limited by resources such as the Food Supply copyright cmassengale 25
Population Growth • Malthus Reasoned That If The Human Population Continued To Grow Unchecked, Sooner or Later There Would Be Insufficient Living Space & Food For Everyone • Death Rate Will Increase To Balance Population size & Food Supply copyright cmassengale 26
• Population Growth Darwin Realized Malthus’s Principles Were Visible In Nature • Plants & Animals Produce Far More Offspring Than Can Be Supported o Most Die o If They Didn’t – Earth Would Be Overrun copyright cmassengale 27
Organisms Change Over Time Darwin’s Theory of Evolution 28 copyr ight cmas senga
Common Descent with Modification • Darwin proposed that organisms descended from common ancestors • Idea that organisms change with time, diverging from a common form • Caused evolution of new species copyright cmassengale 29
Natural Selection • Driving force for evolution • During the struggle for resources, strongest survive & reproduce • Idea that at least some of the differences between individuals, which impact their survival and fertility, are inheritable. copyright cmassengale 30
Publication of “On The Origin of Species” • Darwin Knew That His Theory Would Be Extremely Controversial And Would Be Attacked • His Theory Challenged Established Religious & Scientific Beliefs, Particularly About The Creation Of Man copyright cmassengale 31
Publication of “On The Origin of Species” • He Refused To Publish Until He Received An Essay From Alfred Wallace o Fellow Naturalist o Independently Developed The Same Theory o After 25 Years, Someone Else Had Come To The Same Conclusions From Their Observations Of Nature copyright cmassengale 32
Wallace’s Contribution • Alfred Russel Wallace Independently came to same Conclusion as Darwin that species changed over time because of their struggle for existence • When Darwin read Wallace’s essay, he knew he had to publish his findings copyright cmassengale 33
Natural Variation and Artificial Selection • Abandoned The Idea That Species Were Perfect & Unchanging • Observed Significant Variation in All Species • Observed Farmers Use Variation To Improve Crops & Livestock • Called Selective Breeding copyright cmassengale 34
Natural Variation and Artificial Selection • Natural Variation o Differences Among Individuals Of A Species • Artificial Selection o Selective Breeding To Enhance Desired Traits Among Stock or Crops copyright cmassengale 35
Natural Variation and Artificial Selection Key Concept: In Artificial Selection, Nature Provided The Variation Among Different Organisms, And Humans Selected Those Variations That They Found Useful copyright cmassengale 36
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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) copyright cmassengale 38
• Survival of the Fittest Fitness o • Ability of an Individual To Survive & Reproduce Adaptation o Inherited Characteristic That Increases an Organisms Chance for Survival • Adaptations Can Be: o Physical • Speed, Camouflage, Claws, Quills, etc. o Behavioral • Solitary, Herds, Packs, Activity, etc. copyright cmassengale 39
Survival of the Fittest Key Concept Over Time, Natural Selection Results In Changes In The Inherited Characteristics Of A Population. These Changes Increase A Species Fitness In Its Environment copyright cmassengale 40
Natural Selection • Cannot Be Seen Directly • It Can Only Be Observed As Changes In A Population Over Many Successive Generations o Radiation o Fossil Record copyright cmassengale 41
Descent With Modification • Takes Place Over Long Periods of Time • Natural Selection Can Be Observed As Changes In o Body Structures o Ecological Niches o Habitats copyright cmassengale 42
Descent With Modification • Species Today Look Different From Their Ancestors • Each living species has descended with changes from other species over time copyright cmassengale 43
Evidence of Evolution Key Concept Darwin Argued That Living Things Have Been Evolving On Earth For Millions of Years. Evidence For This Process Could Be Found In: o The Fossil Record o The Geographical Distribution of Living Species o Homologous Structures of Living Organisms o Similarities In Early Development copyright cmassengale 44
Chicken Turtle Rat copyright cmassengale 45
Homologous Body Structures • Not All Serve Important Functions o Vestigial Organs • Appendix In Man • Legs On Skinks copyright cmassengale 46
Evolution of pesticide resistance in response to selection copyright cmassengale 47
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