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Transcript of End Show Slide 1 of 20 Copyright Pearson Prentice Hall The Puzzle of Life's Diversity.
Copyright Pearson Prentice Hall
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15-1 The Puzzle of Life's Diversity
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15-1 The Puzzle of Life's Diversity
Evolution - the process by which modern organisms have descended from ancient organisms.
15-1 The Puzzle of Life's Diversity
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Voyage of the Beagle
Voyage of the Beagle
In 1831, Darwin set sail from England aboard the H.M.S. Beagle for a voyage around the world.
Darwin went ashore and collected plant and animal specimens for his collection.
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Voyage of the Beagle
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Darwin's Observations
Darwin's Observations
Organisms were well suited to the environments they inhabited.
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Darwin's Observations
Living Organisms and Fossils
Darwin collected fossils.
Some of those fossils resembled organisms that were still alive.
Others looked completely unlike any creature he had ever seen.
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Darwin's Observations
The Galápagos Islands
Galápagos Islands were close together but had very different climates.
Organisms varied noticeably among the different islands
Darwin wondered if animals living on different islands had once been members of the same species.
These separate species would have evolved from an original South American ancestor species.
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Ideas That Shaped Darwin's Thinking
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An Ancient, Changing Earth
An Ancient, Changing Earth
Hutton and Lyell recognize that the Earth is many millions of years old.
The processes that changed Earth in the past are the same processes that operate in the present.
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An Ancient, Changing Earth
Darwin’s understanding of geology:
If the Earth could change over time, life might change as well.
This would have been possible only if the Earth were extremely old.
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Lamarck's Evolution Hypotheses
Lamarck's Evolution Hypotheses
By selective use or disuse of organs, organisms acquired or lost certain traits during their lifetime.
These traits could then be passed on to their offspring.
Over time, this process led to change in a species.
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Lamarck's Evolution Hypotheses
Lamarck's HypothesisA male fiddler crab uses its front claw to ward off predators and to attract mates.
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Lamarck's Evolution Hypotheses
Lamarck's HypothesisBecause the front claw is used repeatedly, it becomes larger.
This characteristic (large claw) is passed onto its offspring.
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Lamarck's Evolution Hypotheses
Lamarck’s hypotheses of evolution are incorrect in several ways.
Lamarck did not know:
• how traits are inherited.
• that an organism’s behavior has no effect on its heritable characteristics.
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Population Growth
Population Growth
In 1798, Thomas Malthus noted that babies were being born faster than people were dying.
The only forces that worked against this growth were war, famine, and disease.
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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 and food for everyone.
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Population Growth
When Darwin read Malthus’s work, he realized that this reasoning applied to plants and animals.
If all the offspring of almost any species survived for several generations, they would overrun the world.
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Darwin Presents His Case
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Inherited Variation and Artificial Selection
Inherited Variation and Artificial Selection
Members of each species vary from one another
Darwin noted that plant and animal breeders would breed only the best organisms.
Darwin termed this process artificial selection.
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Inherited Variation and Artificial Selection
Brussels Sprouts
Kohlrabi
Ancestral Species
Kale
Broccoli
Cauliflower
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Evolution by Natural Selection
Evolution by Natural Selection
Darwin compared processes in nature to artificial selection.
He developed a hypothesis called Natural Selection to explain how evolution occurs.
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Evolution by Natural Selection
The Struggle for Existence
High birth rates vs shortages of basic needs would force organisms to compete for food, shelter, etc…
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Evolution by Natural Selection
Survival of the Fittest
The ability of an individual to survive and reproduce in its environment is fitness.
An adaptation is any inherited characteristic that increases an organism's chance of survival.
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Evolution by Natural Selection
Individuals with characteristics that are not well suited to their environment either die or leave few offspring.
Individuals that are better suited to their environment survive and reproduce most successfully.
Darwin called this survival of the fittest.
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Evolution by Natural Selection
Over time, natural selection results in changes in the characteristics of a population.
These changes increase a species' fitness in its environment.
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Evidence of Evolution
Evidence of Evolution
Darwin argued that living things have been evolving on Earth for millions of years.
Evidence includes:
●fossil record
●homologous structures
●similarities in embryology
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Evidence of Evolution
Similar, But Unrelated Species
and and
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Evidence of Evolution
Homologous Structures
Turtle Alligator Bird Mammal
Ancient, lobe-finned fish
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Evidence of Evolution
Similarities in Embryology
The embryos of many animals with backbones are very similar.
The same groups of embryonic cells develop in the same order to produce the tissues of all vertebrates.
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Summary of Darwin's Theory
Summary of Darwin's Theory
Individual organisms differ.
Organisms produce more offspring than can survive.
Organisms compete for limited resources.
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Summary of Darwin's Theory
Individuals best suited to their environment survive and reproduce.
These organisms pass their heritable traits to their offspring.
This process of natural selection causes species to change over time.