1. What is Evolution?
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2. Evolution Photo credit: Art Wolfe Incorporated
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3. Voyage of the Beagle
In 1831, Darwin set sail from England aboard the H.M.S. Beagle for a voyage around the world.
Darwin made numerous observations and collected evidence that led him to propose a hypothesis about the way life changes over time.
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4. He was impressed by which organisms survived and produced offspring.
Darwin's Observations
He observed many plants and animals were well suited to the environments they inhabited.
He was impressed by which organisms survived and produced offspring.
Darwin was confused by species lived and did not live.
He had to rely on things that he’d learned from other scientists.
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5. An Ancient, Changing Earth
Before Darwin, there were scientists who shaped the way that scientists viewed a round world.
Hutton and Lyell
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6. Hutton and Lyell's Principles of Geology 1
Hutton and Lyell's Principles of Geology 1. Scientists must explain past events in terms of observed processes. 2. Processes that shaped the Earth millions of years ago still continue.
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7. Understanding geology influenced Darwin:
If the Earth could change over time, life might change too.
It would have taken years for life to change like Lyell suggested.
This is only possible if the Earth is extremely old.
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8. Lamarck's Evolution Hypotheses Jean-Baptiste Lamarck recognized that:
living things have changed over time.
all species were descended from other species.
organisms were adapted to their environments.
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9. Traits could then be passed on to their offspring.
Lamarck proposed:
selective use or disuse of organs: organisms gained or lost certain traits during their lifetime.
Traits could then be passed on to their offspring.
Over time, this process led to change in a species.
Flaws: Tendency toward perfection
Use and Disuse
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10. Lamarck’s Evolution
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11. Lamarck's Hypothesis
A male fiddler crab uses its front claw to ward off predators and to attract mates.
Lamarck proposed that the selective use or disuse of an organ led to a change in that organ that was then passed on to offspring. This proposed mechanism is shown here applied to fiddler crabs. (1) The male crab uses its small front claw to attract mates and ward off predators. (2) Because the front claw has been used repeatedly, it becomes larger.
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12. Because the front claw is used repeatedly, it becomes larger.
Lamarck's Hypothesis
Because the front claw is used repeatedly, it becomes larger.
This characteristic (large claw) is passed onto its offspring.
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13. Evaluating Lamarck's Hypotheses Lamarck did not know:
how traits are inherited.
that an organism’s behavior has no effect on its heritable characteristics.
His idea of evolution was wrong.
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14. 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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15. 15–2 Hutton and Lyell recognized that geological processes
of the past differ from those of the present.
indicate that Earth is many millions of years old.
operate quickly, often over thousands of years.
always involve violent events like volcanoes, earthquakes, and floods.
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16. 15–2
Which of the following scientists proposed the hypothesis of selective use and disuse?
Charles Darwin
Jean-Baptiste Lamarck
Thomas Malthus
Charles Lyell
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17. 15–2
The scientist that proposed that Earth is shaped by geological forces that took place over long periods of time is:
Malthus
Hutton
Darwin
Lamarck
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18. 16-2 Evolution as Genetic Change
Photo credit: ©MURRAY, PATTI/Animals Animals Enterprises
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19. Natural selection affects which individuals survive and reproduce and which do not.
Evolution: any change over time in the relative frequencies of alleles in a population.
Populations, not individual organisms, can evolve over time.
Natural selection on single-gene traits can lead to changes in allele frequencies and thus to evolution.
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20. Natural selection on single-gene traits can lead to changes in allele frequencies and thus to evolution. Organisms of one color, for example, may produce fewer offspring than organisms of other colors.
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21. directional selection stabilizing selection disruptive selection
Natural selection can affect the distributions of phenotypes in any of three ways:
directional selection
stabilizing selection
disruptive selection
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22. Directional Selection: when individuals at one end of the curve have higher fitness than individuals in the middle or at the other end.
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23. Stabilizing Selection: when individuals near the center of the curve have higher fitness than individuals at either end of the curve.
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24. Disruptive Selection: when individuals at the upper and lower ends of the curve have higher fitness than individuals near the middle.
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25. Genetic drift (random change in allele frequency) occurs when a small group of individuals colonizes a new habitat.
Individuals may carry alleles in different relative frequencies than did the larger population from which they came.
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26. Genetic Drift
In small populations, individuals that carry a particular allele may have more descendants than other individuals. Over time, a series of chance occurrences of this type can cause an allele to become more common in a population. This model demonstrates how two small groups from a large, diverse population could produce new populations that differ from the original group.
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27. Evolution Versus Genetic Equilibrium
The Hardy-Weinberg principle states that allele frequencies remain constant unless one or more factors cause the frequencies to change.
Genetic equilibrium: When allele frequencies remain constant.
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28. there must be random mating, the population must be very large,
Five conditions are required to maintain genetic equilibrium from generation to generation:
there must be random mating,
the population must be very large,
there can be no movement into or out of the population,
there can be no mutations, and
there can be no natural selection.
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29. 16-2
The situation in which allele frequencies remain constant in a population is known as
genetic drift.
the founder effect.
genetic equilibrium.
natural selection.
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30. 16-2
Which of the following conditions is required to maintain genetic equilibrium in a population?
movement in or out of the population
random mating
natural selection
small population
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31. Earth's Early History
Photo credit: Jackie Beckett/American Museum of Natural History
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32. Formation of Earth
Scientists infer that about four billion years ago, Earth cooled and solid rocks formed on its surface.
Millions of years later, volcanic activity shook Earth’s crust.
About 3.8 billion years ago, Earth’s surface cooled enough for water to remain a liquid, and oceans covered much of the surface.
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33. The First Organic Molecules
Could organic molecules have evolved under conditions on early Earth?
In the 1950s, Stanley Miller and Harold Urey tried to answer that question by simulating conditions on the early Earth in a laboratory setting.
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34. Miller and Urey’s Experiment
Mixture of gases simulating
atmosphere of early Earth
Spark simulating
lightning storms
Condensation
chamber
Water
vapor
Cold water cools chamber, causing droplets to form.
Miller and Urey produced amino acids, which are needed to make proteins, by passing sparks through a mixture of hydrogen, methane, ammonia, and water. This and other experiments suggested how simple compounds found on the early Earth could have combined to form the organic compounds needed for life.
Liquid containing amino acids and other organic
compounds
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35. Miller and Urey's experiments suggested mixtures of the organic compounds necessary for life could have come from simpler compounds.
Although their simulations were not accurate, experiments with current knowledge yielded similar results.
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36. The Puzzle of Life's Origin
Evidence suggests that 200–300 million years after Earth had liquid water, cells similar to modern bacteria were common.
Formation of Microspheres 
Microspheres are not cells, but they have selectively permeable membranes and can store and release energy.
Evolution of RNA and DNA 
Some RNA sequences help DNA replicate under the right conditions.
Some RNA molecules can grow and duplicate themselves suggesting RNA might have existed before DNA.
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37. The Puzzle of Life's Origin
Evolution of RNA and DNA 
How could DNA and RNA have evolved? Several hypotheses suggest:
Some RNA sequences can help DNA replicate under the right conditions.
Some RNA molecules can even grow and duplicate themselves suggesting RNA might have existed before DNA.
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38. Origin of Eukaryotic Cells
The Endosymbiotic Theory: proposes that eukaryotic cells arose from living communities formed by prokaryotic organisms.
About 2 billion years ago, prokaryotic cells began evolving internal cell membranes.
The result was the ancestor of all eukaryotic cells.
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39. Origin of Eukaryotic Cells
Endosymbiotic Theory
Ancient Prokaryotes
Chloroplast
Plants and plantlike protists
Aerobic
bacteria
Photosynthetic bacteria
Nuclear envelope
evolving
Mitochondrion
Primitive Photosynthetic
Eukaryote
The endosymbiotic theory proposes that eukaryotic cells arose from living communities formed by prokaryotic organisms. Ancient prokaryotes may have entered primitive eukaryotic cells and remained there as organelles.
Animals, fungi, and
non-plantlike protists
Ancient Anaerobic
Prokaryote
Primitive Aerobic
Eukaryote
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40. Origin of Eukaryotic Cells
Aerobic
bacteria
Ancient Prokaryotes
Nuclear envelope
evolving
The endosymbiotic theory proposes that eukaryotic cells arose from living communities formed by prokaryotic organisms. Ancient prokaryotes may have entered primitive eukaryotic cells and remained there as organelles.
Ancient Anaerobic Prokaryote
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41. Prokaryotes that use oxygen to generate energy- rich molecules of ATP evolved into mitochondria.
Mitochondrion
The endosymbiotic theory proposes that eukaryotic cells arose from living communities formed by prokaryotic organisms. Ancient prokaryotes may have entered primitive eukaryotic cells and remained there as organelles.
Primitive Aerobic Eukaryote
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42. Origin of Eukaryotic Cells
Prokaryotes that carried out photosynthesis evolved into chloroplasts.
Chloroplast
Photosynthetic bacteria
The endosymbiotic theory proposes that eukaryotic cells arose from living communities formed by prokaryotic organisms. Ancient prokaryotes may have entered primitive eukaryotic cells and remained there as organelles.
Primitive Photosynthetic Eukaryote
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43. Sexual Reproduction and Multicellularity
Most prokaryotes reproduce asexually. Asexual reproduction:
yields daughter cells that are exact copies of the parent cell.
restricts genetic variation to mutations in DNA.
Sexual reproduction shuffles genes in each generation. In sexual reproduction:
offspring never resemble parents exactly
there is an increased probability that favorable combinations will be produced
there is an increased chance of evolutionary change due to natural selection
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