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1 Charles Darwin The Naturalist

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2 Charles Darwin Born Feb. 12, 1809 Born Feb. 12, 1809 Joined Crew of HMS Beagle, 1831 Joined Crew of HMS Beagle, 1831 Naturalist Naturalist 5 year voyage around world 5 year voyage around world Avid collector of flora (plants) & fauna (animals) Avid collector of flora (plants) & fauna (animals) Astounded by variety of life Astounded by variety of life

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3 A reconstruction of the HMS Beagle sailing off. Darwins Voyage of Discovery

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4 Darwin Left England in 1831 Darwin returned 5 years later in 1836

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5 The Galapagos Islands Small chain of islands off the coast of Ecuador in South America Small chain of islands off the coast of Ecuador in South America Very different climates Very different climates Animals on the islands were unique Animals on the islands were unique Tortoises Iguanas Finches

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6 The Galapagos Islands Darwin noted that the species found on one island looked different from those on nearby islands Darwin noted that the species found on one island looked different from those on nearby islands Many of the islands species looked different than mainland species Many of the islands species looked different than mainland species

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8 The Galapagos Islands Finches on the islands resembled a mainland finch Finches on the islands resembled a mainland finch Different types of finches appeared on the islands where the available food was different (seeds, nuts, berries, insects, etc.) Different types of finches appeared on the islands where the available food was different (seeds, nuts, berries, insects, etc.) Finches had different types of beaks adapted to their type of food gathering Finches had different types of beaks adapted to their type of food gathering

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10 Darwins Observations & Conclusions The Struggle for Existence

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11 Voyage of the HMS 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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12 Darwins Observations Patterns of diversity were shown Patterns of diversity were shown Unique adaptations in organisms Unique adaptations in organisms Species not evenly distributed Species not evenly distributed Australia had kangaroos, but no rabbits S. America the only continent with Llamas

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13 Darwins Observations Both living organisms & fossils collected Both living organisms & fossils collected Fossils included: Fossils included: Trilobites Giant Ground Sloth of South America This species NO longer existed. What had happened to them?

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14 Evidence for Evolution The Fossil Record

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15 Evolution The slow, gradual change in a species over time

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16 Darwins 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 This is because environmental resources are limited

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17 Darwins 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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18 Darwins 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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19 Darwins 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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20 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)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) New species evolveNew species evolve Darwins Theory of Evolution

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21 Darwins Theory of Evolution Organisms Change Over Time

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22 Common Descent with Modification Darwin proposed that organisms descended from common ancestors Darwin proposed that organisms descended from common ancestors Idea that organisms change with time, diverging from a common form/ancestor Idea that organisms change with time, diverging from a common form/ancestor Caused evolution of new species Caused evolution of new species

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23 Natural Selection Driving force for evolution Driving force for evolution During the struggle for resources, only the strongest survive & reproduce During the struggle for resources, only the strongest survive & reproduce Characteristics which impact organisms survival and fertility are inheritable Characteristics which impact organisms survival and fertility are inheritable

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24 Origin of Species Darwin Presents His Case

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25 Publication of On The Origin of Species Upon his return to England, Darwin developed his observations into The Theory of Evolution Upon his return to England, Darwin developed his observations into The Theory of Evolution But he did not publish for 25 years!! But he did not publish for 25 years!!Why???

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26 Publication of On The Origin of Species Darwin knew that his theory would be extremely controversial and would be attacked 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 His theory challenged established religious & scientific beliefs, particularly about the creation of man

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27 Publication of On The Origin of Species He refused to publish until he received an essay from Alfred Wallace He refused to publish until he received an essay from Alfred Wallace Fellow Naturalist Independently developed the same theory of evolution, that species changed over time because of their struggle for existence When Darwin read Wallaces essay, he knew he had to publish his findings

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28 Natural Variation and Artificial Selection Natural Variation Natural Variation Differences among individuals of a species Artificial Selection Artificial Selection Selective breeding to enhance desired traits among stock or crops

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29 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

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30copyright cmassengale

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31 Origin of Species Concepts and Controversy

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32 Evolution By Natural Selection Concepts The Struggle for Existence: compete for food, mates, space, water, etc. The Struggle for Existence: compete for food, mates, space, water, etc. Survival of the Fittest: strongest are able to survive and reproduce Survival of the Fittest: strongest are able to survive and reproduce Descent with Modification: new species arise from common ancestor, replacing less fit species Descent with Modification: new species arise from common ancestor, replacing less fit species

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33 Survival of the Fittest Fitness Ability of an individual to survive & reproduce Adaptation Inherited characteristic that increases an organisms chance for survival

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34 Survival of the Fittest Adaptations can be: Physical Speed, Camouflage, Claws, Quills, etc. Behavioral Solitary, Herds, Packs, Activity, etc.

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35 Survival of the Fittest is central to the process of evolution Fitness is central to the process of evolution Individuals with low fitness Individuals with low fitness die produce few offspring Survival of the Fittest!! AKA AKA Natural Selection!!

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36 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.

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37 Natural Selection Cannot Be Seen Directly Cannot Be Seen Directly It Can Only Be Observed As Changes In A Population Over Many Successive Generations It Can Only Be Observed As Changes In A Population Over Many Successive Generations Radiation Fossil Record

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38 Descent With Modification Takes place over long periods of time Takes place over long periods of time Natural Selection can be observed as changes in: Natural Selection can be observed as changes in: Body Structures Ecological Niches Habitats Behaviors

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39 Descent With Modification Species today look different from their ancestors Species today look different from their ancestors Each living species has descended with changes from other species over time Each living species has descended with changes from other species over time

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40 Descent With Modification copyright cmassengale

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41 Descent With Modification Implies Implies All living organisms are related We all fit onto a single Tree of Life DNA, Body Structures, Energy Sources Common Descent All species, living & extinct, were derived from common ancestors

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42. Major Problem in Darwins Theory No mechanism to explain natural selection How could favorable variations be transmitted to later generations? With the rediscovery of Mendels work in the first half of the 20th century, the missing link in evolutionary theory was found

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43 Opposition to Evolution The upheaval surrounding evolution began with Darwins publication of On the Origin of Species By Means of Natural Selection The debate continues nearly 150 years later