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The Evolution of Evolution Historic Ideas about Organism Change

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1 The Evolution of Evolution Historic Ideas about Organism Change

2 Aristotle (384 - 322 B.C.) “Ladder of life”
Nature is ordered from lower to higher No vacant rungs No movement up or down the ladder Included living and non-living things

3 Jean-Baptiste Lamarck (1744-1829)
First scientist to propose a mechanism for how organisms change (1809) His idea: “Inheritance of Acquired Traits” Greater use of a body part would change it, and the change would pass on to the organism’s offspring.

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5 Lamarck’s Assumptions
Organisms have a desire to change. They have an inborn urge to better themselves for their environment. Ex: Birds tried to fly and eventually grew wings because of their efforts.

6 Lamarck’s Assumptions
2. Organisms can change shape by using or not using their bodies. Ex: The wings of a bird that does not fly would get smaller from generation to generation and the wings would eventually disappear.

7 Lamarck’s Assumptions
3. Organisms can pass on acquired traits to their offspring. Ex: If an animal developed muscles from lifting weights during its lifetime, it could pass those muscles on to its offspring.

8 Charles Darwin (1809-1882) English naturalist
Traveled around the world on the Beagle (1831); famously stopped in the Galapagos Islands Observed many species and fossils Particularly studied finches, tortoises, blue-footed boobies

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10 The Galapagos Islands (Ecuador)

11 “Darwin’s finches” Darwin noticed that finches were different on each Galapagos Island. He concluded that the different finches had descended from a common ancestor and had changed to be able to do and eat different things.

12 Examples of Natural Selection
B. Darwin’s Finches: Darwin noticed that different species of finches on different Galapagos Islands had differently shaped beaks. There were also different types of seeds found on each island. WHY DO THE DIFFERENT SPECIES HAVE DIFFERENT BEAK SHAPES?

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15 Examples of Natural Selection
A. Peppered Moths: (Discuss with a neighbor) – There are two forms of peppered moth, light and dark. Before the Industrial Revolution, light moths survived and reproduced more effectively. After the Industrial Revolution, dark moths survived and reproduced more effectively. WHY WAS THIS THE CASE?

16 2 Forms of Moth: Light and Dark Before Industrialization
After Industrialization Before Industrialization

17 Darwin’s “Descent with Modification” After his studies, Darwin came up with 4 main ideas…
Individuals differ, and some of this variation can be inherited. Organisms produce more offspring than can survive; thus they have to compete for resources, and only the most fit will survive and reproduce. The most fit organisms pass on their heritable traits to their offspring. Species alive today are descended with modification (change) from their ancestors.

18 “Descent with modification” definitions
“Descent with modification” means… …change in organisms over time (many generations) “Natural Selection” means… … “pressure” the environment puts on the specific traits that affects their ability to survive Hey! I thought this unit was about evolution?? “Evolution” means… … change over time Therefore we now call Darwin’s idea “biological evolution.”

19 Lamarck’s explanation for the giraffe’s long neck:

20 Darwin’s explanation for the giraffe’s long neck:

21 Darwin was influenced by the work of others…
Thomas Malthus – Populations James Hutton and Charles Lyell – Geological Record Farmers – Breeding

22 Thomas Malthus (1766-1834) British clergyman and scholar
His prediction: the human population would grow faster than the space and food supplies needed to sustain it. The only checks on the human population would be war, famine, and disease.

23 Influence of Malthus on Darwin
Malthus’ theory of population growth was observed by Darwin in other animal populations as well. In nature, Darwin saw many organisms that produced many offspring. Most died. Darwin wondered, what determines which individuals survive and reproduce?

24 James Hutton, Charles Lyell & Georges Cuvier British Geologists
Hutton is considered the “father of modern geology” Based on layers found in rock structures, Lyell proposed that Earth is millions of years old Lyell proposed that geological features could be built up or torn down over long periods of time = uniformitarianism Cuvier Summarized that layers were different due to catastrophes = catastrophism Grand Canyon, Arizona

25 Influence of Geology on Darwin
After reading Lyell’s book, Darwin was convinced that Earth was old. Darwin reasoned that if geological phenomena could change the earth, then life on Earth could change as well.

26 Farmers Farmers recognize that within a population, there is natural variation. Farmers improve their plants and animals through selective breeding.

27 Influence of Farmers on Darwin
Farmers bred the plants or animals with the most desired traits. This process of humans allowing only the best organisms to reproduce is called artificial selection.

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29 Adaptation vs. Acclimatization
Adaptation – Change in a population over time. Example – whales loosing walking limbs Acclimatization – Change in an individual in its lifetime. Example: 40° in the Fall and 40° in the Spring

30 Everyday vs. Scientific Theories
Everyday – an opinion “My theory is that gas prices are going up because the gas stations are trying to make more money.” Scientific - An extensively tested, well supported explanation. “The theory of evolution states that over loooong periods of time, organisms change to fit their environment.”


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