1 Chapter 22~ Descent with Modification: A Darwinian View of Life

2 I. Early Biology Scientists knew that organisms had changed Fossil evidence Age of the Earth

3 Evolutionary history Linnaeus: taxonomy Hutton: gradualism Lamarck: evolution Malthus: populations Cuvier: paleontology 3 Lyell: uniformitarianism Darwin: evolution Mendel: inheritance Wallace: evolution

4 Lamarck Changes from simple to complex Organisms want to adapt or change Acquired characteristics were inherited (passed on)

5 Lamarck Later disproved

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8 II. Darwin At 21, took a job as a naturalist on the HMS Beagle Collected specimens, took notes of different organisms

9 His voyage:

10 II. Darwin Sailed to Galapagos Islands All new species, but similar to those found elsewhere

11 Finches most famous Had slightly different beaks from island to island Differed by their diet

12 Descent with Modification, I 5 observations: 1- Exponential fertility 2- But Stable population size 3- Limited resources 4- Individuals vary 5- Heritable variation

13 Descent with Modification, II 3 Inferences: 1- Struggle for existence 2- Non-random survival 3- Natural selection (differential success in reproduction)

14 Evolution Evolution: the change over time of the genetic composition of populations Natural selection: populations of organisms can change over the generations if individuals having certain heritable traits leave more offspring than others (differential reproductive success) Evolutionary adaptation: a prevalence of inherited characteristics that enhance organisms’ survival and reproduction 14 November 24, 1859

15 Natural Selection Over time variations become more frequent in population Results in population being different than ancestors

16 Evolution Evolution is the change in a population over time Natural Selection - Remember the Giraffe? How did it get the long neck?

17 Evidence of Change Biogeography Fossil Record Anatomy & Physiology Embryology Biochemistry

18 Evolution evidence: Biogeography Geographical distribution of species Examples: Islands vs. Mainland –Australia vs. Continents

19 Fossils Remains or traces of living organisms

20 Physiology Mimicry-An adaptation Enables one species to resemble another species. Ex.-harmless species looks like a harmful one, good tasting vs. bad tasting.

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22 Anatomy- Homologous Structures Common evolutionary origin. Similar in arrangement or arrangement and function. Example: forelimbs of a whale, a crocodile and a bird wing.

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24 Anatomy- Analogous Structures No common evolutionary origin, but similar in function. Wings of a bat and wings of a butterfly.

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26 Anatomy- Vestigial Structures No function now but was probably useful to an ancestor. Ex. A whale has leg bones, a snake has leg bones

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28 Embryology Earliest stage of growth and development Embryos of a fish, a chicken, a pig, a cow, a rabbit, and a human are almost identical. They all have gill slits and a tail.

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30 Biochemistry Comparisons of DNA and RNA Now monera (prokaryotes) is divided into two separate kingdoms based on their biochemistry.

31 Evolution evidence: Molecular Biology Similarities in DNA, proteins, genes, and gene products Common genetic code

32 Final words…... “Absence of evidence is not evidence of absence.”