AP Biology Evolution by Natural Selection

AP Biology Life’s Natural History is a record of Successions & Extinctions Quaternary Tertiary Cretaceous Jurassic Triassic Permian Carboniferous Devonian Silurian Ordovician Cambrian Ediacaran Precambrian, Proterozoic, & Archarozoic Anaerobic Bacteria Insects Reptiles Dinosaurs Mammals Birds Land Plants Seed Plants Plants Arthropods Chordates Jawless Fish Teleost Fish Amphibians Photosynthetic Bacteria Green Algae Multicellular Animals Molluscs Flowering mya

Where did Darwin and Wallace get the idea of evolution?

Jean Baptiste Lamarck ( ) Lamarck claimed that evolution was driven by "use vs. disuse" A used structure will become larger, stronger and more important. A disused structure will atrophy and become VESTIGIAL. Evolution occurs because organisms have an innate drive to become more complex

Theory of “Use vs. Disuse” The long necks of giraffes were due to their stretching for food, and giraffes passed their stretched necks on to their offspring. Similarly, the big, “ripped” muscles developed by the village blacksmith with all his hammering and slinging of heavy metal objects would be expected to be passed on to his offspring.

Theory of “Acquired Characteristics” Lamarck claimed that traits acquired during an organism's lifetime could be inherited by that organism's offspring.

Georges Cuvier ( ) Created Paleontology (The study of fossils) He noted that deeper layers of sedimentary rock had diversity of organisms far different from present day life found in more recent layers Proposed the idea of extinction based on fossils

James Hutton ( ) A Scottish geologist who challenged Cuvier's view in 1795 with his idea of GRADUALISM Proposed that large changes in the earth's surface could be caused by slow, constant processes e.g. erosion by a river

Charles Lyell ( ) Earth processes had been going on constantly, and could explain the appearance of the earth. This theory, uniformitarianism, was a strong basis for Darwin's later theory of natural selection.

Thomas Malthus ( ) Suggested that much of humanity's suffering (disease, famine, homelessness and war) was the inevitable result of overpopulation: humans reproduced more quickly than their food supply could support them. Malthus showed that populations, if allowed to grow unchecked, increase at a geometric rate.

AP Biology Charles Darwin   British naturalist  Proposed the idea of evolution by natural selection  Collected clear evidence to support his ideas

AP Biology Robert Fitzroy Voyage of the HMS Beagle  Invited to travel around the world  (22 years old!)  makes many observations of nature  main mission of the Beagle was to chart South American coastline

AP Biology Voyage of the HMS Beagle  Stopped in Galapagos Islands  500 miles off coast of Ecuador

AP Biology Unique species

AP Biology Correlation of species to food source Adaptive radiation Seed eaters Flower eaters Insect eaters

AP Biology Warbler finch Woodpecker finch Small insectivorous tree finch Large insectivorous tree finch Vegetarian tree finch Cactus finch Sharp-beaked finch Small ground finch Medium ground finch Large ground finch Insect eaters Bud eater Seed eaters Cactus eater Warbler finch Tree finches Ground finches Darwin’s finches  Differences in beaks  associated with eating different foods  survival & reproduction of beneficial adaptations to foods available on islands

AP Biology Darwin’s finches  Darwin’s conclusions  small populations of original South American finches landed on islands  variation in beaks enabled individuals to gather food successfully in the different environments  over many generations, the populations of finches changed anatomically & behaviorally  accumulation of advantageous traits in population  emergence of different species

AP Biology  Differences in beaks allowed some finches to…  successfully compete  successfully feed  successfully reproduce  pass successful traits onto their offspring Darwin’s finches

AP Biology Correlation of species to food source More observations…

AP Biology Many islands also show distinct local variations in tortoise morphology…

AP Biology This is not just a process of the past… It is all around us today Artificial selection

AP Biology Selective breeding the raw genetic material (variation) is hidden there

AP Biology Selective breeding Hidden variation can be exposed through selection!

AP Biology In historical context  Other people’s ideas paved the path for Darwin’s thinking

AP Biology A Reluctant Revolutionary  Returned to England in 1836  wrote papers describing his collections & observations  long treatise on barnacles  draft of his theory of species formation in 1844  instructed his wife to publish this essay upon his death  reluctant to publish but didn’t want ideas to die with him

AP Biology And then came the letter…. Alfred Russel Wallace a young naturalist working in the East Indies, had written a short paper with a new idea. He asked Darwin to evaluate his ideas and pass it along for publication. Then, in 1858, Darwin received a letter that changed everything…

AP Biology The time was ripe for the idea!

AP Biology Voyage: November 24, 1859, Darwin published “On the Origin of Species by Means of Natural Selection”

AP Biology Essence of Darwin’s ideas  Natural selection  variation exists in populations  over-production of offspring  more offspring than the environment can support  competition  for food, mates, nesting sites, escape predators  differential survival  successful traits = adaptations  differential reproduction  adaptations become more common in population

AP Biology LaMarckian vs. Darwinian view  LaMarck  in reaching higher vegetation giraffes stretch their necks & transmits the acquired longer neck to offspring  Darwin  giraffes born with longer necks survive better & leave more offspring who inherit their long necks

AP Biology (5) Over long periods of time, and given a steady input of new variation into a population, these processes lead to the emergence of new species Essence of Darwin’s ideas (1)Variation exists in natural populations (2) Many more offspring are born each season than can possibly survive to maturity (3) As a result, there is a struggle for existence - competition - competition (4) Characteristics beneficial in the struggle for existence will tend to become more common in the population, changing the average characteristics of the population - adaptations - adaptations