Evidence of Evolution Chapter 17
Overview Current species are descendents of ancestral species Evolution is both a pattern and a process
Origin of Species Views of Aristotle Fixed species Old Testament Others All species created by God Linnaeus Species adapted to their environment because they were originally designed that way
Biogeography Late 1800 s Alfred Wallace Study patterns in the observation of species
Comparative Morphology Body plans and structures among groups of organisms are studied some outwardly are similar, but internally different others differ outwardly, but internally similar some have vestigial features with no apparent function
Geology Fossils are found in strata
A Flurry of New Theories By the 1800s, many scholars realized that life on Earth had changed over time, and began to think about what could have caused the changes
Lamarck s Hypothesis of Evolution Organisms adapted to their environment by acquiring traits Change in their lifetime Use it or lose it Acquired traits can be passed to the next generation
Descent with Modification by Natural Selection Explains the adaptations of organisms and the unity and diversity of life Doubts arising to unchanging species
Charles Darwin 1809-1882 British naturalist Proposed the idea of natural selection Collected clear evidence to support his ideas
Voyage of the HMS Beagle 1831-1836 (22 years old!!) Made many observations of nature Main mission of the Beagle was to chart the South American coastline Robert Fitzroy
Voyage of the HMS Beagle Stopped in the Galapagos Islands 500 miles off the coast of Ecuador
Galapagos Unique Species
Darwin Found Birds Thought he found many different types of species
But Darwin found a lot of All 14 species were finches!! But There was only 1 species of finch on the mainland finches
Darwin s Focus on Adaptation Darwin perceived adaptation to the environment and the origin of new species as closely related processes Tree Thinking Correlation of species to food source
Darwin s Finches Differences in beaks Associated with eating different foods Survival & reproduction of beneficial adaptations to foods available on the island
Rapid speciation: new species filling new niches, because they inherited successful adaptations. Seed eaters Flower eaters Insect eaters
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
Darwin s Finches Differences in beaks allowed some finches to: successfully compete successfully feed successfully reproduce pass successful traits onto their offspring
More Observations Correlation of species to food source Whoa, Turtles, too!
Many islands also show distinct local variations in tortoise morphology perhaps these are the first steps in the splitting of one species into several?
A Reluctant Revolutionary Returned to England in 1836 Wrote papers describing his collections & observations 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
And then came the letter In 1858, Darwin received a letter that changed everything 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.
The time was ripe for the idea! To Lyell Your words have come true with a vengeance I never saw a more striking coincidence so all my originality, whatever it may amount to, will be smashed.
November 24, 1859 it was published
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
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
Question!!! How does over-reproduction and heritable variation relate to evolution by natural selection?
Answer!! Organisms share characteristics (unity of life) because they share common ancestors. The great diversity of life occurs because new species have repeatedly formed when descendent organisms gradually adapt to different environments, becoming different from their ancestors.
The Fossil Record Provides evidence of: the extinction of species the origin of new groups changes in groups over time
Radiometric Dating Researchers use predictable radioisotope decay to estimate the age of rocks and fossils Reveals the age of a material by determining its radioisotope and daughter element content Radioisotope A form of an element with an unstable nucleus Decays into atoms of another element Example: uranium 238 lead 206 Half-life The time it takes for half of a radioisotope s atoms to decay into a daughter element
Homology Similarity resulting from common ancestry Homologous structures anatomical resemblances that represent variations on a structural theme present in a common ancestor
Comparative Embryology Reveals anatomical homologies not found in adult organisms
Question!!! The fossil record shows that dinosaurs originated 200-250 million years ago. Would you expect the geographic distribution of early dinosaur fossils to be broad (on many continents) or narrow (on one or a few continents)? Explain.
Answer!!! Broad! When dinosaurs originated, Earth s landmasses were in a single large continent (Pangaea). Dinos were large and mobile, so they probably lived on all different parts of Pangaea. When Pangaea broke apart, the fossils moved with the rocks in which they were deposited.