rEvolutionary Thinkers

TINTORETTO The Creation of the Animals 1550 DOCTRINE

Evolution: History  Western View Around 1759  No change in organisms  Inhabitants were divinely created  Species did not change over time

But The Fossil record… OBSERVATION

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

Cuvier

 First to to document extinction  Violent and sudden catastrophes  Explains why the fossil record shows abrupt changes in species living in the area  Plants and animals were created for their role in the environment, and were unchanged

LaMarck

 Believed organisms evolve gradually and progressively into more complex forms through striving for perfection  Believed the ultimate goal of perfection was the human  Traits were acquired through use and disuse  Traits were passed on to offspring

Lyell

 Wrote a book called Principles of Geology  Darwin read the book while aboard the HMS Beagle  Showed evidence that the forces of geological change that have been shaping Earth for millennia is observable today  Suggested the Earth had been around for a long time

Malthus

 Population growth theory  Population was growing exponentially  (i.e. 2, 4, 8, 16, 32, 64, 128, etc.)  Whereas the food supply grows at an steady rate  (i.e. 1, 2, 3, 4, 5, 6, 7, 8, etc.)  This difference in growth influenced both Darwin and Wallace

Charles Darwin

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

Voyage of the HMS Beagle

 Darwin was invited to travel around the world on the HMS Beagle  (22 years old!)  makes many observations of nature  HMS Beagle stopped at the Galapagos Islands

Galapagos Islands Most of the animal species on the Galápagos live nowhere else in world, but they resemble species living on South American mainland. 500 miles west of mainland

Armadillos are native to the Americas, with most species found in South America. Glyptodont fossils are also unique to South America. Succession of Types Why should extinct armadillo-like species & living armadillos be found on the same continent?

Unique Species

Darwin found… birds Finch?Sparrow? Woodpecker? Warbler? Collected many different birds on the Galapagos Islands. Thought he found very different kinds…

Darwin was amazed to find out: All 14 species of birds were finches… Finch?Sparrow? Woodpecker? Warbler? But Darwin found… a lot of finches Large Ground Finch Small Ground Finch Warbler FinchVeg. Tree Finch But there is only one species of finch on the mainland! How did one species of finches become so many different species now?

Correlation of species to food source Adaptive radiation Seed eaters Flower eaters Insect eaters Rapid speciation: new species filling new niches, because they inherited successful adaptations.

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

Darwin’s Finches  Darwin’s Conclusions  Small populations landed on islands  Variation enabled individuals differential success  Over many generations, populations changed  Accumulation of advantageous traits  Emergence of different species

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 with all of the information he gathered  Wrote a draft in 1844  Left instructions to publish upon death as he was reluctant to publish with regards towards beliefs at the time

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…

The time was ripe for the idea! 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. To Lyell—

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

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  Those with better suited traits survive and produce more offspring  differential reproduction  adaptations become more common in population  Variation is heritable