DARWIN THEORY OF NATURAL SELECTION.

Regents Biology 2006-2007 Insect eaters Bud eater Seed eaters Cactus eater Darwin & Evolution by Natural Selection Regents Biology Charles Darwin § Proposed a way how evolution works u How did creatures change over time? u by natural selection § Collected a lot of evidence to support his ideas u 1809-1882 u British naturalistRegents Biology Robert Fitzroy Voyage of the HMS Beagle § Invited to travel around the world u 1831-1836 (22 years old!) u makes many observations of nature § main mission of the Beagle was to chart South American coastlineRegents Biology Voyage of the HMS Beagle § Stopped in Galapagos Islands u 500 miles off coast of EcuadorRegents Biology Galapagos Recently formed volcanic islands. Most of animals on the Galápagos live nowhere else in world, but they look like species living on South American mainland. 800 km west of EcuadorRegents Biology Many of Darwin’s observations made him wonder… Why? Darwin asked: Why were these creatures found only on the Galapagos Islands? Darwin found…many unique speciesRegents Biology present day Armadillos Darwin found: Evidence that creatures have changed over time ancient Armadillo Darwin asked: Why should extinct armadillos & modern armadillos be found on same continent? Darwin found…clues in the fossilsRegents Biology Darwin found: Different shells on tortoises on different islands Darwin asked: Is there a relationship between the environment & what an animal looks like? Regents Biology QuickTime™ and a Photo -JPEG decompressor are needed to see this picture. Finch? Sparrow? Woodpecker? Warbler? Darwin found… birds Finch? Sparrow? Woodpecker? Warbler? Darwin found: Many different birds on the Galapagos Islands. He thought he found very different kinds… Regents Biology Darwin was amazed to find out: All 14 species of birds were finches… QuickTime™ and a Photo -JPEG decompressor are needed to see this picture. Finch? Sparrow? Woodpecker? Warbler? Finch? Sparrow? Woodpecker? Warbler? But Darwin found… a lot of finches Large ground finch Small ground finch Warbler finch Tree finch But there is only one species of finch on the mainland! Darwin asked: If the Galapagos finches came from the mainland, why are they so different now? Regents Biology QuickTime™ and a Photo -JPEG decompressor are needed to see this picture. Finch? Sparrow? Woodpecker? Warbler? The finches cinched it! Large ground finch Small ground finch Warbler finch Tree finch Big seed eater Small seed eater Insect eater Leaf & bud eater Darwin said: Ahaaaa! A flock of South American finches were stranded on the Galapagos… Darwin found: The differences between species of finches were associated with the different food they ate. n different beaks are inherited variations n serve as adaptations that help birds compete for food n these birds survive & reproduce n pass on the genes for those more fit beaks n over time nature selected for different species with different beaksRegents Biology Relationship between species (beaks) & foodRegents Biology Darwin’s finches § Darwin’s conclusions u variations in beaks § differences in beaks in the original flock § adaptations to foods available on islands u natural selection for most fit § over many generations, the finches were selected for specific beaks & behaviors u offspring inherit successful traits § accumulation of winning traits: both beaks & behaviors u separate into different speciesRegents Biology Warbler finch Woodpecker finch Small insectivorous tree finch Large insectivorous tree finch Vegetarian tree finch Cactus finch Sharp-beaked finch Small ground finchMedium ground finch Large ground finch Insect eaters Bud eater Seed eaters Cactus eater variation natural selection for best survival & reproduction From 1 species to 14 species…Regents Biology § LaMarck u evolution by acquired traits § creatures developed traits during their lifetime § give those traits to their offspring u example § in reaching higher leaves giraffes stretch their necks & give the acquired longer neck to offspring u not accepted as valid Earlier ideas on EvolutionRegents Biology Darwin’s view of Evolution § Darwin u giraffes that already have long necks survive better u leave more offspring who inherit their long necks § variation § selection & survival § reproduction & inheritance of more fit traitsRegents Biology present day Sloth Darwin found… more fossils Darwin asked: Why should extinct sloths & modern sloths be found on the same continent? (extinct) Giant ground sloth Darwin found: Evidence that creatures have changed over time