Darwin & Evolution by Natural Selection

Transcription

1 Darwin & Evolution by Natural Selection Warbler Cactus eater Insect eaters Seed eaters Bud eater

2 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 u British naturalist

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

4 Voyage of the HMS Beagle Stopped in Galapagos Islands u 500 miles off coast of Ecuador

5 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 Ecuador

6 Darwin found many unique species Many of Darwin s observations made him wonder Why? Darwin asked: Why were these creatures found only on the Galapagos Islands?

7 Darwin found clues in the fossils Darwin found: Evidence that creatures have changed over time present day Armadillos ancient Armadillo Darwin asked: Why should extinct armadillos & modern armadillos be found on same continent?

8 Darwin found: Different shells on tortoises on different islands Darwin asked: Is there a relationship between the environment & what an animal looks like?

9 Darwin found birds Darwin found: Many different birds on the Galapagos Islands. He thought he found very different kinds Finch? Sparrow? Woodpecker? Warbler?

10 But Darwin found a lot of es Darwin was amazed to find out: All 14 species of birds were es But there is only one species of on the mainland! Large Finch? ground Darwin asked: Small Sparrow? ground If the Galapagos es came from the mainland, why are they so different now? Woodpecker? Warbler Tree Warbler?

11 The es cinched it! Darwin found: The differences between species of es were associated with the different food they ate. n different beaks are inherited variations n serve as adaptations that help Darwin birds said: compete for food Ahaaaa! n these birds survive & Big Large seed Finch? ground A eater flock of South reproduce American es n pass on the genes for were stranded on the those more fit beaks Galapagos n over time nature selected for different species with different beaks Small Sparrow? seed ground eater Woodpecker? Warbler Insect eater Leaf Tree Warbler? & bud eater

12 Relationship between species (beaks) & food

13 Darwin s es 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 es were selected for specific beaks & behaviors u offspring inherit successful traits accumulation of winning traits: both beaks & behaviors u separate into different species

14 From 1 species to 14 species Warbler Cactus Woodpecker Sharp-beaked Small insectivorous tree Large insectivorous tree Vegetarian tree Insect eaters Bud eater Warbler Cactus eater Seed eaters Small ground Medium ground Large ground variation natural selection for best survival & reproduction

15 Earlier ideas on Evolution 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

16 Darwin s view of Evolution Darwin u giraffes that already have long necks ü survive better u leave more offspring who inherit their long necks variation selection & survival reproduction & inheritance of more fit traits