2. Chapter 15 EvolutionEvolution What You’ll Learn You will analyze the theory of evolution. You will compare and contrast the processes of evolution.

3. Section Objectives: Summarize Darwin’s theory of natural selection. Explain the 4 principles of natural selection Show how natural selection could change a populati on Darwin’s Theory of Natural Selection

4. What is Evolution? Evolution ~process of change through time – explains how modern organisms have descended from ancient organisms Evolution! Why do we accept this as a Scientific Principle?

5. Evolution: process of change through time The change in characteristics of populations through generations. Thus, existing life forms have evolved from earlier life forms A unifying principle for biology. Provides an explanation for the difference in structure, function, and behavior among organisms

6. What do we know? There are many different creatures on Earth How do we know this? Diversity of Life on Earth OBSERVATION How did all these creatures come about? What accounts for all this biological diversity? Biodiversity of Life on Earth

7. What do we know? All creatures have common characteristics How do we know this? DNA cells Unity of Life on Earth How could all of life have the same basic features? OBSERVATION

8. What do we know? Creatures have changed over time How do we know this? Fossil Record OBSERVATION

9. DNA Evolution explains Unity & Diversity Only evolution explains both – unity of life similarities between all living things – diversity of life wide variety of different creatures on Earth

10. 2006-2007 Insect eaters Bud eater Seed eaters Cactus eater Warbler finch Tree finches Ground finches Darwin & Evolution by Natural Selection

11. Charles Darwin Proposed a way how evolution works – How did creatures change over time? – by natural selection Collected a lot of evidence to support his ideas – 1809-1882 – British naturalist

12. Robert Fitzroy Voyage of the HMS Beagle Invited to travel around the world – 1831-1836 (22 years old!) – makes many observations of nature main mission of the Beagle was to chart South American coastline

13. Voyage of the HMS Beagle Stopped in Galapagos Islands – 500 miles off coast of Ecuador

14. 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

15. 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 species

16. present day Armadillos Darwin found: that creatures have changed over time 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 fossils

17. 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…

18. Darwin was amazed to find out: All 14 species of birds were finches… Finch?Sparrow? Woodpecker? Warbler? Finch?Sparrow? Woodpecker? Warbler? But Darwin found… a lot of finches Large ground finch Small ground finch Warbler finchTree 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?

19. Finch?Sparrow? Woodpecker? Warbler? The finches cinched it! Large ground finch Small ground finch Warbler finchTree finch Big seed eaterSmall seed eater Insect eaterLeaf & 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. different beaks are inherited variations serve as adaptations that help birds compete for food these birds survive & reproduce pass on the genes for those more fit beaks over time nature selected for different species with different beaks

20. Relationship between species (beaks) & food

21. DARWIN’S THEORY AND THE MODERN SYNTHESIS Darwin also saw that humans choose organisms with specific characteristics Breeding organisms with specific traits in order to produce offspring with identical traits is called artificial selection. Darwin hypothesized that there was a force in nature that worked like artificial selection.

22. Darwin proposed natural selection as the mechanism of evolution Darwin hypothesized that there was a force in nature that worked like artificial selection. Darwin saw natural selection as the basic mechanism of evolution Darwin concluded that individuals best suited for a particular environment are more likely to survive and reproduce than those less well adapted – As a result, the proportion of individuals with favorable characteristics increases – Populations gradually change in response to the environment Organisms without these variations are less likely to survive and reproduce.

23. Darwin’s finches Darwin’s conclusions – variations in beaks differences in beaks in the original flock adaptations to foods available on islands – natural selection for most fit over many generations, the finches were selected for specific beaks & behaviors – offspring inherit successful traits accumulation of winning traits: both beaks & behaviors – separate into different species

24. 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 variation natural selection for best survival & reproduction From 1 species to 14 species…

25. What do we know? Populations are a mix of different individuals How do we know this? OBSERVATION Variation

26. How does that work? Variation Over-Production & Competition Natural Selection Nature selects the ones that “fit” the environment better … survive & reproduce Adaptation

27. What determines survival? Natural Selection – traits that help individuals survive survive predators survive disease compete for food compete for territory – traits that help individuals reproduce attracting a mate compete for nesting sites successfully raise young Survival & Reproduction of the Fittest Adaptations

28. Survival & Reproduction of the fittest not the strongest… not the bravest… not the fastest… not the biggest… …the fittest! the traits that help an organism fit the environment better to survive & reproduce the traits that help an organism fit the environment better to survive & reproduce Adaptations

29. Survival & reproduction of the fittest bug…