Introduction to Evolution

1. Introduction to Evolution PHA Biology 9 Moretti/ Dickson

2. 14.1- Darwin’s theory of evolution • As you read 14.1, keep these questions in mind: • What is EVOLUTION? • What are ADAPTATIONS? • What observations led Darwin to his theory of evolution? • What other scientists influenced Darwin’s thinking? • What are the two main ideas of Darwin’s theory?

3. Isn’t Evolution JUST a Theory? • THEORY= a well tested explanation that makes sense of a great variety of scientific observations. • Only become widely accepted when they are supported by lots of evidence (as opposed to our everyday use of theory… speculation, ‘Its only a theory’)

4. EVOLUTION • Genetic changes in a species or population over time

5. Micro-Evolution • Small-scale • Changes in a population’s gene pool over time • Caused by natural selection and/or genetic drift Example: CF allele becomes more common in European populations because it protects against tuberculosis Micro-evolution leads to Macro-evolution • Objectives for Class: • Use actual evidence to explain how the four principles of natural selection shape the evolution of organisms

6. What is EVOLUTION? • EVOLUTION= process of biological change • Descendants differ from their ancestors • Change in genetics of a species Species: group of organisms that can reproduce and have fertile offspring (hybrids-sterile) • ADAPTATION= inherited characteristic that improve an organisms ability to survive & reproduce in a certain environment

7. Who influenced Darwin? • Scientists had a large influence on Darwin • James Hutton • Charles Lyell • Jean Baptiste Lamarck

8. Layers of rock are built very slowly Geological forces shaped Earth’s features (mountains and valleys) Took MILLIONS of years Earth is OLD; NOT a few thousand years old 1. James Hutton

9. Stressed that processes that shaped Earth millions of years ago are the same processes that do so today 2. Charles Lyell

10. Did realize that organisms change over time Published his work the year Darwin was born (1809) 3. Jean-Baptiste Lamarck

11. Lamarck’s Ideas about Evolution A. Tendency Towards Perfection- giraffe has urge to be tall B. “use it or lose it!” – stretching neck C. Inheritance of Acquired Traits • EX: If the giraffe stretched its neck and it got longer, its babies would have longer necks

12. Earlier ideas on Evolution • LaMarck • evolution by acquired traits • creatures developed traits during their lifetime • give those traits to their offspring • example • in reaching higher leaves giraffes stretch their necks & give the acquired longer neck to offspring • not accepted as valid

13. Darwin’s view of Evolution • Darwin • giraffes that alreadyhave long necks survive better • leave more offspring who inherit their long necks • variation • selection & survival • reproduction & inheritance of more fit traits 

14. Who was Charles Darwin? Naturalist who took a 5 year journey around S. America • Map coastline • Studied geology, plants and animals • Collected samples, made observations

15. Voyage of the HMS Beagle • Stopped in Galapagos Islands • 500 miles off coast of Ecuador

16. Darwins Observations • Darwin observed organisms slightly different on each of the islands; but all were related to mainland organisms • DARWIN INFERRED… mainland species had changed after they colonized the islands & adapted to their new environment

17. 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?

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

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

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

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

23. Finch? Sparrow? Warbler? Woodpecker? The finches cinched it! • Different beaks are inherited variations • Beaks adaptations help birds compete for food • These birds survive & reproduce passing on genes w/ more fit beaks. • Over time nature selected for different species with different beaks 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. Large ground finch Big seed eater Small ground finch Small seed eater Warbler finch Insect eater Tree finch Leaf & bud eater

24. Relationship between species (beaks) & food

25. 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

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

27. After the Voyage of the Beagle • Darwin returns to England to analyze his data and observations • Published “The Origin of Species by means of Natural Selection” in 1959 • 2 Main Points • Descent with modification • Natural Selection Darwin Video 1 DARWIN VIDEO 2

28. 1. Descent with Modification • Species today came from ancestral organisms • Descendants spread out over different habitats and environments • Accumulated adaptations to these different environments • Explained diversity of life on earth • Ex. and

29. 2. Natural Selection –explains HOW species evolve/change over time. • “SURVIVAL OF THE FITTEST”-Some organisms have inherited traits that give them an advantage in survival & reproduction over others (of the same species & same envrionment)

30. Principles of Natural Selection: “Survival of the Fittest” • Genetic variation between individuals- (mutationsand gene shuffling) • Overproduction: More born than can survive • Competition/struggle for limited resources • Some individuals are more genetically “fit” than others – they are better at surviving, reproducing, and passing on their genes Result: Over many generations, the “fit” alleles become more common in the whole population because they are more helpful for surviving and reproducing. SUMMARY: SURVIVAL & REPRODUCTION OF THE FITTEST

31. Natural Selection

32. Inherited shell variations make some snails less likely than others to be attacked by predators. Wide, blunt shells increase the chances for snails to survive and pass their traits to the next generation by reproducing.

33. How Does Natural Selection Happen?Video: Hummingbirds in Ecuador • What are some adaptations that these hummingbirds have? • As we watch the video: make a list of Principles of Natural Selection http://www.youtube.com/watch?v=xkwRTIKXaxg • Objectives for Class: • Use actual evidence to explain how the four principles of natural selection shape the evolution of organisms

34. Hidden Benefits: Carrier for Cystic Fibrosis • Cystic FibrosisCarriers of CF do not have the breathing difficulties, they are immune to cholera. During the devastating cholera epidemics, individuals carrying mutant CF alleles had a selective advantage, and they transmitted those alleles to future generations. • Cholera epidemics- • In the summer of 1831, an epidemic killed 10 percent of the population of St. Louis, and in 1991, an epidemic swept Peru.

35. Examples of Natural Selection: Ex. 1: Long beaks become more common in a hummingbird population because long beaks help get food Ex. 2: Sickle cell anemia becomes more common in African populations because SCA protects against malaria Ex. 3: CF becomes more common in Europeans because it protects against tuberculosis and cholera. Ex. 4: Some TB bacteria have evolved to resist antibiotics

36. 14.1- Darwin’s theory of evolution You should be able to answer the following….. • What is EVOLUTION? • What are ADAPTATIONS? • What observations led Darwin to his theory of evolution? • What other scientists influenced Darwin’s thinking? • What are the two main ideas of Darwin’s theory?

37. Geographic Distribution of Organisms