1. Mechanisms of Evolution Concept 2 – Analyzing Descent with Modification: A Darwinian View of Life (Ch 22) Part 2: Evidence for Evolution

2. Try This! If a NEW trait is to arise and flourish in a population, what two events must occur?

3. Try This! If a NEW trait is to arise and flourish in a population, what two events must occur? New traits appear because of random mutation and sexual recombination. (RARE) The new trait must increase the fitness of individuals in their environment (to be passed on). This is natural SELECTION.

4. Try This! Reminder… selection usually occurs on existing traits within the varied population!

5. Try This! Define: Fitness Adaptation Mutations Variation Evolution Natural Selection

6. Common Misconceptions Fitness –

7. Common Misconceptions Fitness – NOT an organism’s general health, vigor, strength, or intelligence! Any trait that increases an organism’s relative reproductive success increases its fitness. Fitness = reproductive success

8. Common Misconceptions Adaptation –

9. Common Misconceptions Adaptation – NOT an individual changing over its lifetime in response to the environment. IT IS: An inherited characteristic that increased previous generation’s reproductive success (and most likely the individual’s)

10. Common Misconceptions Mutations –

11. Common Misconceptions Mutations – NOT intentional events! NOT adaptive responses to environmental conditions! Mutations – ARE rarely positive and random events where the DNA code is altered.

12. Common Misconceptions Variation -

13. Common Misconceptions Variation – Every population exhibits natural variation in characteristics. Variation is maintained via shuffling of genetic alleles during sexual reproduction during: Gamete formation Random fertilization

14. Evolution – Natural Selection – Evolution

15. Evolution – Descent with Modification. In other words, present species are descendants of ancestral species. Natural Selection – Evolution

16. Evolution – Descent with Modification. In other words, present species are descendants of ancestral species. Natural Selection – This is the process by which Evolution occurs in which organisms with certain inherited characteristics are more likely to survive and reproduce than organisms with other inherited characteristics. Evolution

17. Concept 2: Descent with Modification You must know: How Lamarck’s view of the mechanism of evolution differed from Darwin’s Several examples of evidence for evolution The differences between structures that are homologous and those that are analogous, and how this relates to evolution The role of adaptations, variation, time, reproductive success, and heritability in evolution

18. Darwin vs Lamarck Any Questions? Finish the handout from last class! (Answers posted online)

19. Try This! True or False? An organism mutates in order to adapt to its environment

20. Try This! True or False? An organism mutates in order to adapt to its environment FALSE. Positive mutations are rare and random events! An organism cannot “decide” to mutate! Even if new traits can appear through random mutation and sexual recombination, it must increase the fitness of individuals in their environment the trait will be selected for. IT IS THE POPULATION, NOT THE INDIVIDUAL, THAT EVOLVES!

21. Try This! If selection favours increased antibiotic resistance in a population of bacteria: A. The bacteria become more resistant over time. B. More bacteria become resistant over time.

22. Try This! If direction selection favours increased antibiotic resistance in a population of bacteria: A. The bacteria become more resistant over time. B. More bacteria become resistant over time!

23. Darwin vs Lamarck Lamarck thought that evolution worked through the inheritance of acquired characteristics... Hmm... Let’s look at Epigenetics Daphnia (Water Flea) Did Lamarck have a point after all?