Introduction to Evolution

1. Introduction to Evolution PHA Biology 9 Moretti/ Dickson

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

3. Connecting Genetics and Evolution:Cystic Fibrosis Case Study Figure 1. Chest Radiograph of CF Diffuse Interstitial Disease • Image: http://www.eradimaging.com/site/article.cfm?ID=327: Reprinted with permission from LearningRadiology.com. Case of the Week Archives—2003. Cystic Fibrosis. Available at: http://www.learningradiology.com/toc/tocsubsection/tocarchives2003.htm. Accessed January 28, 2008.11

4. Agenda & Goals for Today: • Share ideas from the Do Now • How does cystic fibrosis illustrate evolution? • What causes evolution? • Notes • Vocabulary – Define population, gene pool, and fitness • Levels of Evolution – Explain the difference between micro and macro-evolution • Natural Selection – Identify key principles of natural selection • Videos: • Evolution in Hummingbirds • Evolution in Bacteria ** Announcement: Optional Challenge Questions **

5. Vocabulary • Population • Group of individuals from the same species that live in the same area and interbreed • Gene Pool • All the genes and all of their alleles in a population • Evolution (on a population scale) • Any change in the proportions of alleles over time • (One allele becomes more common, another becomes less common) • Change in a population NOT change in an individual • Fitness • How well a particular organism can survive and reproduce to pass on its genes to the next generation • Objectives for Class: • Use actual evidence to explain how the four principles of natural selection shape the evolution of organisms

6. Macro-Evolution • Large-scale, often over a very long time • Branching of one species into two species • All species share a common ancestor Example:Evolution of whales from four-legged land mammals • Objectives for Class: • Use actual evidence to explain how the four principles of natural selection shape the evolution of organisms

7. 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

8. 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.pbs.org/wgbh/evolution/library/11/2/e_s_4.html • Objectives for Class: • Use actual evidence to explain how the four principles of natural selection shape the evolution of organisms

9. Principles of Natural Selection • Genetic variation between individuals • Due to mutation and gene shuffling (sexual reproduction) • More offspring are 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

10. 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 Ex. 4:Some TB bacteria have evolved to resist antibiotics

11. Video: Evolution in bacteria (6 minute video)

12. Notes: SPECIES and SPECIATION Species - • A group of similar organisms • Can breed with each other and produce fertile offspring Examples: • Human species (Homo sapiens) • Horses and donkeys = two separate species because their offspring (mules) aren’t fertile • Objectives for Class: • Explain the defining characteristics of a species • Describe the 2 steps of speciation

13. Speciation - • The formation of new species from a common ancestor • The gene pools of two populations must become separated Ex: The Galapagos Finches • Objectives for Class: • Explain the defining characteristics of a species • Describe the 2 steps of speciation

14. Two Main Steps of Speciation • Reproductive Isolation • Changes in the Gene Pool • Gene Pools Diverge (become different) • Genetic Barriers to Reproduction Arise • Objectives for Class: • Explain the defining characteristics of a species • Describe the 2 steps of speciation

15. Reproductive Isolation One population becomes separated and stops breeding with the rest of the species • Behavior: • Changes in courtship or other reproductive strategies • Geographic • Geographic barrier splits population (i.e.: river, mountain, body of water, etc.) • Populations are separated and cannot interbreed • Temporal • Species reproduce at different times or have other behavior that becomes time sensitive (i.e.: feeding) • Objectives for Class: • Explain the defining characteristics of a species • Describe the 2 steps of speciation

16. Changes in the Gene Pool • Gene Pools Diverge (become different): • The isolated populations become genetically different. • The new environments or behaviors favor different genetic traits (natural selection) • Genetic Barriers to Reproduction Arise • The two populations can no longer interbreed • Due to genetic differences in habitat preference, mating behavior, or physical compatibility They are now two separate species! • Objectives for Class: • Explain the defining characteristics of a species • Describe the 2 steps of speciation

17. Hybrid - • The offspring of a mating between two different species • If a hybrid can’t have offspring, there are still two separate species!

18. Reproductive Barriers That Maintain Separate Species • Before mating occurs • Geographic barriers • Ecological/habitat differences • Temporal differences • Behavioral/courtship differences • Mechanical differences • Chemical differences • Objectives for Class: • Explain the defining characteristics of a species • Describe the 2 steps of speciation

19. Reproductive Barriers That Maintain Separate Species • After mating occurs: • Hybrid dies before birth • Hybrid is weak and sickly • Hybrid is sterile (can’t reproduce) • Objectives for Class: • Explain the defining characteristics of a species • Describe the 2 steps of speciation

20. Famous Hybrids that are strong but STERILE!