Vocab. ! Evolution - change in a kind of organism over time; process by which modern organisms have descended from ancient organisms

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2 Vocab! Evolution - change in a kind of organism over time; process by which modern organisms have descended from ancient organisms! Theory - well-tested explanation that unifies a broad range of observations

3 Voyage of the Beagle ( ) Darwin s Voyage - During his travels, Darwin made numerous observations & collected evidence that led him to propose a revolutionary hypothesis about the way life changes over time.

4 Galapagos Islands! During his travels, Darwin was amazed how different organisms were so well adapted to many different environments. ( Perfect fit )! He saw patterns of diversity! Not just in living organisms, but also in fossil records.! The Galapagos Islands were a microcosm of Evolution

5 Darwin s Finches

6 Development of Evolutionary Theory What could cause such great diversity? Why have so many species died out? Why have some species not changed at all? Charles Darwin offered an explanation based on careful observations.

7 Idea s that shaped Darwin s Thinking 1. James Hutton and Charles Lyell helped scientists recognize that Earth is many millions of years old, & the processes that changed Earth in the past are the same processes that operate in the present. 2. Thomas Malthus (English Economist) - reasoned that if the human population continued to grow unchecked, sooner or later there would be insufficient living space & food for everyone. 3. Jean-Baptiste Lamarck proposed that by selective use or disuse of organs, organisms acquired or lost certain traits during their lifetime. These traits could then be passed on to their offspring. Over time, this process led to change in a species

8 Lamarck (His theory is wrong) 1. Tendency Toward Perfection Innate tendency toward complexity & perfection Birds acquired urge to fly Kept trying to fly 2. Use and Disuse Using a trait (wings) causes them to become stronger & larger Disuse causes it to disappear 3. Inheritance of Acquired Traits Passing acquired traits from one generation to the next

9 Lamarck

10 Development of Evolutionary Theory The Survival of the Fittest But What determines Fitness???

11 Development of Evolutionary Theory Darwin Concluded:! Physical traits & behaviors enable organisms to survive and reproduce (Fitness)! Fitness results from adaptations! Darwin reasoned that adaptations result from natural selection & result in evolution Evolution is process by which living things change & diversify over time

12 Natural Selection

13 Evolution Through Natural Selection Premises of Natural Selection! Populations overproduce.! Resources are limited, so competition ensues.! Genetic variations directly impact ability of organisms to survive.! Organisms with beneficial differences will have a better chance of survival.! Surviving individuals pass their traits onto future generations.! This results in a slow change in populations over time.

14 Evolution Through Natural Selection! These end results can be attributed to 3 distinct selection type models. All of which are as a result of environmental pressures.! Directional Selection! Stabilizing Selection! Disruptive Selection

15 Evolution Through Natural Selection Directional Selection! form of natural selection in which entire curve moves; occurs when individuals at one end of a distribution curve have higher fitness than individuals in the middle or at other end of curve

16 Evolution Through Natural Selection Directional Selection

17 Evolution Through Natural Selection Directional Selection e.g.

18 Evolution Through Natural Selection Stabilizing Selection! form of natural selection by which center of curve remains in its current position; occurs when individuals near center of a distribution curve have higher fitness than individuals at either end

19 Evolution Through Natural Selection Stabilizing Selection

20 Evolution Through Natural Selection Stabilizing Selection e.g.

21 Evolution Through Natural Selection Disruptive Selection! form of natural selection in which a single curve splits into two; occurs when individuals at upper and lower ends of a distribution curve have higher fitness than individuals near middle

22 Evolution Through Natural Selection Disruptive Selection

23 Evolution Through Natural Selection Disruptive Selection e.g.

24 QUESTION???????! Are we as Human Beings exempt from Natural Selection? WHY?

25 QUESTION???????! Biologists believe that Achaebacteria living today are similar to ancient achaebacteria. Many of these are found in extreme locations. Some scientists believe that this provides a good example of origins of life.! Why do you think that these organisms have not changed over the years?! Why would understanding the origins of life on earth help with discovering life on other planets?

26 Genetic Drift! Genetic Drift - random change in allele frequencies that occurs in small populations! In small populations, individuals that carry a particular allele may leave more descendants than other individuals do, just by chance. Over time, a series of chance occurrences of this type can cause an allele to become common in a population.! founder effect - change in allele frequencies as a result of migration of a small subgroup of a population

27 Genetic Drift and Founder Effect

28 Does Evolution occur all of the time? NO

29 Hardy-Weinberg principle! The principle that allele frequencies in a population will remain constant unless one or more factors cause frequencies to change If there are no factors causing allele frequencies to change then population is in..! genetic equilibrium - situation in which allele frequencies remain constant

30 Genetic Equilibrium! Five conditions are required to maintain genetic equilibrium from generation to generation:! random mating! population must be very large! there can be no movement into or out of population! no mutations (that filter into gene pool)! no natural selection

31 When evolution DOES OCCUR! The process of SPECIATION - formation of new species! Speciation has occurred when population have become reproductively isolated from one another! reproductive isolation - separation of species or populations so that they cannot interbreed & produce fertile offspring! Reproductive isolation can develop in a variety of ways, including behavioral isolation, geographic isolation, and temporal isolation.

32 Behavioral Isolation! form of reproductive isolation in which two populations have differences in courtship rituals or other types of behavior that prevent them from interbreeding! Examples! Mating calls! Mating dances

33 Geographic Isolation! form of reproductive isolation in which two populations are separated physically by geographic barriers such as rivers, mountains, or stretches of water

34 Temporal Isolation! form of reproductive isolation in which 2 populations reproduce at different times

35 Speciation of Darwin s Finches! Speciation in Galápagos finches occurred by the:! founding of a new population! geographic isolation! changes in new population s gene pool! reproductive isolation! ecological competition

36 Darwin s Finches

37 The Peppered Moth Example of Evolution

38 Background Information! 1850 s: Industrial Revolution! Moths (Biston betularia) come in both light & dark colors.! Until 1850 s, dark color was rare.! After almost 100 years, darker color was dominant form.! Birds are predators of moths

39 What is happening?! Hypothesis: Evolution by natural selection is taking place in peppered moths.! In polluted areas, dark moths have higher fitness (blend in with soot-covered trees) than light moths.! In non-polluted areas, light moths have higher fitness.

40 What is driving this evolution?! Selective Pressure: Predators! Selective Agent: BIRDS!! Therefore, moths that blend in with trees have a higher fitness (survive to reproduce) than those that do not.

41 The Moths:

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44 Conclusion about the moths:! Due to natural selection, in polluted areas darker moths have a higher fitness.

45 Summary of Darwin s Theory! Individual organisms in nature differ, & some variation is inherited! Organisms in nature produce more offspring than can survive & reproduce! Members of each species compete for limited resources! Unique organisms have different advantages & disadvantages in struggle for existence! Individuals best suited to their environment survive & reproduce, passing characteristic to their offspring. Individuals without characteristic die! Species change over time due to natural selection new species arise & others disappear! Species alive today have descended with modification from species of the past! All organisms on Earth are united by a common descent

46 Do Now.. 1. Describe how natural selection can affect traits controlled by single genes. 2. Describe three patterns of natural selection on polygenic traits. Which one leads to two distinct phenotypes? 3. How does genetic drift lead to a change in a population s gene pool? 4. What is the Hardy-Weinberg principle?