2VocabEvolution - change in a kind of organism over time; process by which modern organisms have descended from ancient organismsTheory - well-tested explanation that unifies a broad range of observations
3Voyage of the Beagle (1839 - 1844) Darwin’s Voyage - During his travels, Darwin made numerous observations and collected evidence that led him to propose a revolutionary hypothesis about the way life changes over time. What was it?
4Galapagos IslandsDuring his travels, Darwin was amazed how different organisms were so well adapted to many different environments. (“Perfect fit”)He saw patterns of diversityNot just in living organisms, but also in fossil records.The Galapagos Islands were a microcosm of Evolution
6Development 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 anexplanation based on carefulobservations.
7Idea’s that shaped Darwin’s Thinking James Hutton and Charles Lyell helped scientists recognize that Earth is many millions of years old, and the processes that changed Earth in the past are the same processes that operate in the present.Thomas Malthus (English Economist) - reasoned that if the human population continued to grow unchecked, sooner or later there would be insufficient living space and food for everyone.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
8Lamarck (His theory is wrong) Tendency Toward PerfectionInnate tendency toward complexity and perfectionBirds acquired the urge to flyKept trying to flyUse and DisuseUsing a trait (wings) causes them to become stronger and largerDisuse causes it to disappearInheritance of Acquired TraitsPassing acquired traits from one generation to the next
10“The Survival of the Fittest” EvolutionDevelopment of Evolutionary Theory“The Survival of the Fittest”But …What determines Fitness???
11Development of Evolutionary Theory Darwin Concluded:Physical traits and behaviors enable organisms to survive and reproduce (Fitness)Fitness results from adaptationsDarwin reasoned that adaptations result from natural selection and result in evolutionEvolution is the process by which living things change and diversify over time
13Premises of Natural Selection Evolution Through Natural SelectionPremises of Natural SelectionPopulations overproduce.Resources are limited, so competition ensues.Genetic variations directly impact the 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.
14Evolution 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 SelectionStabilizing SelectionDisruptive Selection
15Directional Selection Evolution Through Natural SelectionDirectional Selectionform of natural selection in which the entire curve moves; occurs when individuals at one end of a distribution curve have higher fitness than individuals in the middle or at the other end of the curve
16Directional Selection Evolution Through Natural SelectionDirectional Selection
17Directional Selection – e.g. Evolution Through Natural SelectionDirectional Selection – e.g.
18Stabilizing Selection Evolution Through Natural SelectionStabilizing Selectionform of natural selection by which the center of the curve remains in its current position; occurs when individuals near the center of a distribution curve have higher fitness than individuals at either end
19Stabilizing Selection Evolution Through Natural SelectionStabilizing Selection
20Stabilizing Selection – e.g. Evolution Through Natural SelectionStabilizing Selection – e.g.
21Evolution Through Natural Selection Disruptive Selectionform of natural selection in which a single curve splits into two; occurs when individuals at the upper and lower ends of a distribution curve have higher fitness than individuals near the middle
22Evolution Through Natural Selection Disruptive Selection
23Disruptive Selection e.g. Evolution Through Natural SelectionDisruptive Selection e.g.What will disruptive selection eventually result in?
24WHY? Are we as Human Beings exempt from Natural Selection? QUESTION???????Are we as Human Beings exempt fromNatural Selection?WHY?
25QUESTION???????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 the 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?
27Genetic DriftGenetic Drift - random change in allele frequencies that occurs in small populationsIn 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 the migration of a small subgroup of a population
30Hardy-Weinberg principle The principle that allele frequencies in a population will remain constant unless one or more factors cause the frequencies to changeIf there are no factors causing allele frequencies to change then the population is in……..genetic equilibrium - situation in which allele frequencies remain constant
31Genetic EquilibriumFive conditions are required to maintain genetic equilibrium from generation to generation:random matingthe population must be very largethere can be no movement into or out of the populationno mutations (that filter into the gene pool)no natural selection
32Do Now…..Describe how natural selection can affect traits controlled by single genes.Describe three patterns of natural selection on polygenic traits. Which one leads to two distinct phenotypes?How does genetic drift lead to a change in a population’s gene pool?What is the Hardy-Weinberg principle?
33When evolution DOES OCCUR The process of SPECIATION - formation of new speciesSpeciation has occurred when – population have become reproductively isolated from one anotherreproductive isolation - separation of species or populations so that they cannot interbreed and produce fertile offspringReproductive isolation can develop in a variety of ways, including behavioral isolation, geographic isolation, and temporal isolation.
34Behavioral Isolation Examples form of reproductive isolation in which two populations have differences in courtship rituals or other types of behavior that prevent them from interbreedingExamplesMating callsMating dances
35Geographic Isolationform of reproductive isolation in which two populations are separated physically by geographic barriers such as rivers, mountains, or stretches of water
36Temporal Isolationform of reproductive isolation in which two populations reproduce at different times
37Speciation of Darwin’s Finches Speciation in the Galápagos finches occurred by the:founding of a new populationgeographic isolationchanges in the new population’s gene poolreproductive isolationecological competition