1. NATURAL SELECTION Ch 14 p. 296-324

2. THE MODERN THEORY Key discoveries: Invention of more powerful microscopes & precision tools Use of short lived organisms for breeding experiments Rigorous application of the scientific method

3. BEYOND NATURAL SELECTION THE SYNTHETIC THEORY OF EVOLUTION We now understand that natural selection is just ONE of a number of processes that can lead to evolution. This knowledge has resulted in the development of a more complex understanding of genetic change = THE SYNTHETIC THEORY OF EVOLUTION = a combo of Charles Darwin’s Natural Selection & Gregory Mendel’s Genetic Inheritance along with population genetics and molecular biology of the 20 th century

4. NATURAL SELECTION Genes are the carriers of inheritable characteristics They are also the source of random variation upon which natural selection operates Mutation causes some variation Meiosis is when most variation occurs during the copying, shuffling and dealing of genes to the gametes and crossing over Remember, genetic variation is random, it is not controlled or directed toward a goal

5. How Natural Selection Works In the struggle for survival, entire organisms, not genes, either survive & reproduce, or do not Natural Selection operates on the phenotypic variation between individuals Phenotypic = physical & behavioral characteristics produced by the interaction of genotype & environment More “fit” individuals will have more success mating and will live longer therefore producing more offspring in the next generation In essence, this is selection because individuals who are phenotypically fit will produce more offspring, thus causing a change in the genetics of the next generation

6. EVOLUTION AS GENETIC CHANGE POPULATIONS: individuals of the same species in an area who breed with one another GENE POOL: all of the alleles of genes within a population RELATIVE FREQUENCY: number of times an allele appears in a population compared to the other alleles of the same gene EVOLUTIONARY CHANGE INVOLVES A CHANGE IN THE RELATIVE FREQUENCIES OF ALLELES IN THE GENE POOL OF A POPULATION

7. POPULATION GENETICS Study of genetic traits in individuals Genotype – actual allele inherited from each parent that the individual has (blue eyes, brown eyes) Phenotype – resulting observable characteristic from the interaction of the individuals genotype (brown eyes) Study of genetic traits in populations Gene Pool: combined genetic material of all the members of a population Alleles: name for the 2 or more different forms of a gene. (gene = eye color, alleles = blue, brown, green ) Allele Frequency: is a fraction that represents the frequency of a particular allele within a population

8. HARDY-WEINBERG PRINCIPLE 1. If a population is not evolving, allele frequencies are in Genetic Equilibrium Under specific conditions allele frq. Remain constant If those conditions are not met the population may EVOLVE 2. Conditions required to maintain G.E. are: No natural selection Random mating No mogration No mutation Very large population size 3. Even when Hardy- Weinberg conditions are met, equilibrium can be affected by RANDOM CHANGES in allele frequencies 4. A random change in allele frequencies in a popultion due to chance events is called GENETIC DRIFT

9. DISTRUBUTION & SELECTION The normal distribution of variations in a population can change by natural selection Evolution results from disruptions in genetic equilibrium

10. STABALIZING SELECTION These curves are called normal distributions because the patterns is so common in nature

11. DIRECTIONAL SELECTION This type of selection occurs when a change in the environment makes it infavorable to have an extreme phenotype

12. DISRUPTIVE SLELECTION This type of selection occurs when an environmental change makes it unfavorable to have the most common phenotype

13. CONCEPT OF A SPECIES Speciation and extinction were extremely important in determining the history of life on earth Before we can know whether speciation has occurred in a group of organisms, we have to know what a species is! A species is a group of interbreeding individuals or populations that are reproductively isolated from other such groups

14. SPECIATION Speciation involves environmental processes that lead to the splitting of a gene pool into two or more separate pools MAJOR CAUSES: Reproductive isolating mechanisms Geographic isolation Courtship behaviours

15. SPECIATION - REPODUCTIVE ISOLATING MECHANISMS The key event in speciation is Reproductive Isolation between two diverging populations Isolating mechanisms are all genetically based and can be either pre-zygotic or post-zygotic PRE-ZYGOTIC = Prevent fertilization Seasonal/habitat barriers to mating, behavioral isolation, physical isolation POST-ZYGOTIC = Come into play despite fertilization Gamete mortality, hybrid non- viability, hybrid sterility

16. SPECIATION - GEOGRAPHIC ISOLATION Simplest mechanism of isolation Continents collide, mountains are uplifted & suddenly a population finds that it is splintered into a large population as well a number of geographically isolated smaller population Most of these small populations eventually go extinct

17. SPECIATION - COURTSHIP BEHAVIORS Often the behaviors a male must engage in to convince the female of his proper species-hood are quite elaborate and cannot be reproduced by member of a different species Various behavioral cues allow males & females to recognize their own species

18. PUNCTUATED EQUILIBRIUM VS GRADUALISM Darwin saw evolution as a slow, continuous process, without sudden jumps (GRADUALSIM) however, if you study the fossil record, you will see long intervals in which nothing changed (EQUILLIBRIUM) punctuated by short, revolutionary transitions in which species became extinct and replaced by new forms (PUNCTUATED EQUILIBRIUM) Instead of a slow progression, evolution of life seems more like the life of a fire-fighter: long periods of boredom interrupted by rare moments of terror.

19. TYPES OF EVOLUTION The basic evolutionary mechanisms-mutation, migration, genetic drift, and natural selection- can produce major evolutionary can change if given enough time THERE ARE 3 MAJOR TYPES OF EVOLUTION: Divergent Convergent Co-evolution

20. DIVERGENT EVOLUTION = THE PROCESS OF 2+ RELATED SPECIES BECOMING MORE DISSIMILAR Ex. Red Fox (forests, red) and Kit Fox (prairies, tan) Similarities in structure show that they have a common ancestor, but as they adapted to different environments, they diverged

21. CONVERGENT EVOLUTION = WHEN ORGANISMS THAT ARE NOT CLOSLY RELATED EVOLVE SIMILAR TRAITS Ex. Antifreeze proteins in both Antarctic and Arctic fish Ex. Wings of a bat and bird

22. COEVOLUTION = JOINT CHANGE IN 2+ SPECIES IN CLOSE INTERACTION Often occurs between Predators and prey Parasites and hosts Ex. Plants and the animals that pollinate them

23. EXTINCTION 99% of the species that have ever lived on earth have gone extinct! Present day biodiversity is a result of an accumulation of changes due to extinction events over millions of years EXTINCTION CONTAINS 3 KEY ELEMENTS: For geographically widespread species extinction is rare Large mass extinctions produce major restructuring of the biosphere and allowing previously minor groups of expand and diversify It is generally impossible to predict which species will be victims of an extinction event

24. SUMMARY EVOLUTION CAN RESULT FROM: Mutation Natural selection Genetic recombination Non-random mating Genetic drift Gene flow Extinction EVOLUTIONARY PROCESSES ALLOWS US TO UNDERSTAND: Crossing over Mutation Extinction Convergent evolution Divergent evolution Co-evolution