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EVOLUTION & SPECIATION

EVOLUTION & SPECIATION. VOCABULARY REVIEW. EVOLUTION – CHANGE OVER TIME NATURAL SELECTION - INDIVIDUALS BETTER ADAPTED TO THE ENVIRONMENT ARE ABLE TO SURVIVE & REPRODUCE. A.K.A. “SURVIVAL OF THE FITTEST”. NEW VOCABULARY. POPULATION – GROUP OF INDIVIDUALS OF SAME SPECIES THAT INTERBREED

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EVOLUTION & SPECIATION

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  1. EVOLUTION & SPECIATION

  2. VOCABULARY REVIEW • EVOLUTION – CHANGE OVER TIME • NATURAL SELECTION - INDIVIDUALS BETTER ADAPTED TO THE ENVIRONMENT ARE ABLE TO SURVIVE & REPRODUCE. • A.K.A. “SURVIVAL OF THE FITTEST”

  3. NEW VOCABULARY • POPULATION – GROUP OF INDIVIDUALS OF SAME SPECIES THAT INTERBREED • GENE POOL – COMMON GROUP OF ALL GENES PRESENT IN A POPULATION

  4. Gene Pool Combined genetic info. of all members Allele frequency is # of times alleles occur

  5. Variation in Populations 2 processes can lead to this: Mutations - change in DNA sequence Gene Shuffling – from sexual reproduction

  6. Genetic Drift changes populations……. • Random change in allele frequency causes an allele to become common

  7. Founder Effect: a cause of genetic drift attributable to colonization by a limited number of individuals from a parent population

  8. Gene Flow: genetic exchange due to the migration of fertile individuals or gametes between populations (reduces differences between populations)

  9. Nonrandom mating: inbreeding and assortive mating (both shift frequencies of different genotypes)

  10. Natural Selection: differential success in reproduction; only form of microevolution that adapts a population to its environment

  11. Sexual selection • Sexual dimorphism: secondary sex characteristic distinction • Sexual selection: selection towards secondary sex characteristics that leads to sexual dimorphism

  12. Evolution of Populations Occurs when there is a change in relative frequency of alleles

  13. Phenotype Expression • Depends on how many genes control that trait

  14. Single-Gene vs. Polygenic Traits (EG: tongue rolling) Single-Gene: 2 Distinct Phenotypes Polygenic: Many Phenotypes

  15. Natural Selection on Polygenic Traits • Shifts to middle range • Shifts to 2 extremes • Shifts to 1 extreme

  16. Conditions needed for Genetic Equilibrium

  17. SPECIATION • THE FORMATION OF NEW SPECIES • AS NEW SPECIES EVOVLVE, POPULATIONS BECOME REPRODUCTIVELY ISOLATED • REPRODUCTIVE ISOLATION – MEMEBERS OF 2 POPULATIONS CANNOT INTERBREED & PRODUCE FERTILE OFFSPRING.

  18. 3 ISOLATING MECHANISMS…….. • BEHAVIORAL ISOLATION- CAPABLE OF BREEDING BUT HAVE DIFFERENCES IN COURTSHIP RITUALS (EX. MEADOWLARKS) • GEOGRAPHICAL ISOLATION – SEPARATED BY GEOGRAPHIC BARRIERS LIKE RIVERS, MOUNTAINS, OR BODIES OF WATER (EX. SQUIRREL) • TEMPORAL ISOLATION – 2 OR MORE SPECIES REPRODUCE AT DIFFERENT TIMES.

  19. Table 23.1a

  20. Tigon Result of male tiger and female lion mating incaptivity. Offspring are infertile. Separated both geographically and ecologically.

  21. Liger Result of male lion and female tiger mating in captivity. Offspring are infertile.

  22. Table 23.1b

  23. Fig. 23.6 Four species of leopard frogs: differ in their mating calls. Hybrids are inviable.

  24. These squirrels live on opposite sides of the Grand Canyon. This is an example of allopatric speciation.

  25. Hawaiian Honeycreepers An example of adaptive radiation – these species all diverged from a common ancestor (founder species) FOUNDER SPECIES

  26. SPECIATION IN DARWIN’SFINCHES • SPECIAITON IN THE GALAPAGOS FINCHES OCCURRED BY: - FOUNDING OF A NEW POPULATION, - GEOGRAPHIC ISOLATION which led to -- REPRODUCTIVE ISOLATION and CHANGES IN THE NEW POPULATION’S GENE POOL due to COMPETITION.

  27. Evidence of Evolution • Fossil Record • Geographic Distribution of Living Species • Homologous Body structures • Similarities in Embryology

  28. Evidence of Evolution Fossil Record provides evidence that living things have evolved Fossils show the history of life on earth and how different groups of organisms have changed over time

  29. Flying Squirrel Sugar Glider Marsupial Mammals Convergent Evolution and AnalogousStructures Placental mammals Mammalia Rat like common ancestor

  30. Big Question!!! • How did life arise on the big blue planet?? • Scientists attempt to answer this question scientifically.

  31. Relative Dating versus Absolute Dating

  32. Relative Dating • Can determine a fossil’s relative age • Performed by estimating fossil age compared with that of other fossils • Drawbacks – provides no info about age in years

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