Topics: Speciation and Reproductive Isolation Patterns of Evolution Rates of Evolution

1. Topics: • Speciation and Reproductive Isolation • Patterns of Evolution • Rates of Evolution • Origin of Life

2. Speciation Species: population whose members can interbreed in nature and produce viable, fertile offspring Evolution: change in the allelic frequencies in a population

3. Speciation • Anagenesis • Phyletic evolution • One species replaces another • Pattern of evolution that results in linear descent with no branching or splitting of the population. • - Cladogenesis • Branching evolution • When a new species branches out from a parent species • evolutionary change and diversification resulting from the branching off of new taxa from common ancestral lineages

4. Anagenesis • Cladogenesis

5. Speciation • Allopatric Speciation • Sympatric Speciation • Adaptive Radiation Animation

6. Allopatric Speciation “speciation by geographic isolation” • Caused by geographic isolation • Mountain ranges, canyons, rivers, lakes • Interbreeding is prevented • Gene frequencies diverge due to natural selection, mutation, or genetic drift.

7. Allopatric Speciation • Can occur even if the barrier is a little “porous,” that is, even if a few individuals can cross the barrier to mate with members of the other group. • In order for a speciation even to be considered “allopatric,”gene flow between the soon-to-be species must be greatly reduced—but it doesn’t have to be reduced completely to zero.

8. Sympatric Speciation Barriers to Reproduction (sexual)

9. Sympatric Speciation • Without geographic isolation • Examples: • Balanced Polymorphism • Polyploidy • Hybridization • Habitat isolation • Temporal isolation • Mechanical isolation • Behavioral isolation • Gametic isolation Prezygotic barriers Postzygotic barriers • Prezygotic barriers • PREVENT mating • Postzygotic barriers • Prevent the production of fertile offspring after mating has occurred

10. Balanced Polymorphism Sympatric Speciation • Maintain stable frequencies of two or more phenotypic forms • natural selection preserves variation • heterozygote advantage (i.e. heterozygotes have the highest relative fitness). • sickle cell anemia. • Ex: • Population of insects that possess polymorphism for color. • Can only survive where they are camouflaged. • Become reproductively isolated, and their gene pools diverge creating new species.

11. Polyploidy Sympatric Speciation • When a cell has more than two complete sets of chromosomes • Common in plants • Causes: nondisjunction • Plants that are polyploid cannot breed with others of the same species that are not polyploid • The two groups become isolated from one another

12. Hybridization Parapatric Speciation • When two closely related species mate and produce offspring along a geographic boundary. • Called a “hybrid zone” • Hybrids adapt to the area and eventually diverge from both parents.

13. Sympatric Speciation • Habitat isolation • Species do not encounter one another • Temporal Isolation • Mating takes place at different times of the year • Flowers open at different times of the day. • Mechanical Isolation • Male and female genitalia are structurally incompatible

14. Behavioral Isolation • Populations are capable of interbreeding, but have different courtship rituals or other type of behavior. • Do not recognizes another species as a mating partner.

15. Gametic isolation • Male gametes do not survive in the environment of the female gamete or when female gametes do not recognize male gametes

16. Postzygotic isolating mechanisms • Hybrid inviability • Zygote fails to develop and aborts • Hybrid sterility • Hybrids become functional adults, but are sterile. (ex: mule) • Hybrid breakdown • Offspring have reduced viability or fertility

17. Adaptive Radiation lineage rapidly diversifies • The evolution of many diversely adapted species from a common ancestor • Relatively rapid • Usually occurs when a population colonizes an area of diverse geographic or ecological conditions. • New niches • Each species becomes specialized for a different set of conditions.

18. lineage rapidly diversifies

19. Patterns of Evolution Evolution: change in the allelic frequencies in a population

20. Patterns of Evolution • Divergent Evolution • Convergent Evolution • Parallel Evolution • Coevolution

21. Divergent Evolution • Occurs when a population becomes isolated from the rest of the species. • Becomes exposed to new selective pressures • Evolves into a new species

22. Convergent Evolution • When unrelated species occupy the same environment and are subjected to similar selective pressures. • Show similar adaptations. • Ex: Whale and Shark • Not related, but have similar features that are adapted for their environment.

23. Parallel Evolution • Two related species that have made similar evolutionary adaptations after their divergence from a common ancestor. • Ex: Marsupial mammals of Australia and placental mammals of North America. • Similar environments

24. Coevolution • Predators and their prey • Parasites and their hosts • Plant-eating animals and the plants upon which they feed • One example of coevolution is between plants and the animals that pollinate them. Coevolution is the joint change of two or more species in close interaction.

25. Rates of Evolution Evolution: change in the allelic frequencies in a population

26. Rates of Evolution • Punctuated Equilibrium • Phyletic Gradualism

27. Gradualism • Organisms descend from a common ancestor slowly over a long period of time.

28. Punctuated Equilibrium • Favored theory • New species appear suddenly after long periods of stasis. sporadically (by splitting) and occurs relatively quickly

29. Origin of Life

30. History of Life 1. Life on Earth originated between 3.5 and 4.0 billion years ago. (Anaerobic heterotrophic prokaryotes) 2. Prokaryotes dominated evolutionary history from 3.5 to 2.0 billion years ago 3.Oxygen began accumulating in the atmosphere about 2.7 billion years ago (Photosynthesis) 4.Single celled eukaryote began by 2.1 billion years ago. (Theory of Endosymbiosis) 5.Multicellular eukaryotes evolved 1.2 billion years ago 6.Plants, fungi, and animals colonized the land about 500 million years ago.

33. Most scientists favor the hypothesis that life on Earth developed from nonliving materials that became ordered into aggregates that were capable of self-replication and metabolism. From the time of the Greeks until the 19th century, it was common “knowledge” that life could arise from nonliving matter, an idea called spontaneous generation. While this idea had been rejected by the late Renaissance for macroscopic life, it persisted as an explanation for the rapid growth of microorganisms in spoiled foods. The first cells may have originated by chemical evolution on a young Earth

34. In 1862, Louis Pasteur conductedbroth experimentsthat rejected the idea of spontaneousgeneration even for microbes. A sterile brothwould “spoil” onlyif microorganismscould invade fromthe environment. -created the first vaccine for rabies -pasteurization. Swan flask

35. Early life: Under one hypothetical scenario this occurred in four stages: (1) The abiotic synthesis of small organic molecules; (2) The joining these small molecules into polymers: (3) The origin of self-replicating molecules; (4) The packaging of these molecules into “protobionts.” This hypothesis leads to predictions that can be tested in the laboratory. Protobionts: aggregates of abiotically produced molecules surrounded by a membrane or membrane-like structure

36. AI Oparin and J.B.S. Haldane 1920s Hypothesized separately that under the conditions of early earth, organic molecules could form. A"primeval soup" of organic molecules could be created in an oxygen-less atmosphere through the action of sunlight AI Oparin Could not demonstrate theory. • J.B.S. Haldane

37. Stanley Miller and Harold Urey • 1953, Tested the Oparin-Haldane hypothesis Stanley Miller Harold Urey

38. Stanley Miller and Harold Urey 1953, Tested the Oparin-Haldane hypothesis • Proved that almost any energy sources would have converted the molecules in the early atmosphere into organic molecules like amino acids • Discharged sparks in an “atmosphere” ofgases and water vapor • Produced a variety of amino acids and other organic molecules

39. Sidney Fox Carried out similar experiments to Miller and Urey He began with organic molecules and was able to produce membrane-bound, cell-like structures he called proteinoid microspheres. -Early work demonstrated that under certain conditions amino acids could spontaneously form small polypeptides -studied the spontaneous formation of protein structures

40. Outbreeding Opposite of inbreeding Mating with individual that are not closely related Ex: plants that have male and female parts that mature at different times Helps insure genetic diversity Evolutionary neutral traits Trait that have no selective value Ex: blood type, fingerprints EXTRAS…Additions

41. Life on Earth-David Attenbourgh Pt3-Video CLip