Evolution

1. Evolution IB BIO II Van Roekel 4/1/14

2. Assessment Statements • D.1 Origins of Life on Earth • D.1.1 Describe the process needed for the spontaneous origin of life on Earth • D.1.2 Outline the experiments of Miller and Urey into the origin of organic compounds • D.1.3 State that comets may have delivered organic compound to Earth • D.1.4 Discuss possible locations where conditions would have allowed the synthesis of organic compounds • D.1.5 Outline two properties of RNA that would have allowed it to play a role in the origin of life • D.1.6 State that living cells may have been preceded by protobionts, with an internal chemical environment different from their surroundings • D.1.7 Outline the contribution of prokaryotes to the creation of an oxygen-rich atmosphere • D.1.8 Discuss the endosymbiotic theory for the origin of eukaryotes

3. Problems for Starting Life • Life is based on organic molecules, such as amino acids. • Early Earth only had inorganic matter, so either these materials somehow combined to form organic molecules, or they were extre-terrestrial • Organisms must be organized • Organic molecules must become polymers, larger molecules necessary for life such as polypeptides (proteins) • Living things must reproduce • Needed self-replicating molecules (RNA is needed to form DNA) • Water dissolves molecules • Living organisms needed to form membranes to separate internal and external environments

4. Miller and Urey • Simulated Earth’s believe atmosphere in a lab to see if they could recreate formation of organic molecules by chemical evolution • Introduced gases believed to be present at the time (methane, hydrogen, ammonia, water vapor, etc) • Heated and cooled water to recreate water cycle • Heated water (simulate volcanic activity) • Sparked electricity (lightning) • Exposed “atmosphere” to UV radiation (sun)

6. Miller and Urey Results • Organic compounds formed! • 13 of naturally occurring 20 amino acids were found • Some sugars and nucleic acids • Does not represent life, but now have building blocks of life and know they can be formed from inorganic material

7. Comets Delivery • Panspermia: idea that life originated on Earth from materials delivered on a comet in the form of amino acids, or bacteria • Late Heavy Bombardment: shower of comets 4 billion years ago • Existing bacteria and archaebacteria have been found in odd and extreme environments, making it feasible that they could survive on comets in space.

8. Synthesis of Organic Compounds • Several Hypotheses about where synthesis of organic compounds could have taken place, including: • Space • Volcanoes • Deep Ocean • Intertidal zones with alternating wet/dry environments

9. Synthesis of Organic Material • Space • Astronomers claim to have found glycine (simple amino acid) in space • Cosmic radiation could provide energy necessary for formation of complex compounds • Materials from Mars could have been thrown into space from comets • Does not prove life originated in space, just that it can travel through it

10. Synthesis of Organic Compounds • Alternating Wet/Dry Zones • Intertidal zones or flood plains have drying clay particles that could have created catalyzing reactions • When clay dries out and is heated, up to 200 amino acids can spontaneously join as polypeptide chain. • Stromatolites, one of earth’s oldest life forms, live in intertidal zones. • Suggests conditions that were favorable for early life

11. Synthesis of Organic Compounds • Volcanoes • Eruptions release water vapor and other gases and minerals into atmosphere, which could be used to create organic compounds • Rich source of materials and warm environment are favorable in formation of amino acids

12. Synthesis of Organic Compounds • Deep Ocean • Hydrothermal vents in deep ocean release hot water from beneath ocean floor • Hot water rises from earth’s crust, carrying minerals along the way • Hot bed for strange and ancient creatures, supporting idea of early life • http://exploringorigins.org/fattyacids.html

13. Review Questions • Outline the Role of clay molecules in the possibility of creating organic compounds • What is the theory of panspermia • Outline the experiments of Miller and Urey in the origin of organic compounds.

14. Review Answers • Organic Molecules Stick to the clay, which can then act as a catalyst causing organic molecules to be brought together • Panspermia is the theory of the origin of species by the arrival of organic compounds from space. • Simulated the conditions of pre-biotic earth in a sealed apparatus. They used gases such as methane, ammonia, water vapor, and hydrogen. Then using boiling water to simulate temperature, electricity to simulate lightning, and uv radiation to simulate the sun, they recreated the conditions of earth to see if organic compounds could form from inorganic compounds. Found organic compounds such as amino acids, sugar, and nucleic acids.

15. Early Reproduction • Most organisms today pass genetic info using DNA and enzymes to replicate DNA • PROBLEM!! • Prebiotic Earth had no enzymes, meaning DNA unlikely hereditary source • What is a likely source that can store, transmit, and replicate genetic informatin? • RNA

16. Early Reproduction • RNA, however, can replicate without the use of enzymes in some situations. • RNA acts as a catalyst (enzyme) helping certain chemical reactions occur, such as formation of peptide bonds, polymerization of nucleotides • RNA acting as an enzyme is called ribozyme • Believe to be genetic material in early earth.

17. Protobionts • Protobionts: evolutionary precursors to prokaryotic cells • Proteinoid: microsphere, tiny bubble of polypeptide chains that surrounded polymers, establishing and maintaining different internal environments from the external • Coacervate: microscopic sphere formed from lipids that formed spontaneously due to hydrophobic forces. Also maintain separate internal environment and are selectively permeable

19. Protobionts • Protobionts served the purpose of separating internal environments from external, to protect polynucleotides such as RNA, and allow different chemical reactions to take place • Over time true cell membranes evolved and other cellular abilities such as respiration and reproduction were developed

20. Oxygen Production • Remember, no oxygen was present in prebiotic earth, meaning earliest life forms were anaerobic • Anaerobes consumed food, increased in population, and eventually food ran scarce • Some bacteria developed a form a chlorophyll allowing the ability to perform photosynthesis and began producing oxygen

21. Importance of Oxygen • Oxygen is toxic to anaerobes, so many were destroyed • Broke down chemicals in atmosphere to carbon dioxide and oxidized certain sediments • Formed ozone layer, blocking harmful UV radiation

22. Endosymbiotic Theory • States that organelles found insinde modern cells were once independent prokaryotic cells that were engulfed by a bigger cell. Rather than being digested, they formed a mutualistic relationship with the host • Supported by the fact that Mitochondria and Chloroplast : • have double membrane • Have own circular DNA (similar to prokaryotes) • Can perform protein synthesis using small ribosomes (prokaryotes) • Can make copies of themselves when more are needed by binary fission

24. Review Questions • State the name of one organic monomer and one organic polymer on prebiotic Earth • Describe one hypothesis of how prebiotic polymers solved the problem of depolymerization • Explain why UV radiation levels were higher in the atmosphere of early Earth than they are today. • Outline the theory of Endosymbiosis.

25. Answers • State the name of one organic monomer and one organic polymer on prebiotic Earth • Monomers could be amino acids, simple sugars, or nucleotides • Polymers could include polypeptide chains, polysaccharides, or RNA

26. Answers • Describe one hypothesis of how prebiotic polymers solved the problem of depolymerization • Surrounds themselves with proetinoid microspheres or coacervates that would protect them from the external environments

27. Answers • Explain why UV radiation levels were higher in the atmosphere of early Earth than they are today. • There was no oxygen present in early earth and consequently, no ozone layer. After oxygen began to be produced by organisms that performed photosynthesis, the formation of the ozone layer began.

28. Answers • Outline the theory of Endosymbiosis. • A bacteria cell engulfed another bacterial cell but instead of digesting it, they formed a mutualistic relationship. The smaller cell provided energy to both cells and the larger cell provided protection to the smaller cell.

29. Species & Speciation 4/7/14

30. Assessment Statements • D.2.1 Define allele frequency and gene pool • D.2.2 State that evolution involves a change in allele frequency in a population’s gene pool over a number of generations • D.2.3 Discuss the term species • D.2.4 Describe three examples of barriers between gene pools • D.2.5 Explain how polyploidy can contribute to speciation • D.2.6 Compare Allopatric and sympatric speciation • D.2.7 Outline the process of adaptive radiation • D.2.8 Compare Convergent and divergent evolution • D.2.9 Discuss ideas of the pace of evolution, including gradualism and punctuated equilibirium • D.2.10 Describe one example of transient polymorphism • D.2.11 Describe sickle cell anemia as an example of balanced polymorphism

31. Gene Pools • Gene Pool: all the genetic information present in the reproducing members of a population at a given time. • Large gene pools in populations with substantial variety in traits • Small gene pool in populations with little variation, most notably in cases of inbreeding

32. Allele Frequency • Allele Frequency measures the proportion of a specific variation of a trait in a population, or the chance a chromosome carries that specific allele • i.e 25% of fruit flies have an allele for white eyes • Does not mean that that many members of the population have the allele, just that it is present on one of the chromosomes

33. What is the allele frequency of A and a in population 1 & 2 • ¾ A & ¼ a in population 1 ¾ A & ¼ a in population 2 • How many individuals express the trait coded for by the allele a in population 1 & 2? • O in population 1 and 2 in population 2

34. Evolution and Alleles • Gene pools are relatively stable over time, however, when changes occur, evolution is seen • New combinations of alleles lead to new phenotypes, that can then be selected for or against by the environment • Alleles that are advantageous to a populations survival will be passed on and have a higher frequency in later generations • Alleles that are disadvantageous will not be passes on and have a lower frequency in later generations

35. Evolution and Alleles • Immigrations and emigrations will also have an effect on allele frequencies • For whatever reason, when a gene pool in modified, some degree of evolution has occurred.

36. Species • Species is the basic unit for classifying organisms which included organisms that: • Have similar physiological and morphological characteristics which can be observed and measured • Have the ability to interbreed and produce fertile offspring • Genetically distinct from other species • Have common phylogeny

37. What about Horses and Donkeys? • When they mate, they produce an offspring called a mule. Why aren’t they the same species? • Both parents are equines (of the same family) so they are related but are not the same species. They do not posses the same number of chromosomes which is one of the reasons the offspring are infertile.

38. Barriers between Gene Pools • Occasionally, there are barriers between populations of the same species • Barriers can be: • Geographical Isolation • Temporal Isolation • Behavioral Isolation • Hybridization

39. Geographical Isolation • Physical barriers such as land or water prevent males and females from find each other and breeding • Rivers • Mountains • Clearing a forest

40. Temporal Isolation • Incompatible time frames which prevent the populations or gametes from encountering each other • Female parts of flowers of one population mature at a different time from the release of pollen on another population • One population is still hibernating or has not returned from migrations when another population is ready to mate

41. Behavioral Isolation • Population’s lifestyle and habits are not compatible with those of another population • Birds rely on courtship displays in order for one sex to mate with the other, if displays of one population are different from another, they will not consider each other for mating • Hybrids are infertile, so difficult to continue population on their own.

42. Questions • Compare and Contrast Geographical and Temporal Isolation • Both are examples of barriers to gene pools but geographical isolation is a physical barrier such as a mountain or a river whereas temporal isolation is a problem in the synchronization of time when populations try to connect. • Explain why a zebroid (combination of a zebra and a horse) is not considered a new species. • Because like most hybrids, it is considered infertile and cannot produce offspring.

43. Speciation • The process of an evolving population changing significantly enough so that the production of offspring with the original population is no longer possible • Two types of speciation: • Allopatric • Sympatric

44. Allopatric Speciation • Occurs when a new species forms because it is physically separated from an existing species. • Gene flow is cut off between these two populations, causing different evolutionary directions • Once populations have been separated into 2 gene pools they can diverge through natural selection or through random genetic drift.

45. http://www.mhhe.com/biosci/esp/2001_gbio/folder_structure/ev/m3/s2/evm3s2_4.htmhttp://www.mhhe.com/biosci/esp/2001_gbio/folder_structure/ev/m3/s2/evm3s2_4.htm

46. Sympatric Speciation • When a new species forms from an existing species while living in the same geographical area • Temporal and behavioral isolations could produce a new species

48. Speciation Activity • You will simulate the process of speciation in a specific environment • You will work in groups of 3 and will be isolated on a island that has a specific climate • You must select and write down all the phenotypic characteristics that exist in your group to improve your group’s survival on the island. • Answer the questions on the activity on a separate piece of paper (1 per group) • Draw individual on poster paper • Compare your species to classmates species and answer questions

49. Polyploidy • Polyploidy refers to individuals or populations with three or more sets of chromosomes • 3n = triploid • 4n = tetraploid • 5n = pentaploid • Occurs when cell division does not completely separate copies of chromosomes

50. Polyploidy • Having multiple sets of chromosomes makes errors more likely to occur during replication. • Makes polyploidy individuals great source of speciation • Much more common in plants, which results in more vigorous plants that produce bigger fruits or are more resistant to diseases