Evolution and Darwin

1. EvolutionandDarwin

2. Evolution • The processes that have transformed life on earth from it’s earliest forms to the vast diversity that characterizes it today. • A change in the genes!!!!!!!!

3. Old Theories of Evolution • Jean Baptiste Lamarck(early 1800’s) proposed: “The inheritance of acquired characteristics” • He proposed that by using or not using its body parts, an individual tends todevelopcertaincharacteristics, which itpasseson to itsoffspring.

4. “The Inheritance of Acquired Characteristics” • Example: A giraffe acquired its long neck because its ancestor stretched higher and higher into the trees to reach leaves, and that the animal’s increasingly lengthened neck was passed on to its offspring.

5. Charles Darwin • Influenced by Charles Lyell who published “Principles of Geology”. • This publication led Darwin to realize that natural forces gradually change Earth’s surface and that the forces of the past are still operating in modern times.

6. Charles Darwin • Darwin set sail on the H.M.S. Beagle (1831-1836) to survey the south seas (mainly South America and the Galapagos Islands) to collect plants and animals. • On the Galapagos Islands, Darwin observed species that lived no where else in the world. • Patterns of diversity, e.g., Pinta, Isabela and Hood island tortoises that ate vegetation, birds (finches) on Galapagos islands • Far more species than previously known • Similar ecosystems did not have same species • Species adapted to their habitat • Fossils – preserved remains of ancient organism • These observations led Darwin to write a book.

7. Charles Darwin • Wrote in 1859: “On the Origin of Species by Means of Natural Selection” • Two main points: 1. Species were not created in their present form, but evolved from ancestral species. 2. Proposed a mechanism for evolution:NATURAL SELECTION

8. Natural Selection • Individuals with favorabletraits are more likely to leave more offspring better suited for their environment. • Also known as “Differential Reproduction” • Example: English peppered moth (Biston betularia) - light and dark phases

9. Peppered moths rest on trees and depend on camouflage for protection.

10. Evolution by Natural Selection • Evolution by Natural Selection • Struggle for existence – competition for resources • Survival of the fittest (natural selection)– Fitness is a result of adaptations • Adaptation – any inherited characteristic that increases an organism’s chance of survival • Types of adaptation- • Camouflage • Mimicry – one species resembles another • Antimicrobial resistance

11. Darwin’s Beliefs About Descent • Descent with modification – over long periods of time, natural selection produces organisms that have different structures, niches or occupy different habitats. Each species has descended with changes from other species over time. • Common descent – all living and extinct species were derived from common ancestors

12. Artificial Selection • Artificial selection – nature provides the variation, but humans select the variations they find useful, e.g. breeding the largest hogs, fastest horses • The selective breeding of domesticated plants and animals by man. • Question: What’s the ancestor of the domesticated dog? • Answer:WOLF

13. Evidence of Evolution 1. Biogeography: Geographical distribution of species. Convergent Evolution - similar environments leads to unrelated species with similar traits 2. Fossil Record: Fossils and the order in which they appear in layers of sedimentary rock (strongest evidence).

14. Evidence of Evolution 3. Comparative anatomy Homologous structures: Structures that are similar because of common ancestry Vestigal structures: traces of homologous organs in other species

15. Evidence of Evolution 4. Comparative embryology: Study of structures that appear during embryonic development. 5. Molecular biology: DNA and proteins (amino acids) 6. Experimental evidence

16. Population Genetics • The science of genetic change in population.

17. Population • A localized group of individuals belonging to the same species.

18. Species • A group of populations whose individuals have the potential to interbreed and produce viable offspring.

19. Gene Pool • The total collection of genes in a population at any one time.

20. Genetics and Evolution • Relative frequency – number of times an allele is present in a gene pool, compared to the number of times other alleles for the same gene are present o EX: Black (B) fur 40% and b fur 60% in mice o In genetic terms, evolution is the change in relative frequency of alleles in a population o May not match Mendelian ratios • Sources of genetic variation o Mutations – change in sequence of DNA o Gene shuffling – different combinations of genes during gamete production and crossing over • Single gene and polygenic traits o Natural selection on single gene traits can lead to changes in allele frequencies and thus evolution (Ex: lizard color, red easy to see and black keeps lizard warmer, reduction in normal brown which has no advantage) o Polygenic – Natural selection is more complex and can affect distributions of phenotypes in 3 modes of action

21. Number of Individuals Small Large Size of individuals Modes of Action • Natural selection has three modes of action: 1. Stabilizing selection 2. Directional selection 3. Diversifying selection

22. Number of Individuals Small Large Size of individuals 1. Stabilizing Selection • Acts upon extremes and favors the intermediate.

23. Number of Individuals Small Large Size of individuals 2. Directional Selection • Favors variants of one extreme.

24. Number of Individuals Small Large Size of individuals 3. Diversifying Selection • Favors variants of opposite extremes.

25. Hardy-Weinberg Principle • The concept that the shuffling of genes that occur during sexual reproduction, by itself, cannot change the overall genetic makeup of a population.

26. Hardy-Weinberg Principle • This principle will be maintained in nature only if all five of the following conditions are met: 1. Very large population 2. Isolation from other populations 3. No net mutations 4. Random mating 5. No natural selection

27. Hardy-Weinberg Principle • Remember: If these conditions are met, the population is at equilibrium. • This means “No Change” or “No Evolution”.

28. Macroevolution • The origin of taxonomic groups higher than the species level.

29. Microevolution • A change in a population’s gene pool over a secession of generations. • Evolutionary changes in species over relatively brief periods of geological time.

30. Five Mechanisms of Microevolution 1. Genetic drift: Change in the gene pool of a small population due to chance. • Two examples: a. Bottleneck effect b. Founder effect

31. a. Bottleneck Effect • Genetic drift (reduction of alleles in a population) resulting from a disaster that drastically reduces population size. • Examples: 1. Earthquakes 2. Volcano’s

32. b. Founder Effect • Genetic drift resulting from the colonization of a new location by a small number of individuals. • Results in random change of the gene pool. • Example: 1. Islands (first Darwin finch)

33. Five Mechanisms of Microevolution 2. Gene Flow: The gain or loss of alleles from a population by the movement of individuals or gametes. • Immigration or emigration.

34. Five Mechanisms of Microevolution 3. Mutation: Change in an organism’s DNA that creates a new allele. 4. Non-random mating: The selection of mates other than by chance. 5. Natural selection: Differential reproduction.

35. Speciation • The evolution of new species.

36. Reproductive Barriers • Any (isolation) mechanism that impedes two species from producing fertile and/or viable hybrid offspring. • Two barriers: 1. Pre-zygotic barriers 2. Post-zygotic barriers

37. 1. Pre-zygotic Barriers a. Temporal isolation: Breeding occurs at different times for different species. b. Habitat isolation: Species breed in different habitats. c. Behavioral isolation: Little or no sexual attraction between species.

38. 1. Pre-zygotic Barriers d. Mechanical isolation: Structural differences prevent gamete exchange. e. Gametic isolation: Gametes die before uniting with gametes of other species, or gametes fail to unite.

39. 2. Post-zygotic Barriers a. Hybrid inviability: Hybrid zygotes fail to develop or fail to reach sexual maturity. b. Hybrid sterility: Hybrid fails to produce functional gametes. c. Hybrid breakdown: Offspring of hybrids are weak or infertile.

40. Allopatric Speciation • Induced when the ancestral population becomes separated by a geographical barrier. • Example: Grand Canyon and ground squirrels

41. Adaptive Radiation • Emergence of numerous species from a common ancestor introduced to new and diverse environments. • Example: Darwin’s Finches

42. Parent population reproductive sub-population Sympatric Speciation • Result of a radical change in the genome that produces a reproductively isolated sub-population within the parent population (rare). • Example: Plant evolution - polyploid A species doubles it’s chromosome # to become tetraploid.

43. Interpretations of Speciation • Two theories: 1. Gradualist Model (Neo-Darwinian): Slow changes in species overtime. 2. Punctuated Equilibrium: Evolution occurs in spurts of relatively rapid change.

44. Convergent Evolution • Species from different evolutionary branches may come to resemble one another if they live in very similar environments. • Example: 1. Ostrich (Africa) and Emu (Australia). 2. Sidewinder (Mojave Desert) and Horned Viper (Middle East Desert)

45. Coevolution • Evolutionary change, in which one species act as a selective force on a second species, inducing adaptations that in turn act as selective force on the first species. • Example: 1. Acacia ants and acacia trees 2. Humming birds and plants with flowers with long tubes

46. Fossils • Fossil - traces and preserved remains of ancient life, formed in sedimentary rock • Types of fossils • Trace - indirect evidence, e.g., footprints • Mold – impression b of an organism • Cast – mold filled with sediment • Replacement – original organism replaced with mineral crystals • Petrified – empty pore spaces filled with minerals, e,g petrified wood • Amber – preserved tree sap traps organism • Original material – mummified or frozen

47. How Are Fossils Dated? • Relative dating – age of a fossil is determined by comparing placement with that of fossils in other layers of rock • Index species – compared with other fossils because they are easily recognized, lived for a short time and had wide geographic range • Radioactive dating – use radioactive decay to assign absolute ages to rocks • Half life – length of time required for half of the radioactive atoms in a sample to decay

48. Early history of life • Solar system~ 12 billion years ago (bya) • Earth~ 4.5 bya • Life~ 3.5 to 4.0 bya • Prokaryotes~ 3.5 to 2.0 bya stromatolites • Oxygen accumulation~ 2.7 bya photosynthetic cyanobacteria • Eukaryotic life~ 2.1 bya • Muticelluar eukaryotes~ 1.2 bya • Animal diversity~ 543 mya • Land colonization~ 500 mya

49. The Origin of Life • Old theory of origin of life – spontaneous generation (from non-living)• Theory of biogenesis (life from life) – Redi, Pasteur Early Atmosphere - hydrogen cyanide, carbon dioxide, carbon monoxide, nitrogen, hydrogen sulfide and water

50. Early Life • How did first cells (bacteria) form? • Protenoid microspheres – large organic molecules form tiny bubbles • First life anaerobic, living in the oceans • Microfossils (microscopic) 3.5 billion years old, when little oxygen in atmosphere • By 2.2 billion years, fossil evidence of microfossils that were photosynthetic