Mechanisms Of Evolution PDF

LIFE CHAPTER 9 The Mechanisms of Evolution CHAPTER 6 The Mechanisms of Evolution Copyright © 2011 Brooks/Cole — Cengage Learning LIFE...

LIFE CHAPTER 9 The Mechanisms of Evolution CHAPTER 6 The Mechanisms of Evolution Copyright © 2011 Brooks/Cole — Cengage Learning LIFE CHAPTER 9 The Mechanisms of Evolution Resistance on the Rise Patients can become extremely ill due to infections by the Staphylococcus aureus type of bacteria Some organisms are developing resistance to all antibiotics This is a modern day example of evolution by natural selection Copyright © 2011 Brooks/Cole — Cengage Learning LIFE CHAPTER 9 The Mechanisms of Evolution Emergence of Evolution as a Concept A commonly held belief during the 19th century was that each species was created individually Species were not thought to change over time Copyright © 2011 Brooks/Cole — Cengage Learning LIFE CHAPTER 9 The Mechanisms of Evolution Emergence of Evolution as a Concept Charles Baptiste Lamarck Was one of the first to suggest that species descended from other species and can change over time 1.Physical needs resulted in change 2.Changes in organ size were a product of use and disuse Inheritance of acquired characteristics Copyright © 2011 Brooks/Cole — Cengage Learning LIFE CHAPTER 9 The Mechanisms of Evolution Emergence of Evolution as a Concept Was Jean Baptiste Lamarck’s theory of inheritance of acquired characteristics wrong? Yes and no! He was wrong about the inheritance of acquired characteristics. He was right about the idea of change over time! Copyright © 2011 Brooks/Cole — Cengage Learning LIFE CHAPTER 9 The Mechanisms of Evolution Emergence of Evolution as a Concept Darwin and Wallace – HMS Beagle Proposed that all species descended with modification from a common ancestor Proposed that through natural selection, a species that is able to adapt to an environment, increases its chance for survival and reproduction Copyright © 2011 Brooks/Cole — Cengage Learning LIFE CHAPTER 9 The Mechanisms of Evolution Emergence of Evolution as a Concept Evolution by natural selection Nature “selects” favorable traits or adaptations that allow for the survival of the species These traits can be passed on to future generations Copyright © 2011 Brooks/Cole — Cengage Learning LIFE CHAPTER 9 The Mechanisms of Evolution Emergence of Evolution as a Concept Evolution by natural selection Natural selection is the main mechanism behind evolution in nature Evolution acts on populations, not individuals, through genes Copyright © 2011 Brooks/Cole — Cengage Learning LIFE CHAPTER 9 The Mechanisms of Evolution Evidence for Evolution Fossil records, geologic records, comparative morphology, and comparative biochemistry all provide evidence of evolution We find similarities and differences in body form, function, behavior, and biochemistry Copyright © 2011 Brooks/Cole — Cengage Learning LIFE CHAPTER 9 The Mechanisms of Evolution Evidence for Evolution Fossil record Provide records of organisms with different shapes and sizes who lived during earlier times Fossils are found in sedimentary rock Copyright © 2011 Brooks/Cole — Cengage Learning LIFE CHAPTER 9 The Mechanisms of Evolution Evidence for Evolution Fossils in sedimentary rock This type of rock is formed in layers In general, layers closest to the top were formed most recently In general, older rocks contain simpler forms Copyright © 2011 Brooks/Cole — Cengage Learning Layers of Sedimentary Rock  Meter s Time Heigh Million t Fee s of t 450 years 130 Oreodont ago 120 400 110 350 25 100 90 300 Mesohippus 80 250 70 28 60 200 Titanothere 50 150 40 30 100 Ammonite 30 20 50 70 10 Stepped Art Fig. 9-1, p. 159 LIFE CHAPTER 9 The Mechanisms of Evolution Evidence for Evolution Paleontologists have discovered intermediate forms between major groups of an organism Ex. Archaeopteryx Feathers Copyright © 2011 Brooks/Cole — Cengage Learning LIFE CHAPTER 9 The Mechanisms of Evolution Fossil Intermediates of Modern Birds Tail acts as counterbalance Tail feather Copyright © 2011 Brooks/Cole — Cengage Learning  How does fossil evidence support the concept of evolution? 1. Different organisms lived at different times 2. Past organisms were different 3. Fossils in neighboring layers are similar 4. Intermediate fossil forms have surfaced 5. Adaptability to the environment allowed for survival or species disappeared LIFE CHAPTER 9 The Mechanisms of Evolution Evidence for Evolution Evidence from comparative anatomy Homologous elements - organisms with similar organs Similar structures on different organisms help support the idea of descent with modification Copyright © 2011 Brooks/Cole — Cengage Learning Comparative Anatomy  Whale Cheetah Bat Human Ancestral amphibian Stepped Art Fig. 9-3, p. 161 LIFE CHAPTER 9 The Mechanisms of Evolution Evidence for Evolution (a) Fish (b) Human embryo embryo Gill arches Copyright © 2011 Brooks/Cole — Cengage Learning LIFE CHAPTER 9 The Mechanisms of Evolution Comparative Anatomy How does comparative anatomy support descent with modification? By comparing these homologous structures, we can see how natural selection aided in the modification of a body part (e.g., forelimb) of a common ancestor for different functions in different environments Copyright © 2011 Brooks/Cole — Cengage Learning LIFE CHAPTER 9 The Mechanisms of Evolution Evidence for Evolution Vestigial organs Left over organs No apparent use for the organ now Appendix and wisdom teeth are vestigial structures in humans Copyright © 2011 Brooks/Cole — Cengage Learning LIFE CHAPTER 9 The Mechanisms of Evolution Evidence for Evolution Comparative Embryology Looking for similarities between the embryonic stages of different organisms Shows that these organisms may share a common ancestor Copyright © 2011 Brooks/Cole — Cengage Learning  How does comparative embryology provide evidence for evolution? In humans, if a neck pouch fails to form into the eustachian tube, a tube will form leading from the mouth to the neck – like a fish! LIFE CHAPTER 9 The Mechanisms of Evolution Evidence for Evolution Evidence from molecules Thus far, we have found out that all life evolved from a common ancestor that underwent gradual genetic changes If this is true, all living organisms today should share basic molecules Copyright © 2011 Brooks/Cole — Cengage Learning LIFE CHAPTER 9 The Mechanisms of Evolution Evidence for Evolution Evidence from molecules All organisms share –Four DNA bases –20 amino acids –Similar genetic codes Copyright © 2011 Brooks/Cole — Cengage Learning LIFE CHAPTER 9 The Mechanisms of Evolution Evidence for Evolution Evidence from molecules Researchers can compare DNA base pair sequences and amino acids from different species Molecular family trees are drawn and very close to trees based on molecular data collected from fossils Copyright © 2011 Brooks/Cole — Cengage Learning LIFE CHAPTER 9 The Mechanisms of Evolution Evidence for Evolution Evidence from biogeography Geographic distribution of an organism Darwin found similar large birds on three different southern continents He attributed this find to descent with modification Copyright © 2011 Brooks/Cole — Cengage Learning LIFE CHAPTER 9 The Mechanisms of Evolution Evidence for Evolution Gradual change – takes place over a long period of time Divergent Evolution- splitting of the population into two reproductively isolated populations Copyright © 2011 Brooks/Cole — Cengage Learning  Pathways of Descent Presen t Gradual Time Evolutionary Change Past Range of variation within the population Pathways of Descent Divergent Evolution LIFE CHAPTER 9 The Mechanisms of Evolution Evidence for Evolution Adaptive radiation – evolution occurs in a single ancestral group where changes take place to adapt better to different environments Convergent evolution – development of similar characteristics in unrelated species Copyright © 2011 Brooks/Cole — Cengage Learning  Pathways of Descent Adaptive Radiation Pathways of Descent Convergent evolution LIFE CHAPTER 9 The Mechanisms of Evolution Pathways of Descent Tempo of evolution How fast do old species converge, diverge, or radiate into new ones? Copyright © 2011 Brooks/Cole — Cengage Learning Phyletic gradualism All lines change at about the Transitional same rate Ancestor over time  Punctuated equilibrium Extinct Structural changes occur in fits and Ancestor starts LIFE CHAPTER 9 The Mechanisms of Evolution Genetic Variation Single-gene mutation Mutations alter old genes Some are harmful, some helpful, and some are neutral Mutation Copyright © 2011 Brooks/Cole — Cengage Learning LIFE CHAPTER 9 The Mechanisms of Evolution Genetic Variation Gene duplication Chance error creates two copies of a gene One gene retains the original function A mutated copy takes on a new function Copyright © 2011 Brooks/Cole — Cengage Learning Genetic Duplication Ancestral gene Tandem gene duplication Divergenc e One gene copy changes Duplicate gene copy little and retains mutates to new but old function related functions LIFE CHAPTER 9 The Mechanisms of Evolution Genetic Variation Genetic recombination Shuffling the existing alleles around Frequency of alleles in a population’s gene pool remains the same Would shuffling a deck of cards be a good example of genetic recombination? Copyright © 2011 Brooks/Cole — Cengage Learning Genetic Recombination Potions of two homologous chromosomes of a diploid parent Recombination during meiosis A new genetic combination LIFE CHAPTER 9 The Mechanisms of Evolution Genetic Variation Genetic variation Populations like the Cheetah, have very little genetic variation Why could this be a dangerous scenario for this species? Copyright © 2011 Brooks/Cole — Cengage Learning LIFE CHAPTER 9 The Mechanisms of Evolution How is Genetic Variation Inherited The Hardy-Weinberg Principle Allele frequencies and the frequency of genotypes in a population will remain constant in the absence of outside influences Copyright © 2011 Brooks/Cole — Cengage Learning LIFE CHAPTER 9 The Mechanisms of Evolution How is Genetic Variation Inherited The Hardy-Weinberg Principle is true under the following conditions: No mutation No migration or emigration Large population size Random mating No natural selection Copyright © 2011 Brooks/Cole — Cengage Learning LIFE CHAPTER 9 The Mechanisms of Evolution How is Genetic Variation Inherited Hardy-Weinberg Equilibrium When stable allele and genotype frequencies exist in the absence of external pressure The Hardy-Weinberg principle is a theoretical standard to compare against real populations Copyright © 2011 Brooks/Cole — Cengage Learning LIFE CHAPTER 9 The Mechanisms of Evolution Agents of Evolution Mutations Changing an original allele into a new one Natural selection will act upon the new allele Copyright © 2011 Brooks/Cole — Cengage Learning LIFE CHAPTER 9 The Mechanisms of Evolution Agents of Evolution Gene flow Physical flow of alleles into a population through migration Important in the evolution of antibiotic resistant bacteria Copyright © 2011 Brooks/Cole — Cengage Learning LIFE CHAPTER 9 The Mechanisms of Evolution Agents of Evolution Genetic drift Random change in allele frequencies brought about by chance over generations occurring in a small population Ex. bottleneck and founder effects Copyright © 2011 Brooks/Cole — Cengage Learning LIFE CHAPTER 9 The Mechanisms of Evolution Agents of Evolution Bottleneck effect A severe reduction in population size Disease, habitat loss, hunting, natural disaster Causes pronounced genetic drift Copyright © 2011 Brooks/Cole — Cengage Learning LIFE CHAPTER 9 The Mechanisms of Evolution Agents of Evolution Bottleneck effect The elephant seal population had been hunted down to just 20 individuals Population rebounded to tens of thousands Genetic diversity is now very limited Copyright © 2011 Brooks/Cole — Cengage Learning LIFE CHAPTER 9 The Mechanisms of Evolution Agents of Evolution Founder effect Effect of a genetic drift when a small number of individuals start a new population By chance, allele frequencies of founders may not be same as those in original population Copyright © 2011 Brooks/Cole — Cengage Learning LIFE CHAPTER 9 The Mechanisms of Evolution Agents of Evolution Nonrandom mating-inbreeding Nonrandom mating between related individuals Leads to increased homozygosity Can lower fitness when deleterious recessive alleles are expressed Copyright © 2011 Brooks/Cole — Cengage Learning LIFE CHAPTER 9 The Mechanisms of Evolution Agents of Evolution Inbreeding depression Homozygotes become more common Many individuals are produced that are less fit than a normal random- breeding population Copyright © 2011 Brooks/Cole — Cengage Learning LIFE CHAPTER 9 The Mechanisms of Evolution Natural Selection Revisited Natural selection can alter the course of evolution in 3 ways: 1. Directional selection 2. Stabilizing selection 3. Disruptive selection Copyright © 2011 Brooks/Cole — Cengage Learning LIFE CHAPTER 9 The Mechanisms of Evolution Natural Selection Revisited Results of natural selection Directional Selection – population shifts towards a extreme form which is favored – Ex. cheetahs Copyright © 2011 Brooks/Cole — Cengage Learning LIFE CHAPTER 9 The Mechanisms of Evolution Natural Selection Revisited (a) Directional selection Present Tim Number of individuals e Past Many Few Heavier Lighter Phenotyp e Copyright © 2011 Brooks/Cole — Cengage Learning LIFE CHAPTER 9 The Mechanisms of Evolution Natural Selection Revisited Results of natural selection Stabilization Selection –Intermediate forms are favored and extremes are eliminated – extreme forms are less successful Copyright © 2011 Brooks/Cole — Cengage Learning LIFE CHAPTER 9 The Mechanisms of Evolution Natural Selection Revisited (b) Stabilizing selection Present Ti me Past Many individuals Number of Few Short Tall Phenotype Copyright © 2011 Brooks/Cole — Cengage Learning LIFE CHAPTER 9 The Mechanisms of Evolution Natural Selection Revisited Results of natural selection Disruptive selection – the opposite of stabilizing selection Forms at both ends of the range of variation are favored Intermediate forms are selected against Copyright © 2011 Brooks/Cole — Cengage Learning LIFE CHAPTER 9 The Mechanisms of Evolution Natural Selection Revisited (c) Disruptive selection Present Ti me Past Many individuals Number of Few Blue Orange Phenotype Copyright © 2011 Brooks/Cole — Cengage Learning LIFE CHAPTER 9 The Mechanisms of Evolution How Do New Species Originate Reproductive isolating mechanisms Heritable traits that, one way or another, prevent interbreeding Copyright © 2011 Brooks/Cole — Cengage Learning LIFE CHAPTER 9 The Mechanisms of Evolution How Do New Species Originate Examples of reproductive isolating mechanisms Different mating rituals A species’ sperm may not be able to fertilize another species’ eggs Offspring do not survive Offspring may be sterile Copyright © 2011 Brooks/Cole — Cengage Learning LIFE CHAPTER 9 The Mechanisms of Evolution How Do New Species Originate Allopatric speciation Speciation in geographically isolated populations Populations may be separated by a physical barrier Geographic isolation followed by reproductive isolation Copyright © 2011 Brooks/Cole — Cengage Learning  Past Present Allopatric speciation Genetic Barrier Environment Reproductive variation causes is different on isolating split each side of the mechanisms mountain LIFE CHAPTER 9 The Mechanisms of Evolution How Do New Species Originate Sympatric speciation New species arise without barriers Common in development of new species of plants Copyright © 2011 Brooks/Cole — Cengage Learning