Question

37.E Coli evolve rapidly via natural selection. Specifically, which of the 3 steps of natural selection accounts for small mutations improving efficiency, ultimately allowing E. Coll to eat citrate? a. Potentiation b. Acclimation c. Actualization d. Refinemente. Rearrangement 38. Pocket mice with different coat colors living in 2 distinct habitats in the Sonoran Desert are an example of which type of natural selection? a. Directional b. Stabilizing c. Disrupting d. Correlating e. None of the above 39. Explain how natural selection and artificial selection differ. 40. T/F: Disruptive selection is harmful to the species and always favors one trait? 41. T/F Reinforcement only occurs when species live in the same geographic location 42. What is one example of a species concept and what are its uses and limitations? 43. Which of the following examples does not match the given type of Natural Selection? A. Directional: Pocket Mice B. Stabilizing: Sickle Cell anemia C. Disruptive, Mocker Swallowtail D. None are contact

Answer 1

37. Potentiation, Actualization and Refinement are three steps of natural selection which accounts for small mutations improving effeciency, ultimately allowing E.coli to eat citrate.

The adaption of E.coli to consume citrate is finding of experimental evolution which is done by Richard lenski on E. coli. During the course of evolution a wide variety of phenotypic and genotypic changes have observed in E. coli population. The most striking observation is evolution of aerobic growth of bacteria on citrate which is not the characteristic of E.coli. Normally E.coli is unable to grow on citrate due to absence of expressed citrate transporter protien in presence of oxygen. It has complete citric acid cycle and uses citrate as an intermediate. It grows anaroebically on citrate through fermentation process because of the presence of citrate-succinate antiporter gene. The ability of E.coli to grow aroebically on citrate arouse due to nonadaptive potentiating mutation which increase the rate of mutation and happned in three distinctive steps: 1.a small mutation happned which increase the mutation rate in order to make it accesible (Potentaition). 2. Mutation results in a particular trait in its weak form (Actualization). 3.Once a particular trait become visible according to its fitness and natural selection process it is improved by later mutations making it more effctive and beneficial for the organism (Refinement).