Question

2) Earth’s oceans contains 1027 cells of Prochlorococcus, a tiny single-celled cyanobacterium. They have a generation time of approximately 1 generation per day. One of them gets a mutation that increases its exponential growth rate by 5%. The total Prochlorococcus population size is virtually constant from day to day: as many are killed by phage as are born by cell division.

a. What is the exponential growth rate of the ancestor? The mutant?

b. Assuming the ocean is well-mixed and no other mutants occur, how long would it take that single mutant to become 99% of the world’s Prochlorococcus population? c. Humans have been enriching Earth’s atmosphere with Prochlorococcus’ primary growth resource, CO2, for about 150 years. What is the smallest relative fitness advantage that could have become 99% of the Prochlorococcus population in that time period?

d. In practice, would it take more or less time than this for a particular mutation to “sweep” the Prochlorococcus population? Why?

Answer 1

The masuie an acheen abundance in the reans via exclenie lve genomu c avd Paopic dveui E paensel hoth an be calclakel by domla mela! - Berause tMe tu Ine en enichry Earutts c about 150 yeaM. "Th)s would be a near 히than advantage thast could ave becoma 19-J the lochloio caccus