Dr. Ratcliff's Evolutionary Study

The current evolutionary model has all forms of life originating from one original single celled microbial organism. The transition from microbes to life took roughly 3 billion years. The transition is rather intriguing as cells go from individual organisms into one large codependent ones that work together to ensure survival. Yet despite the difficulty to make that leap, many different organisms have made it successfully.

Dr. Ratcliff wanted to study this very transition. In order to study it Dr. Ratcliff had to set up an environment which would put evolutionary pressure on brewer’s yeast cells, which are single celled organisms, to become multicellular. To do that, Dr. Ratcliff put lines of yeast in 10 different flasks of broth. Dr. Ratcliff and his team then let flasks shake for a day so that the yeast would settle. The next day a drop was removed from the flask and placed in a new one. This would select for yeast cells with a mutation that would lead to settling towards the bottom the fastest, as yeast from the bottom would be taken to a new flask and allowed to reproduce.

Several weeks later the yeast was beginning to fall to the bottom more quickly, and when Ratcliff observed the cells under a microscope he found that they had clustered together by the
To measure the effectiveness we measured how much of the sugar solution was lost to the reaction over a fixed period of time. The yeast uses the sugar in order to provide energy for the daughter cells when the parent cells reproduce. Like in Dr. Ratcliff’s experiment our experiment made use of the principles of fermentation to learn more about yeast. However, whereas our experiment sought to find more about the use of different sugars, Dr. Ratcliff’s sought to use it for reproductory