the largest extinction, measured as a percentage of species that disappeared, occurred at the end of which geological period?

Guard cells control which event? the growth of plants capture of solar energy gas exchange in leaves water absorption in roots

Aresearcher created three groups based on participants bmi: normal weight, overweight and obese. the hypothesis being tested is that the three groups differ in the mean number of artificially sweetened drinks consumed weekly. which statistical test might the researcher use, assuming a reasonably normal distribution of values.

Suppose you are provided with an actively dividing culture of e. coli bacteria to which radioactive thymine has been added. what would happen if a cell replicates once in the presence of this radioactive base?