Over millions of years, a flowing river cut a canyon through a mountain exposing many different layers of rock. Upon examining the strata, paleontologists discovered an amazing assortment of
fossils! Examine the images below this block of text. You will see pictures of 7 different living
organisms. These organisms lived at different times in Earth's history. Using the "Geologic Time
Scale Reference Table" determine where each of the 7 organisms would be found in the rock
strata and the approximate time each organism first appeared on Earth. Drag and drop each
picture into the correct square below. In the rectangular boxes to the right of the picture, type
the approximate time (in millions of years) to indicate the age of each organism.

You are studying several alleles of an e. coli helicase gene. one allele, called rsr, confers resistance to rs2014, an antibiotic that works by inhibiting helicase activity. bacteria with the rss allele are sensitive to rs2014. another allele, called ts-, produces a temperature sensitive mutation of the helicase. in bacteria with the ts- allele, helicase is inactivated at 42 °c but functions normally at 37 °c. helicase functions normally at both temperatures in bacteria with the ts allele. you obtain the following data while testing four strains of e. coli at different temperatures and doses of rs2014. each number represents the percentage of maximal dna synthesis. based on this data, assign the appropriate genotype to strains a–d in the spaces provided