11. You are a research scientist for the National Institutes of Health (NIH) interested in performing
a controlled experiment to determine the effects of caffeine on human blood pressure. One group
of people will get caffeinated coffee and one will get decaffeinated coffee. Briefly explain why
you would want that to be the only variable that differs between the two groups.

Joe is breeding cockroaches in his dorm room. he finds that the average wing length in his population of cockroaches is 4 cm. he chooses the six cockroaches that have the largest wings; the average wing length among these selected cockroaches is 10 cm. joe interbreeds these selected cockroaches. from earlier studies, he knows that the narrow-sense heritability for wing length in his population of cockroaches is 0.6. a. calculate the selection differential and expected response to selection for wing length in these cockroaches. b. what should be the average wing length of the progeny of the selected cockroaches?

Color blindness is a recessive trait. the gene for color blindness is on the x chromosome. the family tree below shows the trait of color blindness. the only unknown is the mother in the first generation

Which statements describe resources? one of the factors people use when deciding where they will live is the availability of resources. renewable resources have little value for people. resources are unevenly distributed throughout the world. energy is the world resource which has the highest use. the use of nonrenewable resources has decreased in recent history. the use of resources is evenly distributed throughout the world. the world's oil supply will last for the next forty years if its use continues as expected.