I spend about eight hours a day in front of a microscope. I generally have a student on either side of me. I look at the first rotifer in our population and report how many eggs and juveniles it has, whether it is alive, and anything else notable about it. "Two forty six dash bee five is alive has three eggs, two juveniles and extended foot syndrome. The largest juvenile has one egg."
The student on my left, at the computer, enters all of this into the spreadsheet and tells me what to do with the juveniles, based on our established culling rules. "Put the biggest juvi in two forty eight dash a one, cull the other two."
I pick up the mom rotifer in a specially bent glass pipette and wiggle my eyebrows such that my glasses slide off my forehead and onto my nose so that I can see the student to my right. She uses her pipette to point at the hole where the rotifer is going. I squeeze the bulb at the end of my pipette to eject the rotifer into that hole. She looks through a second microscope to make sure the rotifer is actually there. I push my glasses back up, look through my microscope, pick up the juvenile, wiggle my eyebrows again, move it to the well where it needs to go, then move on. All of this takes 15 seconds to one minute, depending on the complexity and which students are working with me. We repeat this process 450 more times each day. By the end of each day we have gathered more demographic data than many field studies of long-lived vertebrates do in several decades. By the end of a month we can see significant evolutionary changes based on the selective pressures we apply through our decisions about who to cull and how much to feed them. It is not glamorous, but it is effective.