9 An experiment is described below. A student was interested in comparing sunblock lotions, which contain chemicals that protect the skin from sunburn. The student purchased three different brands of losion at three different prices and performed an experiment to see which one best protected the skin. The lotions cost $3, $5, and $7 for an 8-ounce bottle. The sun protection factor (SPF) was 30 for all three lotions. The student applied equal amounts of each lotion next to each other on one of her arms. The three areas covered by the lotions were the same size. The student observed the three areas for color change after two hours of sun exposure. Identify two conditions that were held constant in this experiment. There are three.​

Bisphenol a (often called bpa) is a chemical found in products that people use every day, from water bottles to food containers to children's toys. unfortunately, bpa leaches out of its many products and makes its way into our bodies. what are the health effects of bpa exposure? ongoing research is finding that elevated exposure to bpa can affect a wide variety of developmental and physiological processes, but one of the first studies of bpa's health effects came about because of a simple mistake in the lab. at a laboratory at case western reserve university in 1998, geneticist patricia hunt was making a routine check of her female lab mice. as she extracted and examined developing eggs from the ovaries, she began to wonder what had gone wrong. she noticed that many of the eggs showed problems with their chromosomes, and some had irregular amounts of genetic material, which can lead to miscarriages and birth defects in mammals. she learned that a lab assistant had mistakenly washed the plastic mouse cages and water bottles with a harsh soap, releasing bpa from the plastic. knowing that bpa is an endocrine disruptor, a chemical that can enter organisms and mimic hormones, hunt set out to discover whether it had adversely affected her mice.

What happens when water’s salinity increases? mass decreases. freezing point decreases. buoyancy of objects decreases. the amount of dissolved minerals decreases.

Which statement describes characteristics of planarians? a they live in oceans, are parasites, and reproduce only sexually. b they live in fresh water, are parasites, and reproduce only asexually. c they live in oceans, are free living, and reproduce sexually and asexually. d they live in fresh water, are free living, and reproduce sexually and asexually.