Read the following selection and use the passage to answer the following questions Usually, large secondary or tertiary consumers near the top of the food web, such as wolves, sea stars, sharks, and sea otters, are considered keystone
species. Theses predators, control populations of herbivores, which, in the absence of predators, other types, could multiply and greatly change the plant
community. However, other types if organisms also can exert strong community-wide effects. "Ecosystem engineers' physically modify the environment
shared by community members. Beavers build dams and turn streams into ponds that flood acres of dry land and turn them to swamp. Small organisms
and those toward the bottoms of food web may have even greater impact. Remove the fungi that decompose dead matter or the insects that control plant
growth, and a community may change very rapidly indeed.
Question:
Which of the following would make the best BEST title for this selection?
"Keystone Species in Yellowstone Park"
"Defining Trophic Levels
"Surprising Keystone Species
"Do Keystone Species Exist?

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.