A sea star is removed from a rocky shore, and mussels then crowd out most other species. What role had the sea star played?

Sea otters decline in a coastal kelp forest; sea urchins increase and kelp disappears. The otters are best classified as what?

After wolves return to an area, elk browse less along streams and willow stands recover. Which species role does this trophic cascade demonstrate?

When beavers disappear from a watershed, their dams vanish and many wetland-dependent species decline. What role did the beavers have?

In a tropical forest, one fig tree species fruits during the dry season when little other fruit is available. Its loss causes several animal populations to fall. The fig tree is what?

Pacific salmon die after spawning, transferring marine nutrients to streams and nearby forests; their loss affects bears, insects, and plants. What role do salmon play?

A gopher tortoise's burrows shelter snakes, frogs, insects, and other animals during fires and droughts. Why is the tortoise important to this community?

A prairie dog colony is eradicated, followed by declines in burrowing owls, black-footed ferrets, and grassland predators. What does this pattern identify the prairie dog as?

In a savanna, elephant removal allows dense woody vegetation to replace open grassland, reducing habitat for grassland specialists. The elephants are functioning as what?

Lichens vanish from tree trunks near an industrial district while many other plants persist. What does their absence most strongly indicate?

A stream survey finds many mayfly, stonefly, and caddisfly larvae. What conclusion is most supported by these indicator organisms?

A water sample contains high levels of Escherichia coli. What condition does this indicator most directly signal?

Why are amphibians often used as indicator species in wetland studies?

In the 1960s, peregrine falcons, which eat other birds, laid thin-shelled eggs that broke during nesting. What environmental problem did these birds indicate?

Native freshwater mussels decline downstream from a factory's effluent pipe. Why can this decline be useful to scientists?

A reef-monitoring program records coral bleaching across many reefs during the same summer. What condition does this widespread bleaching most often indicate?

A pond near farm fields suddenly develops a dense, green algal bloom in midsummer. The bloom is most likely an indicator of what?

A stream once dominated by pollution-tolerant worms now supports diverse mayflies and stoneflies. What does this shift indicate?

A reserve is designed large enough to support a wide-ranging tiger population. What additional conservation result is most likely?

Wildlife managers protect connected forest habitat used by grizzly bears. Why can grizzlies serve as umbrella species?

A recovery plan protects large areas of connected forest and swamp for Florida panthers. Which species is LEAST likely to benefit from the plan?

Conserving old-growth forest for northern spotted owls also protects many organisms that live in old-growth stands. This is an example of what conservation strategy?

A reserve network in Central America is planned around jaguars. What feature makes jaguars useful umbrella species?

Managers protect a large boreal landscape and migration routes for woodland caribou. What is a likely benefit for other wildlife?

Why might a conservation organization protect a wide-ranging mountain lion population rather than only a small isolated patch of habitat?