ENVIRONMENT

Big, fierce animals—lions and tigers and bears, for example—are relatively scarce in nature. That’s normal. But top predators are now so rare that many are in danger of disappearing. That’s creating ripple effects throughout the natural world that scientists are still trying to figure out. (NPR)

Use our resources to better understand predators and their role in a region’s ecology.

Discussion Ideas

• Scientists in the NPR article are studying the predators and their impact on food webs and ecosystems. What is the difference between a food web and an ecosystem? Read the introduction to our encyclopedic entry for “ecosystem” for a clue.
  • An ecosystem includes inorganic, or never-living, parts of a geographic area. For instance, an ecosystem will include climate, rocks, and other features of the landscape. A food web is limited to living and once-living organisms—what eats and gets eaten!

• Scientists in the NPR article describe predators’ position at the top trophic level. A trophic level describes an organism’s position in a food web: autotrophs (first), herbivores (second), and carnivores, omnivores, and scavengers (third). Take a look at our activity “Marine Food Webs” to better understand trophic relationships.

• Scientists in the NPR article describe a “trophic cascade” as “a type of connecting-the-dots in nature.” Take a look at our diagram of an imaginary food web. This model student work connects the dots on a marine food web, the rocky intertidal zone. Sketch your own food web like the model student work—be sure to include an apex predator!
  • Use our media spotlights on “Marine Communities” or the “African Savanna” for inspiration, but don’t be afraid to imagine your own food web with predators like the ones mentioned in the NPR article—lions, tigers, bears, wolves, cougars, sharks, etc.

• Connect the dots to hypothesize a trophic cascade in your food web, involving different parts of an ecosystem—predator and prey, living and non-living.
  • The NPR article gives a great example. “Armies of deer, grown out of control because of a lack of predators that eat them [such as mountain lions], can devour all the vegetation along streambanks, and that causes erosion along those banks.”