Trophic Cascades
What Is a Trophic Cascade?
Word of the Week
Keystone Species
A keystone species is an organism that has a very high impact on its ecosystem even when its populations are small.
Without the keystone species, the ecosystem would fall apart!
BRAIN BLAST
What are these important organisms called "keystone" species? Figure out what a keystone is and how it relates to keystone species!
Species Spotlight
Sea Otter
Enhydra lutris
If you are traveling along the Pacific coast of the United States and Canada, you may be lucky enough to catch a glimpse of an adorable sea otter in a pile of kelp! Sea otters spend most of their time resting or eating on the surface of the water or diving more than 100-ft looking for food. They hold their breath for up to 6-minutes while they dive to the ocean floor to collect clams, mussels, crabs, fish, and sea urchins. Cracking open the hard shells of their prey is no problem for a sea otter. They smash the shells using a rock that they often carry under their arm.
Sea otters are much more than just a cute face! They are a keystone species in kelp forest ecosystems where they feed heavily on sea urchins. Sea urchins move along the ocean floor and use their five sharp teeth to chew through vegetation, including kelp. If too many sea urchins are in an area, they can quickly destroy an entire region of kelp forest, which thousands of other species depend on. Sea otters do a great job at keeping urchins populations from growing too large. Without otters, the kelp forest as we know it could be destroyed.
Conservation Corner
What Animals Do We Protect First?
With so many endangered animals in the world, how do scientists decide who to protect? Well, like many things in science, it is complicated!
A group called the International Union for Conservation of Nature (IUCN) works to classify animals based on how close they are to going extinct. When scientists are looking to classify an organism, they look at things like...
- How many individuals are left?
- What threats are they facing?
- How is the health of their habitat?
- What is this animals role in the habitat?
- What can we do to help?
The answers to these questions help scientists determine which animals need help right now and which will need our help in the future. Using the information from the IUCN, we can focus our conservation efforts on animals that need our help the most.
What Would Happen?
For each food chain below, determine what would happen if the species with an "X" is removed from the ecosystem.
Trophic Cascade Challenge
Learn More!
Glossary
Carnivore
An animal that eats other animals.
Decomposer
An organism that breaks down dead matter and returns nutrients to the environment.
Energy
[In biology] The properties used by living organisms to perform normal functions that originate as light energy from the sun and move throughout an ecosystem through food webs.
Food Chain
A tool used by scientists to describe how energy transfers through a single pathway in an ecosystem.
Food Web
A tool used by scientists to describe how different food chains overlap and the different pathways of energy transfer.
Herbivore
An animal that mostly eats plants.
Keystone Species
A species whose presence has an unusually high impact on the ecosystem relative to its population size.
Omnivore
An animal that eats both plants and animals.
Photosynthesis
The process used by plants to take energy from the sun and change it into energy for themselves that can then move through the ecosystem.
Phytoplankton
Microscopic algae that float near the surface of aquatic (water) ecosystems.
Predator
An animal that hunts other animals for food.
Prey
An animal that is hunted and eaten by another animal.
Primary Consumer
The second trophic level composed of animals that eat plants (herbivores).
Primary Producer
Plants! The first trophic level and the foundation of most food webs.
Secondary Consumer
The third trophic level composed of animals that eat herbivores.
Tertiary Consumer
The fourth trophic level composed of animals that eat other carnivores.
Trophic Cascade
A domino effect that occurs throughout an ecosystem when an organism is removed or added.
Trophic Level
Describes the position an organism holds in a particular ecosystem or food chain.
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