Trophic Cascades and Keystone Species

What defines a keystone species in an ecosystem?

• They are the most abundant species in an ecosystem.

• They are the largest species in an ecosystem.

• They have a disproportionately large impact on their ecosystem relative to their abundance.

• They are the first species to colonize a new habitat.

What is the likely outcome if a keystone species is removed from an ecosystem?

• The ecosystem will experience a slight decrease in biodiversity.

• Other species will quickly adapt and fill the vacant niche.

• The ecosystem's primary producers will increase significantly.

• The entire ecosystem structure may collapse or undergo drastic changes.

How do urchins typically impact kelp populations in a marine ecosystem?

• Urchins consume kelp, preventing its growth and establishment.

• Urchins provide nutrients that are essential for kelp growth.

• Urchins create shelter for kelp, protecting it from strong currents.

• Urchins compete with kelp for sunlight, limiting its photosynthetic rate.

What is the primary role of sea otters in maintaining the health of kelp forest ecosystems?

• They directly consume kelp, maintaining its population size.

• They prey on sea urchins, which in turn allows kelp forests to thrive.

• They compete with other marine mammals for food resources.

• They act as decomposers, breaking down dead organic matter in the ecosystem.

What was the state of the kelp forest ecosystem when sea otters were largely absent?

• Kelp forests were abundant and thriving.

• Sea urchin populations were low, allowing kelp to flourish.

• The ecosystem was dominated by sea urchins, with little to no kelp.

• Fish populations increased significantly due to the absence of otters.

What is a trophic cascade?

• The process by which a species becomes extinct due to habitat loss.

• The direct effect of one species on another in a food web.

• The cascading effects of one species' population changes on other species at different trophic levels.

• The movement of energy through different trophic levels in an ecosystem.

Why did killer whale predation on sea otters increase?

• Sea otters became a more preferred food source than their usual prey.

• A decline in the killer whales' traditional prey, large whales, forced them to broaden their diet.

• Sea otter populations had grown too large, leading to increased competition for food.

• Killer whales developed a new hunting strategy specifically for sea otters.

What was the ultimate impact of killer whales preying on sea otters in the kelp forest ecosystem?

• It led to an increase in kelp forests as killer whales also consumed sea urchins.

• It caused a decrease in sea urchin populations, allowing kelp to recover.

• It resulted in an increase in sea urchin populations and a decline in kelp forests.

• It had no significant impact on the kelp forest ecosystem, as otters were not a primary food source.