Exploring Keystone Species and Trophic Cascades

The video explores the concept of keystone species and trophic cascades in ecosystems. It begins with the green world hypothesis, which suggests predators control herbivore populations. Robert Paine's starfish experiment demonstrated the significant impact of predators on community composition. Further studies on sea otters and orcas revealed complex interactions in marine ecosystems, highlighting the importance of top-down regulation.

What was the primary question Robert Paine sought to answer with his starfish experiment?

• How do starfish reproduce?

• What is the lifespan of a starfish?

• How do predators influence the structure of ecosystems?

• What determines the color of starfish?

What concept did Fred Smith introduce that challenged the existing view of food chains?

• The energy flow hypothesis

• The green world hypothesis

• The producer-consumer hypothesis

• The bottom-up hypothesis

What was the unexpected result of removing starfish from the ecosystem?

• The starfish population increased

• The number of species decreased

• The ecosystem remained unchanged

• The number of species increased

What term did Robert Paine coin to describe the influence of a single species on an ecosystem?

• Primary species

• Keystone species

• Dominant species

• Apex species

What was the main finding of James Estes' research on sea otters?

• Sea otters are primary producers

• Sea otters have no impact on their ecosystem

• Sea otters control the population of sea urchins

• Sea otters are herbivores

What happens to kelp forests when sea otters are removed?

• Kelp forests become more diverse

• Kelp forests disappear

• Kelp forests thrive

• Kelp forests remain unchanged

What did Paine call the cascading effects of one species on others?

• Trophic cascade

• Food chain reaction

• Predator-prey cycle

• Ecological ripple

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Why did orcas start eating sea otters, according to James Estes?

• Sea otters were easier to catch

• Orcas preferred otters over other prey

• The population of whales, their usual prey, was depleted

• Orcas were introduced to new hunting grounds

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What broader implication does the study of keystone species and trophic cascades have for ecology?

• It indicates that predators have no significant role in ecosystems

• It shows that all species have equal impact on ecosystems

• It highlights the importance of top-down regulation in ecosystems

• It suggests that ecosystems are primarily controlled by producers

What is the risk of ignoring the role of apex predators in ecosystems?

• Ecosystems will remain stable

• It will have no impact on ecosystems

• Ecosystems will become more diverse

• It can lead to significant ecological mistakes