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All 20 Flashcards — Keystone Species
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Question
What is a trophic cascade?
Answer
A trophic cascade is a chain reaction of population changes through a food web after a species is added or removed.
💡 Hint
Domino effect in food web
Question
Define a keystone species.
Answer
A keystone species is a species with a disproportionately large effect on ecosystem structure or function relative to its abundance.
💡 Hint
Big impact, not necessarily common
Question
Define an ecosystem engineer.
Answer
An ecosystem engineer is a species that modifies the physical environment and creates or maintains habitats for other species.
💡 Hint
Changes habitat structure
Question
Quick check: Small population but big ecosystem impact.
Answer
Keystone species.
💡 Hint
Disproportionate impact
Question
Why can ecosystem engineers be keystone species?
Answer
Because habitat changes can affect many other populations, increasing biodiversity and altering community structure.
💡 Hint
One change affects many species
Question
Why are keystone species important for stability?
Answer
They help maintain food-web balance by controlling populations or supporting key interactions, which keeps biodiversity higher.
💡 Hint
Balance + biodiversity
Question
What often happens when a keystone predator is removed?
Answer
Herbivore numbers can increase, plant biomass can decrease, and biodiversity may fall as habitats become simplified.
💡 Hint
More herbivores, fewer plants
Question
Quick check: Domino effect through a food web.
Answer
Trophic cascade.
💡 Hint
Chain reaction
Question
Exam cue: How do you spot a keystone species in a question?
Answer
If removing one species causes major changes across many other species (food web shifts, biodiversity drops), it is likely a keystone species.
💡 Hint
Remove it → big change
Question
Name two ways keystone species support biodiversity.
Answer
They control dominant populations and maintain habitat/food-web structure, allowing more species to coexist.
💡 Hint
Control + structure
Question
Give one ecosystem engineer example and its effect.
Answer
Beavers build dams that create wetlands, increasing habitat for fish, birds, insects and plants.
💡 Hint
Creates new habitat
Question
Why can keystone loss reduce resilience?
Answer
Food-web links weaken and key functions fail, so the ecosystem is less able to recover after disturbance.
💡 Hint
Less stable → slower recovery
Question
Give one example role of a keystone predator.
Answer
A top predator can prevent one prey species from becoming too abundant, protecting plant communities and keeping habitats diverse.
💡 Hint
Controls prey populations
Question
Exam cue: What must you mention for full marks on keystone questions?
Answer
State the keystone has a large effect, then describe knock-on impacts on other populations and biodiversity/food-web stability.
💡 Hint
Effect + knock-on impacts
Question
Exam structure: In 2 steps, explain keystone removal.
Answer
Step 1: remove keystone → immediate population change. Step 2: knock-on effects spread → community structure and biodiversity change.
💡 Hint
Immediate effect + knock-on
Question
How do ecosystem engineers affect abiotic factors?
Answer
They can change water flow, soil moisture, light levels or sedimentation, which reshapes the habitat.
💡 Hint
Think: water, soil, light
Question
Link keystone species to resilience in one phrase.
Answer
Keystone species maintain stability, supporting faster recovery after disturbance.
💡 Hint
Stability → recovery
Question
Link keystone species to resilience in one line.
Answer
Keystone species increase resilience by keeping key ecosystem functions and food-web relationships stable after disturbance.
💡 Hint
Stable function = better recovery
Question
Exam cue: What phrase often signals an ecosystem engineer?
Answer
Look for “creates habitat”, “builds”, “digs”, “modifies environment”, or “changes water flow/soil structure”.
💡 Hint
Creates or modifies habitat
Question
What is one conservation reason to protect keystone species?
Answer
Protecting a keystone species can protect many other species and maintain ecosystem services by keeping the system stable.
💡 Hint
Umbrella effect via stability
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Topic 2.2 hub
Communities and ecosystems
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