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All 25 Flashcards — Human impacts
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Question
Define bioaccumulation.
Answer
Bioaccumulation is the buildup of toxins in a single organism over its lifetime because uptake is faster than removal.
💡 Hint
Builds up in one organism
Question
State the big idea: how can humans disrupt food webs without eating organisms?
Answer
By adding pollutants and changing habitats, humans alter survival, reproduction, and energy transfer across trophic levels.
💡 Hint
Pollution + habitat change disrupt energy transfer
Question
State the best one-line definition of bioaccumulation.
Answer
Toxin builds up within one organism over time.
💡 Hint
Within one organism
Question
Define a tipping point in an ecosystem.
Answer
A tipping point is a threshold beyond which an ecosystem undergoes rapid and often irreversible change.
💡 Hint
Threshold → rapid, hard-to-reverse change
Question
Define planetary boundaries.
Answer
Planetary boundaries are limits within which humanity can operate safely without destabilising Earth systems.
💡 Hint
Safe operating limits
Question
State why planetary boundaries matter for ecosystems.
Answer
Crossing boundaries increases the risk of large-scale ecosystem change and loss of resilience.
💡 Hint
Crossing limits increases collapse risk
Question
State the typical tipping point sequence (4 steps).
Answer
Gradual pressure builds → threshold crossed → sudden ecosystem flip → new stable state forms.
💡 Hint
Pressure → threshold → flip → new state
Question
Define pollution (ESS context).
Answer
Pollution is the introduction of harmful substances or harmful energy into the environment.
💡 Hint
Harmful matter or energy
Question
Define biomagnification.
Answer
Biomagnification is the increasing concentration of toxins at higher trophic levels as predators consume contaminated prey.
💡 Hint
Increases up trophic levels
Question
State the best one-line definition of biomagnification.
Answer
Toxin concentration increases at higher trophic levels.
💡 Hint
Up the food chain
Question
State why plastics are a food web problem even when they fragment.
Answer
Plastics persist and fragment into microplastics (<5 mm) that can be ingested at low trophic levels and passed upward.
💡 Hint
Microplastics enter low trophic levels
Question
State one example of a planetary boundary category.
Answer
Examples include climate change, biodiversity loss, nitrogen/phosphorus cycles, and ocean acidification.
💡 Hint
Any one boundary category
Question
State the key difference between bioaccumulation and biomagnification.
Answer
Bioaccumulation happens within one organism over time. Biomagnification happens between trophic levels and increases up the food chain.
💡 Hint
One organism vs up the chain
Question
State why non-biodegradable pollutants are especially damaging.
Answer
They persist, build up in organisms, and can move through food chains for long periods.
💡 Hint
Persistent + builds up
Question
Explain why tipping points link to resilience.
Answer
Low resilience means an ecosystem cannot absorb disturbance, so it reaches a threshold and flips more easily.
💡 Hint
Low resilience → closer to tipping point
Question
Explain how pollutants can reduce energy transfer in a food web.
Answer
Pollutants can reduce growth, survival, or reproduction, so less biomass is passed to higher trophic levels.
💡 Hint
Lower survival/growth → less biomass transfer
Question
Give one named example of a tipping point.
Answer
Coral reefs can flip from coral-dominated to algae-dominated after repeated warming and pollution, and recovery can be very slow.
💡 Hint
Coral → algae shift
Question
Explain how nutrient cycle disruption links to food webs.
Answer
Excess nitrogen/phosphorus can cause eutrophication, leading to oxygen depletion and loss of consumers in aquatic food webs.
💡 Hint
Eutrophication → low oxygen → food web collapse
Question
State one reason pollution can reduce biodiversity.
Answer
Pollutants reduce survival and reproduction, causing population declines and local extinctions.
💡 Hint
Lower survival/reproduction
Question
Explain why apex predators are most affected by biomagnification.
Answer
They eat many contaminated prey, so toxins stored in tissues reach the highest concentrations in top predators.
💡 Hint
Eat many prey → highest toxin concentration
Question
Give one example food chain that shows biomagnification.
Answer
Mercury can move from plankton → small fish → larger fish → tuna, leading to highest concentrations in top consumers (including humans).
💡 Hint
Plankton → fish → tuna → humans
Question
State the exam-ready structure for a short biomagnification answer.
Answer
Define biomagnification, describe a simple food chain, and state why top predators (and humans) get the highest concentration.
💡 Hint
Define → chain → top predator highest
Question
State the best one-sentence exam link for planetary boundaries.
Answer
Planetary boundaries show that exceeding environmental limits can reduce resilience and trigger major ecosystem shifts.
💡 Hint
Exceed limits → resilience down
Question
State why tipping point change can be “hard to reverse”.
Answer
Feedback loops can lock the system into a new stable state and restoring original conditions may be costly or impossible.
💡 Hint
Feedbacks lock in new state
Question
State one human activity that commonly introduces pollutants to ecosystems.
Answer
Industry, agriculture, transport, and waste disposal can all introduce pollutants.
💡 Hint
Industry/agriculture/transport/waste
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