Ecosystems
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50 free Ecosystems trivia questions with answers — science & nature quiz, new questions added Oct 2026.
An ecosystem is never still. A single new arrival, a missing predator or one dry decade can reshape everything that lives in a place, and some of the best stories in science come from watching that happen. This quiz draws on those stories as well as the core ideas behind them. The questions cover the jobs living things do, from making food to clearing up the dead, the partnerships and rivalries between them, and the factors that hold a population in check whether it is crowded or sparse. They also follow ecosystems through change: recovery after eruptions and fires, the damage done by newcomers and pollution, and the people who first worked out the rules. It is written for students reviewing a unit on ecosystems, teachers who want a ready-made multiple-choice set, and anyone curious about how nature holds together. Every answer comes with a short explanation, so a wrong guess still teaches something.
30 of 50 questions with answers and explanations. Play the quiz
Q 01Which rodents, the textbook ecosystem engineers, turn streams into ponds that other species use?
Beavers
Beavers dam streams with trees they fell themselves, and the ponds and wetlands that form behind the dams trap sediment and pollutants that would otherwise wash downstream.
Q 02Which animals, freed for hunting in Australia in 1859, grew into a plague of hundreds of millions?
Rabbits
Rabbits spread so fast that within ten years two million a year could be shot or trapped with no visible effect. A virus released in 1950 finally cut an estimated 600 million down to about 100 million.
Q 03Gray wolves, moose and wild horses now roam the evacuated zone around which nuclear disaster site?
Chernobyl
Chernobyl was evacuated in 1986, and since then its wolves, wild boar, red deer and moose have multiplied so much that they have begun spreading beyond the zone.
Q 04Which giant snakes from Southeast Asia, once sold as pets, now hunt the mammals of the Everglades?
Burmese pythons
Burmese pythons were recognized as a breeding population in the Everglades in 2000, and road surveys since then suggest sightings of raccoons, opossums and bobcats have fallen sharply where the snakes spread.
Q 05Which bird, once the most abundant in North America at some three billion, was extinct by 1914?
Passenger pigeon
Passenger pigeon flocks could take hours to pass overhead, but commercial hunting on a huge scale and the clearing of forests wiped them out. The last bird, Martha, died at the Cincinnati Zoo.
Q 06Coral bleaching happens when heat-stressed corals expel which tiny partners living in their tissues?
Algae
Algae called zooxanthellae give corals their color and up to 90 percent of their energy, so a coral that stays bleached for long may begin to starve.
Q 07Which volcano's 1980 eruption has been studied by ecologists more than any other eruption?
Mount St. Helens
Mount St. Helens has had more ecological study than any other eruption, because researchers moved in at once and the blast had not sterilized the ground around it.
Q 08Which Japanese vine, planted in the American South to hold soil, now smothers trees and buildings?
Kudzu
Kudzu arrived from Japan at the 1876 Centennial Exposition in Philadelphia and was first sold as a vine to shade porches, before farmers were handed it as cattle fodder and ground cover.
Q 09Which Central Asian lake shrank to a tenth of its size after its rivers were diverted to farms?
Aral Sea
The Aral Sea began shrinking in the 1960s, when Soviet planners diverted the two rivers feeding it to irrigate cotton fields. Part of the old lake bed is now called the Aralkum Desert.
Q 10Which 1930s disaster hit the Great Plains after farmers plowed up the grasses that held the soil?
Dust Bowl
The Dust Bowl followed a decade of deep plowing that stripped the plains of native grasses, so when drought came, the wind lifted the loose earth into clouds that reached New York and Washington.
Q 11Which role in an ecosystem do trees, grasses and seaweeds fill by making their own food from sunlight?
Producers
Producers sit at the bottom of every food chain, supplying both the energy that other living things consume and the oxygen that they breathe.
Q 12Which term names primary consumers such as deer and grasshoppers?
Herbivores
Herbivores are called primary consumers because they are the first animals in a food chain, able to live on tough, fibrous plants alone. The Latin form, herbivora, turns up in Charles Lyell's 1830 Principles of Geology.
Q 13Millipedes, woodlice and slugs fill which ecosystem role by eating dead leaves and droppings?
Detritivores
Q 21Which term, written as K in growth equations, is the largest population an environment can support?
Carrying capacity
Carrying capacity is set by the food, water, shelter and other resources on offer, and as a growing population closes in on it, growth slows and the numbers level off.
Q 22Which kind of factor is a flood or wildfire, which kills no matter how crowded a population is?
Density-independent
Density-independent factors are usually physical, such as weather, natural disasters and pollution, whereas disease and competition bite harder as a population gets more crowded.
Q 23Which term covers anything in short supply, such as light on a forest floor, that holds back growth?
Detritivores swallow lumps of dead matter and so speed up decay, unlike fungi and bacteria, which cannot take in solid pieces and must absorb their food molecule by molecule.
Q 14Which word do ecologists use for the role a species plays in its ecosystem?
Niche
Niche sums up how a species makes its living, and two species cannot share an identical one for long: when they compete, one eventually drives the other out.
Q 15Which label do ecologists give a species whose removal would drastically change its whole ecosystem?
Keystone
Keystone species matter far more than their numbers suggest. Robert Paine showed it by removing starfish from a Washington shore: the mussels they had been eating quickly crowded out the other species.
Q 16Clownfish shelter in sea anemones and chase off fish that eat them, a case of which relationship?
Mutualism
Mutualism means both partners come out ahead: the anemone's stinging tentacles keep predators off the clownfish, and the clownfish chase away the butterflyfish that feed on anemones.
Q 17Which bird lays its eggs in the nests of reed warblers and pipits, leaving them to raise the chick?
Cuckoo
Cuckoo chicks can hatch before the host's own young and push the remaining eggs out of the nest, so the foster parents pour all their effort into feeding the intruder.
Q 18Which service do bees, butterflies and hummingbirds perform as they feed from flower to flower?
Pollination
Pollination lets most flowering plants set seed, and it pays farmers too: fields close to wild habitat get more insect visitors and so produce higher crop yields.
Q 19Which diagram shows what eats what across a whole ecosystem by joining many feeding paths together?
Food web
A food web is many food chains woven together. The name replaced 'food cycle', the term Charles Elton used in his 1927 book Animal Ecology.
Q 20Which fish rides on sharks and turtles using a sucker on its head, a classic case of commensalism?
Remora
Remora cling on with a dorsal fin reshaped into an oval suction disc, and spend most of their lives attached to a host, which earned them the nickname sharksucker.
Limiting factor
A limiting factor works by Liebig's law of the minimum: growth is set by the scarcest resource, not by the total amount of resources available.
Q 24Which animals, 29 of them left on Alaska's St. Matthew Island in 1944, boomed to 6,000 and then crashed?
Reindeer
Reindeer were put ashore by the US Coast Guard as an emergency food supply and then abandoned. The herd peaked at about 6,000 in 1963, fell to 42 within two years and had died out by the 1980s.
Q 25White-nose syndrome, a fungus first spotted in a New York cave in 2006, has killed millions of which animals?
Bats
Bats with the disease carry a fungus on their skin, and by 2012 an estimated 5.7 to 6.7 million had died across North America, leaving huge numbers of insects uneaten.
Q 26Yeast in a test tube booms, slows and levels off, tracing which curve shape typical of logistic growth?
S-shaped
S-shaped curves appear whenever resources run short: growth is fast at first, slows as supplies get scarce and then flattens, while unlimited resources would give a J-shaped curve instead.
Q 27Which effect describes animals in a very small population struggling to find mates or defend themselves as a group?
Allee
The Allee effect is named for Warder Clyde Allee, who showed in the 1930s that goldfish survive better when more of them share a tank, reversing the usual rule that crowding slows growth.
Q 28Which English clergyman's 1798 essay on population outrunning food supply influenced Charles Darwin?
Thomas Malthus
Thomas Malthus argued that population grows exponentially while food production grows only arithmetically, and both Charles Darwin and Alfred Russel Wallace were among his readers.
Q 29In ecology, which word names all the populations of different species living together in one area?
Community
A community is only the living part of the picture: add the non-living surroundings, such as air, water and soil, and the whole thing becomes an ecosystem.
Q 30Which word, coined by geologist Eduard Suess in 1875, names the worldwide sum of all ecosystems?
Biosphere
The biosphere is also called the zone of life on Earth, and Suess defined it simply as the place on the planet's surface where life dwells.