Ecology, Food Chains & Ecosystems MCQs 2026

What type of symbiotic relationship benefits both species involved

1. A Mutualism ✓
2. B Commensalism ✓
3. C Parasitism ✓
4. D Predation ✓

What term describes organisms that produce their own food through photosynthesis, forming the base of most food chains

1. A Producers ✓
2. B Consumers ✓
3. C Decomposers ✓
4. D Predators ✓

What term describes organisms that obtain energy by consuming other organisms

1. A Producers ✓
2. B Consumers ✓
3. C Decomposers ✓
4. D Autotrophs ✓

What term describes organisms that break down dead organic matter, returning nutrients to the ecosystem

1. A Producers ✓
2. B Consumers ✓
3. C Decomposers ✓
4. D Predators ✓

What term describes an animal that eats only plants

1. A Carnivore ✓
2. B Herbivore ✓
3. C Omnivore ✓
4. D Decomposer ✓

What term describes an animal that eats only other animals

1. A Carnivore ✓
2. B Herbivore ✓
3. C Omnivore ✓
4. D Producer ✓

What term describes an animal that eats both plants and animals

1. A Carnivore ✓
2. B Herbivore ✓
3. C Omnivore ✓
4. D Decomposer ✓

What is the term for the linear sequence showing energy transfer from producers through various consumer levels

1. A Food web ✓
2. B Food chain ✓
3. C Trophic pyramid (related concept) ✓
4. D Ecosystem ✓

What is the term for a more complex, interconnected network of multiple overlapping food chains

1. A Food web ✓
2. B Food chain (simpler, linear version) ✓
3. C Trophic level ✓
4. D Biome ✓

What is the term for each successive feeding level in a food chain

1. A Trophic level ✓
2. B Biome ✓
3. C Habitat ✓
4. D Niche ✓

Approximately what percentage of energy is transferred from one trophic level to the next in a food chain

1. A 1% ✓
2. B 10% ✓
3. C 50% ✓
4. D 90% ✓

What is the term for the specific physical location or environment where an organism lives

1. A Niche ✓
2. B Habitat ✓
3. C Biome ✓
4. D Population ✓

What is the term for the specific functional role an organism plays within its ecosystem, including its interactions and resource use

1. A Niche ✓
2. B Habitat ✓
3. C Biome ✓
4. D Community ✓

What is the term for a large geographic area characterized by specific climate conditions and characteristic plant and animal communities

1. A Habitat ✓
2. B Niche ✓
3. C Biome ✓
4. D Population ✓

What is the term for all the individuals of a single species living in a specific area

1. A Population ✓
2. B Community ✓
3. C Ecosystem ✓
4. D Biome ✓

What is the term for all the different populations of various species living and interacting in a specific area

1. A Population ✓
2. B Community ✓
3. C Ecosystem ✓
4. D Biome ✓

What is the term encompassing a community of organisms together with their physical, non-living environment

1. A Population ✓
2. B Community ✓
3. C Ecosystem ✓
4. D Biosphere ✓

What is the term for the entirety of Earth's regions supporting life, encompassing all ecosystems

1. A Ecosystem ✓
2. B Biome ✓
3. C Biosphere ✓
4. D Habitat ✓

What is the term for the cycling of carbon between the atmosphere, living organisms, oceans, and geological formations

1. A Nitrogen cycle ✓
2. B Carbon cycle ✓
3. C Water cycle ✓
4. D Phosphorus cycle ✓

What is the term for the cycling of nitrogen through the atmosphere, soil, and living organisms, essential for protein synthesis

1. A Carbon cycle ✓
2. B Nitrogen cycle ✓
3. C Water cycle ✓
4. D Sulfur cycle ✓

What is the term for the continuous movement of water between the atmosphere, land, and oceans, through evaporation, condensation, and precipitation

1. A Carbon cycle ✓
2. B Nitrogen cycle ✓
3. C Water cycle (Hydrological cycle) ✓
4. D Phosphorus cycle ✓

Which process, part of the nitrogen cycle, converts atmospheric nitrogen gas into forms usable by plants, often performed by certain bacteria

1. A Nitrification ✓
2. B Nitrogen fixation ✓
3. C Denitrification ✓
4. D Ammonification ✓

Which type of bacteria, found in the root nodules of legume plants, are particularly important for nitrogen fixation

1. A Rhizobium bacteria ✓
2. B E. coli bacteria ✓
3. C Salmonella bacteria ✓
4. D Streptococcus bacteria ✓

What term describes a close, long-term biological interaction between two different species

1. A Symbiosis ✓
2. B Competition ✓
3. C Predation ✓
4. D Extinction ✓

What type of symbiotic relationship benefits one species while having no significant effect on the other

1. A Mutualism ✓
2. B Commensalism ✓
3. C Parasitism ✓
4. D Competition ✓

What type of symbiotic relationship benefits one species (the parasite) at the expense of the other (the host)

1. A Mutualism ✓
2. B Commensalism ✓
3. C Parasitism ✓
4. D Mutualism (repeat, incorrect) ✓

What term describes the interaction between organisms competing for the same limited resources

1. A Symbiosis ✓
2. B Competition ✓
3. C Mutualism ✓
4. D Commensalism ✓

What term describes the interaction where one organism (predator) hunts and consumes another organism (prey)

1. A Competition ✓
2. B Predation ✓
3. C Mutualism ✓
4. D Commensalism ✓

What term describes the maximum population size an environment can sustainably support given available resources

1. A Population growth rate ✓
2. B Carrying capacity ✓
3. C Biodiversity index ✓
4. D Ecological footprint ✓

What term describes the variety of different species and genetic diversity within an ecosystem or region

1. A Population density ✓
2. B Biodiversity ✓
3. C Carrying capacity ✓
4. D Trophic level ✓

What is the term for a species found exclusively in one specific geographic region and nowhere else naturally

1. A Native species ✓
2. B Endemic species ✓
3. C Invasive species ✓
4. D Indicator species ✓

What is the term for a species found naturally in a particular region, not introduced by humans

1. A Invasive species ✓
2. B Native species ✓
3. C Endangered species ✓
4. D Indicator species ✓

What term describes the relatively stable, mature ecological community that develops at the endpoint of succession

1. A Pioneer community ✓
2. B Climax community ✓
3. C Primary community ✓
4. D Transitional community ✓

What term describes the first organisms to colonize a newly available or disturbed habitat during succession

1. A Pioneer species ✓
2. B Climax species ✓
3. C Keystone species ✓
4. D Endemic species ✓

Which major terrestrial biome is characterized by extremely low precipitation, found in both hot and cold variations

1. A Tundra ✓
2. B Desert ✓
3. C Grassland ✓
4. D Taiga ✓

Which major terrestrial biome is characterized by permanently frozen subsoil (permafrost) and low-growing vegetation

1. A Desert ✓
2. B Tundra ✓
3. C Grassland ✓
4. D Rainforest ✓

Which major terrestrial biome is dominated by grasses, with relatively few trees, such as the African savanna

1. A Desert ✓
2. B Tundra ✓
3. C Grassland (Savanna) ✓
4. D Taiga ✓

What is the term for a non-native species introduced to an ecosystem, often causing ecological or economic harm

1. A Keystone species ✓
2. B Invasive species ✓
3. C Native species ✓
4. D Endemic species ✓

Which major terrestrial biome has the highest biodiversity, characterized by dense vegetation and consistent warm, wet conditions

1. A Desert ✓
2. B Tundra ✓
3. C Taiga ✓
4. D Tropical rainforest ✓

Which major terrestrial biome, also called boreal forest, is characterized by coniferous trees and cold climates

1. A Tundra ✓
2. B Taiga ✓
3. C Desert ✓
4. D Tropical rainforest ✓

What term describes a wetland ecosystem characterized by standing water and typically dominated by trees, such as a swamp

1. A Marsh ✓
2. B Swamp ✓
3. C Bog ✓
4. D Estuary ✓

What term describes a wetland ecosystem where a river meets the sea, characterized by a mix of fresh and salt water

1. A Marsh ✓
2. B Swamp ✓
3. C Bog ✓
4. D Estuary ✓

What is the term for a species that plays a disproportionately large role in maintaining the structure of an ecosystem

1. A Keystone species ✓
2. B Invasive species ✓
3. C Endangered species ✓
4. D Indicator species ✓

What is the term for planting trees or forests on land that previously did not have forest cover

1. A Deforestation ✓
2. B Afforestation ✓
3. C Reforestation (restoring previously forested land) ✓
4. D Desertification ✓

What is the term for large-scale removal of forests, often for agriculture or development, significantly affecting ecosystems

1. A Afforestation ✓
2. B Deforestation ✓
3. C Reforestation ✓
4. D Conservation ✓

What term describes an aquatic ecosystem's zone nearest the shore, where sunlight can reach the bottom

1. A Intertidal zone ✓
2. B Photic zone (general term) ✓
3. C Benthic zone ✓
4. D Pelagic zone ✓

What is the term for a legally protected area specifically designated to conserve natural ecosystems and wildlife

1. A National park (protected area, general term) ✓
2. B Farmland ✓
3. C Industrial zone ✓
4. D Residential zone ✓

What term describes the ocean or lake floor and the organisms that live there

1. A Photic zone ✓
2. B Pelagic zone ✓
3. C Benthic zone ✓
4. D Littoral zone ✓

What term describes the open water zone of an ocean or large lake, away from the shore or bottom

1. A Benthic zone ✓
2. B Pelagic zone ✓
3. C Intertidal zone ✓
4. D Littoral zone ✓

What term describes the coastal area between high and low tide marks

1. A Pelagic zone ✓
2. B Benthic zone ✓
3. C Intertidal zone ✓
4. D Abyssal zone ✓

What term describes measures taken to protect and preserve natural ecosystems and biodiversity for future generations

1. A Exploitation ✓
2. B Conservation ✓
3. C Extraction ✓
4. D Deforestation ✓

What is the term for the overall impact a person or activity has on the environment, often measured in terms of resource use and waste

1. A Carbon footprint ✓
2. B Ecological footprint ✓
3. C Biodiversity index ✓
4. D Carrying capacity ✓

What term specifically measures the amount of greenhouse gases produced by an individual, organization, or activity

1. A Ecological footprint (broader) ✓
2. B Carbon footprint ✓
3. C Water footprint ✓
4. D Biodiversity index ✓

What term describes practices that meet current needs without compromising the ability of future generations to meet their own needs

1. A Exploitation ✓
2. B Sustainability ✓
3. C Extraction ✓
4. D Depletion ✓

What term describes succession occurring in an area that previously supported life but was disturbed, retaining existing soil

1. A Primary succession ✓
2. B Secondary succession ✓
3. C Climax succession ✓
4. D Tertiary succession ✓

What term describes succession occurring in a completely new area with no prior soil or living organisms, such as after a volcanic eruption

1. A Primary succession ✓
2. B Secondary succession ✓
3. C Climax succession ✓
4. D Tertiary succession ✓

What term describes the process by which an ecosystem's species composition gradually changes over time following a disturbance

1. A Biodiversity ✓
2. B Ecological succession ✓
3. C Natural selection ✓
4. D Adaptation ✓

What term describes a species whose presence, abundance, or absence reflects the overall health of an ecosystem

1. A Keystone species ✓
2. B Indicator species ✓
3. C Invasive species ✓
4. D Endemic species ✓

What organization maintains the internationally recognized "Red List" tracking the conservation status of species worldwide

1. A WWF (World Wildlife Fund) ✓
2. B IUCN (International Union for Conservation of Nature) ✓
3. C UNESCO ✓
4. D WHO ✓

What is the term for a species at risk of extinction throughout all or a significant portion of its range

1. A Invasive species ✓
2. B Endangered species ✓
3. C Native species ✓
4. D Keystone species ✓

What term describes the use of living organisms, such as certain bacteria, to clean up environmental contamination

1. A Bioaccumulation ✓
2. B Biomagnification ✓
3. C Bioremediation ✓
4. D Biodegradation (related, more general) ✓

What is the term for the process by which fertile land becomes increasingly arid, often due to drought or unsustainable land use

1. A Afforestation ✓
2. B Desertification ✓
3. C Reforestation ✓
4. D Conservation ✓

What term describes the gradual increase in concentration of certain substances, like pesticides, as they move up the food chain

1. A Bioaccumulation ✓
2. B Biomagnification ✓
3. C Bioremediation ✓
4. D Biodegradation ✓

What term describes the accumulation of substances within an individual organism over time, from its environment

1. A Bioaccumulation ✓
2. B Biomagnification (broader, food-chain concept) ✓
3. C Bioremediation ✓
4. D Biodegradation ✓

What famous historical case study, involving the pesticide DDT, highlighted the dangers of biomagnification, particularly affecting bird populations

1. A DDT and eagle/raptor population decline ✓
2. B Chernobyl disaster ✓
3. C Exxon Valdez oil spill ✓
4. D Bhopal gas tragedy ✓

Which influential book, published in 1962 by Rachel Carson, raised widespread public awareness about pesticide dangers, notably DDT

1. A Silent Spring ✓
2. B A Sand County Almanac ✓
3. C Walden ✓
4. D The Origin of Species ✓

What is the term for the layer of gases surrounding Earth that traps heat, contributing to a habitable temperature range

1. A Ozone layer ✓
2. B Greenhouse effect (process, not layer) ✓
3. C Atmosphere (general term for the gas layer itself) ✓
4. D Troposphere (specific atmospheric layer) ✓

What natural process, essential for life, involves certain atmospheric gases trapping heat from the sun, maintaining Earth's temperature

1. A Ozone depletion ✓
2. B Greenhouse effect ✓
3. C Photosynthesis (unrelated process) ✓
4. D Nitrogen fixation (unrelated process) ✓

Which gas is the primary contributor to the enhanced (human-caused) greenhouse effect and climate change

1. A Nitrogen ✓
2. B Carbon dioxide ✓
3. C Argon ✓
4. D Neon ✓

Besides carbon dioxide, which other significant greenhouse gas is released from sources like livestock digestion and landfills

1. A Oxygen ✓
2. B Methane ✓
3. C Nitrogen ✓
4. D Argon ✓

What is the term for the protective atmospheric layer that absorbs most of the sun's harmful ultraviolet radiation

1. A Greenhouse layer ✓
2. B Ozone layer ✓
3. C Troposphere ✓
4. D Ionosphere ✓

Which class of chemicals, once widely used in refrigerants and aerosols, was found to significantly deplete the ozone layer

1. A CFCs (Chlorofluorocarbons) ✓
2. B Carbon dioxide ✓
3. C Methane ✓
4. D Nitrogen oxides ✓

Which international agreement, signed in 1987, successfully phased out ozone-depleting substances like CFCs

1. A Kyoto Protocol ✓
2. B Montreal Protocol ✓
3. C Paris Agreement ✓
4. D Rio Declaration ✓

Which major international agreement, adopted in 2015, aims to limit global temperature rise through coordinated climate action

1. A Kyoto Protocol ✓
2. B Montreal Protocol ✓
3. C Paris Agreement ✓
4. D Rio Declaration ✓

What renewable energy source captures energy directly from sunlight

1. A Wind energy ✓
2. B Solar energy ✓
3. C Hydroelectric energy ✓
4. D Geothermal energy ✓

What renewable energy source captures energy from moving air

1. A Solar energy ✓
2. B Wind energy ✓
3. C Hydroelectric energy ✓
4. D Geothermal energy ✓

What renewable energy source captures energy from flowing or falling water

1. A Solar energy ✓
2. B Wind energy ✓
3. C Hydroelectric energy ✓
4. D Geothermal energy ✓

What renewable energy source captures heat energy from within the Earth itself

1. A Solar energy ✓
2. B Wind energy ✓
3. C Hydroelectric energy ✓
4. D Geothermal energy ✓

What renewable energy source is derived from organic materials such as plants and waste, often converted into fuel

1. A Solar energy ✓
2. B Biomass energy ✓
3. C Hydroelectric energy ✓
4. D Geothermal energy ✓

What non-renewable energy source, formed from ancient organic matter over millions of years, includes coal, oil, and natural gas

1. A Renewable energy (general category) ✓
2. B Fossil fuels ✓
3. C Nuclear energy (different category) ✓
4. D Biomass energy (renewable) ✓

What energy source relies on nuclear fission reactions, typically using uranium, to generate significant electrical power

1. A Solar energy ✓
2. B Wind energy ✓
3. C Nuclear energy ✓
4. D Geothermal energy ✓