Trace Matter in Ecosystems - Middle School Life Science

What is the main carbon source for plants in the carbon cycle model?

Atmospheric $CO_2$ . Plants absorb $CO_2$ from air during photosynthesis.
Identify the abiotic reservoir in this model: leaf litter → fungi → soil nutrients → plant roots.

Soil nutrients. Decomposers release minerals that plants absorb through roots.
What process moves water into soil and rock, becoming groundwater?

Infiltration. Water seeps through soil pores to become underground water storage.
Which statement best matches matter conservation in ecosystem models?

Atoms are rearranged and transferred, not created or destroyed. Conservation of mass: atoms change form but total amount stays constant.
Find the correct label for this model arrow: dead leaves $\rightarrow$ soil nutrients. What process is shown?

Decomposition. Dead organic matter breaks down into inorganic nutrients.
What is the correct term for organisms that break down dead matter and wastes?

Decomposer. They recycle nutrients from dead organisms back to the ecosystem.
What process moves water vapor from plant leaves into the atmosphere?

Transpiration. Plants release water vapor through stomata during gas exchange.
What process moves matter from dead organisms into soil or water as simpler substances?

Decomposition. Breaks down complex organic matter into simple nutrients.
Which term describes nonliving parts of an ecosystem such as air, water, and soil?

Abiotic components. Abiotic means non-living environmental factors.
What process moves water from liquid to gas from oceans or lakes in models?

Evaporation. Heat energy changes liquid water to water vapor.
What is the term for uptake of water by plant roots from soil?

Absorption (root uptake). Roots take up water and dissolved minerals from surrounding soil.
What is the role of consumers in moving matter through an ecosystem?

They obtain matter by eating other organisms. Consumers transfer matter through food chains.
Which process moves carbon from air into living things in many ecosystems?

Photosynthesis. Plants convert atmospheric $CO_2$ into organic matter.
Which component is abiotic in a model: mushroom, soil nitrate, grass, rabbit?

Soil nitrate. Nitrate is a dissolved mineral nutrient, not a living organism.
Which process moves water vapor from the atmosphere into liquid droplets forming clouds?

Condensation. Cooling water vapor forms tiny droplets that create clouds.
What is the term for organisms that obtain matter by eating other organisms?

Consumers (heterotrophs). Must consume other organisms for energy and matter.
What is the term for nonliving parts of an ecosystem such as water, air, and soil?

Abiotic factors. Non-living components provide physical and chemical conditions for life.
What process moves carbon from atmospheric $CO_2$ into plant biomass?

Photosynthesis. Plants convert $CO_2$ and water into glucose using light energy.
Which arrow direction correctly traces matter in a food chain: resource $\rightarrow$ organism or organism $\rightarrow$ resource?

Resource $\rightarrow$ organism. Arrows point from what is consumed to the consumer.
Choose the correct label for this arrow in a carbon model: animal → atmosphere (released gas).

$CO_2$ . Animals release $CO_2$ during cellular respiration.
Identify the correct path for carbon atoms: $CO_2$ in air → plant → animal → ______.

$CO_2$ back to air (via respiration and decomposition). Carbon returns to atmosphere when organisms respire or decompose.
Which process moves carbon from air into plants: photosynthesis or cellular respiration?

Photosynthesis. Plants convert atmospheric $CO_2$ into glucose using light energy.
What term describes nonliving components in an ecosystem model?

Abiotic factors. Non-living parts like water, air, and minerals.
What are the products of cellular respiration in a matter-tracing model?

Carbon dioxide and water. Respiration releases the same molecules photosynthesis uses.
What is the term for a place where a large amount of matter is stored (for example, atmosphere or soil)?

Reservoir. A storage location where matter accumulates in an ecosystem.
What process moves carbon atoms from atmospheric $CO_2$ into plant sugars?

Photosynthesis. Converts $CO_2$ and water into glucose using light energy.
What is the key rule about energy in ecosystems: is it recycled or does it flow one way?

Energy flows one way and is not recycled. Unlike matter, energy dissipates as heat and can't be reused.
What process returns carbon from organisms to the atmosphere as $CO_2$ ?

Cellular respiration. All organisms release $CO_2$ when breaking down glucose for energy.
Identify the correct arrow for decomposition in a model: Dead organisms → Soil nutrients or Soil nutrients → Dead organisms?

Dead organisms → Soil nutrients. Decomposers break down dead matter, releasing nutrients to soil.
What is meant by movement of matter in an ecosystem model?

Transfer and cycling of atoms among organisms and the environment. Atoms move between living things and nonliving parts like air and soil.
Which arrow direction correctly traces matter in a food chain: producer to consumer or consumer to producer?

Producer to consumer. Arrows show matter flow from eaten to eater in food chains.
Find the abiotic component in this set used in a matter model: algae, fish, water, bacteria.

Water. Only water is nonliving; the others are living organisms.
Which process moves matter from living organisms to the soil as waste materials?

Excretion (waste production). Organisms release nitrogen-rich waste products into the environment.
What is the key rule about matter in ecosystems: is it recycled or created and destroyed?

Matter is recycled; it is not created or destroyed. Follows conservation of mass - atoms rearrange but aren't lost.
What is the name of the process that converts atmospheric $N_2$ into usable nitrogen compounds?

Nitrogen fixation. Bacteria convert $N_2$ gas into ammonia and nitrates.
Find the incorrect statement about matter in ecosystems: "Matter is created during decomposition." What is the correction?

Matter is recycled; it is not created during decomposition. Matter follows conservation law - it transforms but isn't created.
Which process returns carbon to the air when organisms die and are broken down?

Decomposition. Bacteria and fungi break down dead matter, releasing stored carbon.
What is the main way nitrogen enters most food webs from the atmosphere?

Nitrogen fixation by bacteria. Special bacteria convert atmospheric $N_2$ into usable forms.
What is the main abiotic source of carbon used by plants for photosynthesis?

Carbon dioxide in the atmosphere. Plants absorb $CO_2$ from air to build glucose molecules.
What is the term for movement of matter between organisms and the environment in an ecosystem?

Biogeochemical cycling. Matter cycles between living things and their environment continuously.
What is the main nonliving reservoir for nitrogen in the nitrogen cycle?

The atmosphere as $N_2$ gas. 78% of air is nitrogen gas, unusable by most organisms.
Which process moves matter from living organisms to the soil when organisms die?

Death (followed by decomposition). Dead organisms become food for decomposers, returning nutrients to soil.
What is nitrogen fixation in a nitrogen-cycle model?

Conversion of $N_2$ into usable nitrogen compounds by bacteria. Most organisms cannot use atmospheric nitrogen directly.
What is the role of decomposers in returning matter to soil and water?

They release nutrients by breaking down dead organisms and wastes. Decomposition returns essential elements to ecosystems.
Which process moves water from clouds to Earth as rain, snow, sleet, or hail?

Precipitation. Water falls when cloud droplets combine and become too heavy.
Which group is the correct example of abiotic components in an ecosystem model?

Air, water, soil, rocks, and sunlight. These non-living factors store and transport matter.
What is the role of producers in moving matter through an ecosystem?

They take in inorganic matter and build organic molecules. Producers convert simple substances into complex organic matter.
What is the role of decomposers in returning matter to nonliving components?

They break down dead matter and release nutrients to soil and air. Decomposition recycles nutrients back to the environment.
Which process returns nitrogen gas (N $_2$ ) to the atmosphere in nitrogen-cycle models?

Denitrification. Bacteria convert nitrates back to N $_2$ gas.
Identify the abiotic reservoir that stores most available nitrogen for ecosystems.

The atmosphere (as N $_2$ gas). 78% of air is nitrogen gas, the main nitrogen source.
What term describes matter moving repeatedly through living and nonliving parts of an ecosystem?

Biogeochemical cycling. Matter cycles between organisms and the environment.
What are organisms called that make their own food and add biomass to food webs?

Producers (autotrophs). They convert inorganic matter into organic biomass.
Which term names the path matter follows as it moves through an ecosystem model?

Matter cycle (biogeochemical cycle). Shows continuous movement of elements between living and nonliving parts.
Which term describes living parts of an ecosystem such as plants, animals, and fungi?

Biotic components. Biotic refers to all living organisms in an ecosystem.
Which option correctly traces carbon matter: atmosphere $\rightarrow$ plant $\rightarrow$ animal $\rightarrow$ atmosphere?

$CO_2$ (air) $\rightarrow$ photosynthesis $\rightarrow$ feeding $\rightarrow$ respiration. Shows complete carbon cycle through living organisms.
What process returns carbon atoms from organisms back to the atmosphere as $CO_2$ ?

Cellular respiration. Breaks down organic molecules, releasing $CO_2$ as waste.
What is the definition of a nutrient in ecosystem matter models?

A chemical substance organisms need for growth and life processes. Nutrients include elements like carbon, nitrogen, and phosphorus.
What is the main source of carbon atoms for plants in most ecosystem models?

Carbon dioxide ( $CO_2$ ) in the atmosphere. Plants absorb $CO_2$ during photosynthesis to build organic molecules.
What is the difference between living (biotic) and nonliving (abiotic) components?

Biotic are living or once-living; abiotic are nonliving physical factors. Living includes organisms; nonliving includes air, water, soil, rocks.
What is the correct term for an organism that gets matter and energy by eating others?

Consumer (heterotroph). Heterotrophs cannot make their own food from inorganic matter.
Which arrow correctly shows nitrogen uptake by plants: Soil nitrates → Plant roots or Plant roots → Soil nitrates?

Soil nitrates → Plant roots. Plants absorb dissolved nitrates through their root systems.
What is the role of bacteria in many nitrogen-cycle models?

They convert nitrogen into forms plants can absorb. Most plants cannot use atmospheric $N_2$ directly.
What is the definition of matter cycling in an ecosystem model?

Matter is reused and moves between organisms and the environment. Unlike energy, atoms are conserved and cycle continuously.
What is the process that moves carbon from the atmosphere into plants as sugars?

Photosynthesis. Plants convert atmospheric $CO_2$ into glucose using light energy.
What is the term for organisms that make organic molecules from $CO_2$ and water using energy?

Producers (autotrophs). Create their own food through photosynthesis or chemosynthesis.
Which group converts inorganic matter into organic matter in ecosystem models?

Producers (autotrophs). They make organic compounds from inorganic materials.
What is a consumer in a matter-tracing model?

An organism that gets matter by eating other organisms. Consumers obtain matter by consuming other organisms.
What is the term for water falling from clouds to Earth in water-cycle models?

Precipitation. Includes rain, snow, sleet, and hail returning water to Earth.
What is the term for organisms that break down dead matter and return nutrients to soil and water?

Decomposers. Recycle nutrients by breaking down dead organic material.
What is a model in ecosystem science used to trace the movement of matter?

A representation used to track where matter goes and changes form. Models show pathways and transformations of matter in ecosystems.
Which label is correct for soil bacteria that break down a dead leaf: producer, consumer, or decomposer?

Decomposer. Bacteria break down dead organic matter, not produce or consume it.
What are the two main ecosystem components that matter moves through?

Living (biotic) and nonliving (abiotic) components. Matter cycles between organisms and their physical environment.
Which model shows many connected feeding relationships in an ecosystem?

Food web. More complex than food chains, showing multiple pathways.
Identify where matter goes in a model when a leaf dies and decomposes: atmosphere, soil, or sun?

Soil (as nutrients) and atmosphere (as CO $_2$ ). Decomposition releases CO $_2$ to air and minerals to soil.
Which model statement is correct: matter is recycled or matter is destroyed in ecosystems?

Matter is recycled. Atoms are conserved and reused in ecosystem cycles.
Which arrow correctly shows respiration in a carbon model: animal → $CO_2$ or $CO_2$ → animal?

Animal → $CO_2$ . Animals release $CO_2$ as waste product of cellular respiration.
Which process returns nutrients from dead organisms to soil and water?

Decomposition. Decomposers break down organic matter into inorganic nutrients.
Which statement best describes matter in ecosystems: it is recycled or used up?

Matter is recycled. Atoms are reused, not destroyed, in ecosystems.
What is the correct direction of matter flow in a food chain model?

From food to consumer (from eaten to eater). Matter moves from prey to predator when consumed.
Choose the correct arrow direction for matter transfer: grass and rabbit, if the rabbit eats grass.

Grass → rabbit. Arrow points from food source to consumer.
What process moves carbon from atmospheric $CO_2$ into plant biomass?

Photosynthesis. Plants convert $CO_2$ and water into glucose and oxygen.
Identify the process that returns carbon from organisms to the atmosphere as $CO_2$ .

Cellular respiration. All organisms release $CO_2$ when breaking down glucose for energy.
Which term names organisms that obtain matter by eating other organisms?

Consumers (heterotrophs). They must consume other organisms for energy and matter.
Identify the missing step in the carbon path: plant $\rightarrow$ animal $\rightarrow$ ? $\rightarrow$ $CO_2$ in air.

Cellular respiration. Animals release $CO_2$ through respiration.
What process converts atmospheric $N_2$ into forms plants can use (such as nitrates)?

Nitrogen fixation. Bacteria convert unusable $N_2$ gas into ammonia or nitrates.
What term names organisms that break down dead matter and recycle nutrients?

Decomposers. Bacteria and fungi convert dead tissue to simple nutrients.
What process turns water vapor into liquid droplets in the atmosphere in models?

Condensation. Cooling causes water vapor to form tiny liquid droplets.
In a matter-tracing model, which label best fits bacteria that convert wastes into soil nutrients?

Decomposer. Bacteria break down organic waste into inorganic nutrients.
What type of organism is a decomposer in matter-cycle models?

Bacteria or fungi that break down organic matter. These microorganisms recycle nutrients from dead organic material.
What process moves water from clouds to Earth as rain, snow, sleet, or hail?

Precipitation. Gravity pulls condensed water from clouds back to Earth's surface.
Identify the correct order in a model: plant → rabbit → fox. Which is the secondary consumer?

Fox. Fox eats the primary consumer (rabbit) in this chain.
What process moves carbon from the atmosphere into plant sugars?

Photosynthesis. Plants convert atmospheric $CO_2$ and water into glucose using sunlight.
What is a producer in a matter-flow model of an ecosystem?

An organism that makes its own food, usually by photosynthesis. Producers convert inorganic matter into organic compounds.
Which model component represents living parts of an ecosystem: biotic or abiotic?

Biotic. Includes all organisms like plants, animals, and bacteria.
Choose the correct matter statement for a food chain model: atoms are destroyed or atoms are rearranged?

Atoms are rearranged into new substances. Matter cannot be created or destroyed, only transformed.
What is the term for water falling from clouds to Earth as rain, snow, sleet, or hail?

Precipitation. Condensed water in clouds falls when droplets become too heavy.
Identify the correct arrow direction for carbon in a food chain: plant to herbivore or herbivore to plant?

Plant to herbivore. Matter flows from producers to consumers in food chains.
In a matter model, where do atoms in a dead leaf go next: decomposers or top predators?

Decomposers. Dead material goes to decomposers, not up the food chain.
Identify the correct matter pathway after death in a model: dead leaf to decomposer to soil nutrients, or dead leaf to sunlight?

Dead leaf → decomposer → soil nutrients. Decomposers recycle dead matter into soil nutrients.
Which process moves carbon from organisms to the atmosphere as $CO_2$ : photosynthesis or respiration?

Cellular respiration. Organisms release $CO_2$ when breaking down glucose for energy.
Identify the nonliving reservoir that stores most nitrogen in the nitrogen cycle model.

The atmosphere (mostly $N_2$ gas). 78% of air is nitrogen gas, the largest nitrogen reservoir.
What term names a living thing that makes its own food from nonliving resources?

Producer. Producers convert sunlight and $CO_2$ into organic matter.
Which process moves carbon from atmospheric $CO_2$ into plant biomass?

Photosynthesis. Plants convert atmospheric $CO_2$ into glucose and organic compounds.
Identify the correct arrow direction for carbon in a food chain: plant to herbivore or herbivore to plant?

Plant to herbivore. Matter flows from producers to primary consumers.
In a food chain model, which direction does matter move: producer to consumer or consumer to producer?

Producer to consumer. Matter flows up the food chain as organisms eat each other.
Which model statement is correct: energy is recycled or energy flows one-way in ecosystems?

Energy flows one-way. Energy enters as sunlight and exits as heat, never recycled.
Which process moves matter from an organism into the environment as waste?

Excretion (elimination of wastes). Organisms release nitrogen and other matter through waste products.
What molecule is taken from the atmosphere during photosynthesis in carbon-cycle models?

Carbon dioxide (CO $_2$ ). Plants absorb this gas through stomata for photosynthesis.
What is the nonliving carbon reservoir that plants take in during photosynthesis?

Atmospheric $CO_2$ . Plants absorb $CO_2$ from air through stomata.
Which statement best describes matter movement in ecosystems: matter cycles or matter is destroyed?

Matter cycles; it is conserved and reused. Matter cannot be created or destroyed, only transformed and recycled.
What process moves carbon from atmospheric $CO_2$ into plant biomass?

Photosynthesis. Plants convert $CO_2$ and water into glucose using light energy.
What is the process that moves carbon from organisms to the atmosphere as $CO_2$ ?

Cellular respiration. Organisms release $CO_2$ when breaking down glucose for energy.
What is the main abiotic reservoir of carbon that plants use during photosynthesis?

Carbon dioxide in the atmosphere. Plants absorb $CO_2$ from air during photosynthesis to make sugars.
Identify the correct arrow direction for matter: plant sugar → rabbit → fox.

Plant → rabbit → fox. Matter flows from producers to primary then secondary consumers.
What term describes living parts of an ecosystem, such as plants, animals, and fungi?

Biotic factors. Living organisms that interact and exchange matter in ecosystems.
What is the definition of a nutrient in ecosystem matter-tracing models?

A chemical element or compound organisms need to build tissues. Essential substances like nitrogen, phosphorus, and carbon.
Which component is the abiotic reservoir in this model: fish → heron → bacteria → dissolved nutrients?

Dissolved nutrients (water). Non-living water stores nutrients between living organisms in aquatic systems.
Which term names organisms that break down dead matter and wastes into simpler substances?

Decomposers. They recycle nutrients back to the environment.
Which statement best describes matter in ecosystems: recycled or destroyed?

Matter is recycled; it is not destroyed. Conservation of matter - atoms rearrange but aren't created/destroyed.
Which abiotic reservoir stores carbon in many models besides the atmosphere?

Oceans and rocks (carbonates) store carbon. Most Earth's carbon is stored in nonliving reservoirs.
What is a producer in a matter-tracing model of an ecosystem?

An organism that makes its own food, usually by photosynthesis. Converts inorganic matter into organic matter, starting food chains.
Choose the correct movement of carbon in a model: atmosphere CO $_2$ → plant → animal.

Carbon moves from CO $_2$ into plants, then into animals. Photosynthesis fixes atmospheric carbon into organic molecules.
Identify the correct arrow direction for carbon in photosynthesis: $CO_2$ in air $\rightarrow$ plant biomass or reverse?

$CO_2$ in air $\rightarrow$ plant biomass. Shows carbon moving from atmosphere into plant during photosynthesis.
Which statement best describes matter movement versus energy movement in ecosystems?

Matter cycles; energy flows one-way and is not recycled. Matter is conserved and reused; energy dissipates as heat.
Which option describes matter in ecosystems: recycled or destroyed?

Recycled. Matter cycles continuously through ecosystems, never lost.
What process moves carbon from organisms to the atmosphere as $CO_2$ ?

Cellular respiration. All organisms release $CO_2$ when breaking down glucose for energy.
Choose the correct label for this model arrow: plant → rabbit (arrow shows transfer of matter).

Consumption (rabbit eats plant; atoms move into rabbit). Matter transfers when one organism eats another.
What is the primary form of nitrogen that plants commonly absorb from soil in models?

Nitrates ( $NO_3^-$ ). Plants absorb this dissolved nitrogen compound through roots.
Identify the main abiotic reservoir for carbon in the short-term carbon cycle.

Atmosphere as $CO_2$ . Most available carbon exists as $CO_2$ gas in the atmosphere.
What is the term for a process that moves matter from one reservoir to another in a model?

Flux (transfer process). The movement or flow of matter between reservoirs.
Which arrow correctly shows photosynthesis in a carbon model: $CO_2$ → plant or plant → $CO_2$ ?

$CO_2$ → plant. Plants take in $CO_2$ during photosynthesis to build organic molecules.
What is the definition of abiotic components in a matter-tracing model?

Nonliving physical and chemical parts of an ecosystem. Abiotic means 'non-living' - includes air, water, minerals, and climate.
What is a producer in a matter-tracing food web model?

An organism that makes organic molecules from inorganic matter. Producers convert inorganic substances into organic compounds.
What is the living part of an ecosystem called, including plants, animals, fungi, and bacteria?

Biotic factors. Biotic refers to all living organisms in ecosystems.
Which reservoir is biotic in a model: atmosphere $CO_2$ , soil nitrate, grass, or ocean water?

Grass. Only grass is living; the others are non-living matter reservoirs.
What are the reactants of cellular respiration in a matter-tracing model?

Glucose and oxygen. Cells break down sugar with oxygen to release energy.
What is the definition of biotic components in a matter-tracing model?

Living or once-living parts of an ecosystem. Biotic means 'life-related' - includes all organisms and their remains.
Identify the abiotic reservoir that receives matter when animals breathe out carbon dioxide.

The atmosphere. Respiration releases $CO_2$ back to the air.
Which statement best describes energy vs. matter in models: energy cycles or matter cycles?

Matter cycles; energy flows one-way. Matter reuses atoms in cycles; energy flows from sun through organisms to heat.
Which process moves nitrogen from soil into plants in a matter model?

Assimilation (plant uptake of nitrates or ammonium). Plants absorb nitrogen compounds through roots for protein synthesis.
What is the main process producers use to move carbon from air into biomass?

Photosynthesis. Plants convert CO $_2$ and water into glucose using light.
What does an arrow represent in a matter-flow model of an ecosystem?

The direction matter moves from source to receiver. Arrows show flow direction in ecosystem diagrams.
What is the term for a diagram that shows how matter moves among parts of an ecosystem?

Model (a representation used to trace matter movement). Models help visualize complex matter cycles in ecosystems.
Which process moves carbon from living things back into the atmosphere as $CO_2$ ?

Cellular respiration. All organisms release $CO_2$ when breaking down food for energy.
Which organisms break down dead matter and wastes into simpler substances: decomposers or predators?

Decomposers. Bacteria and fungi recycle nutrients from dead organisms back to soil.
Which process moves water from liquid surface water to water vapor in the atmosphere?

Evaporation. Heat energy changes liquid water to gas, rising to atmosphere.
Identify the process that moves water from plant leaves to the atmosphere as water vapor.

Transpiration. Plants release water vapor through stomata in their leaves.
What is the product of decomposition that becomes available in soil for plants?

Inorganic nutrients (mineral nutrients). Decomposition releases minerals plants can absorb.
Which arrow correctly traces nitrogen after decomposition: soil nitrates to plant roots or plant roots to soil nitrates?

Soil nitrates to plant roots. Plants absorb nitrogen compounds through their roots.
Identify the missing component in this matter path: dead leaves $\rightarrow$ decomposers $\rightarrow$ ____.

Soil nutrients (inorganic matter). Decomposers release minerals back to soil.
Identify the correct direction of arrows in a matter-tracing model between components.

Arrows point from source of matter to where it moves next. Shows the direction of matter transfer between components.
What do arrows in a matter-cycle model usually represent?

Direction of matter movement between reservoirs. Shows the flow and transfer of matter between different storage locations.
Which process returns carbon dioxide to the atmosphere from organisms?

Cellular respiration. All organisms release $CO_2$ when breaking down food for energy.
In a food web model, which trophic level directly takes in matter from abiotic sources?

Producers (autotrophs). Only producers can convert inorganic matter into organic compounds.
Which term describes a diagram that shows how matter moves between organisms and the environment?

Model. Models visually represent complex ecosystem processes.
Which model component represents nonliving parts of an ecosystem: biotic or abiotic?

Abiotic. Includes air, water, soil, and minerals that support life.
What process changes liquid water to water vapor in the water cycle model?

Evaporation. Heat energy transforms liquid water into gaseous water vapor.
What process moves water from plant leaves to the atmosphere in water-cycle models?

Transpiration. Water exits through leaf pores (stomata) as vapor.
Choose the correct path for carbon atoms in this model: plant → rabbit → fox → decomposers.

Carbon moves by feeding, then returns to soil/air through decomposition. Matter transfers through feeding, then cycles via decomposition.
Which component receives matter last in this sequence: leaf litter → fungi → soil minerals → plant roots?

Plant roots. Nutrients cycle from decomposers through soil to plants.
What is the term for living parts of an ecosystem such as plants, animals, and microbes?

Biotic components. Living organisms that interact and exchange matter.
Choose the correct model label for a nonliving reservoir: atmosphere $CO_2$ or rabbit biomass?

Atmosphere $CO_2$ . Atmospheric $CO_2$ is abiotic; rabbit biomass is biotic.
What are organisms called that chemically break down dead matter into simpler substances?

Decomposers (for example, fungi and bacteria). They recycle organic matter back to inorganic forms.
What is the definition of a biotic component in a matter-tracing model?

A living part of an ecosystem (organisms). Biotic means 'living' - includes all organisms in the ecosystem.
What is the rule about matter in ecosystems: is it created, destroyed, or recycled?

Matter is recycled (conserved). Matter cannot be created or destroyed, only transformed between forms.
What are the main products of photosynthesis that appear in ecosystem matter models?

Sugars (biomass) and oxygen. Plants produce glucose for energy and release $O_2$ as waste.
What process converts atmospheric N $_2$ into forms plants can use in nitrogen-cycle models?

Nitrogen fixation. Bacteria convert N $_2$ to ammonia that plants can use.
What is the main nitrogen-containing gas in the atmosphere before fixation?

$N_2$ . Nitrogen gas makes up 78% of Earth's atmosphere.
What is a consumer in a matter-tracing model of an ecosystem?

An organism that gets matter by eating other organisms. Obtains organic matter and nutrients by consuming other organisms.
What term describes nonliving parts of an ecosystem, such as water, air, and soil?

Abiotic factors. Non-living components that provide resources and conditions for life.
Identify the correct path for carbon atoms in a simple model: air $CO_2$ → plant → animal → _____.

Air $CO_2$ . Respiration by the animal returns carbon to the atmosphere.
Which option best traces carbon atoms: $CO_2$ → plant sugar → animal tissue → $CO_2$ ?

Photosynthesis → consumption → respiration. Carbon moves from air to plants, then animals, then back to air.
What is the term for the place where matter is stored in a cycle, such as ocean water or soil?

Reservoir. Storage location where matter accumulates between active cycling phases.
What is the main abiotic reservoir for carbon in the short-term carbon cycle?

Atmosphere as $CO_2$ . Most accessible carbon exists as gas in the air for photosynthesis.
Identify the missing step in a water-cycle model: ocean → evaporation → clouds → _____ → river → ocean.

Precipitation. Water falls from clouds to Earth, completing the atmospheric cycle.
What is the role of consumers in tracing matter through an ecosystem model?

They obtain matter by eating other organisms and build biomass. Matter transfers up food chains as organisms consume each other.
What are the reactants of photosynthesis in a matter-tracing model?

Carbon dioxide and water. Plants combine these simple molecules to make glucose.
Which process transfers matter from one organism to another in a food chain?

Feeding (consumption). Matter moves up the food chain when organisms eat each other.
Which group is the correct example of biotic components in an ecosystem model?

Plants, animals, fungi, and bacteria. These are all living organisms that cycle matter.
What is a consumer in a matter-flow model of an ecosystem?

An organism that gets matter by eating other organisms. Consumers obtain matter from other organisms through feeding.
What are the main abiotic inputs plants use to build sugars during photosynthesis?

Carbon dioxide and water. Plants combine these using light energy to make glucose.
What is the term for a diagram that shows how matter moves among reservoirs using arrows?

A matter-cycle (box-and-arrow) model. Visual model using boxes for reservoirs and arrows for matter flow.
Identify the nonliving component in matter-cycle models: biotic or abiotic?

Abiotic. Includes air, water, soil, and rocks - non-living cycle parts.
What is the term for organisms that make organic molecules from $CO_2$ and $H_2O$ ?

Producers (autotrophs). Convert inorganic carbon and water into organic compounds.
What process returns nitrogen from dead organisms and waste back into the soil as ammonia?

Ammonification. Decomposers convert organic nitrogen into ammonia ( $NH_3$ ).
What process changes water vapor into liquid droplets that form clouds?

Condensation. Cooling causes water vapor to form liquid droplets in the atmosphere.
What process moves carbon from living organisms back into the atmosphere as $CO_2$ ?

Cellular respiration. Organisms release $CO_2$ when breaking down glucose for energy.
What is the definition of matter in an ecosystem model?

Anything that has mass and takes up space. Matter includes all physical substances with measurable properties.
What is the correct direction of arrows in a matter-flow model: from source to destination or the reverse?

From source reservoir to destination reservoir. Arrows point in the direction matter flows.
Which model arrow should be added to show nitrogen moving from dead organisms into soil nitrates?

Decomposition (ammonification) to soil nutrients. Bacteria convert organic nitrogen into inorganic soil nutrients.
Choose the correct arrow direction for matter: grass and cow. Which way should the arrow point?

Grass → cow. Arrow points from food source to consumer.
What is the correct order for carbon movement in a simple chain: plant, rabbit, fox, air ( $CO_2$ )?

Plant → rabbit → fox → atmosphere ( $CO_2$ ). Carbon moves through food chain, then returns to air via respiration.
Which label fits this nitrogen model step: $N_2$ (air) → ______ → plant proteins?

Nitrogen fixation to usable nitrogen compounds. Bacteria convert atmospheric $N_2$ into ammonia and nitrates plants can use.
Which process releases $CO_2$ to the atmosphere when organisms break down sugars for energy?

Cellular respiration. Organisms release $CO_2$ when breaking down glucose for energy.
Find the living component in this matter model: sunlight, water, bacteria, air.

Bacteria. Bacteria are microscopic living organisms.
What is the term for movement of water from plant leaves to the atmosphere in the water cycle?

Transpiration. Water vapor exits through leaf pores called stomata.
What are the two main categories of ecosystem components when tracing matter movement?

Living (biotic) and nonliving (abiotic) components. Biotic means living organisms; abiotic means non-living factors.
In a model, which organisms directly take up nitrates ( $NO_3^-$ ) from soil?

Producers (plants). Plants absorb nitrates through roots as their nitrogen source.
Which process changes atmospheric $N_2$ into ammonia that can enter food webs?

Nitrogen fixation. Bacteria convert atmospheric $N_2$ into usable ammonia.
Which term names organisms that make their own food from nonliving matter?

Producers (autotrophs). They convert inorganic matter into organic compounds.
Identify the missing label: $CO_2$ (air) → plant → animal → ____ → $CO_2$ (air).

Cellular respiration. Animals release $CO_2$ when breaking down food for energy.
What is the main source of nitrogen atoms for plants in most ecosystems?

Nitrates ( $NO_3^-$ ) absorbed from soil. Plants absorb dissolved nitrates through their roots.
What is the definition of matter in an ecosystem model?

Anything that has mass and takes up space. Matter includes all physical substances in ecosystems.
What is the term for nonliving parts of an ecosystem such as air, water, and soil?

Abiotic components. These nonliving factors provide essential resources for life.
What is the definition of matter in an ecosystem model?

Anything that has mass and takes up space. Matter is the physical substance that ecosystems exchange and recycle.
What is the correct term for an organism that makes its own food using sunlight?

Producer (autotroph). Autotrophs produce organic matter from inorganic sources like $CO_2$ .
Which label best completes this model arrow: soil nitrates $\rightarrow$ plant roots $\rightarrow$ ____?

Plant proteins and other organic nitrogen compounds. Plants convert inorganic nitrogen into organic molecules.
Find the missing model component: dead organisms → decomposers → ______ (abiotic).

Soil nutrients (minerals in soil and water). Decomposers release minerals that dissolve in soil water.
What is the definition of energy flow in an ecosystem model?

Energy moves one-way through a food chain and is not recycled. Energy enters as sunlight and exits as heat, never cycling back.
What is the role of producers in tracing matter through an ecosystem model?

They convert $CO_2$ and $H_2O$ into biomass (organic matter). Photosynthesis captures carbon from air to build plant tissues.
Identify the correct arrow direction for carbon in respiration: plant biomass $\rightarrow$ $CO_2$ in air or reverse?

Plant biomass $\rightarrow$ $CO_2$ in air. Shows carbon returning to atmosphere when organisms respire.
What are organisms called that obtain matter by eating other organisms?

Consumers (heterotrophs). They must consume organic matter for energy and nutrients.
What process moves carbon from dead organisms into soil as organic matter?

Decomposition. Bacteria and fungi break down tissues, releasing stored carbon.
Identify the correct matter path in a model: $CO_2$ in air → plant → animal → air as $CO_2$ ; what final process returns it?

Cellular respiration. Animals release $CO_2$ when breaking down food for energy.
Which statement best describes energy in ecosystems: it cycles or flows one way?

Energy flows one way. Energy enters as sunlight and exits as heat.
What do food webs and food chains model in an ecosystem: energy flow, matter cycling, or both?

Both energy flow and matter cycling. Shows organisms eating each other (energy) and recycling nutrients (matter).
What term names organisms that break down dead matter and wastes and return nutrients to the environment?

Decomposer. Decomposers recycle nutrients from dead organic matter.
Which process returns carbon to the atmosphere as $CO_2$ from organisms?

Cellular respiration. All organisms release $CO_2$ when breaking down glucose for energy.
What is cellular respiration in a matter-tracing model?

Sugars + oxygen → carbon dioxide + water. Organisms break down glucose for energy, releasing $CO_2$ .
Identify the nonliving reservoir in the water cycle where water is stored as ice for long periods.

Glaciers and ice caps. Ice stores water in solid form for thousands of years.
What is the key difference between matter cycling and energy flow in ecosystems?

Matter cycles; energy flows one way and is lost as heat. Matter is conserved and reused; energy cannot be recycled.
Identify the missing label: Atmosphere ( $CO_2$ ) → ____ → Consumer → Respiration → Atmosphere ( $CO_2$ ).

Producer (photosynthesis). Producers take in $CO_2$ to make food, starting the carbon cycle.
Which model best shows matter movement: a cycle diagram or a one-way arrow chain?

A cycle diagram. Shows continuous recycling with arrows returning to start.
What process returns carbon to the atmosphere as $CO_2$ from living organisms?

Cellular respiration. Organisms release $CO_2$ when breaking down glucose for energy.
What is the definition of matter in an ecosystem model?

Anything that has mass and takes up space. Matter is the physical substance that cycles through ecosystems.
Identify the main abiotic reservoir for nitrogen that begins the nitrogen cycle.

Atmosphere as $N_2$ gas. 78% of atmosphere is $N_2$ , the largest nitrogen reservoir.
Which statement best describes matter in ecosystems: it cycles or it is used up?

Matter cycles; it is not used up. Matter is conserved and reused, following the law of conservation of mass.
Which process breaks down dead organisms and wastes, returning nutrients to soil and water?

Decomposition. Microorganisms recycle nutrients from dead matter back to the environment.
What is the main carbon-containing gas in the atmosphere that plants use to build sugars?

Carbon dioxide ( $CO_2$ ). Plants convert atmospheric $CO_2$ into glucose during photosynthesis.
Which organisms are decomposers in ecosystem matter models?

Bacteria and fungi. Break down dead material, recycling nutrients back to soil.
Which process converts atmospheric $N_2$ into usable nitrogen compounds for plants?

Nitrogen fixation. Bacteria convert inert $N_2$ gas into ammonia plants can use.
What is the definition of an abiotic component in a matter-tracing model?

A nonliving part of an ecosystem (air, water, soil). Abiotic means 'non-living' - the physical environment.
What is the term for living parts of an ecosystem such as plants, animals, and bacteria?

Biotic factors. Living organisms that interact and depend on each other in ecosystems.
Which statement is correct: Matter cycles or energy cycles through ecosystems?

Matter cycles; energy flows. Matter is reused; energy enters as sunlight and exits as heat.
What process returns water vapor to the atmosphere from plant leaves?

Transpiration. Water evaporates from leaf stomata during gas exchange.
What is the difference between matter cycling and energy flow in ecosystems?

Matter cycles; energy flows one way and is lost as heat. Matter recycles endlessly; energy passes through once and exits as heat.
What is the main source of carbon atoms for plants during photosynthesis?

Atmospheric $CO_2$ . Plants absorb $CO_2$ from air to build organic molecules.
What does an arrow in a food chain model represent?

Direction of matter and energy transfer. Shows who eats whom and how matter moves between organisms.
Which process returns carbon to the atmosphere as $CO_2$ from organisms?

Cellular respiration. Organisms break down glucose for energy, releasing $CO_2$ as waste.
Which group turns inorganic carbon dioxide into organic molecules: producers or consumers?

Producers. Use photosynthesis to convert $CO_2$ into glucose and other organic compounds.
Which process moves matter from organisms to the environment when they die?

Death followed by decomposition. Dead organisms are broken down, returning their atoms to the environment.
Which model label is correct for a dead leaf becoming soil nutrients: consumption, decomposition, or condensation?

Decomposition. Dead organic matter breaks down into simpler nutrients.
Identify the living component in matter-cycle models: biotic or abiotic?

Biotic. Refers to living organisms like plants, animals, and bacteria.
What is the term for a nonliving storage location of matter in a cycle (for example, air or soil)?

Reservoir. Stores matter in nonliving parts of cycles like atmosphere or rocks.
What is the term for the movement of water from plant leaves to the atmosphere as water vapor?

Transpiration. Plants release water vapor through stomata in their leaves.
What process breaks down dead organisms and wastes, returning matter to soil and water?

Decomposition. Decomposers recycle nutrients from dead material.
What term names an organism that gets matter and energy by eating other organisms?

Consumer. Consumers obtain matter by eating other organisms.
Which process best completes this water-cycle model step: liquid water → water vapor?

Evaporation. Heat energy changes liquid water to gaseous water vapor.
What term describes plant uptake of nitrate or ammonium from soil in models?

Assimilation. Plants absorb nitrogen compounds through their roots.
What is the definition of biomass in an ecosystem matter model?

The total mass of living organic matter. Includes all organic material from living or recently living organisms.
Which process moves carbon from atmospheric $CO_2$ into glucose in a plant?

Photosynthesis. Plants convert $CO_2$ and water into glucose using sunlight.
Which process returns nitrogen gas ( $N_2$ ) to the atmosphere from soil nitrates?

Denitrification. Bacteria convert nitrates back to atmospheric $N_2$ gas.
Identify the missing step in this matter path: dead leaves → decomposers → _____ → plant roots.

Nutrients in soil (such as nitrates and phosphates). Decomposers release nutrients that plants absorb through roots.
What is the term for water vapor cooling and forming liquid water in the atmosphere?

Condensation. Water vapor changes to liquid when air temperature drops.
Which process moves carbon from the atmosphere into living biomass?

Photosynthesis. Plants capture atmospheric $CO_2$ to build organic molecules.
Identify the correct direction of matter transfer during feeding: prey to predator or predator to prey?

Prey to predator. Matter moves from eaten organism to the eater.
What is the main abiotic reservoir of nitrogen that starts the nitrogen cycle?

Nitrogen gas in the atmosphere. $N_2$ makes up 78% of air but must be fixed before organisms can use it.
Which option describes energy in ecosystems: recycled or flows one-way?

Flows one-way. Energy enters as sunlight and exits as heat, not recycled.
What are the products of photosynthesis in a matter-tracing model?

Glucose and oxygen. Photosynthesis converts $CO_2$ and $H_2O$ into sugar and $O_2$ .
What is a decomposer in a matter-cycle model?

An organism that breaks down dead matter and wastes into simpler substances. Decomposers recycle nutrients back to the environment.
Identify the correct direction of matter movement in a food chain model.

From food source to consumer (prey/plant to eater). Matter flows from eaten organism to eater.
What is the role of decomposers in tracing matter through an ecosystem model?

They break down dead matter and return nutrients to soil or water. Recycling releases minerals for producers to absorb and reuse.
Which process moves water from plant leaves into the atmosphere as water vapor?

Transpiration. Plants release water vapor through leaf pores called stomata.
Which model step returns nutrients from dead organisms back to abiotic soil and water: consumption or decomposition?

Decomposition. Decomposers break down organic matter into soil nutrients.
What is the main abiotic reservoir for water in the water cycle?

Oceans (largest reservoir of water). Contains about 97% of Earth's water in liquid form.
What is the term for organisms that break down dead organisms and wastes?

Decomposers. These organisms recycle nutrients from dead material.
What is the main carbon-containing gas in the atmosphere used by producers?

$CO_2$ . Carbon dioxide provides carbon atoms for photosynthesis.
What is a decomposer in a matter-tracing model?

An organism that breaks down dead matter and wastes into simpler substances. Decomposers recycle nutrients by breaking down dead material.
What process returns carbon dioxide to the atmosphere from organisms in models?

Cellular respiration. All organisms release CO $_2$ when breaking down glucose for energy.
What is the key idea about matter in ecosystems that models must show: is it recycled or created?

Matter is recycled; it is not created or destroyed. Conservation of matter: atoms rearrange but total mass stays constant.
What is the nonliving part of an ecosystem called, including air, water, sunlight, and minerals?

Abiotic factors. Abiotic means non-living components of ecosystems.
Which component is missing in this matter-cycle model: dead organisms → _____ → soil nutrients?

Decomposers. They break down dead matter into soil nutrients.
Identify the missing step: dead leaves → decomposers → ______ in soil for plant reuse.

Nutrients (mineral ions). Decomposers break down organic matter into mineral nutrients plants can absorb.
What term describes living components in an ecosystem model?

Biotic factors. Living organisms like plants and animals.
Which process moves carbon from atmospheric $CO_2$ into plant biomass?

Photosynthesis. Plants convert atmospheric $CO_2$ into glucose during photosynthesis.
What is the term for matter moving between living (biotic) and nonliving (abiotic) parts of an ecosystem?

Biogeochemical cycling. Describes the cycling of chemical elements between organisms and the environment.

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