Describe Matter Movement in Ecosystems - Biology

What is the correct term for the total mass of living organic matter in a given area?

Biomass. Measures the total amount of living organic matter present.
What is the nitrogen cycle?

The movement of nitrogen among atmosphere, soil, water, and organisms. Nitrogen moves between air, soil, water, and living organisms.
What is ammonification (mineralization) in the nitrogen cycle?

Decomposers convert organic nitrogen to $NH_3$ / $NH_4^+$ . Releases nitrogen from dead organisms back to the soil.
What process returns water vapor to Earth as liquid or solid water?

Precipitation. Water vapor condenses and falls as rain, snow, or other forms.
Which environmental condition most strongly favors denitrification?

Low oxygen (anaerobic) soils or sediments. Denitrifying bacteria use nitrate as an electron acceptor without oxygen.
Which option correctly traces nitrogen atoms from air into a plant protein? Choose the best sequence.

$N_2$ → fixation → $NH_4^+$ / $NO_3^-$ → assimilation. Shows nitrogen conversion from atmospheric gas to bioavailable form to organic compounds.
What process moves water from liquid to vapor from oceans, lakes, and soil?

Evaporation. Solar energy converts liquid water to water vapor.
What is an ecosystem nutrient reservoir (pool) in matter cycling?

A storage location for matter, such as soil, biomass, or atmosphere. These pools hold matter temporarily during biogeochemical cycles.
What process moves carbon from dead organic matter into soil organic carbon?

Decomposition and humification. Decomposers break down organic matter and form stable soil carbon.
What is the carbon cycle?

The movement of carbon among atmosphere, biosphere, oceans, and rocks. Carbon moves between living and nonliving reservoirs on Earth.
Identify the process: decomposers convert organic nitrogen in dead leaves into $NH_4^+$ .

Ammonification (mineralization). Bacteria break down organic nitrogen compounds to release ammonium.
What is transpiration and how does it move matter?

Release of water vapor from plant stomata to the atmosphere. Plants lose water vapor during gas exchange for photosynthesis.
What is detritus in the context of matter movement through ecosystems?

Dead organisms and organic waste (feces, leaf litter). Non-living organic matter that serves as food for decomposers.
What is nitrification in the nitrogen cycle?

Bacterial conversion of $NH_4^+$ to $NO_2^-$ then $NO_3^-$ . Oxidizes ammonia to nitrites then nitrates in aerobic conditions.
What is eutrophication and how does it relate to matter movement in ecosystems?

Excess nutrients cause algal blooms and oxygen depletion in water. Nutrient pollution stimulates excessive plant growth and ecosystem disruption.
Which organisms carry out most biological nitrogen fixation in ecosystems?

Nitrogen-fixing bacteria (free-living or in root nodules). They have the enzyme nitrogenase that converts atmospheric $N_2$ .
What process returns phosphorus from organisms to the environment?

Decomposition and excretion. Death and waste products release phosphate back to the environment.
What is the role of producers in moving matter through an ecosystem?

They convert inorganic matter into organic biomass. They build organic compounds from simple inorganic molecules like $CO_2$ .
Identify the process: bacteria convert $NO_3^-$ into $N_2$ gas in waterlogged soil.

Denitrification. Bacteria reduce nitrate to nitrogen gas in oxygen-poor conditions.
What is the most direct way carbon atoms in a dead tree return to the atmosphere?

Decomposition and respiration releasing $CO_2$ . Decomposer respiration releases carbon stored in wood as $CO_2$ .
What is nitrogen fixation?

Conversion of atmospheric $N_2$ into ammonia ( $NH_3$ )/ $NH_4^+$ . Breaks the strong triple bond in $N_2$ to make bioavailable nitrogen.
Which human activity most directly adds reactive nitrogen to ecosystems and can cause eutrophication?

Use of nitrogen fertilizers and runoff into waterways. Fertilizers introduce excess nitrogen that can overstimulate plant growth.
Which option best describes where matter goes when a hawk eats a mouse?

Matter is incorporated into hawk biomass and released as waste and $CO_2$ . Matter is either assimilated into tissues or excreted as waste.
Which option identifies the immediate cause of oxygen depletion after a large algal bloom dies?

Decomposers consume $O_2$ during decomposition. Bacterial decomposition of dead algae consumes dissolved oxygen rapidly.
Which term describes the movement of elements through living and nonliving parts of Earth?

Biogeochemical cycle. Elements move through biological, geological, and chemical processes.
What is the role of decomposers in the cycling of matter in ecosystems?

They break down detritus and recycle nutrients to the environment. They return nutrients to soil and water for producer uptake.
What is the primary source of phosphorus for plants and algae in ecosystems?

Phosphate ions ( $PO_4^{3-}$ ) from weathered rock/soil. Rock weathering releases phosphate ions that plants can uptake.
What is the detrital food web and how does it move matter?

A pathway where detritus is consumed and nutrients are recycled. It processes dead matter and returns nutrients to ecosystem pools.
What is the primary source of water molecules used by plants for photosynthesis?

Water ( $H_2O$ ) absorbed from soil by roots. Plants absorb water through roots for the light-dependent reactions.
What is biomagnification, and does it describe cycling of matter or accumulation in food webs?

Accumulation in food webs; it is not a nutrient cycle. Toxins concentrate up food chains rather than cycling through ecosystems.
What is infiltration in the water cycle?

Movement of water from the surface into soil and groundwater. Water soaks into soil and recharges underground water supplies.
Which reservoir stores the largest amount of carbon on Earth on geologic time scales?

Sedimentary rocks and carbonate minerals. These geological formations hold carbon for millions of years.
What is denitrification in the nitrogen cycle?

Bacterial conversion of $NO_3^-$ to atmospheric $N_2$ (and $N_2O$ ). Returns nitrogen to the atmosphere, completing the cycle.
What is assimilation in the nitrogen cycle?

Uptake of $NO_3^-$ or $NH_4^+$ to build organic nitrogen compounds. Plants absorb inorganic nitrogen to synthesize proteins and nucleic acids.
Which option correctly traces carbon atoms from air into a wolf? Choose the best sequence.

$CO_2$ → grass → rabbit → wolf. Shows carbon moving through a complete food chain from producer to tertiary consumer.
What process returns carbon to the atmosphere as $CO_2$ from living organisms?

Cellular respiration. All organisms break down organic compounds and release $CO_2$ .
Identify the process: bacteria convert $NH_4^+$ to $NO_3^-$ in aerated soil.

Nitrification. Bacteria oxidize ammonium to nitrate in well-oxygenated soil.
What is the phosphorus cycle and what key feature distinguishes it from the nitrogen cycle?

Phosphorus cycles via rocks/soil; it has no major atmospheric gas phase. Phosphorus lacks a gaseous form and moves only through solid/liquid phases.
What is the primary source of carbon atoms that plants use to build sugars in photosynthesis?

Carbon dioxide ( $CO_2$ ) from the atmosphere. Plants fix atmospheric $CO_2$ during photosynthesis to make glucose.
What is a flux in biogeochemical cycling?

The rate of movement of matter between reservoirs. Measures how fast matter moves from one pool to another.
What is the role of consumers in the movement of matter through ecosystems?

They transfer matter by eating and assimilating biomass. They move organic matter through food webs by consuming other organisms.
Which statement best explains why phosphorus often limits growth in freshwater ecosystems?

Phosphate is scarce and has no large atmospheric reservoir for rapid replacement. Limited supply and slow replacement make phosphorus growth-limiting.
Which human activity most directly increases atmospheric $CO_2$ in the carbon cycle?

Burning fossil fuels (combustion). Releases stored carbon from fossil fuels into the atmosphere.
What is the water (hydrologic) cycle?

The movement of water among ocean, atmosphere, land, and organisms. Water moves through different reservoirs driven by solar energy.
Which option best distinguishes macronutrients from micronutrients in ecosystem matter cycling?

Macronutrients are needed in larger amounts; micronutrients in trace amounts. Macronutrients like carbon and nitrogen are needed in large quantities.
What is runoff in the water cycle?

Surface flow of water into streams, rivers, lakes, and oceans. Water flows over land surfaces back to water bodies.
What process releases phosphate ( $PO_4^{3-}$ ) from rocks into soil and water?

Weathering and erosion. Physical and chemical breakdown of rocks makes phosphate available.
What process returns carbon to the atmosphere as $CO_2$ from burning fuels or biomass?

Combustion. Burning organic matter or fossil fuels oxidizes carbon to $CO_2$ .
What is the primary source of nitrogen atoms for most plants in natural ecosystems?

Nitrate ( $NO_3^-$ ) or ammonium ( $NH_4^+$ ) in soil. These are the bioavailable forms of nitrogen that plant roots can absorb.
What process removes $CO_2$ from the atmosphere and stores carbon in biomass?

Photosynthesis. Plants convert atmospheric $CO_2$ into organic carbon compounds.
What is carbon sequestration in ecosystems?

Long-term storage of carbon in biomass, soils, oceans, or rocks. Carbon is removed from active cycling and stored long-term.
Which statement best describes how matter moves through ecosystems compared with energy?

Matter cycles; energy flows one-way through trophic levels. Matter is recycled while energy is lost as heat at each trophic level.

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