Ecosystem nutrient cycling

what governs ecosystem functioning

energy transfer and internal cycling of nutrients

what is the role of autotrophs (1° producers)

they harvest the sun’s energy (photosynthesis) to convert inorganic carbon (co2) into organic carbon compounds (carbohydrates)

how does energy flow in an ecosystem

energy stored in chemical bonds of carbon compounds flow from 1° producers up the food chain

what are heterotrophs

organisms that consume organic compounds for energy, divided into grazing and detrital food chains

what is the grazing food chain

consumers use organic compounds found in living tissue as a food source

what is the detrital food chain

decomposers use organic compounds found in dead tissue and waste products as a food source

what is detritus

waste and dead matter

what components are part of the grazing food chain

• Heterotrophs: top predator (carnivore), secondary consumers intermediate species (carnivores), primary consumers intermediate species (herbivores)

• Autotrophs: primary producers basal species (plants)

what components are part of the detrital food chain

secondary consumers intermediate species (carnivores), primary consumers intermediate species (decomposers - bacteria, fungi, detritivores), detritus

what role does the detrital food chain play in ecosystems

it plays a dominant role in energy flow and nutrient cycling in most terrestrial and aquatic ecosystems

what are the two main sources of nutrients in ecosystems

the atmosphere and weathering of rocks and minerals

where are most nutrients stored in an ecosystem

in organic form within living tissues (plants/animals)

how are essential nutrients recycled in ecosystems

by decomposers through internal cycling

what happens when living tissue dies

it enters the soil or aquatic sediments where decomposers break it down

why is internal cycling important in ecosystems

it ensures the continuous recycling of essential nutrients

what are the two main functions of decomposers in nutrient cycling

1. release energy fixed in photosynthesis

2. convert organic compounds into inorganic nutrients (mineralization) for plant use

how are production and decomposition zones typically arranged in most ecosystems

they are vertically separated, with production (photosynthesis) occurring in one zone and decomposition in another

how are production and decomposition zones connected in terrestrial ecosystems

plants link the production zone (canopy) and the decomposition zone (soil)

how do production and decomposition zones differ in aquatic ecosystems

plants do no occupy both zones - production occurs in surface waters, while decomposition happens in bottom sediments

why is water mixing important in aquatic ecosystems

seasonal mixing (fall and spring) brings nutrients from bottom sediments to surface waters, enabling primary production

what is decomposition

a complex process involving various decomposer organisms that feed on dead organic matter

what are the two main types of microbial decomposers

bacteria and fungi

what type of organic matter do bacteria primarily decompose and same for fungi

• bacteria = dead animal matter

• fungi = dead plant matter

what are the two types of bacteria involved in decomposition

aerobic (require o2) and anaerobic (do not require o2 - fermentation)

how do bacteria and fungi break down organic material

they secrete enzymes that break down complex organic compounds, absorbing some products as food

what is succession in decomposition

different decomposer species take over as material breaks down until it’s fully reduced to inorganic nutrients

what are detritivores

animals (mostly invertebrates) that feed on dead organic material and waste but do not mineralize it

what is the role of detritivores in decomposition

they fragment leaves, twigs, and other dead organic matter, increasing surface area for microbial decomposers

what are the four major groups of detritivores based on body size

• Microfauna & Microflora (< 100 μm): Protozoans, nematodes (inhabit water in soil)

• Mesofauna (100 μm – 2 mm): Mites, springtails (live in soil air spaces)

• Macrofauna (2–20 mm): Amphipods

• Megafauna (> 20 mm): Millipedes, earthworms, snails (terrestrial) and crustaceans, crabs (aquatic)

how do detritivores influence soil and sediment structure

by burrowing into soil or sediment, creating space and altering structure

why do different types of organic matter decompose at different rates

carbon compounds vary in their quality as an energy source for decomposers

how does carbon compound complexity affect decomposition rates

• High quality (fast decomposition): Simple carbohydrates (e.g., glucose) provide high net energy gain.

• Low quality (slower decomposition): Complex compounds like cellulose require more energy to break down.

• Lowest quality (very slow decomposition): Lignins (found in wood) yield almost no net energy.

how do abiotic factors influence decomposition rates

• cool, dry conditions: reduce decomposition rates

• warm, moist environments: optimal for decomposition

what two process directly control the rate of internal nutrient cycling

1. primary production - determines the rate of nutrient uptake (inorganic → organic)

2. decomposition - determines the rate of mineralization (organic → inorganic)

how does reduced availability of inorganic nutrients affect an ecosystem

it lowers photosynthetic rates (primary production), reducing the input of dead organic matter to decomposers

what does the relationship between primary production and decomposition create

a feedback system in the internal cycling of nutrients within an ecosystem