Ecosystem Structure, Function, Productivity, Decomposition, and Energy Flow

Vocabulary flashcards reviewing core ecological concepts including ecosystem components, productivity parameters, decomposition steps, energy flow, and ecological pyramids based on Chapter 12 lecture notes.

Ecosystem

A functional unit of nature where living organisms interact among themselves and also with the surrounding physical environment.

Stratification

The vertical distribution of different species occupying different levels in an ecosystem, such as trees occupying the top layer, shrubs the second, and herbs and grasses the bottom layers.

Species Composition

The identification and enumeration of plant and animal species that belong to a specific ecosystem.

Primary Production

The amount of biomass or organic matter produced per unit area over a time period by plants during photosynthesis, expressed as $gm^{-2}$ or $kcal\,m^{-2}$.

Productivity

The rate of biomass production in an ecosystem, expressed in terms of $gm^{-2}\,yr^{-1}$ or $(kcal\,m^{-2})\,yr^{-1}$ to compare different ecosystems.

Gross Primary Productivity (GPP)

The total rate of production of organic matter during photosynthesis in an ecosystem.

Net Primary Productivity (NPP)

The available biomass for consumption by heterotrophs, calculated as gross primary productivity minus respiration losses ($GPP - R = NPP$).

Secondary Productivity

The rate of formation of new organic matter by consumers in an ecosystem.

Decomposition

The process by which decomposers breakdown complex organic matter into simple inorganic substances like carbon dioxide, water, and nutrients.

Detritus

The raw material for decomposition, consisting of dead plant remains such as leaves, bark, and flowers, alongside dead remains of animals and fecal matter.

Fragmentation

The step in decomposition where detritivores (such as earthworms) break down detritus into smaller particles.

Leaching

The process in decomposition where water-soluble inorganic nutrients go down into the soil horizon and get precipitated as unavailable salts.

Catabolism

The process in decomposition where bacterial and fungal enzymes degrade detritus into simpler inorganic substances.

Humification

A process during soil decomposition that leads to the accumulation of humus, a dark-coloured amorphous substance highly resistant to microbial action.

Mineralisation

The process by which humus is further degraded by certain microbes, releasing inorganic nutrients back into the ecosystem.

Terrestrial Decomposition Cycle

The pathway through which organic detritus from plants and animals is progressively broken down by decomposers and soil fauna into mineral nutrients.

Photosynthetically Active Radiation (PAR)

The portion of incident solar radiation (less than 50 per cent) that can be captured and utilized by plants for photosynthesis.

Grazing Food Chain (GFC)

A food chain that starts with primary producers (green plants) and moves to herbivores and carnivores (e.g., Grass \rightarrow Goat \rightarrow Man).

Detritus Food Chain (DFC)

A food chain that begins with dead organic matter and is made up of heterotrophic decomposers, mainly fungi and bacteria.

Saprotrophs

Heterotrophic decomposers (mainly fungi and bacteria) that secrete digestive enzymes to break down dead and waste organic material for absorption.

Trophic Level

The specific functional position occupied by an organism in a food chain based on its source of nutrition or feeding relationships.

Standing Crop

The mass of living material (biomass) or number of living organisms present at a specific trophic level in a unit area at a given time.

10 Per Cent Law

The law governing energy transfer in a grazing food chain, stating that only 10 per cent of the energy at a lower trophic level is transferred to the next higher trophic level.

Inverted Pyramid of Biomass

An ecological pyramid where a small standing crop of primary producers supports a larger standing crop of consumers, commonly seen in aquatic ecosystems like seas.