ECOSYSTEM · Comparison Tables

1. Biotic vs abiotic ecosystem components

Parts of an ecosystem
Feature	Biotic components	Abiotic components
Nature	Living organisms.	Non-living physical and chemical factors.
Includes	Producers, consumers and decomposers.	Air, water, soil, solar input, temperature and dissolved substances.
Pond example	Phytoplankton, zooplankton, fish, insects, fungi and bacteria.	Water, rich bottom soil and inorganic/organic substances.

2. Gross vs net vs secondary productivity

Rates of biomass production
Feature	GPP	NPP	Secondary productivity
Meaning	Total organic matter produced by photosynthesis.	GPP remaining after plant respiration.	Rate of new organic matter formation by consumers.
Formula	GPP	GPP - R = NPP	Consumer biomass production
Importance	Total producer capture of solar energy.	Biomass available to herbivores and decomposers.	Shows consumer assimilation into biomass.

3. Detritus vs litter

Material entering decomposition
Feature	Detritus	Litter
Meaning	Dead organic matter and waste.	Dead plant material such as leaves, bark, flowers and twigs on soil surface.
Role	Starts detritus food chain and feeds decomposers.	Important terrestrial detritus input.
Fate	Fragmented, leached, catabolised, humified and mineralised.	Becomes detritus and undergoes decomposition.

4. Humification vs mineralisation

Late stages of decomposition
Feature	Humification	Mineralisation
Process	Formation of dark, amorphous humus from detritus.	Microbial release of inorganic nutrients from humus/organic matter.
Rate	Humus is resistant to microbial action and decomposes very slowly.	Releases usable inorganic nutrients.
Significance	Colloidal humus acts as a nutrient reservoir.	Returns nutrients to ecosystem circulation.

5. Grazing vs detritus food chain

Two routes of energy flow
Feature	Grazing food chain (GFC)	Detritus food chain (DFC)
Starts with	Living producers.	Dead organic matter (detritus).
Main organisms	Producers, herbivores and carnivores.	Decomposers, mainly fungi and bacteria; detritivores.
Dominance	Major conduit in aquatic ecosystems.	A larger fraction of energy flows here in terrestrial ecosystems.
Connection	Food chains interconnect into food webs; omnivores can link GFC and DFC.

6. Producers, consumers and decomposers

Trophic roles
Group	Trophic role	Examples
Producers	First trophic level; fix solar energy into food.	Green plants, phytoplankton, algae and photosynthetic bacteria.
Primary consumers	Second trophic level; feed on producers.	Herbivores, zooplankton.
Higher consumers	Feed on lower consumers.	Carnivores and top carnivores.
Decomposers	Break down dead matter into simple inorganic substances.	Fungi and bacteria.

7. Energy flow vs nutrient cycling

Two major ecosystem processes
Feature	Energy flow	Nutrient cycling
Direction	Unidirectional: sun to producers to consumers/decomposers.	Materials are recycled between biotic and abiotic pools.
Source / loss	Sun is ultimate source (except deep-sea hydrothermal systems); energy is lost as heat.	Mineralisation returns inorganic nutrients for uptake.
Key rule	Only about 10% passes to next trophic level.	Decomposition makes nutrients available again.

8. Pyramid of numbers, biomass and energy

Ecological pyramids
Pyramid	Represents	Shape / exception
Numbers	Number of organisms at each trophic level.	Usually upright; can be inverted in a tree ecosystem.
Biomass	Standing crop measured as biomass.	Usually upright on land; inverted in sea where phytoplankton biomass is lower than zooplankton/fish.
Energy	Energy available at each trophic level.	Always upright because energy decreases along chain.

9. Standing crop vs standing state

What is present at a given time
Feature	Standing crop	Standing state
Meaning	Mass of living material at a trophic level at a given time.	Amount of inorganic nutrients in abiotic components at a given time.
Measurement	Biomass or number per unit area; dry weight is more accurate.	Pool of nutrients such as phosphorus in soil or water.
Change	Changes with growth, consumption and death.	Varies with season and nutrient cycling.