The key elements of ecosystem structure and dynamics (biotic and abiotic elements, food chains and webs, biomass, trophic levels, flows of matter and energy)

Question 1

Biotic and abiotic elements

Answer 1

Biotic components:
-The living organisms that shape an ecosystem
-Each biotic component needs energy to do work and food for proper growth
-Include the interactions between the living components of an ecosystem e.g., parasitism, disease and human influence

Abiotic components:
-The non-living components of an organism’s environment e.g., temperature, light, moisture
-Tend to be limiting factors such as the available water or nutrients for plant growth or the growing season length
-Can change over time, which can cause the ecosystem to change as well

Question 2

Food chains

Answer 2

-The simplest representation of energy flow within an ecosystem, following a direct, linear pathway one animal at a time from producers down to decomposers
-Vary in length from 3-6 or more levels

Question 3

Food webs

Answer 3

-The natural interconnection of food chains and generally a graphical representation of what-eats-what in an ecological community
-All life forms broadly categorised into autotrophs and/or heterotrophs
-Autotrophs produce organic matter from inorganic substances to maintain their bodies, grow, develop and reproduce
-Heterotrophs obtain organic matter by feeding on autotrophs and other heterotrophs

Question 4

Biomass

Answer 4

The total quantity or weight of living organisms in a given area

Question 5

Trophic level

Answer 5

The position an organism occupies in a food chain. Primary producers occupy the first trophic level, and the organisms that consume them the second trophic level and so on.

Question 6

Ecological pyramid

Answer 6

-An ecological pyramid roughly represents the biomass (usually measured as total dry-weight) at each level.
-Names of trophic categories are shown to the right of the pyramid
-Three kinds: a pyramid of numbers; a pyramid of biomass; or a pyramid of energy

Question 7

Biogeochemical cycle

Answer 7

-A pathway by which a chemical substance moves through both biotic and abiotic compartments of the Earth
-A cycle is a series of changes which comes back to the starting point and can be repeated e.g., the water cycle
-Biological, geological and chemical factors are all involved