2.2.1 Energy in The Ecosystem

Learning Objectives

Starter Activity: Terminologies

2.2 Terminologies Activity.docx

Match these role, example and description

Use this chart to match

Producer

Herbivores

Predator

Scavenger

Detritivores

Saprotrophs

Parasite

Decomposers

First Law of Thermodynamics

energy can be neither created nor destroyed, it can only change form. This means that the total energy in any system, including the entire Universe, is constant and all that can happen is a change in the form the energy takes

Second Law of Thermodynamics

energy goes from a concentrated form (e.g. the Sun) into a dispersed form (ultimately heat) and that the availability of energy to do work therefore decreases

Photosynthesis

Respiration

The term ‘productivity’ in ecology refers to the rate of accumulation of new biomass
Productivity can further be divided into gross productivity (GP) and net productivity (NP)
NP is the gain in energy or biomass per unit area per unit time remaining after allowing for respiratory losses (R).
NP represents the energy that is incorporated into new biomass and is therefore available for the next trophic level

Formula:

GP = NP + R

With light, the change in biomass is NP

Without light, the change is only respiration, R

Biomass can be measured at each trophic level.
Rather than measuring the mass of the total number of organisms at each trophic level (clearly impractical) an extrapolation method is used
the mass of one organism (or the average mass of a few organisms) is multiplied by the total number of organisms present to estimate total biomass
Biomass is calculated to indicate the total energy within a living being or trophic level.
Biological molecules are held together by bond energy, so the greater the mass of living material, the greater the amount of energy present.
Biomass is taken as the mass of an organism minus water content

Once dry biomass has been obtained, the combustion of samples under controlled conditions gives quantitative data about the amount of energy contained per unit sample (e.g. per gram) in the material
One criticism of this method is that it involves killing living organisms.
It is also difficult to measure the biomass of very large plants, such as trees.
There are further problems in measuring the biomass of roots and underground biomass because these are difficult to remove from the soil.

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