Ecological Pyramids : Ecological Pyramids Revision : Revision We have looked at the use of food chains and food webs to the direction of energy flow in ecological systems.
A trophic level?
A secondary consumer?
A heterotroph? Ecological pyramids : Ecological pyramids There are three types of pyramid that can be used to display ecological systems
Pyramids of NUMBER
Pyramids of BIOMASS
Pyramids of ENERGY Pyramids of Number : Pyramids of Number The simplest example of an ecological pyramid
Produced by a simple count of the organisms in each trophic level of the ecosystem.
The number of each type of organism is represented by a rectangle that’s length is proportional to the number of individual organisms in a given area (or volume) Pyramids of Number : A typical pyramid of numbers Pyramids of Number Log numbers Producers herbivores 1st level carnivore 2nd level carnivore 3rd level carnivore Pyramids of Number : An inverted pyramid of numbers Pyramids of Number numbers Producers herbivores 1st level carnivore 2nd level carnivore Pyramids of Number : Advantage
Data relatively easy to collect using simple sampling
Producers vary in size
Large range of numbers
Trophic level difficult to work out Pyramids of Number Pyramids of Biomass : Pyramids of Biomass These are based on an estimation of the total mass of the organisms at each trophic level
How might this data be collected?
Individual organisms weighed and counted. Dry mass should be compared to eliminate errors due to water content Pyramids of Biomass : Pyramids of Biomass Advantages
The data is more accurate.
Eliminates misleading problems of producer size differences
Laborious and expensive
Can also be misleading in some circumstances Pyramids of Biomass : Pyramids of Biomass For example, in certain aquatic ecosystems a pyramid of biomass may look like this phytoplankton zooplankton 1st level carnivore WHY? Pyramids of Biomass : Sample only takes into STANDING BIOMASS not PRODUCTIVITY
Producers are small with a high turnover rate
The rate of consumption is about equal to rate of production Pyramids of Biomass Pyramids of energy : Pyramids of energy Each bar represents the total amount of energy used by the trophic level per unit area over a set period of time (remember KJm-2yr-1?) Pyramids of energy : Pyramids of energy Gross production Herbivores to carnivores Producers to herbivores Carnivores to top carnivores 87110 88 1603 14098 Energy (in KJm-2yr-1) Pyramids of energy : Advantages
Takes into account the PRODUCTIVITY
Addresses the fact that weight for weight, two species do not necessarily have the same energy content
Very difficult to obtain data
Problems identifying trophic level Pyramids of energy Please get out your information booklets! : Please get out your information booklets!