Ecological pyramids Flashcards
What is an ecological pyramid used for?
show trends in an ecosystem.
What are the 3 ecological pyramids?
- Pyramid of numbers
- Pyramid of biomass
- Pyramid of energy
What type of data do these pyramids use and how are they represented?
contain data for various trophic levels within an ecosystem which are represented as boxes stacked one on top of the other, often forming a pyramid shape.
Pyramids of numbers characteristics
Organisms belonging to various trophic levels are identified
The numbers of organisms are counted for each trophic level
Remember that the trophic levels are moving up, so start with the producer
What are the advantages of using the pyramid of numbers?
Easy to count organisms
No special training required
No harm to organisms
What are the disadvantages of using the pyramid of numbers?
Time-consuming
Difficult to count all organisms in a large area
Data is representative of a particular period of time since population numbers change
The pyramid may be inverted because the size of organisms are not taken into account
What is biomass?
the mass of an organism
Characteristics of biomass pyramid
The numbers of organisms are counted for each trophic level
This is a more accurate pyramid than the pyramid of numbers
How is the total biomass calculated?
The biomass of each organism is measured and multiplied by the number of organisms at theta trophic level.
Advantages of the pyramid of Biomass
Fixes problem encountered with pyramids of number since the size of the organisms are taken into consideration in addition to the numbers of organisms
More accurate than pyramids of number
Disadvantages of the pyramid of biomass.
The wet mass is not very accurate. The wet mass is the mass of the whole organisms and can be measured when the organism is alive. > Dry mass is the mass of the organism after all the water has been removed.
Data is only representative for a particular period of time since the mass of organisms changes; pregnant mammals will weigh more
Sometimes the pyramid may still be inverted eg in winter the mass of producers may be less than that of primary consumers
PYRAMID OF ENERGYYYY
the energy contained in organisms for each trophic
level, moving up as you move along the food chain
How is energy measured?
Energy is measured in Joules (J) or kiloJoules (kJ)
Advantages of pyramids or energy are?
Pyramids of energy are never inverted
What are the disadvantages of pyramids of energy?
Collecting data is difficult
