Download Net production

Option G:
Ecology and Conservation
G.2 Ecosystems and Biomes
F.2.1 Define gross production, net production and biomass
Units: kJ m-2 yr-1
Gross production = net production + respiration OR total
amount of organic matter produced by plants in an
ecosystem
Net production = gross production - respiration
Biomass = dry weight of an organism measured in g m-2 yr-1
F.2.2 Calculate values for gross production and net production
using the equation:
gross production – respiration = net production
Example:
Construct an pyramid of energy using the following information:
Tropic level
Producers
Primary consumers
Secondary consumers
Tertiary consumers
Energy flow (kJ m-2 yr-1)
20 810
3368
383
21
F.2.3 Discuss the difficulties of classifying organisms into trophic
levels
F.2.4 Explain the small biomass and low numbers of organisms in
higher trophic levels
• Biomass is lost during respiration at each trophic level
• Predators at the top of the pyramid must be large enough
to catch prey; there can only be a few of them
F.2.5 Construct a pyramid of energy giving appropriate formation
The total solar energy received by a grassland is 5 x 105 kJ m-2 y1. The net production of the grassland is 6 x 102 kJ m-2 y-1. The
total energy passed onto the primary consumers is 60 kJ m-2 y-1.
Only 10% of this energy is passed onto its secondary consumers.
a) Calculate energy lost by plant respiration
b) Construct a pyramid of energy for this grassland.
F.2.5 Construct a pyramid of energy giving appropriate formation
The total solar energy received by a grassland is 5 x 105 kJ m-2 y1. The net production of the grassland is 6 x 102 kJ m-2 y-1. The
total energy passed onto the primary consumers is 60 kJ m-2 y-1.
Only 10% of this energy is passed onto its secondary consumers.
b) Construct a pyramid of energy for this grassland.
F.2.6 Distinguish between primary and secondary succession,
using an example of each
Ecological succession: change in species composition in a
community over time.
Primary Succession
Secondary succession
• Plants begin growing on
previously lifeless area
• Lacks organic soil
• Example:
• New volcanic island (lichen
moss)
• After primary succession
• Upheaval of primary succession
(plants) but has organic
component (seeds/roots)
• Example:
• Recolonisation after forest fire
F.2.7 Outline the changes in species diversity and production
during primary succession
Example: Coastal sand dunes
Foredune  Yellow dune  Grey dune  Mature dune
• thin soil layer
•
• Sedge and sand bindweed;
• no soil
dandelion and thistles
• Pioneer plants:
lyme and marram • Rabbits (droppings)
•
•
Diversity
increases
grass
• Limited diversity
Humus
develops
(holds water)
Thick shrubs
• Thick humus
• Supports
forest
• High
diversity
F.2.8 Explain the effects of living organisms on the abiotic
environment with reference to the changes occurring during
primary succession
•
•
•
•
Few species
No soil
New area
Lichen and mosses
are pioneer plants
• Low biomass
• Low production
•
•
•
•
Many species
Soil present
Old area
Seeds and roots
already present
• Higher biomass
• Higher production
F.2.9 Explain how rainfall and temperature affect the distribution of
biomes
• Climograph plots temperature and rainfall in a particular region
F.2.10 Outline the characteristics of the major biomes