Energy And Ecosystems Flashcards
What are producers?
Photosynthetic organisms that manufacture organic substances using light energy
What are consumers?
Organisms that obtain their energy by feeding on other organisms
Primary consumers eat producers
Secondary and tertiary eat primary
What are decomposers?
A group of organisms that break down dead matter releasing valuable minerals
Detritivores
What is a food chain?
The feeding relationship in which the producers are eaten by primary consumers
What is a trophic level?
Each stage in the chain
Energy loss from plants
Convert only 1-3% of the Sun’s energy into organic matter
- 90% reflected back into space
- may not fall in a chlorophyll molecule
- limiting factors reduce rate of photosynthesis
Equation for net production
Net production =
Gross production - respiratory losses
What is gross production?
The total quantity of energy that the plants in a community convert to organic matter
Energy loss at each stage
Some isn’t eaten
Bone, teeth, hair can’t be digested so lost in faeces
Energy lost through heat due to respiration
Lost in excretion such as urine
How is energy measured?
Kilojoules per square metre per year
kJ m-2 year-1
Pyramids of number
Bar length is proportional to the number of organisms at each level
Therefore the shape isn’t always pyramid
Pyramid of biomass
More reliable and quantitative
Biomass - the total dry mass of plants or animals in a place
Have to be killed to measure so small samples
Seasonal differences are not apparent
Pyramid of energy
Most accurate representation
The measure of energy stored in an organism
What is productivity?
The rate at which something is produced
So gross productivity is the rate at which a plant assimilates chemical energy
Biological control
Slow at acting on the pest
Can become a pest itself
Very specific
Doesn’t need to be reintroduced
Pests don’t become resistant
