Ecosystems Flashcards
Define ‘Ecosystem’
All the living organisms and all the non-living components in a specific habitat, and their interactions. They are dynamic systems.
Define ‘Abiotic Factor’, giving examples
Abiotic factors describe the effects of the non-living components of an ecosystem, e.g. pH, temperature, soil type etc.
Define ‘Biotic Factor’, giving examples
The ways living organisms can effect each other in an ecosystem, e.g. food supply, predation, disease etc.
Define ‘Producer’
Organisms that supply chemical energy to all other organisms by way of photo/chemisynthesis.
Define ‘Consumer’
Organisms that feed on other organisms (they could be animals or fungi, feeding off plants or animals)
Define ‘Decomposer’
Organisms that feed on waste material or dead organisms
Define ‘Trophic Level’
The level at which and organism feeds in a food chain.
How is energy transferred through ecosystems?
Some energy is lost at each trophic level for the organism to carry out life processes: respiration releases chemical energy that could be converted to heat. Energy in dead organisms and waste material (material that can’t be digested) can only be released by decomposers.
What does the energy loss at each trophic level result in?
If all species in a food chain are the same size, there will be less consumers at the top than there are producers, as there will be less energy to sustain them. We can draw a pyramid of numbers to represent this.
How can we measure the efficiency of energy transfer?
- Draw a pyramid of biomass, where the area of the bar is proportional to the dry mass of all the organisms at that trophic level. However, this is destructive, so can take wet mass and calculate dry mass
- Draw pyramid of energy (as different organisms release different energy per unit mass, so biomass pyramid not ideal). Would have to burn organisms in a calorimeter for this: very destructive and time consuming!
What are the limitations of a) pyramids of number; b) pyramids of biomass; c) pyramids of energy
a) Doesn’t provide an accurate picture of how much living tissue there is at each level
b) Measuring dry mass is very destructive; different species may release different amounts of energy per unit mass
c) Measuring energy is very destructive; they only take a snapshot of an ecosystem in time; population size fluctuates, providing a distorted idea of the efficiency of energy transfer
What is ‘Productivity’?
The rate of flow of energy through each trophic level - can draw a pyramid of energy flow. Gives an idea of how much energy is available to the organisms at a particular trophic level in a given time. Measured in kJ or MJ.
Define ‘Gross Primary Productivity’
The rate at which plants convert light energy into chemical energy.
Define ‘Net Primary Productivity’
As not all the light energy plants convert to chemical energy (GPP) is available to consumers (some used in respiration), the rest is the NPP.
How can humans increase the energy we get from plants (NPP)?
- Light intensity limits photosynthesis, and therefore NPP: more light
- Increase water availability/breed drought resistant crops
- Temperature limits speed of chemical reactions: increase temperature to optimum temperature
- Increase availability of nutrients (would otherwise limit photosynthesis and growth
- Pesticides to stop insects etc. eating our yield!
- Prevent fungal diseases of crop plants by spraying with fungicides/breeding resistant crops
- Kill weeds with herbicides to reduce competition for light, water and nutrients
