Flashcards in 5. Energy And Ecosystems Deck (50)
What are producers?
Photosynthetic organisms which manufacture organic substances using light energy, water and carbon dioxide
What are consumers?
Organisms that derive their energy from eating plants and other organisms rather than through photosynthesis
What is a decomposer?
Organisms such as detritivores that break down complex molecules into simple components
What is each stage in a food chain called?
What do the arrows on food chains represent?
The flow of energy
What is the source of energy in all ecosystems?
How much of the sun's energy available to them do plants convert into organic matter by photosynthesis?
Why is so little converted into organic matter?
Between one percent and three percent.
-Over 90% of the sun's energy is reflected back into space by clouds and dust or absorbed by the atmosphere
-Not all wavelengths of light can be absorbed for use in photosynthesis
-Light may not fall on a chlorophyll molecule
-There may be factors limiting the rate of photosynthesis such as carbon dioxide concentration
What is the total amount of energy plants in a community convert to organic matter called?
What is the rate at which plants store energy called?
What is the equation for net production?
Net production = gross production - respiratory losses
Why is there such a low percentage of energy transferred at each stage?
-Not all of the organism is eaten
-Not all of the organism can be digested (therefore lost in faeces)
-Energy lost in excretory materials such as urine
-Energy losses as heat from respiration
How is the efficiency of energy transfer calculated? (equation)
Energy transfer = (energy available after the transfer)/ (energy available before the transfer) x100
What are the drawbacks of using a pyramid of numbers to describe a food chain?
-No account is taken of size (eg oak tree is massive but still only counts as 1)
-Number of individuals can be so great that it is hard to represent them on the same scale as other organisms
Why can pyramids of biomass be unreliable if done incorrectly?
-The fresh mass can be easily calculated however in different organisms there are different levels of water so the mass will vary
-Therefore you must use the dry mass by heating in an oven
>However organisms must be killed so therefore only a few measurements can be taken which means the results may not be representative of the population.
-Only valid at the time of sampling- doesn't take into account seasonal changes
What is the unit for biomass in the context of pyramids of biomass?
or gm^-3 when a volume is being sampled
What is the most accurate representation of flow through an ecosystem?
Pyramids of energy (measuring energy stored in organisms)
What is the unit used for energy flow in the context of pyramids of energy?
Why are the results of a pyramid of energy much more reliable than a pyramid of biomass?
Organisms with the same dry mass may contain different amounts of stored energy eg fat stores more energy than carbohydrate, even though their biomasses are equal
What is the purpose of an agricultural ecosystem?
Ensure as much of the available energy from the sun is transferred to humans (increasing the productivity of the human food chain)
What factors is net productivity affected by?
-Efficiency of the crop carrying out photosynthesis
-Area of ground covered by the leaves of the crop
In which ways does an agricultural ecosystem differ to a natural ecosystem?
-There is additional energy input into an agricultural ecosystem (eg energy from food (labour) and fossil fuels (machinery and transport))
-Less species diversity
-Less genetic diversity within a species
-Populations are controlled both by natural means and by use of pesticides and cultivation
-Prevented from reaching a climax community
-Natural recycling limited and supplemented by the addition of artificial fertilisers
What are the qualities of a good pesticide?
-Cost-effective because development costs are high an pesticides only remain efficient for a limited amount of time as pests become resistant
-Does not accumulate (eg bioaccumulation)
-Biodegradable- break down into harmless substances in the soil
-Specific- only toxic to the pest that it is trying to control- harmless to humans and other organsisms
What is the aim of a biological control?
To reduce the numbers of the pest below the economic injury level but NOT eradicate the pest
What are the advantages of using biological control rather than chemical pest control?
-Once introduced the control organism reproduces itself
-Pests to not become resistant
What are the disadvantages of chemical pest control?
-May affect species other than the target species
-Must be reapplied regularly (expensive)
-Pests develop genetic resistance and so new pesticides need to be developed.
What are the disadvantages of using biological pest control?
-The control species may become a pest itself
-Do not usually act very quickly- lag between the time of application and the reduction of the pest.
What is an integrated pest control?
Using all forms/ a combination of pest controls
How can maximum yield of product be achieved through intensive farming?
-Limiting movement (keeping in confined spaces)
-Keeping environment warm to reduce heat loss
-Optimum food quantity and food type so there is as little waste as possible
-Predators excluded so no loss to other organisms in the food web
This all limits the energy losses through respiration so there is more energy available for growth/ milk production etc...
Describe ways other than intensive farming that can increase the energy conversion rate.
-Using hormones to increase growth rate
-Selective breeding to produce varieties that are more efficient at converting the food they eat into body mass.