4: Energy and Ecostystems Flashcards
Advantages of integrated system to control agricultural pests?
Biological advantages:
- specific
- reproduces so only needs one application
- maintains low population
- pests don’t develop resistance
- can use less chemicals (no bioaccumulation)
Chemical advantages:
- acts quickly
- can apply to only a specific area
- kills a greater variety of pests
Explain how the use of pesticides can result in resistant strains of insect pests?
- variation amongst pest population
- due to a mutation
- give rise to allele for resistance
- through selection
- pests with resistance are more likely to survive and breed
- increase in allele frequency
Explain how intestine rearing of livestock increases productivity
- slaughtered while still growing so more energy transferred to biomass
- fed on controlled diet so higher proportion of food assimilated and transferred to biomass
- movement restricted so less respiratory loss
- kept warm inside to reduce respiratory loss
- selectively bred for high productivity
Explain how leaving if nitrates into ponds and lakes causes the death of fish
- growth of algae on the surface blocks light
- reduced photosynthesis so submerged plants die
- saprobiotic bacteria respire aerobically to break down dead plant
- less oxygen for fish to respire so they die
Explain how farming practices increase the productivity of crops
- fertilisers added to soil - contain nitrates for proteins and phosphates for ATP
- pesticides prevent crop damage and competition from weeds
- selective breeding for high productivity
- greenhouses to enhance light, temperature and CO2
- ploughing aerates soil to decrease amount of denitrification
- crop rotation ensures nutrient levels are kept high
- watering to remove water as a a limiting factor
- protection of crops from pests using covers and netting
How to calculate Net production
Gross production - respiratory losses
Most of the Suns energy is not converted into organic matter by photosynthesis because…..
Over 90% of the Suns energy is reflected back in to space
Not all wavelengths of light can be absorbed by chlorophyll
Light may not fall on chlorophyll
Some light passes through leaf
May be limiting factor e.g low CO2 levels
The low % of energy transfer end at is stage is the result of:
Some of the organism not eaten
Some parts cannot be digested
Some lots in excretions
Lost as heat from respiration
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Most food chains only have 4 trophic levels, insufficient energy to sustain breeding population
The total mass of organisms is less at higher trophic levels
The total amount of energy stored is less at each level
Give an example and explanation of when a pyramid of biomass is not pyramidal
Wen they are based on plant plankton
The amount of plant plankton at any given time is quite small, but because they have a short life span and reproduce very quickly there’s a lot around over a period of time
Which pyramids are always pyramidal?
Pyramids of energy because energy is always lost between trophic levels
State two disadvantage of pyramids of numbers
In a pyramid of numbers, no account is taken of size
The number of individuals may be so great that it is impossible to represent than in the same scale as other species in the food chain
What units are used for each type of ecological pyramid?
Number: no units
Biomass: grams per square meter/cubic meter
Energy: kJ per metre squared per year
How does energy input differ in agricultural ecosystems compared to natural ecosystems?
Natural, energy solely from the sun
Agricultural, energy from the sun, energy from food (for workers), fossil fuels for machinery
The additional energy input into agricultural ecosystems is used to increase productivity
What is meant by the term ‘net productivity’?
The rate at which chemical energy is assimilated by plants minus the chemical used by plants in respiration
The energy available to the next trophic level
