Energy and Ecosystems
- Created by: Sophie
- Created on: 05-11-14 20:31
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- Energy and Ecosystems
- Energy Transfer
- Plants are producers
- Energy is indigestible material is decomposed and is returned into the ecosystem
- Not all light energy is used by plants:
- Different wavelengths
- Light may not fall on chlorophyll molecule
- 90% reflected back into space
- CO2 may limit photosynthesis
- Not all energy is transferred to next trophic level
- Indigestible material
- Thermal energy is lost during respriation
- Gross productivity= how much energy that the plant converts to organic matter
- Net productivity= 10% = biomass
- Net = Gross - Respiratory Losses
- Energy transfer= energy available after / energy available before x 100
- Net productivity= 10% = biomass
- Pyramid Diagarams
- Area of block = size of trophic level
- Number
- Don't account for size of an organism
- Biomass
- Dry mass= kgm-2
- Fresh mass is easy to access but varying amount of water make this unreliable
- Seasonal differences aren't apparent, one moment in time
- Amount of plankton is very small at any moment as they have a short life span and reproduce very quickly
- Energy
- kJm-2year-1
- Most accurate of energy flow
- 2 organisms with same biomass may store different amounts of energy
- Intensive ecosystems vs natural
- Natural hasn't been changed by human activity
- Intensive farming controls biotic and abiotic factors to make it more favourable for organisms
- Warm, resitricted movement, high energy food
- More food in short time at low cost
- Crops or livestock have greater net productivity
- Restricted energy loss from movement and recovering from disease
- More energy input, more energy available for growth
- Energy input to intensive farms may be greater
- Controlling conditions= more biomass
- Pest control
- Pests are organisms that competes with humans for food or space
- Chemical Pesticides
- Fungicides kill fungi which damage crops. Crops use less energy on fighting infection and more for growth
- Killing pests means less biomass is lost from crops so greater productivity
- May affect non target species, bioaccumulation, can be expensive
- Biological Control
- Natural predators
- Parasites, Pathonogenic bacteria or viruses- produce toxins
- May become pests themselves, affect non target species, less cost effective, slower acting
- Intergrated Pest Systems
- Both chemical and biological
- Productivity increased, costs reduced if one method is particularly expensive
- Less pesticides used so better for environment
- Fertilisers
- Nitrates added to sil, more energy for higher efficiency
- Natural = organic matter, artificial =inorganic e.g ammonium nitrate
- Fertilisers washed into rivers, fish and plants die because of eutrophication
- Too much of a nutrient harms plants
- Excess fertiliser is washed away = waste of money
- Energy Transfer
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