Energy and Ecosystems

Food chains and webs
1. Organisms can be divided into three groups according to how they obtain their energy
  1. PRODUCERS- Photosynthetic organisms (green plants) that manufacture organic substances using light energy, water and co2. 6CO2+6H2O+Light=C6H12O6+6O2
  2. CONSUMERS- Organisms that obtain their energy be feeding on other organisms. Eg animals. Primary consumer if eat plants. Secondary and Tertiary if eat animals which feed on plants
  3. DECOMPOSERS- when producers and consumers die. releases minerals to plants to absorb.mainly bacteria and earthworms
2. FOOD CHAIN- feeding relationship, producers eated by primary consumers.each stage refered to as trophic level
3. FOOD WEB- many food chains linked. relationships change depending on age, time of year, population size. helps understand populations
Energy Transfer
1. As little as 1% of light is captured by plants.organisms pass smal fraction of energy they recieve.
2. Most of suns energy is not used in photosynthesis
  1. 90% reflected back, not all wavelengths used, light may not reach chlorophyll, low c02 may limit rate.
3. Net production = Gross production - Respiratory Losses
  1. GROSS PRODUCTION- total quantity of energy that plant converts to organic matter
  2. NET PRODUCTION- rate at which they store energy
4. Only 10% of food stored in plant is used by primary consumer. secondary and tertiary are more efficient and transfer 20% to their bodies.
  1. Some of organism may not be eaten.
  2. Some parts cant be digested
  3. Lost in excretion
5. energy available after transfer evergy available before transfer
  1. x100
Ecological Pyramids
1. Diagrams of number, mass, amount of energy stored by organism at each tropic level.
2. PYRAMIDS OF NUMBERS- Bars which are proportional to numbers present at each trophic level and length of bars. Easy to compare and collect. However doesnt take size of organism into consideration
3. PYRAMIDS OF BIOMASS- total mass of plant/animal compared. higher mass of organism, larger the bar. more reliable, however organisms must be dead so can only use a small sample which isnt representative
4. PYRAMINDS OF ENERGY- measures energy stored in organisms. the most accurate representation of energy flow in food chains. however collecting data is difficult
Agricultural Ecosystems
1. Fertilisers
2. High productivity
3. Less genetic/species Diversity
4. Solar Energy
5. Prevented from reaching climax
  1. CLIMAX COMMUNITY- organisms that make up final stage of succession
6. Uses pesticides
7. energy from food and fossil fuels
Pests and Pesticides
1. PEST- an organism that competes with humans for food or space, or is danger to our health
2. PESTICIDES- poisonout chemicals which kill pests. eg- Herbicides kill plants, fungicides kill fungi, insecticides kill insects
  1. To be effective the pesticide must...
    1. Be specifit- only kill target organism
    2. Biodegradeable- Breakdown to harmless substances
    3. Cost effective
    4. Not accumulate
3. PEST CONTROL
Natural Ecosystems
1. More species/genetic diversity
2. Nutrients Recycled
3. Natural climax community
4. Low productivity
5. Solar energy
6. Populations controlled by natural means

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Energy and Ecosystems

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