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34 Cards in this Set
- Front
- Back
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Define producers |
photosynthetic organisms that manufacture organic substances using light energy, CO2, water, and mineral ions |
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Define consumers |
organisms that obtain their energy by feeding on other organisms rather than using sunlight directly |
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Define saprobionts (decomposers) |
group of organisms that break down the complex materials in dead organisms into simple ones |
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Define biomass |
The total mass of all living material in a specific area at a given time |
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How can you make sure all the water is removed from some biomass? |
1) Put in oven at low temp to dry 2) Weight sample at regular intervals 3) When mass is constant, all water has been removed |
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Define gross primary production (GPP) |
total amount of chemical energy converted from light energy by plants, in a given area, at a given time |
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Define respiratory loss (R) |
the GPP lost to environment as heat when plants respire |
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NPP = ? |
NPP = GPP -R |
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Name 4 reasons why 100% of energy isn't transferred to the next trophic level |
1) some of organism (eg bones) isn't consumed 2) some parts aren't digested + lost in faeces 3) some energy lost in excretory materials (urine) 4) energy lost for maintaining body temp |
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Net production of consumers can therefore be calculated as: |
N = I - (F + R) where: N = net prod. I = ingested materials F = E lost in Faeces + urine R = respiratory losses |
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Define pest |
An organism that reduces the amount of energy available for crop growth and therefore NPP of crops |
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How do insecticides reduce pest numbers? |
Kill insects that eat + damage crops Kill insects = less biomass lost from crops = crops grow larger = NPP greater |
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How do herbicides work? |
They kill weeds Removes direct competition with crop for energy from sun Removes preferred habitat + food source for pests |
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Name two biological agents to reduce number of pests |
Parasites - they kill insects or prevent them from functioning properly Pathogenic - kills pests |
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Name 2 ways of reducing respiratory losses |
Reduce movement - less respiration Keep warm - less energy wasted generating body heat |
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Benefits of reducing respiratory losses |
More food produced in shorted space of time at lower cost |
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Why do plants + animals need Nitrogen |
To make nucleic acids and proteins |
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What is nitrogen fixation? |
When nitrogen gas in the atmosphere --> nitrogen containing compounds N --> ammonia Carried out by bacteria such as Rhizobium |
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Rhizobium is found inside root nodules of leguminous plants. They form a mutualistic relationship with plants what does this mean? |
They provide the plant with N-compounds and plants provides them with carbohydrates |
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What is ammonification? |
nitrogen compounds from dead organisms --> ammonia by saprobionts |
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What is nitrification? |
ammonium ions in soil --> nitrogen compounds by nitrifying bacteria |
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What is denitrificaiton? |
nitrates in soil converted to N-gas by denitrifying bacteria anaerobic conditions |
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STEP 1 of phosphorous cycle |
1) Phosphate ions in rocks released into soil by erosion and weathering |
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STEP 2 of phosphorous cycle |
2) Phosphate ions become dissolved and so are available for absorption by plants |
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STEP 3 of phosphorous cycle |
3) Phosphate ions pass into animals which feed on the plants and excess phosphate ions excreted by animals |
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STEP 4 of phosphorous cycle |
Plants and animals die and saprobionts break them down releasing phosphate ions into water/soil |
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STEP 5 of phosphorous cycle |
Weathering of rocks releases phosphate ions into seas, lakes and rivers |
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Explain how intensive farming can result in the loss of nutrients |
1) mineral ions continuously taken up by crops being grown on it 2) crops sold for food and consumed away from site 3) faeces, urine etc. aren't returned to land 4) conc of mineral ions falls |
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What is a natural fertiliser? |
consist of manure, slurry, bone meal, dead remains of plants + animals |
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What is a artificial fertiliser? |
contain pure chemicals as powders or pellets |
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How do fertilisers increase productivity? |
More nitrogen = plants grow taller = develop further = larger leaf sf |
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What is leaching? |
When nutrients are removed from soil 1) rainwater dissolves any soluble nutrients and carries them deep into soil 2) leached ions drain into lakes + watercourses 3) cause harm to humans plants and animals and cause eutrophication |
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What is eutrophication? |
1) Mineral ions leached from fertilised fields stimulate rapid growth of algae in lakes 2) algal bloom blocks light 3) plants die as no photosynthesis 4) bacteria feed on dead plant matter 5) increased bacteria mean more anaerobic respiration = less O2 5) fish and other aquatic organisms die as not enough dissolves oxygen |
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What happens when anaerobic organisms decompose dead material lots? |
more toxins and H2S released = water becomes putrid |
