Energy And Ecosystems Flashcards
What is a trophic level
Each stage in a food web
What happens to the energy in each trophic level
Majority is lost due to respiration and excretion
Remaining energy is used to form biomass
What is biomass
Mass of carbon within the organism
What is GPP
Gross Primary Production
Chemical energy stored in plant biomass in a given area/ volume
Total energy resulting from photosyn
What is NPP
Net primary production
GPP- energy lost by respiration
Energy left to go towards making biomass
How to work out net production of consumers
N = I - F + R
I= chemical energy stored in ingested food (Eaten)
F = chemical energy lost to environment in faeces and urine
R = respiratory losses
What units are used in rates of productivity and why
kJ ha-1 year-1
kJ unit for energy
Recorded as per unit area to STANDARDISE the results - environment can be compared, takes into account that different environments will vary in size
PER YEAR - take into account impact seasons (rain, light, temp) = annual average - comparison
Why is the nitrogen cycle important?
Nitrogen is within proteins, ATP and nucleic acids
Cannot gain nitrogen through nitrogen gas because of its triple bond which plants and animals cannot break
Microorganisms are needed to convert nitrogen gas into nitrogen containing substances that plants and animals can absorb
What are the key processes of nitrogen cycle
- saprobiotic nutrition and microbes (essential for all other stages) = microbes feeding on dead plant matter/waste
- ammonification
- nitrification
- nitrogen fixation
- denitrification
2 ways nitrogen is extracted from atmosphere in soil
Leguminous plants
Nitrogen fixing bacteria in root nodules of plants directly converts nitrogen from atmosphere into ammonia into their roots
Free living nitrogen fixing bacteria within soil which can fix nitrogen into ammonium
What is nitrification
Nitrifying bacteria Can oxidise ammonium into nitrites
Oxidise further into nitrates
Absorbed by AT into plant roots (assimilation)
Animal absorb through digestion and absorption
Explain saprobiotic nutrition
Have to name nitrogen containing compounds (urea, protein, DNA)
Decomposers break down proteins to release nitrogen
Converts back to ammonium
IF LACK OF O2 in soil = anaerobic denitrifying bacteria convert nitrates back into nitrogen gas
NITROGEN GOES BACK TO ATMOSPHERE
Why is phosphorus cycle important
Used in phosphate groups of DNA RNA ATP and phospholipid bilayer
Essential element of life for all organisms
Where is phosphorus found
As a phosphate ion in mineral form in sedimentary rock
What are the mycorrhizae and why are they beneficial for plant growth
Fungal associations between plant roots and beneficial fungi - acting like extensions of the plant’s root system
- fungi increases the SA for absorption of water and mineral ions
- mycorrhizae acts like a sponge so holds water and minerals around roots
- this makes plants more drought resistant and able to take up more inorganic ions
IMPROVING THE UPTAKE OF RELATIVELY SCARCE IONS
Why do plants have mutual relationship with mycorrhizae
Plant provides advantage to fungus, through photosynthesis it creates carbohydrates and share them with fungus
BOTH PROVIDE MUTUAL BENEFIT TO EACH OTHER FOR SURVIVAL
Explain the phosphorus cycle
How phosphorus is passed through organisms and rocks and back into the oceans/ soils
Phosphate ions in oceans/ soil
Plants absorbs ions through AT in root hair cells
Animals consume plants to absorb ions
Excretion from animals releases phosphorus back into soil and oceans in form of phosphate ions
ALSO decomposition - excess phosphate ions from waste materials (guano, bones)
These are eroded and released back into soil/ ocean
Deposition - phosphate ions build up to create rocks
Sedimentation - phosphate ions within soil compaction through sedimentation to create sed rocks
Sed rocks eroded and release phosphate ions back to soil/ ocean
What are fertilisers
Damage without fertilisers?
Diff fertilisers
Added to soul to replace the nítrate and phosphates ions lost when plants are harvested and removed from nutrient cycles
Continue to do so = plant and soils which are mineral deficient
Natural (manure)
Artificial (inorganic chemicals)
How do fertilisers increase productivity
Nitrogen is essential for plant growth (component of amino acids, atp, DNA)
Nitrate ions are readily available = plants develop taller, larger leaves
= increases rate of photosynthesis and improves crop productivity
Pros and cons of
natural
artificial fertilisers
-cheaper (free if farmer owns animals)
- extract minerals and proportions cannot be controlled
- (synthetically created) so have exact proportion of minerals plants need
- inorganic substances are more water soluble = more these ions dissolve in water surrounding the soil (advantage) - plant can absorb
- BUT larger quantities are washed away with rainfall = greater impact on environment
What is leaching and what causes it
When water-soluble compounds are washed away often into river or ponds
Can be harmful to humans if reaches sources of drinking water
What is eutrophication and what causes it
Nitrates leached from fertilised fields stimulate growth of algae in pond - Nutrient concentrations increase in bodies of water
Excessive growth of algae creates blanket on surface (upper layers of water become densely populated with algae) which blocks out light
Plants below cannot photosynthesise and die
Bacteria within water feed and repisé on dead plant matter
= increase in bacteria (all respiring and using up oxygen in the water)
EVENTUALLY - lack of dissolved oxygen in water which means fish and aquatic organisms die (no oxygen for respiration)
