Energy Transfer and Nutrient Cycle Flashcards
Define biomass
Chemical energy stored in plants
Define dry mass and outline how you measure it
- Mass of the organism w/ water removed
- Sample of organism is dried in oven. Sample is weighed at regular intervals. Once mass is constant, water is fully removed
- Unit: kg m-2
- Mass of C present usually takes 50% of dry mass
Outline how you can estimate the amount of chemical energy stored in biomass
- Sample of dry biomass is burnt + energy released is used to heat known vol of water (calorimeter)
- Change in temp of water is used to calculate chemical energy of dry mass
Define gross primary production (GPP)
Total amount of chemical energy converted from light energy by plants
Define respiratory loss (R)
50% of GPP is lost to env as heat when plants respire
Define net primary production (NPP)
- Energy available to plant for growth + reproduction
- Energy available to organisms at next stage of food chain
What is it called when primary production is expressed as a rate?
Primary productivity
Net primary production equation
NPP = GPP - Respiratory loss
What percentage of chemical energy stored in consumers’ food is not transferred to the next trophic level?
90% of total available energy is lost
Give examples of how energy is lost
- Not all the food is eaten eg. bones
- Egested as faeces
- Respiration
- Excretion of urine
Net production of consumer equation
N = I - (F+R)
- N = Net production
- I = chem energy in ingested food
- F = chem energy lost in faces + urine
- R = energy lost during respiration
What does food chains and food webs show
- How energy is transferred through an ecosystem
- Food chain: simple lines, each stage = trophic level
- Food web: Lots of food chains that overlap
Define decomposers
Break down dead or undigested material, allowing nutrients to be recycled
Outline how farmers simplify food webs to reduce energy loss to non-humans
- Reduce pests using chemical pesticides:
- Insecticides kill insects
- Herbicides kill weeds removing direct competion
- Biological agents also reduce no. pests:
- Paracites kill insect or reduce ability to function
- Pathogenic bacteria + viruses
Outline how farmers reduce respiratory losses w/i humanfood chain
- Controlling conditions so energy is used for growth + less lost in respiration:
- Movement is restricted
- Indoors + kept warm so less energy is lost by generating body heat
Define a natural ecosystem
Ecosystem that hasn’t been changed by human activity
Define saprobionts and outline what they do
- Feed on remains of dead plants and animals and on their waste products
- Secrete enzymes + digest food externally, then absorb nutrients they need - extracellular digestion
Outline how fungi form symbiotic relationships (mycorrhizae) w/ roots of plants
- Fungi made up of long, thin strands called hypae, which connect to plant’s roots
- Hypae inc SA of plant’s root system, helping plant to absorb ions from soil, also inc uptake of water
- In turn fungi obtain organic compound from plant
Why do plants and animals need nitrogen?
To make protein and nucleic acids
What are the 4 different processes in the nitrogen cycle?
- Nitrogen fixation
- Ammonification
- Nitrification
- Denitrification
Outline what happens during nitrogen fixation
- N gas from atm is turned into nitrogen-containing bacteria
- Carried out by bacteria (rhizobium) which turn N into ammonia, going on to form ammonium ions that can be used by plants
- Rhizobium: found inside root nodules of leguminous plants
- Form mutualistic releationship w/ plants: provide plants w/ N compounds + plants provide carbs
Outline what happens during ammonification
- N compounds from dead organism are turned into ammonia by saprobionts, forming ammonium ions
- Animal waste (faeces + urine) also contains N compounds + so go through the same process
Outline what happens during nitrification
- Ammonium ions in soil change into nitrogen compounds that can be used by plants
- Nitrifying bacteria change ammonium ions into nitrites
- Other nitrifying bacteria change nitrites to nitrates
Outline what happens during denitrification
- Nitrates in soil are converted into N gas by denitrifying bacteria - use nitrates for respiration
- Happens under anaerobic respiration eg. waterlogged soil
Why do plants and animals need phosphorus?
To make phospholipids, DNA and ATP
Outline the phosphorus cycle
- Phosphate ions in rocks are released in soil by weathering
- Ions taken in by plants through roots. Mycorrhizae inc rate ions can be assimilated (absorbed + used to make complex ions)
- Ions transferred through food chain
- Lost from animals in waste
- When plants + animals die, saprobionts break down organic compound, releasing ions into soil for assimilation by plants. Also release in urine + faeces
- Weathering of rocks release ions in seas, lakes + rivers - taken in by aquatic producers (algae) + passed to birds
- Waste product of sea bird (guano) contains high proportion of ions + return to soil - natural fertilisers
Describe how mineral ions are lost from the env
- Crops take in minerals to make new tissue, when harvested they’re removed from field - decomposers unable to return minerals to soil
- Animals that eat the grass and take in the nutrients are removed from land - unable to replace nutrients through remains or waste
Why are fertilisers added to soils?
Replace lost nutrients, more energy from ecosystem used for growth, inc efficiency of energy transfer
What are artificial fertilisers?
- Inorganic
- Contain pure chemicals as powders/pellets
What are natural fertilisers?
- Organic matter
- Manure, composted veg, crop residue + sewage sludge
Describe the process of leaching when using fertilisers
- When water soluble compounds in soil are washed away into ponds/rivers
- Can lead to eutrophication
- More likely to occur if fertiliser applied before heavy rainfall
- Inorganic fertilisers: relatively soluble, excess minerals not used up immediately more likely to leach
- Organic fertilisers: organic molecules need to be decomposed before being absorbed so more controlled + less leaching
- Phosphate less soluble than nitrates so less leaching
Nitrate from fertiliser applied to crops may enter ponds and lakes. Explain how nitrate may cause the death of fish in fresh water (5)
- Stimulate rapid growth of algae
- Block light reaching plants below
- Plants die bc unable to phototsynthesise
- Saprobionts feed on dead plant matter, inc no. bacteria reduce O2 conc in water by carrying out aerobic respiration
- Fish die bc not enough oxygen to respire
Upwelling often results in high primary productivity in coastal waters.
Explain why some of the most productive fishing areas are found in coastal waters (2)
- Nutrients used by algae/plants for growth
- More food = fish produce more
Describe the role of microorganisms in producing nitrates from the remains of dead organisms (3)
- Saprobionts break down remains into ammonia
- Ammonia/ammonium ions into nitrite then into nitrate
- By nitrifying bacteria
Denitrification requires anaerobic conditions. Ploughing aerates the soil. Explain how ploughing would affect the fertility of the soil (2)
- Fertility inc bc more nitrates are formed
- Less/no denitrification
