13.4 13.5 Energy Transfers and Nutrient Cycles Flashcards
(36 cards)
What is biomass?
Total mass of carbon in a specific area at a given time.
How is biomass measured?
In terms of mass of carbon or dry mass of tissue per given area.
Chemical energy stored in dry biomass can be measured using calorimetry.
Food chain
Producer–> Primary consumer –> Secondary consumer –> Tertiary consumer
What can energy loss occur due to?
Respiration
Excretion of faeces or urine
Percentage efficiency equation
Percentage efficiency= energy after/ energy before x100
How to measure energy loss mostly in plants?
NPP= GPP - R
NPP= Net primary productivity
GPP= Gross primary production
R= Respiratory losses
How to measure energy loss mostly in consumers?
N= I - (F+R)
N= net production
I= chemical energy ingested
F= chemical energy lost in faeces and urine
R= chemical energy lost by respiration
Units for rate of productivity
kJ m-2 year-1
Suggest one reason for conserving woodlands.
Conserving habitats.
Increasing biodiversity.
Suggest what you should do to ensure all water is removed from a tissue / sample.
- Regularly weigh and Heat (less than 100 °C)
- Until mass is constant
Gross Primary Productivity
Net Primary Production
- GPP= Chemical energy store in plant biomass, in a given area or volume. (Rate of photosynthesis)
- NPP= Chemical energy store in plant biomass after respiratory losses to the environment have been taken into account.
NPP= GPP -R - NPP is available for new plant growth and reproduction OR available for other trophic levels in the ecosystem, such as herbivores and saprobionts.
- kJ ha–1 year–1 OR kJ km–2 year–1 OR kJ km–3 year–1
The percentage of the light energy trapped by the producers is very low. Give two reasons why.
- Reflected / absorbed by water vapour;
- Reflected from producers / wrong wavelength;
- Transmitted / passes between chloroplasts/ between plants / too few chloroplasts;
The biomass of primary consumers is less than the biomass of producers. Explain why.
- Loss of energy/heat / use of energy / less energy to be passed on;
- In respiration;
- In excreta / excretion / urine / carbon dioxide;
- Inedible parts / indigestible parts / egesta / egestion / to decomposers;
Describe how and explain why the efficiency of energy transfer is different at different stages in the transfer.
- Some light energy fails to strike/is reflected/not of appropriate wavelength;
- Efficiency of photosynthesis in plants is low/approximately
- 2% efficient;
- Respiratory loss / excretion / faeces / not eaten;
- Loss as heat;
- Efficiency of transfer to consumers greater than transfer to producers/approximately 10%;
- Efficiency lower in older animals/herbivores/ primary consumers/warm blooded animals;
- Carnivores use more of their food than herbivores;
Explain how the intensive rearing of domestic livestock increases net productivity
- Slaughtered when still growing/before maturity/while young so more energy transferred to biomass/tissue/production;
- Fed on concentrate /controlled diet /controlled conditions/so higher proportion of (digested) food absorbed/lower proportion lost in faeces / valid reason for addition;
- Movement restricted so less respiratory loss / less energy used;
- Kept inside/heating/shelter / confined so less heat loss / no predators;
- Genetically selected for high productivity;
Describe the need for plants to both photosynthesise AND respire
- In the dark no ATP production in photosynthesis;
- Some tissues unable to photosynthesise/produce ATP;
- ATP cannot be moved from cell to cell/stored;
- Plant uses more ATP than produced in photosynthesis;
- ATP for active transport;
- ATP for synthesis (of named substance);
Define carbon sink.
Store of carbon
e.g peat
What are mycorrhizae?
- Fungal associations between plant roots and fungi.
- Provide large SA for uptake of water and inorganic ions.
- Absorbs and holds minerals and water easily.
Outline advantages of having mycorrhizae growth near plants.
- Mycorrhizae help plants to defend themselves (causing an increase in crop yield);
- Mycorrhizae help plants to take up nitrates/phosphates (causing an increase in crop yield);
Saprobiants
Organisms that digest their food externally and then absorb products.
What is nitrogen cycle needed for?
To create DNA, RNA, amino acids, ATP etc.
Stages of nitrogen cycle
- Nitrogen fixation
- Ammonification
- Nitrification
- Denitrification
Nitrogen fixation
Nitrogen fixing bacteria convert nitrogen gas (N2) to ammonia (NH3).
Ammonification
Saprobiants convert nitrogen containing compounds to ammonia.
