13.1 - 13.5 Energy and ecosystems Flashcards
What are the sugars produced during photosynthesis used for?
- Respiration
- Starch
- Cellulose
- Lipids
- Proteins (sugars combine with nitrates to form amino acids)
Why is not all sunlight used in photosynthesis?
- Most light is reflected back into atmosphere by clouds
- Not all wavelengths of light are used for photosynthesis
- Light may not fall on chlorophyll molecule
- Another factor is limiting the rate of photosynthesis (e.g CO2 conc)
Define biomass
Total mass of living material in a specific area at a given time
Give the 2 ways in which biomass can be measured
Dry mass:
- Mass of an organism or tissue after all the water in it has been removed
Mass of carbon:
- Generally 50% of the dry mass
How do you obtain the dry mass of a sample?
- Place sample in oven
- Heat at 100*c to evaporate water but not burn sample
- Remove and weigh sample at regular intervals
- Once the mass is constant this means all water has been removed
Be careful not to burn sample as this will mean mass is lost in the carbon
Define gross primary production
Total quantity of the chemical store in a plant biomass, in a given area or volume in a given time
Explain why such a low % of energy is transferred between trophic levels
- Some of the organism is not eaten
- Some parts are not digested and therefore lost in faeces
- Some of the energy is lost in excretory materials (e.g urea in urine)
- Some energy losses occur as heat from respiration
Give the equation for calculating the net primary production of consumers
N = I - (F+R)
N = Net production
I = Chemical energy store of ingested food
F = Energy lost in faeces and urine
R = Energy lost in respiration
% energy transfer calculation
Energy transfer = (Energy after/Energy before) x 100
Define producer/autotroph
An organism that synthesises organic molecules from simple inorganic ones such as carbon dioxide and water
Define consumer/heterotrophs
Any organism that gains energy by feeding on another organism
Define trophic level
Each stage in a food chain
Define herbivore
An animal that eats plants and is therefore a primary consumer
Define carnivore
An animal that eats animals and may therefore be a secondary or tertiary consumer
Define saprobiont
An organism that obtains its food from the dead or decaying remains of other organisms
Give the 2 methods by which farmers can increase the efficiency of energy transfer
- Simplifying food webs
- Reducing respiratory losses
Describe how farmers may use to simplify food chains
- Insecticides/pesticides
- Herbicides
Biological agents:
- Introducing parasites that kill pests such as lady birds that aphids
Describe how greenhouse conditions may be optimised
- Control temp
- Light lamps
- Hydroponics
- Increase CO2 (burners)
Describe how respiratory losses are reduced during factory farming
- Movement is restricted (less energy used in muscle contraction)
- Environment kept warm (reduce heat loss from the body)
- Feeding can be controlled (animals receive optimum amount and type of food for growth without wastage)
- Predators excluded
- Given antibiotics
Give the 3 ways in which nitrogen gas is converted into nitrogen-containing compounds
- Nitrogen fixing bacteria (free and in root nodules)
- Lightning (N2 and 02 react to form nitrogen oxide which then dissolves in rain water)
- Haber process (Nitrogen and hydrogen used to make ammonia which is then converted to ammonium nitrate for use in fertiliser)
Define ammonification
Production of ammonia from organic nitrogen-containing compounds
Saprobionts feed on dead organisms and waste and release ammonium into the soil
Define nitrification
The oxidation of ammonium ions into nitrate ions
(NH4+) –> (NO2-) –> (NO3-)
Define denitrification
Denitrifying bacteria convert soil nitrates into gaseous nitrogen. This requires anaerobic conditions such as waterlogged soils.
How can farmers increase the productivity using the nitrogen cycle?
Ploughing - for aeration
Drainage - to prevent anaerobic conditions
What is the name of the nitrogen fixing bacteria in plant root nodules?
Rhizobium
What do plant and animals need phosphorus for?
To make biological molecules:
- Phospholipids
- DNA
- ATP
Describe the role of mycorrhizae in nutrient cycles?
Mycorrhizae are associations between certain types of fungi and the roots of the vast majority of plants
- The act as an extension of the plant’s root system to increase the total surface area
- They also act as a sponge and allow pants to hold water and minerals around the roots
Why are fertilisers needed in agriculture?
Crops are harvested so the mineral ions they contain are removed from the environment, as they are not returned to the soil by decomposers
Define leeching
Nutrients are removed from the soil by rainwater and washed into watercourses
Must also learn
- Nitrogen cycle
- Phosphorus cycle
- Eutrification
Describe how and explain why the efficiency of energy transfer is different at different stages in the transfer of energy through the ecosystem
1.Some light energy fails to strike / is reflected / not of appropriate wavelength
2.Efficiency of photosynthesis in plants is low
3.Respiratory loss / excretion / faeces / not eaten
4.Loss as heat
5.Efficiency of transfer to consumers greater than transfer to producers
6.Efficiency lower in older animals / herbivores / primary consumers / warm blooded animals
