3.5.3.1 - Energy and Biomass/GPP and NPP (C13) Flashcards
Define ecosystem
All the organisms living in a particular area and all the abiotic conditions.
What are producers?
Organisms that make their own food - usually by photosynthesis.
What is biomass?
The mass of living material in a given area (g per m2)
Define dry mass
The mass of the organism with the water removed
What unit are typically used to measure biomass?
dry mass of tissue per unit area per time.
How do you measure dry mass?
The sample is heated (low temperature). The sample is then reweighed at intervals until a constant mass is reached.
How can you estimate the chemical energy stored in biomass?
Burn it in a calorimeter. The amount of heat given off tells you how much energy is in it.
What is the unit of energy?
Joules or kilojoules
What does GPP stand for?
Gross primary production
Define GPP
The total amount of chemical energy converted from light energy by plants, in a given area, in a given time.
Define respiratory loss?
The amount of GPP that is lost to the environment as heat when the plants respire.
How can you calculate NPP?
NPP = GPP - R
What does NPP stand for?
Net primary production
Define net primary production
The energy available to the plant for growth and reproduction. The energy is stored in the plants biomass.
Why does only 90% of the chemical stored in the consumers food transferred to the next trophic level?
Some parts aren’t eaten (bones) and some parts are eaten and are not absorbed (faeces)
Some parts are eaten, absorbed but excreted (urine)
Some biomass us broken down and lost as heat in respiration (temp regulation/movement)
How can Net production of consumers (N)be calculated?
N = I - (F+R)
N Net production
I Chemical energy in ingested food
F Chemical energy lost in faeces and urine
R Energy lost through respiration
Why is not all of the energy from the sun converted into GPP?
Some light is the wrong wavelength (e.g. green)
Some doesn’t hit a chlorophyll molecule/transmitted
Most light is reflected by other molecules in the atmosphere
Other limiting factors may be involved
How do farmers increase productivity
Food chains/webs are simplified (pests are removed)
Respiration of livestock is reduced (movement limited, temperature regulated)
Describe two ways that farming practises can increase the amount of energy available for human consumption.
- Reduce the energy lost to other organisms e.g pest control.
Reduce the energy lost through respiration e.g restrict movement, control temp.
What are insecticides used for?
To kill insect pests that eat and damage crops.
What are herbicides used for?
To kill weeds to remove direct competition for sunlight.
How do biological agents increase crop yield?
They reduce the number of pests, so crops lose less energy and biomass.
What type of biological agents can be used?
Parasites to either kill the insect or reduce it’s ability to function or
Pathogenic bacteria and viruses
What is an integrated system ?
A system of using both chemical and biological methods to reduce pests.
What ethical issues might arise from keeping animals in pens?
It may cause animals pain, distress and restrict their natural behaviours.
Why are intensively reared animals kept indoors?
To control the environmental temperature so less energy is wasted by generating body heat.
Keeping cattle indoors, in barns, leads to a higher efficiency of energy transfer.
Explain why.
Less energy lost as heat / in maintaining body
temperature / in movement
Explain 3 advantages for a farmer of removing hedgerows.
- source of pests / animals, this effect on crop;
- source of weeds / no longer taking nutrients, hence competition / reduced yield;
- creation of larger fields / leaving room, hence more efficient use of machinery / grow more crops;
Apart from providing a habitat for predators of crop pests, give 3 biological benefits of replanting hedgerows.
- increases biodiversity;
- source of food for animals;
- habitat / nest for animals;
Give one reason why not all the light energy falling on the producers is used in photosynthesis.
transmission / reflected / misses chlorophyll / chloroplasts / wrong wavelength;
What is meant by the term ecological niche?
An organism’s role / in the ecosystem / community;
