Energy Transfer And Nutrient Cycles Flashcards
What is an ecosystem?
All the organisms living in a particular area and all the non-living conditions.
What are producers?
Organisms that make their own food - e.g. plant and algae via photosynthesis
What are the sugars produced during photosynthesis used for?
In respiration to release energy
To make other biological molecules
What is Biomass?
The chemical energy stored in the plant / the mass of living material
When is energy transferred through living organisms?
When organisms eat other organisms.
Produces are eaten by…
Primary consumers who are then eaten by secondary consumers.
How can biomass be measured?
Mass of carbon or the dry mass of its tissue per unit area
What is dry mass?
The mass of the organism with the water removed.
How can you measure dry mass?
A sample of the organism is dried in an oven at a low temp
Sample weighed at regular intervals, once it becomes constant, you know the water has been removed
Kg m-2
What is 50% of dry mass?
The mass of carbon
How can you estimate the amount of chemical energy in biomass?
Sample of dry biomass is burnt and the energy released is used to heat a known volume of water - change in temp measured.
What is GPP?
The total amount of chemical energy converted from light energy by plants in a given area.
What is respiratory loss and how much usually is it?
50% of the GPP is lost to the environment as heat when the plants respire.
What is NPP?
The remaining chemical energy.
NPP =
GPP - R
What is the NPP?
The energy available for plant growth and reproduction.
What are herbivores?
Animals that eat plants.
What are decomposers?
Organisms which break down dead or indigestes material, allowing nutrients to be recycled.
Each of the stages in a food chain is called…
A tropic level.
What do the lines (going left to right) show on a food chain?
“Eaten by”
What do farming practices aim to do?
Increase the amount of energy that is available for human consumption - increase the efficiency.
How do farming practices increase the efficiency of energy transfer? (2)
- the energy lost to other organisms can be reduced e.g. to pests.
- the energy lost through respiration can be reduced.
Simplifying the food web means…
Getting rid of pests.
How can farmers reduce pests using chemical pesticides? (2)
- using pesticides that kill pests which eat and damage crops - less biomass lost - NPP greater.
- herbicides milk weed, less competition with the crop for energy from the sun.
How can farmers use biological agents to reduce the number of pests? (2)
- parasites used to kill the insect or reduce its ability to function.
- pathogenic bacteria and virus are used to kill pests.
How can farmers increase the NPP of their livestock?
By controlling the conditions they live in so more energy is used for growth and less is lost through respiration
E.g. restrictions their movements, keeping them inside = more food at a shorter space of time, lower cost. (More biomass produced and more chemical energy can be stored)
Enhancing NPP production of animals raises…
Ethical concerns.
How are nutrients lost when crops are harvested?
Crops take in minerals from the soil as they grow, they’re harvested and removed so the mineral ions are not returned to the soil by decomposers.
When are phosphates and nitrates lost from the system?
When animals or animal products are removed from the land - animals eat grass, taking in nutrients then they are moved away and the nutrients aren’t replaced.
What do Fertilisers do?
Replace the lost minerals, so more energy from the ecosystem can be used for growth - increasing efficiency.
What are Artificial Fertilisers?
They are inorganic - contain pure chemicals as powders or pellets.
What are Natural Fertilisers?
Organic matter including manure, composed vegetables, crop residues and sewage sludge.
What is Leaching?
When water soluble compounds in the soil are washed away into nearby ponds and rivers - leads to Eutrophication.
Why do Fertilisers raise environmental issues?
- changes the balance of nutrients in the soil.
- leaching is more likely to occur just before heavy rainfall
Eutrophication:
- mineral ions leached from fertilised fields stimulate the rapid growth of algae in ponds and rivers.
- large amounts of algae block light from reaching plants below, plants die.
- bacteria feed on dead plant, increased bacteria reduce oxygen concentration in by water by carrying out aerobic respiration.
- not enough oxygen for fish and other aquatic organisms, die.
