farming practices and production Flashcards
what do food chains AND food webs show
Food chains and food webs show how
energy is transferred through an ecosystem.
what do food chains show
Food chains show simple lines of
energy transfer. Each of the stages
in a food chain is called a trophic level.
what do food webs show
Food webs show lots of food chains
in an ecosystem and how they overlap
what do decomposers do
Decomposers (e.g. fungi) are also part of food we bs.
Decomposers break down dead or undigested material,
allowing nutrients to be recycled
what do farming practices increase
efficiency of energy transfer
what do most farming practices aim to increase
the amount of energy that is available for human consumption.
what are the two ways farming practices can increase the amount of energy that is available for human consumption.
1) The energy lost to other organisms, e.g. pests, can be reduced.
2) The energy lost through respiration can be reduced
what can simplifying food webs do
reduces energy loss to other organisms
how do farmers reduce pests
Farmers can reduce pest numbers using chemical pesticides. For example:
• Insecticides kill insect pests that eat and damage crops. Killing insect pests means
less biomass is lost from crops, so they grow to be larger, which means NPP is greater.
• Herbicides kill weeds (unwanted plant species). Killing we eds can remove direct competition
with the crop for energy from the Sun. It can also remove the preferred habitat or food source
of the insect pests, helping to further reduce their numbers and simplify the food web.
what do biological agents also do
reduce the numbers of pests, so crops lose less energy
and biomass, increasing the efficiency of energy transfer to humans.
what are two examples of biological agents and what they do
• Parasites live in or lay their eggs on a pest insect. Parasites either kill the
insect or reduce its ability to function, e.g. some wasp species lay their
eggs inside caterpillars — the eggs hatch and kill the caterpillars.
• Pathogenic
(disease-causing) bacteria and viruses are used to kill pests,
e.g. the bacterium Bacillus thuringiensis produces a toxin that kills a wide range of caterpillars
farmers can use integrated systems, what are these
systems that com bine both chemical and biological methods.
The combined effect of using both can reduce pest numbers even more than either
method alone, meaning NPP is increased even more.
