Cycles within Ecosystems Flashcards
All 19 cards in this deck
Why must materials such as carbon and nitrogen be recycled through the abiotic and biotic components of an ecosystem?
The supply of these elements is limited, and organisms need them to build the molecules (e.g. carbohydrates, proteins) needed for growth.
Name the processes that release carbon dioxide into the atmosphere in the carbon cycle.
Respiration (by plants, animals and decomposers), combustion of fossil fuels and volcanic activity.
What is the role of decomposers (bacteria and fungi) in the carbon cycle?
They break down dead organisms and waste, and release carbon dioxide when they respire; they also return mineral ions to the soil.
Name the four main processes of the water cycle.
Evaporation, transpiration, condensation and precipitation.
Why is the water cycle important to living organisms?
It continually supplies fresh (liquid) water, which organisms need as a solvent for reactions and transport in cells.
What is potable water?
Water that is safe to drink — it has low levels of dissolved salts and microbes, but it is not chemically pure.
What are the steps in producing potable water by desalination using distillation?
e.g. making drinking water from seawater in an area of drought- Heat the seawater so the water evaporates, leaving the salt behind
- Cool the water vapour so it condenses
- Collect the liquid water — now potable.
How does reverse osmosis produce potable water from seawater?
Seawater is forced at high pressure through a partially permeable membrane that lets water through but holds back the dissolved salt ions.
What do nitrifying bacteria do in the nitrogen cycle?
They convert ammonia into nitrites and nitrates.
What do denitrifying bacteria do in the nitrogen cycle?
They convert nitrates (or nitrites) back into atmospheric nitrogen gas.
Which organisms break down dead animals and plants into ammonia in the nitrogen cycle?
Decomposers — fungi and decomposing bacteria.
Why do farmers plant leguminous crops such as peas and beans as part of crop rotation?
They have nitrogen-fixing bacteria in root nodules that fix atmospheric nitrogen, increasing nitrate/ammonia levels in the soil.
True or false? Plants absorb nitrogen gas from the air to make proteins.
False. Plants absorb nitrates from the soil through their roots and use them to make amino acids and proteins.
In global carbon-flux data, what does it mean if the total carbon released into the atmosphere each year is greater than the total absorbed?
Atmospheric carbon dioxide is rising.
e.g. released 216.0 gigatonnes vs absorbed 212.9 gigatonnes per year means a riseTrue or false? In the carbon cycle, carbon passes from plants to animals as carbon dioxide.
False. It passes as carbon compounds (e.g. glucose) when the plants are eaten; carbon dioxide is the form moved between organisms and the atmosphere.
Which process in the carbon cycle takes carbon dioxide out of the air and into living organisms?
Photosynthesis. Plants and algae take in carbon dioxide and build its carbon into glucose and other carbon compounds.
What is desalination?
Removing dissolved salts from salt water, such as seawater, to make potable (drinkable) water, e.g. in areas of drought.
How does spreading manure or compost on a field increase the nitrates in the soil?
Decomposers break down the proteins and wastes in it, returning the nitrogen to the soil, where nitrifying bacteria turn it into nitrates. (Artificial fertilisers add nitrates directly.)
What do nitrogen-fixing bacteria do in the nitrogen cycle?
They convert nitrogen gas from the air into ammonia, which forms ammonium ions that plants can use. Some live free in the soil; others live in the root nodules of legumes.