Cycles within Ecosystems Flashcards
All 25 cards in this deck
What is transpiration?
The loss of water vapour from a plant, mainly through the stomata of the leaves.
What are the stages of the water cycle, in order?
e.g. water moving from the sea back into a river- Evaporation from seas and lakes (and transpiration from plants) — water vapour rises.
- Condensation — the vapour cools and forms clouds.
- Precipitation — rain or snow falls and runs back into rivers and the sea.
What is potable water?
Water that is safe to drink — it has low levels of dissolved salts and microorganisms.
Name the two methods of desalination used to make potable water in areas of drought.
Distillation and reverse osmosis.
What are the steps in producing potable water from seawater by distillation?
e.g. heating a sample of seawater- Heat the seawater so the water evaporates — the dissolved salts are left behind.
- Cool the water vapour so it condenses.
- Collect the condensed water — it is salt-free and potable.
True or false? Potable water is chemically pure water.
False. Potable water is safe to drink but may still contain dissolved substances.
Which process removes carbon dioxide from the atmosphere in the carbon cycle?
Photosynthesis, carried out by plants and algae.
Which three processes return carbon dioxide to the atmosphere in the carbon cycle?
Respiration, combustion and decomposition.
What is fossilisation in the carbon cycle?
Dead organisms that are not fully decomposed are compressed over millions of years to form fossil fuels, locking carbon away.
What is the role of decomposers (bacteria and fungi) in the carbon cycle?
They break down dead organisms and waste, releasing carbon dioxide by respiration and mineral ions into the soil.
Why must materials such as carbon and nitrogen be recycled between the biotic and abiotic parts of an ecosystem?
The supply of these elements is finite, so they must be released from dead organisms and waste to be reused by living organisms.
True or false? Burning fossil fuels is the only process that adds carbon dioxide to the atmosphere.
False. Respiration by all living organisms and decomposition also release carbon dioxide.
What do nitrogen-fixing bacteria do?
They convert nitrogen gas from the air into nitrogen compounds (ammonia/nitrates); they live in soil and in root nodules of legumes such as peas and beans.
What do nitrifying bacteria do?
They convert ammonia in the soil into nitrites and then into nitrates.
True or false? Denitrifying bacteria convert nitrates in the soil into nitrogen gas.
True. This removes nitrates from the soil and returns nitrogen to the atmosphere.
What do decomposing bacteria convert urea and proteins in dead matter into?
Ammonia.
What two farming methods increase the nitrates available to crops?
Adding fertiliser (manure or artificial nitrate fertiliser), and crop rotation with legumes, whose root nodules contain nitrogen-fixing bacteria.
How does temperature affect the rate of decomposition?
The rate increases as temperature rises up to an optimum, then falls because the decomposers' enzymes are denatured.
How does oxygen availability affect the rate of decomposition?
Increasing oxygen concentration increases the rate, because decomposers can respire (aerobically) more.
How does water content affect the rate of decomposition?
Moist conditions speed up decay, as decomposers need water to grow and for enzyme reactions; drying food slows or stops decay.
What are the steps to calculate the rate of decay of biological material?
e.g. leaves of mass g fall to g in days- Find the mass lost: g
- Divide by the time taken:
- Give the units: g per day
What conditions give the fastest decomposition in a compost bin?
Warm temperature, moist (but not waterlogged) conditions, and plenty of oxygen — achieved by turning the compost.
True or false? Frozen food does not decay because freezing kills all the microorganisms.
False. Freezing only slows decay — microorganisms and enzymes become inactive but are not killed.
What do plants use the nitrates they absorb from the soil for?
To make amino acids, which are joined to form proteins.
True or false? A plant growing in soil that is low in nitrates will show stunted growth.
True. Without enough nitrates the plant cannot make enough protein for growth.