Material Cycles

Abiotic are the non-living parts of an ecosystem; biotic are the living parts.

The Earth has a limited supply of matter, so living things must use the same materials again and again.

About 0.04 percent.

Photosynthesis.

By feeding, in carbon compounds such as carbohydrates and proteins.

Respiration, decay (decomposers' respiration) and combustion.

Yes, so they put carbon dioxide into the air as well as taking it in.

A microorganism, bacteria or fungus, that breaks down dead material and waste.

They release enzymes that break it into small soluble molecules, which they absorb.

They return carbon dioxide and mineral ions to the environment.

Dead material would pile up and nutrients would stay locked in it.

From dead remains that did not fully decay, buried without oxygen, over millions of years.

It releases the carbon in wood or fossil fuels as carbon dioxide.

Burning fossil fuels and deforestation add carbon dioxide faster than it is removed.

It is a greenhouse gas that contributes to global warming.

Increase divided by the starting value, times 100.

It gives a continuous supply of carbon and keeps the carbon dioxide level balanced.

Name each process shown by an arrow in the carbon cycle.

Photosynthesis takes carbon dioxide into plants. Feeding passes carbon to animals. Respiration by plants, animals and decomposers, and combustion, release carbon dioxide. Death and decay return carbon from dead organisms, and fossilisation makes fossil fuels.

Respiration, decay and combustion add carbon dioxide. Photosynthesis removes it.

Energy from the Sun.

Liquid water turning into water vapour.

The loss of water vapour from plant leaves through the stomata.

Water vapour cooling and turning into liquid droplets, forming clouds.

Rain, snow, sleet or hail falling from clouds.

Water flowing over the land and in rivers back to the sea.

Evaporation leaves the salts behind.

It supplies fresh water, and water is needed for cell reactions and photosynthesis.

Safe to drink.

No. Potable water can contain low levels of dissolved substances; pure water has only water molecules.

Chlorine, ozone or ultraviolet light (any two).

To remove solid particles, using sand and gravel.

Removing the salt from sea water to make potable water.

Sea water is boiled, and the steam is condensed, leaving the salt behind.

Sea water is forced through a partially permeable membrane at high pressure, which keeps the salt out.

It needs a lot of energy, so it is expensive and may release carbon dioxide.

Very salty brine, which has to be disposed of.

Storing rainwater, recycling waste water, pumping groundwater or piping water in.

Name each process in the water cycle shown by an arrow.

Evaporation from the sea, condensation in the cloud, precipitation from the cloud, run-off down the hill to the sea and transpiration from the trees. The Sun provides the energy.

Distillation: the sea water is boiled, the steam is cooled in a condenser to liquid water, and the salt is left behind. Reverse osmosis: the sea water is forced at high pressure through a partially permeable membrane that lets water through but not the salt.

About 78 percent.

It is very unreactive, so plants cannot take it in and use it.

Amino acids, and then proteins.

By active transport.

Slow growth and yellow leaves.

By eating plants or other animals.

Change nitrogen gas into ammonia and other nitrogen compounds.

In the soil, and in root nodules of legumes.

Break down proteins and urea in dead material and waste, releasing ammonium compounds.

Change ammonium compounds into nitrates.

Change nitrates into nitrogen gas.

Denitrifying bacteria thrive where oxygen is scarce and turn nitrates into nitrogen gas.

It makes nitrogen and oxygen combine into nitrogen oxides, which dissolve in rain as nitrates.

To replace the nitrates removed when crops are harvested.

It is washed into rivers and lakes and can cause eutrophication.

Growing a different crop each year, in a repeating order.

Its root nodule bacteria fix nitrogen, which adds nitrates to the soil.

Peas, beans or clover.

The plant gives sugars to the bacteria and the bacteria give nitrogen compounds to the plant.

Name each box and each bacterium shown in the nitrogen cycle.

The ring is plants and animals, dead organisms and waste, ammonium compounds and nitrates. Decomposers make ammonium compounds, nitrifying bacteria make nitrates, plants take up nitrates, denitrifying bacteria return nitrogen to the air, and nitrogen-fixing bacteria and lightning bring it from the air.

Nitrifying bacteria make nitrates from ammonium compounds. Denitrifying bacteria remove nitrates by changing them to nitrogen gas.

Temperature, water content and oxygen availability.

The enzymes of the decomposers work faster, until the optimum temperature.

The decomposers' enzymes are denatured and the microorganisms are killed.

Their enzymes work in solution and they absorb nutrients dissolved in water.

Most respire aerobically, which releases the most energy for growth.

At about 1 to 5 degrees Celsius the enzymes of microorganisms work slowly.

The water is frozen, so the microorganisms cannot grow.

It removes the water that the microorganisms need.

Water leaves the microorganisms by osmosis, so they dry out.

It removes oxygen, so aerobic microorganisms cannot respire.

Heating kills the microorganisms, and the seal keeps out oxygen and new microorganisms.

Rotted plant waste, made by decomposers, that is spread on soil.

The decomposers respire, which releases heat.

As damp as a squeezed sponge.

The water drives out the air, so only slow anaerobic decay takes place.

To let air in, so the decomposers respire aerobically.

A larger surface area lets the decomposers work faster.

Change in mass divided by time taken.

(Starting mass minus final mass) divided by starting mass, times 100.

Label the compost bin and say what each feature does for the decomposers.

The lid keeps in heat and moisture. Air in through the slots gives the decomposers oxygen. Green and brown waste give food, and the twigs let air in and water drain. The decomposers respire, which releases heat and carbon dioxide.

Compare the rates of decay at the three temperatures and explain the pattern.

Decay is fastest at 40 degrees Celsius, then 25, and slowest at 10. Warmer conditions make the enzymes of the decomposers work faster, so the mass falls faster.