Nutrient Cycles

Question 1

All the living and non-living components of a particular area.

Answer 1

Ecosystem

Question 2

Also known as saprophyte – an organism that obtains its food from the dead or decaying remains (detritus) of other organisms.

Answer 2

Saprobiontic microorganism

Question 3

Detritrivores

Answer 3

Organisms that help saprophytes do their job. They feed on pieces of dead and decaying material and finely break it up increasing its surface area.

Question 4

Decomposer

Answer 4

Any organism which breaks down organic matter. Include saprophytes and detritivores.

Question 5

Four main stages: ammonification, nitrification, nitrogen fixation and denitrification. This is because all living organisms require a source of nitrogen from which to manufacture proteins, nucleic acids and other nitrogen-containing compounds.

Answer 5

Nitrogen cycle

Question 6

Nitrogen fixation

Answer 6

Conversion of nitrogen gas into nitrogen-containing compounds. Carried out by free-living nitrogen fixing bacteria and mutualistic nitrogen-fixing bacteria which live in nodules on the roots of plants such as peas and beans. It can also be carried out industrially and occurs naturally when lightning passes through the atmosphere.

Question 7

Carry out the process of nitrogen fixation. Can be free-living or mutualistic bacteria.

Answer 7

Nitrogen fixing bacteria

Question 8

Production of ammonia from organic nitrogen-containing compounds e.g. urea and proteins. Saprobiontic microorganisms feed on faeces and dead organisms materials, releasing ammonia which then forms ammonium ions in the soil.

Answer 8

Ammonification

Question 9

Nitrification

Answer 9

Carried out by free-living nitrifying bacteria. Some convert ammonia into nitrites and some convert nitrites into nitrates using oxidation reactions which release energy. Good drainage and ploughing prevents air spaces from being filled with water and allows nitrification to continue.

Question 10

Carried out by anaerobic denitrifying bacteria which convert of soil nitrates into nitrogen gas.

Answer 10

Denitrification

Question 11

Phosphorus cycle

Answer 11

Enables the cycling of phosphorous which is an important biological element as it is a component of ATP, phospholipids and nucleic acids. There is no gaseous phase in the phosphorous cycle.

Question 12

Phosphate

Answer 12

PO43- ions are how phosphorous exists mostly in the form of sedimentary rock deposits.

Question 13

Weathering

Answer 13

How rocks are worn away - how phosphate ions in wastes and remains e.g. guano, bones and shells and in rocks are released into oceans, lakes and soils as dissolved phosphate ions.

Question 14

Mutualistic association between certain types of fungi and the vast majority of plants. The fungi act like extensions of the plant’s root system and increase the surface area for absorption of water and minerals. The fungi receives organic compounds such as sugars and amino acids from the plant. The mycorrhiza act like a sponge and so holds water and minerals in the neighbourhood of the roots, enabling the plant to better resist drought and take up inorganic ions more readily. They improve the uptake of relatively scarce ions such as phosphate ions.

Answer 14

Mycorrhizae

Question 15

The excrement of seabirds and bats.

Answer 15

Guano

Question 16

Symbiotic

Answer 16

When two species live in close proximity. Mutualistic is a type of symbiotic relationship where the relationship is mutually beneficial for two organisms.

Question 17

Fertiliser

Answer 17

Using these replenishes mineral ions, especially nitrates. They are necessary to improve productivity because in agriculture crops are harvested and mineral ions are not returned to the soil by decomposition by microorganisms, like would normally happen. They increase productivity because they provide minerals such as nitrogen for plants to build proteins, ATP and DNA nucleotides.

Question 18

Type of fertiliser which are mined from rocks and deposits and then converted into different forms and blended together to give the appropriate balance of minerals for a particular crop. Contain nitrogen, phosphorous and potassium.

Answer 18

Inorganic

Question 19

Type of fertiliser which consist of the dead and decaying remains of plants and animals as well as animal wastes such as manure, slurry and bone meal.

Answer 19

Organic

Question 20

Leaching

Answer 20

Process by which nutrients are washed from the soil into watercourses. Rainwater will dissolve any soluble nutrients, such as nitrate ions and carry them deep into the soil, eventually beyond the reach of plant roots.

Question 21

Consequence of an increase in nutrient concentrations in watercourses that leads to an algal bloom, leading to light being the limiting factor for the growth of plants and algae at lower depths, leading to saprobiontic bacteria creating an increased demand for oxygen. This leads to aerobic organisms dying and anaerobic organisms populations rising. It leads to a decrease in biodiversity.

Answer 21

Eutrophication

Question 22

Gases such as methane and CO2 which trap more heat energy, raising the Earth

Answer 22

Greenhouse Gases