Nutrient cycles

Question 1

Definition of producer

Answer 1

An organism that can synthesise organic molecules from simple inorganic molecules.

Question 2

Definition of a molecule

Answer 2

Group of atoms bonded together to form the smallest functional unit for the chemical.

Question 3

Definition of biomass

Answer 3

Total mass of living material, normally measured in a specific area over a given period of time.

Question 4

Definition of an ion

Answer 4

An atom or molecule with a net overall charge due to loss or gain of electrons.

Question 5

Definition of a consumer

Answer 5

Organism that contains energy transfer by ‘eating.’

Question 6

Definition of inorganic

Answer 6

Moleules/ions not derived from living matter.

Question 7

Describe stage 1 of the phosphorus cycle (2 points).

Answer 7

1. Phosphorus eroded from sedimentary rocks or fertiliser.
2. Dissolve in water making phosphate ions.

Question 8

Describe stage 2 of the phosphorus cycle (3 points).

Answer 8

1. Dissolved phosphate uptaken by roots of producer.
2. Dissolved phosphates uptaken by mycorrhizae.
3. Converted into biomass, for example: ATP, DNA, RNA.

Question 9

Describe stage 3 of the phosphorus cycle (1 point).

Answer 9

1. Producer is eaten by consumer passing on phosphate ions.

Question 10

Describe stage 4 of the phosphorous cycle (3 points).

Answer 10

1. Excess ions exctreted in waste or death of producer/consumer.
2. Fixed into bones/shells.
3. Saprobionts breakdown biomass releasing phosphate ions into soil.

Question 11

Describe stage 5 of the phosphorous cycle (1 point).

Answer 11

1. Phosphate ions in water forming sedimentary rocks.

Question 12

Describe Mycorrhizae fungi role in the phosphorous cycle.

Answer 12

Mycorrhizae is the symbiotic relationship between plant and fungi.

Question 13

Describe saprobionts role in the phosphorus cycle.

Answer 13

Organisms that release hydrolytic enzymes to digest their food externally and then absorb the products.

Question 14

Describe ammonification in the nitrogen cycle (3 points).

Answer 14

1. Produces ammonium ions from organic nitrogen containing compounds released into the soil.
2. Includes urea, proteins, nucleic acids and vitamins.
3. Saprobiotic fungi and bacteria- feed on waste/dead matter.

Question 15

Describe nitrification in the nitrogen cycle (1 point).

Answer 15

1. Free-living bacteria: ammonium ions … nitrite ions … nitrate ions.

Question 16

Describe nitrogen fixation in the nitrogen cycle (4 points).

Answer 16

1. Lightning.
2. Haber process.
3. Free-living bacteria: nitrogen … ammonia / ammonium ions- NH4+.
4. Mutualistic bacteria: live in nodules of legumous plants called Rhizobium, which live in aerobic conditions.

Question 17

Describe denitrification in the nitrogen cycle (2 points).

Answer 17

1. Nitrates .. nitrogen gas.
2. Bacteria in water-logged soil (anaerobic).

Question 18

Describe saprobiotic nutrition.

Answer 18

1. Secretes hydrolytic enzymes.
2. Extracellular digestion.
3. Absorbs soluble products.

Question 19

How can dead plant/animal material affect soil content/abiotic factors (5 points)?

Answer 19

1. Saprobiotic bacteria/fungi use oxygen to carry out aerobic respiration
2. Proteins are hydrolysed into amino acids.
3. Amino acids are converted into ammonium ions (ammonification).
4. Nitrifying bacteria converted ammonium ions into nitrates.
5. Nitrates are available to plants for uptake into roots.

Question 20

Describe natural fertiliers

Answer 20

Consist of dead and decyaing remains of plants, animals and their waste.

Question 21

Describe artificial fertilisers.

Answer 21

Mined from rocks before being converted into different forms with their composiiton tailored for specific crops.

Question 22

Describe how fertilisers increase productivity (4 points).

Answer 22

1. Nitrogen is needed to make proteins and DNA.
2. Where there are more nitrates available, plants are likely to develop earlier, grow quicker and taller and cover a greater area with their leaves.
3. This therefore increases the rate of photosynthesis and also increases productivity.
4. Artificial fertiliers have been very beneficial with providing cheaper food.

Question 23

Describe the 3 effects of using nitrogen fertiliers.

Answer 23

1. Reduces species diversity- Nitrogen favours the growth of rapidly growing species, such as grasses, nettles and weeds. Some species grow quickly and out-compete the other.
2. Leaching- Leads to polution of watercourses.
3. Eutrophication- Caused by leaching of fertilisers into watercourses.

Question 24

Describe leaching (3 points).

Answer 24

1. Rain water can dissolve souble nitrates and carry them deeper into the soil beynd the reach of plant roots.
2. The nitrates may travel to water courses and into water that is used for human consumption.
3. High levels of nitrates in water can cause inefficient transport of oxygen to the brain.

Question 25

Describe eutrophication (8 points).

Answer 25

1. Very few nitrates in most lakes, so this is a limiting factor on plant/algae growth.
2. Nitrate levels increase due to leaching. There is no longer a limiting factor, so plants/algae grow exponentially.
3. Algae grows and covers the upper layers of the water- algae bloom.
4. The algae ontop of the water absorbs sunlight, preventing it from reaching the bottom of the lake.
5. Light becomes a limiting factor for plants/alage at the bottom of the lake, causing them to die.
6. Saprobiotic algae can grow exponentially feeding on the decaying plant matter. More aerobic saprobiotic bacteria; more oxygen used up in respiration and more nitrates produced from decyaing organisms.
7. Oxygen is a limiting factor for aerobic respiring organisms, such as fish, so they eventually die.
8. Without any aerobically respiring organisms, anaerobically respiring organisms no longer have to compete. Population of anaerobically respiring organisms increase. Anaerobic organisms further breakdown other dead material thus producing more nitrates as well as some toxic wastes, such as hydrogen sulfide which makes water putrid.