3.5.4 - Nutrient Cycling Flashcards

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1
Q

What is a saprobiont?

A

They feed on the remains of dead plants and animals. They secrete enzymes and digest food externally, then absorb the nutrients they need.

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2
Q

What are hyphae?

A

Long, thin strands that make up the fungi.

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3
Q

What is a symbiotic relationship

A

A relationship where two organisms of different species interact.

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4
Q

What do plants and animals use nitrogen for?

A

Making proteins and nucleic acids.

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5
Q

What is nitrogen fixation?

A

When nitrogen gas in the atmosphere is converted into nitrogen-containing compounds.

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6
Q

What are Rhizobium?

A

Bacteria found in root nodules of leguminous plants. They turn nitrogen into ammonia.

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7
Q

What is ammonification?

A

When nitrogen compounds are turned into ammonia. This ammonia then forms ammonium ions.

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8
Q

Define nitrification

A

Ammonium ions in the soil are changed into nitrogen compounds that can be used by plants (nitrates).

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9
Q

Name a bacteria that converts nitrites into nitrates.

A

Nitrobacter

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10
Q

Name a bacteria that converts ammonium ions into nitrites.

A

Nitrosomas

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11
Q

What term is used to describe the conversion of nitrates in the soil into nitrogen gas.

A

Denitrification

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12
Q

Why does denitrification occur in waterlogged soils?

A

Because denitrifying bacteria need anaerobic conditions to convert nitrates into nitrogen gas.

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13
Q

How does nitrogen get into an ecosystem?

A

By lightning, and artificial fertilisers.

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14
Q

Name 4 things plants and animals need phosphorus for?

A
  1. phospholipids
  2. DNA
  3. RNA
  4. ATP
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15
Q

How does phosphate get into the soil?

A

Phosphate ions in rocks are released into the soil by weathering.

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16
Q

When fertilisers are applied to fields next to a lake, nitrogen-containing substances from the fertilisers get into the lake.

(a) (i) Describe how the nitrogen-containing substances get into the lake.

.

A

dissolve (in soil water) / run-off / leaching

17
Q

Describe how the presence of nitrates in a lake may eventually lead to the death of fish

A
  1. increased growth / algal bloom
  2. blocks light; less photosynthesis; plants die;
  3. increase in decomposers / bacteria;
  4. bacteria respire so less oxygen;
18
Q

It is estimated that, each year, a total of 3 × 109 tonnes of ammonia are converted to nitrate. Only 2 × 108 tonnes of ammonia are produced from nitrogen gas. Explain the difference in these figures.

A
  1. Ammonia formed by decay of nitrogenous waste by decomposition.
  2. by action of decomposers / saprobionts;
19
Q

Describe the role of microorganisms in producing nitrates from the remains of dead organisms.

A
  1. Saprobiotic (microorganisms / bacteria) break down remains into ammonia / ammonium;
  2. Ammonia / ammonium ions into nitrite and then into nitrate;
  3. (By) Nitrifying bacteria / nitrification;