3.3.5 Nutrient Cycles Flashcards Preview

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Flashcards in 3.3.5 Nutrient Cycles Deck (55)
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1

Natural ecosystem (not changed by human activity) nutrients are recycled through ___ ___

food webs

2

Many microorganisms (e.g. bacteria and fungi) are ________ (type of decomposer)

saprobionts

3

What do saprobionts do and what does this allow to happen?

  • Feed on remains of dead plants & animals & on waste products = break them down
  • Allows chemical elements to be recycled

4

How do saprobionts digest their food?

  • Saprobionts secrete enzymes & digest their food externally, then absorb soluble molecules (nutrients) they need
  • Known as extracellular digestion

5

What happens during extracellular digestion?

Organic molecules are broken down into inorganic ions

6

What is meant by saprobiotic nutrition?

Obtaining nutrients from dead organic matter using extracellular digestion

7

Some fungi form ___  relationships with roots of plants

symbiotic

8

Relationships between _____ and the ____ of _____ are known as mycorrhizae

Relationships between fungi and the roots of plants are known as mycorrhizae

9

Describe how fungi is connected to the plant's roots

Fungi made up of long, thin strands called hyphae which connect to plant's roots

10

What does the fungi's hyphae help the plant to do?

  • Hyphae increase SA of plant's root system = helps plant to absorb ions from soil that usually are scare (e.g. phosphorus)
  • Also increase uptake of water

11

Fungi obtain _______ _________ (e.g. glucose) from plants

 organic compounds

12

Why do plants and animals need nitrogen?

To make proteins and nucleic acids (DNA & RNA)

13

Why can't animals and plants use nitrogen from the air?

It's inert

14

What does the nitrogen cycle show?

Shows how nitrogen is converted into usable form & then passed between different living + non-living organisms

15

Name the 4 stages in the nitrogen cycle

  1. Nitrogen Fixation
  2. Ammonification 
  3. Nitrification 
  4. Denitrification

16

What is occuring in nitrogen fixation?

Nitrogen gas → ammonia

17

Nitrogen Fixation 

State the equation of nitrogen gas turning into ammonia

N2 + 6H → 2NH3

18

Nitrogen Fixation 

Describe how nitrogen gas is converted into ammonia

Bacteria e.g. Rhizobium turns nitrogen into ammonia

19

Where are Rhizobium are found?

Inside root nodules (growths on roots) of leguminous plants (e.g. peas, beans)

20

Explain how Rhizobium forms a mutualistic relationship with plants

They provide the plant with nitrogen compounds & plant provides them with carbohydrates

21

Nitrogen Fixation 

Name & describe 2 ways other than via bacteria that nitrogen gets into an ecosystem

  • Lightining 
    • Fixes atmospheric nitrogen
  • Artificial fertilisers 
    • Produced from atmospheric nitrogen on industrial scale in Haber process

22

Describe what occurs in ammonification

Nitrogen compounds from dead organisms + animal waste are turned into ammonia by saprobionts via decay, which then forms ammonium ions

23

Ammonification

How can ammonium ions (NH4+) also be produced?

Ammonia can also dissolve in water to produce ammonium ions

24

Describe what occurs in nitrification

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

  1. ammonium ions → nitrites
  2. nitrites → nitrates

25

Nitrification

Describe how first ammonium ions are turned into nitrites

Nitrifying bacteria (Nitrosomonas) change ammonium ions → nitrites

26

Nitrification

Describe how then nitrites are turned into nitrates

Other nitrifying bacteria (Nitrobacter) change nitrites → nitrates

27

Nitrification

State the equation for: ammonium ions → nitrites

NH4+ → NO2-

28

Nitrification

State the equation for: nitrites → nitrates

NO2- → NO3-

29

Nitrifying bacteria is known as chemoautotrophs. What is meant by this?

Called chemoautotrophs ∵ use chemical energy released from these reactions (nitrification) to live

30

What happens during denitrification?

When nitrates in soil → nitrogen gas by denitrifying bacteria

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