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AQA A-Level Biology Year 2 > Chapter 13 > Flashcards

Chapter 13 Flashcards

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1
Q

What is the ultimate source of energy for almost all organisms and what is it used for?

A

Sunlight - Used to carry out all activities in any ecosystem

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2
Q

What do plants use sunlight and CO2 + H20 in the sir for?

A

Use sunlight to make sugars (used as respiratory substrates) and use CO2 + H2O for
biological molecules

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3
Q

What are producers and give an example?

A

Are photosynthetic organisms that manufacture organic substances using light energy, H20, CO2 + Mineral ions for example plants

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4
Q

What are consumers?

A

Organisms that obtain energy by feeding on (consuming) other organisms rather than using the energy of sunlight directly

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5
Q

What are saprobiants and give an example?

A

(decomposers) are a group of organisms that break down complex materials in dead organisms into simple ones for example Fungi and bacteria

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6
Q

What do saprobiants release when they break down complex materials in dead organisms?

A

They can release valuable minerals and elements that can be absorbed by plants which therefore contributes to recycling

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7
Q

What is a food chain?

A

Trophic levels which decribe the feeding relationship: Producer -> Primary -> Secondary -> Tertiary -> Quatanary consumer
(Arror represents direction of flow)

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8
Q

What is a food web?

A

Many food chains linked together forms a food web (in a habitat)
It can be very complex

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9
Q

What is the definition of biomass?

A

is the total mass of living material in a specific area at a given time

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10
Q

How is biomass measured?

A

Measured using dry mass per given area in a given time.
gm-2 (area sampled)
gm-3 (Volume sampled)

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11
Q

Why should you measure the mass of carbon or dry mass?

A

Fresh mass is easy to obtain but the presence of varying H20 makes it unreliable
Measuring carbon or dry mass overcomes this problem
But organisms must be killed (can only with small sample = not representative)

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12
Q

How can the chemical energy store in dry mass be estimated?

A

By using a Calorimetry

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13
Q

Describe the bomb calorimetry experiment?

A

1) Sample of dry mass is weighed
2) Then burnt in pure O2 with sealed chamber (Bomb)
3) Bomb is surrounded by water bath + heat of combustion causes small temp rise in water

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14
Q

How much % of the suns energy do plants convert into the organic matter?

A

1 - 3%

can be captured + made readily available to organisms in food chain

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15
Q

Why isn’t most of the suns energy not converted to organic matter by photosynthesis?

A
  • over 90% reflected into space or absorbed into the atmosphere
  • Not all wavelengths can be absorbed
  • Light may not fall on a chlorophyll molecule
  • A factor may limit the rate of photosynthesis
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16
Q

What is Gross primary production?

A

The total quantity of the chemical energy store in plant biomass, in a given area or volume
(Howvever 20-50% energy in respiration)

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17
Q

What is Net primary production?

A

The chemical energy store which is left when these losses to respiration have been taken into account

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18
Q

What is the equation to work out NPP?

A

NPP = GPP - Respiratory losses

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19
Q

What is NPP available for?

A

for plant growth + reproduction + other trophic levels

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20
Q

How much % do secondary and tertiary consumers transfer energy available from prey into their own bodies?

A

20%

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21
Q

Why is there a low percentage of energy transferred at each stage?

A
  • Some organisms not consumed
  • Some lost in feces
  • Some lost in excretory materials
  • Some lost from occur as heat from respiration lost into the environment
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22
Q

How can Net production of consumers be calculated?

A

N = I (F+R)

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23
Q

The relative inefficiency of energy transfer between trophic levels explains why……

A
  • Most food chains have 4-5 trophic levels as theres not enough energy to support large enough breeding populations (trophic) higher than this
  • Biomass is less at higher trophic levels
  • The total amount of energy available is less at each level as one moves up a food chain
24
Q

Describe the nutrient cycle

A

1) The nutrient is taken up by a producer (Plants) as a simple, inorganic molecules
2) Producer incorporates nutrient into complex organic molecules
3) When producer eaten, nutrient passes into consumer
4) nutrient passes along food chain
5) When producer or consumer complex molecules broken down by saprobiotic microorganisms (decomposers)
6) cycle complete

25
Q

Why do living organisms require nitrogen?

A

To manufacture proteins, nucleic acids and other nitrogen-containing compounds

26
Q

How do plants take up nitrates (NO3-)?

A

Take up nitrate ions soils by active transport by the roots

27
Q

State properties of Nitrates in soil?

A
  • Very soluble and easily leach (wash) through soil
28
Q

What are natural ecosystems?

A

Nitrate conc are restored largely by recycling N-containing compound

29
Q

What are agricultural ecosystems?

A

N conc in soil increased by fertilizers

30
Q

What is ammonification?

A

the production of ammonia from organic N-containing compounds

31
Q

How is ammonia formed from N-containing compounds (ammonification)?

A

Saprobiontic microorganisms feed on faeces + dead organisms which releae ammonia (forms NH4+ ions in soil)

32
Q

What is nitrification?

A

Conversion of ammonium ions into nitrate ions through an oxidation reaction + release of energy

33
Q

Describe the stages of nitrification?

A

1) Oxidation of ammonium ions to nitrite ions (NO2-)

2) Oxidation of nitrite ions into nitrate ions (NO3-)

34
Q

What do nitrifying bacteria require?

A

O2, therefore, require aerated soil

35
Q

What should be done so the soil has more air spaces?

A
  • soil should be ploughed

- The soil should have a good drainage system which prevents air spaces being filled with H2O

36
Q

What is nitrogen fixation?

A

When nitrogen gas is converted into nitrogen-containing compound

37
Q

What are free-living nitrogen-fixing bacteria?

A

Reduce gaseous nitrogen to ammonia(use to manufacture amino acids)

38
Q

What are mutualistic bacteria?

A

Bacteria that live on nodules on roots of plants they obtain carbohydrates from plants + plants require amino acids

39
Q

How are denitrifying bacteria formed?

A

When soils have low O2 fewer aerobic nitrifying + nitrogen-fixing bacteria are found
therefore causes an increase in anaerobic denitrifying bacteria

40
Q

What do denitrifying bacteria do to soil nitrates and how does this affect plants?

A

Convert soil nitrates -> gaseous nitrogen

- Reduce the availability of N-containing compounds for plants

41
Q

What should be done to prevent the build-up of denitrifying bacteria?

A
  • Soil should be well aerated (ploughing)
42
Q

What can increase the build-up of denitrifying bacteria?

A
  • Natural + artificial fertilisers
43
Q

Phosphorus is a biological component for…

A

Phospholipids, ATP + Nucleic acids

- V. important

44
Q

Where are phosphorus ions (PO4 3-)?

A
  • In the form of sedimentary rocks brought to the surface by geological uplifting
  • Weathering + erosion help PO4 3- dissolve + available for absorption
45
Q

What type of relationship between plant + fungi?

A

Mutualistic

46
Q

How is the mycorrhizal relationship a mutualistic relationship?

A

The plant benefits from improved H2O + inorganic ions while receives organic compounds (Sugars +amino acid)

47
Q

What are natural (organic) fertilisers?

A
  • Dead + decaying remains of plants + animals + waste (manure)
    Has limited amount of ions
48
Q

What are artificial (inorganic) fertilisers?

A
  • Mined from rocks + deposites converted into into different forms and blended
    Has many ions
49
Q

How do fertilisers increase productivity?

A

Nitrogen

  • Plant growth
  • Grow earlier, taller, greater leaf area
  • Increased rate of photosynthesis
50
Q

What are the effcts of nitrogen containing fertilisers

A
  • Reduced species diversity
  • Leaching
  • Eutrophication
51
Q

What is leaching?

A

Process by which nutrients are removed from soil

52
Q

Through leaching how do nitrate ions find their way into watercourses?

A

Rainwater dissolves soil nutrients (nitrate) deep into the soil which then find their way into watercourses (lakes, oceans)

53
Q

How can leaching be harmful to humans ?

A

V.high conc of ions in drinking H2O can prevent O2 transport in babies
Could cause cancer

54
Q

How can leaching be harmful to the environment?

A

Can cause eutrophication

55
Q

What is eutrophication?

A

Process by nutrient conc increase in bodies of H2O (natural process occurs mostly in lakes etc)

56
Q

Describe the process of eutrophication?

A

n

AQA A-Level Biology Year 2 (4 decks)

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