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Biology A1 & A2 > 5A & B: Energy transfers > Flashcards

5A & B: Energy transfers Flashcards

Photosynthesis, respiration, energy transfers & nutrient cycles

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1
Q

What do plants need energy for?

A

Photosynthesis, active transport (roots), DNA replication, cell division and protein synthesis

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2
Q

What do animals need energy for?

A

Muscle contraction, maintenance of body temp, active transport, DNA replication, cell division and protein synthesis

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3
Q

What is the overall equation for photosynthesis?

A

6CO2 + 6H2O + energy –> C6H12O6 + 6O2

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4
Q

What is the overall equation for aerobic respiration?

A

C6H12O6 + 6O2 –> 6CO2 + 6H2O + energy

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5
Q

In respiration the energy released from glucose is used to make what molecule?

A

ATP

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6
Q

What is a metabolic pathway?

A

A series of small reactions controlled by enzymes e.g respiration and photosynthesis

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7
Q

What is phosphorylation?

A

Adding a phosphate to a molecule e.g ADP is phosphorylation to ATP

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8
Q

What is photophosphorylation?

A

Adding a phosphate using light

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9
Q

What is photolysis?

A

The splitting of a molecule using light energy

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10
Q

What is photoionisation?

A

When light ‘excites’ the electrons in an atom/ molecule, giving them more energy and causing them to be released. The release of electrons causes the atom/molecule to become a positive ion

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11
Q

What is hydrolysis?

A

The splitting of a molecule using water

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12
Q

What is decarboxylation?

A

The removal of a carboxyl group from a molecule - Co₂ is released

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13
Q

What is dehydrogenation?

A

The removal of a hydrogen from a molecule

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14
Q

What are redox reactions?

A

Reactions that involve oxidation and reduction

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15
Q

What happens in a reduction reaction?

A

Reduction = it has gained electrons, and may have gained hydrogen or lost oxygen

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16
Q

What happens in an oxidation reaction?

A

Oxidation = it has lost electrons, and may have lost hydrogen or gained oxygen

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17
Q

Mnemonic to remember redox reactions?

A

OIL RIG

Oxidation Is Loss, Reduction Is Gain

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18
Q

What is a coenzyme?

A

A molecule that aids the function of an enzyme

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19
Q

What is the coenzyme used in photosynthesis?

A

NADP

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20
Q

What does NADP do?

A

NADP transfers hydrogen from one molecule to another - means it can reduce (give hydrogen) or oxidise (take hydrogen from) a molecule

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21
Q

Which coenzymes are used in respiration?

A

NAD, FAD and coenzyme A

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22
Q

What do NAD and FAD do?

A

NAD and FAD transfer hydrogen from one molecule to another - means they can reduce (give hydrogen) or oxidise (take hydrogen from) a molecule

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23
Q

What does Coenzyme A do?

A

Transfers acetate between molecules

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24
Q

Where does photosynthesis take place?

A

In the chloroplasts

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25
Q

What wavelength does PSI best absorb light at?

A

PSI = 700 nm

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26
Q

What wavelength does PSII best absorb light at?

A

PSII = 680 nm

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27
Q

Where does the light dependent reaction take place?

A

The thylakoid membrane

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28
Q

What is the 1st stage of the light dependent reaction called?

A

Stage 1: Photoionisation

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29
Q

Describe stage 1 of the light dependent reaction. (photoionisation)

A
  1. Light energy is absorbed by PSII
  2. Light excites the electrons in chlorophyll
  3. The electrons move to a higher energy level
  4. These high-energy electrons are released from the chlorophyll and move down the electron transport chain to PSI
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30
Q

Describe stage 2 of the light dependent reaction. (photolysis of water)

A
  1. As the excited electrons from chlorophyll leave PSII to move down the electron transport chain, they must be replaced
  2. Light energy splits water into protons (H+), electrons and oxygen (water is oxidised)
  3. The reaction is H20 –> 2H+ + 1/2 O2
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31
Q

What is the 2nd stage of the light dependent reaction called?

A

Photolysis

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32
Q

Describe stage 3 of the light dependent reaction.

A
  1. The excited electrons lose energy as they move down the electron transport chain
  2. This energy is used to transport H+ ions across the thylakoid membrane (into the thylakoid), so that the thylakoid has a higher conc. of H+ than the stroma - forms a proton gradient across the thylakoid membrane
  3. H+ move down their gradient, into the stroma via ATP synthase
  4. The energy from this movement allows ATP synthase to combine ADP + Pi to form ATP
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33
Q

What is chemiosmotic theory?

A

The process of electrons flowing down the electron transport chain and creating a proton gradient across the membrane to drive ATP synthase to form ATP

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34
Q

What is the light independent reaction also known as?

A

The Calvin cycle

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35
Q

Where does the light independent reaction take place?

A

In the stroma of the chloroplasts

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36
Q

What does the light independent reaction produce?

A

It produces triose phosphate (TP)

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37
Q

What can triose phosphate also be used for?

A

Can be used to make carbohydrates e.g glucose

Hexose sugars are made by joining two TP molecules together

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38
Q

What does the calvin cycle need to keep it going?

A

ATP and H+ ions

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39
Q

Describe the 1st stage of the Calvin cycle

A

Ribulose bisphosphate is combined with CO2 (enters leaf via stomata and diffuses into the stomata) by enzyme Rubisco, which produces an unstable 6C molecule which quickly breaks down into 2 glycerate 3-phosphate molecules (3C)

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40
Q

How many carbons does ribulose bisphosphate have?

A

5 carbons

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41
Q

What enzyme catalyses the combination of CO2 and ribulose bisphosphate?

A

Rubisco

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42
Q

Describe the 2nd stage of the Calvin cycle

A
  • The hydrolysis of ATP (from LDR) provides energy to turn GP into triose phosphate (TP) which has 3 carbons.
  • This reaction also requires H+ ions (from LDR), which come from NADPH. NADPH is converted into NADP
  • Some (1/6) TP is converted into useful organic compounds e.g glucose
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43
Q

How many molecules of glycerate 3-phosphate are produced from ribulose bisphosphate?

A

2 GP molecules are produced from 1 RuBP

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44
Q

NADPH ______ GP to TP, as a result NADPH is _____

A

NADPH reduces GP to TP, as a result NADPH is oxidised

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45
Q

Describe the 4th stage of the Calvin cycle

A
  • 5/6 TP molecules are used to regenerate RuBP

- Regenerating RuBP uses the rest of the ATP produced in the LDR

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46
Q

How many carbons does TP have?

A

TP has 3 carbons

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47
Q

What does the Light dependent reaction produce?

A

ATP and reduced NADP

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48
Q

Name 3 photosynthetic pigments in the chloroplasts

A
  • Chlorophyll a
  • Chlorophyll b
  • Carotene
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49
Q

How many TP molecules are made from every one CO2 molecule?

A

2 TP molecules are made from 1 CO2 molecule

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50
Q

How many turns of the Calvin cycle are needed to produce one hexose sugar, why?

A

6 turns:

  • Because 3 turns produces 6 molecules of TP, but because 5/6 of these molecules are used to regenerate RuBP, 3 turns only produces 1 TP
  • A hexose sugar has 6 Carbons, so 2 TP molecules are needed to form one
  • So 6 turns of the cycle are needed to produce 2 TP’s which make 1 hexose sugar
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51
Q

What are the optimum conditions for photosynthesis, in most plants?

A
  • High light intensity (of a certain wavelength)
  • Temperature (around 25 oC)
  • Carbon dioxide at 0.4%
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52
Q

Describe why high light intensity is an optimum condition for photosynthesis

A
  • Light is needed for energy in the LDR, so the higher the light intensity the more energy it provides
  • Only certain wavelengths of light are used in photosynthesis: chlorophyll a, b and carotene only absorb the red and blue light in sunlight (green is reflected so plants look green)
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53
Q

Describe why temperature at around 25 oC is an optimum condition for photosynthesis

A
  • Photosynthesis involves enzymes (ATP synthase, rubisco): If the temp falls below 10 oC the enzymes become inactive. But, if the temp exceeds 45oC they may start to denature.
  • At high temps stomata close to avoid too much water loss - causes photosynthesis to slow because less CO2 can enter the leaf (used in LIR)
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54
Q

Describe why carbon dioxide at 0.4% is an optimum condition for photosynthesis

A
  • CO2 makes up 0.04% of the gases in the atmosphere

- Increasing this to 0.4% gives a higher rate of photosynthesis, but any higher the stomata start to close

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55
Q

When could CO2 levels be a limiting factor of photosynthesis?

A

On a warm, sunny, windless day

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56
Q

When could light intensity be a limiting factor of photosynthesis?

A

At night

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57
Q

What is the saturation point?

A

Where a factor is no longer limiting the reaction - something else has become the limiting factor

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58
Q

How do agricultural growers manage the limiting factors of photosynthesis?

A

They create optimum conditions, in glasshouses or polytunnels

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59
Q

How do agricultural growers manage carbon dioxide conc. as a limiting factor of photosynthesis?

A

In glasshouses, growers add CO2 to the air. E.g this can be done by burning a small amount of propane in a CO2 generator

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60
Q

How do agricultural growers manage light as a limiting factor of photosynthesis?

A

In glasshouses, light can get through the glass. At night, growers use lamps

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61
Q

How do agricultural growers manage temperature as a limiting factor of photosynthesis?

A
  • Glasshouses trap heat from sunlight, which warms the air.
  • Heaters and cooling systems can also be used to keep a constant optimum temp
  • Air circulation systems make sure the temp is even throughout the glasshouse
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62
Q

Why do agricultural growers create optimum conditions for plant growth?

A

To increase plant growth, which increases yield (and therefore profit)

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63
Q

What are the two types of respiration?

A

Aerobic (requires O2) and anaerobic (doesn’t require O2)

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64
Q

Describe stage one of glycolysis (phosphorylation)

A
  1. Glucose is phosphorylated using a phosphate from ATP. This creates 1 molecule of glucose phosphate and 1 molecule of ADP
  2. ATP is then used to add another phosphate, forming hexose bisphosphate
  3. Hexose bisphosphate is then split into 2 molecules of triose phosphate (TP)
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65
Q

Is glycolysis anaerobic or aerobic?

A

Anaerobic

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66
Q

How many carbons does glucose have?

A

6

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67
Q

Describe stage two of glycolysis (oxidation)

A
  1. TP is oxidised (loses hydrogen), forming 2 molecules of pyruvate
  2. NAD collects hydrogen forming 2 reduced NAD
  3. 4 ATP are produced, but 2 were used up in phosphorylation - so there’s a net gain of 2 ATP
68
Q

What is the first stage of respiration?

A

glycolysis

69
Q

How many ATP molecules does glycolysis produce?

A

4 are produced, but 2 were used in phosphorylation so there’s a net gain of 2

70
Q

Where does glycolysis take place?

A

In the cytoplasm

71
Q

In animals, what happens in anaerobic respiration?

A
  • The (2) pyruvate produced in glycolysis are converted into 2 lactate molecules, using reduced NAD - this regenerates it into oxidised NAD.
  • Lactate builds up in muscles (causes cramp) but Oxygen converts it back into pyruvate
72
Q

In plants, what happens in anaerobic respiration?

A
  • The pyruvate produced in glycolysis is converted into ethanol, using reduced NAD, which produces CO2
  • This regenerates reduced NAD into oxidised NAD
73
Q

Where does the link reaction take place?

A

The matrix of the mitochondria

74
Q

What is the second stage of aerobic respiration?

A

The link reaction

75
Q

Describe the link reaction

A
  1. Pyruvate is decarboxylated (one carbon is removed in the form of CO2)
  2. Pyruvate is oxidised to form acetate and NAD is reduced to form reduced NAD
  3. Acetate is combined with CoA to form acetyl coenzyme A (acetyl CoA)
    - No ATP is produced
76
Q

How many times does the link reaction occur for every glucose molecule?

A

The link reaction occurs twice for every glucose molecule.

- So, for 1 glucose molecule, 2 acetyl CoA go into the Krebs cycle

77
Q

How many pyruvate molecules are made for every glucose molecule?

A

2 pyruvate molecules are made for every 1 glucose molecule that enters glycolysis.

78
Q

Where does the Krebs cycle take place?

A

In the matrix of the mitochondria

79
Q

How many times does the Krebs cycle happen for 1 pyruvate molecule?

A

It happens once for every pyruvate molecule

80
Q

How many times does the Krebs cycle turn for every glucose molecule?

A

The Krebs cycle goes round twice for every glucose

81
Q

Describe what happens to Acetyl CoA in the Krebs cycle (1)

A
  1. Acetyl CoA combines with a 4C molecule to form a 6C molecule (citrate)
  2. CoA goes back to the link reaction to be used again
82
Q

Describe what happens to the 6-C molecule produced from Acetyl CoA in the Krebs cycle (2)

A
  1. The 6-C citrate molecule is converted into a 5C molecule
    - Decarboxylation occurs, CO2 is removed
    - Dehydrogenation occurs, hydrogen is also removed
    - The hydrogen is used to produce reduced NAD from NAD
83
Q

Describe what happens to the 5C molecule in the Krebs cycle (3)

A
  1. The 5C molecule is then converted to a 4C molecule
    - Decarboxylation and dehydrogenation occur = producing one molecule of reduced FAD and two of reduced NAD
  2. ATP is produced by the direct transfer of a phosphate group (from an intermediate compound) to ADP - called substrate-level phosphorylation
84
Q

In the Krebs cycle, what is produced?

A

The Krebs cycle generates reduced coenzymes (NAD and FAD) and ATP by substrate-level phosphorylation, carbon dioxide is lost

85
Q

What is the Krebs cycle made up of?

A

A series of oxidation-reduction reactions

86
Q

What does oxidative phosphorylation produce alot of?

A

It produces alot of ATP

87
Q

Describe the entire process of oxidative phosphorylation

7 stages

A
  1. Hydrogen is released from NADH and FADH when they’re oxidised (=NAD and FAD). The H atoms split into H+ ions and electrons
  2. The electrons move down the electron transport chain losing energy at each carrier
  3. This energy is used by the electron carriers to pump H+ from the matrix into the intermembrane space (via active transport)
  4. The conc. of H+ is higher in the intermembrane space than the matrix - forming an electrochemical gradient
  5. H+ move down the gradient, back across the inner membrane into the matrix, via ATP synthase
  6. This movement causes ATP synthase to go through a conformational change which causes ATP synthesis (from ADP and Pi) - called chemiosmosis
  7. In the matrix, at the end of the transport chain, the H+, electrons and O2 (from the blood) combine to form water
    - Oxygen is said to be the final electron acceptor
88
Q

What is the third stage of aerobic respiration?

A

The Krebs cycle

89
Q

what is the fourth stage of aerobic respiration?

A

Oxidative phosphorylation

90
Q

What is an electron transport chain made up of?

A

Electron carriers

91
Q

Where does oxidative phosphorylation occur?

A

In the mitochondrial membrane, intermembrane space and the matrix of the mitochondria

92
Q

What do mitochondrial disease affect?

A

Mitochondrial diseases affect the functioning of the mitochondria: reducing ATP production

93
Q

How do mitochondrial diseases affect ATP production and what is the result?

A

They can affect how proteins involved in oxidative phosphorylation or the Krebs cycle function, reducing ATP production.

  • This may cause anaerobic respiration to increase, to try and make up for the ATP shortage
  • Which results in lots of lactate being produced which can cause muscle fatigue and weakness
  • Some lactate will also diffuse into the blood stream
94
Q

What are the products of the link reaction?

A
  • 2 x Acetyl CoA
  • 2 CO2
  • 2 reduced NAD
95
Q

What do the electrons lose as they move along the electron transport chain in oxidative phosphorylation?

A

Energy

96
Q

Describe how a 6-C molecule of glucose is converted into pyruvate.

A
  • Glucose is phosphorylated using a molecule of ATP, creating one molecule of glucose phosphate and one of ADP (and Pi)
  • ATP is used to add another phosphate to glucose phosphate, forming hexose bisphosphate (6C), which is then split into 2 molecules of triose phosphate.
  • Triose phosphate is then oxidised/looses hydrogen to from 2 molecules of pyruvate
  • NAD collects the hydrogen, forming 2 molecules of reduced NAD
97
Q

What is a producer? give examples

A

Organisms that make their own food e.g plants and algae produce their own food via photosynthesis

98
Q

What are most of the sugars produced in photosynthesis used for?

A

Respiration, to release energy for growth

99
Q

What is biomass?

A

The total number of biological molecules in an organism (amount of chemical energy stored)

100
Q

How is energy transferred through the ecosystem?

A

Through feeding: Primary consumers eat the producers, primary consumers are then eaten by the secondary consumers and they are ten eaten by the tertiary consumers

101
Q

What is dry biomass?

A

The mass of an organism with the water removed

102
Q

What is dry biomass? Give one + and some -

A 
The mass of an organism with the water removed 
\+ More reliable than fresh mass 
- Organism is killed in the process 
- More time consuming 
- Sometimes is not representative
103
Q

What is the typical unit for dry biomass?

A

kg m2

104
Q

What do you use to measure the amount of chemical energy stored in dry biomass?

A

In a calorimeter

105
Q

What are some of the sugars produced in photosynthesis used for?

A

The rest are used to make other groups of biological molecules. These biological molecules form the biomass of the plants e.g cellulose

106
Q

What is biomass measured in terms of?

A

In terms of mass of carbon or dry mass of tissue per given area

107
Q

Describe how you would estimate the chemical energy store in dry biomass using calorimetry.

A
  1. Weigh sample
  2. Burn in a bomb with pure O2
  3. Measure the temp increase in a fixed volume of water
108
Q

What is Gross Primary product?

A

GPP is the total amount of chemical energy converted from light energy by plants, in a given area

109
Q

What is respiratory loss (R)?

A

Approx. 50% of the GPP is lost to the environment as heat when the plants respire

110
Q

What is Net primary product?

A

The energy available to the plant for growth and reproduction - stored in the plants biomass

111
Q

What is the equation for NPP in producers?

A

NPP = GPP - R

112
Q

What is Net primary product?

A

The energy available to the plant for growth and reproduction - stored in the plants biomass
- Also the energy available to organisms at the next stage of the food chain

113
Q

The grass in an ecosystem has a GPP of 20 000 kJ m-2 yr-1. It loses 8 000 kJ m-2 yr-1 as heat from respiration. Calculate the NPP

A

NPP = GPP = R

20 000 - 8 000 = 12 000 kJ m-2 yr-1

114
Q

How do consumers get energy?

A

By ingesting plant material, or animals who have eaten plant material

115
Q

Most of the chemical energy in a consumers food is not transferred to the next trophic level (90% is lost), why is this?

A
  1. Not all of the food is eaten (e.g bones, plant roots)
  2. Some are indigestible, so are egested as faeces
  3. Some energy is also lost through respiration or excretion of urine
116
Q

How do consumers get energy?

A

By ingesting plant material, or other animals who have eaten plant material

117
Q

What is the equation for efficiency?

A

(NPP/ GPP) x 100 = %

118
Q

What is the equation for efficiency?

A

(energy available after transfer/ energy available before) x 100 = %

119
Q

What is fresh biomass? give one + and -

A

The organisms weight as it is
+ easy to access
- Different organisms have varying amounts of water

120
Q

Describe why there are energy losses from the sun to producer

A
  • Over 90% of the suns energy is reflected back into space
  • Not all wavelengths can be absorbed by the plant (e.g green)
  • Light may not fall on a chlorophyll molecule
121
Q

Describe why there are energy losses from the producers to consumers

A
  • Much of the plant cannot be accessed (e.g roots aren’t eaten)
  • Some material cannot be digested
  • Excretory losses
  • Respiratory losses
  • Death and decay
122
Q

Describe why there are energy losses between consumers

A
  • Excretory losses
  • Respiratory losses (higher in warm blooded animals)
  • Indigestible material (e.g bones)
  • Death and decay
123
Q

What do food chains show?

A

They show simple lines of energy transfer

124
Q

What are the stages in a food chain called?

A

Trophic levels

125
Q

What does a food web show?

A

They show lots of food chains in an ecosystem and how they overlap

126
Q

What do most farming practices aim to do?

A

They aim to increase the amount of energy that is available for human consumption

127
Q

Describe why farmers simplify food webs.

Hint: What do pests to to crop NPP?

A
  • Pests reduce the amount of energy available for crop growth and therefore decrease NPP, which ultimately reduces the amount of energy available to humans
  • By simplifying the food web e.g by getting rid of food chains that don’t involve humans, energy losses will be reduced and NPP of the crop will increase
128
Q

How do farmers simplify the food web? (2 ways)

A

By reducing pests:

  • Chemical pesticides
  • Biological agents
129
Q

What 2 ways do farmers reduce pest numbers by using chemical pesticides

A
  1. Insecticides - kill insect pests that damage crops.

2. Herbicides - kill weeds

130
Q

Give 2 ways that farmers reduce pest numbers by using chemical pesticides

A
  1. Insecticides - kill insect pests that damage crops.

2. Herbicides - kill weeds

131
Q

Give 2 ways that farmers reduce pest numbers by using biological agents

A
  1. Parasites

2. Pathogenic bacteria and viruses

132
Q

How to herbicides increase crop growth?

A

Herbicides kill weeds, this removes direct competition with the crop for energy from the sun. It can also remove the preferred habitat/food source of insect pests (helping to further simplify the food web)

133
Q

How do farmers use parasites to help crop growth?

A

Parasites live in or lay their eggs on a pest insect; parasites either kill the insect or reduce it’s ability to function

e. g some wasps lay their eggs inside caterpillars, when the eggs hatch it kills the caterpillars
- therefore by killing the pests the farmers increase crop growth

134
Q

How do farmers use Pathogenic bacteria and viruses to help crop growth?

A

Pathogenic bacteria and viruses are used to kill pests

e. g A bacteria produces a toxin that kills a wide range of caterpillars
- therefore by killing the pests the farmers increase crop growth

135
Q

How do farmers use pathogenic bacteria and viruses to help crop growth?

A

Pathogenic bacteria and viruses are used to kill pests

e. g A bacteria produces a toxin that kills a wide range of caterpillars
- therefore by killing the pests the farmers increase crop growth

136
Q

Why do farmers restrict the movement of their livestock?

A

Because movement increases the rate of respiration, so respiratory losses will increase - this means that less energy will go towards growth

137
Q

Why are livestock pens often indoors and kept warm?

A

So less energy is wasted through generating body heat (more can go towards growth)

138
Q

Why do farmers want to increase their livestocks net production?

A

More food can be produced in a shorter space of time, often at a lower cost
= higher profit

139
Q

What molecules do plants and animals need nitrogen to make?

A

ATP, DNA and RNA

140
Q

What molecules do plants and animals need nitrogen to make?

A

ATP, DNA and RNA

141
Q

Describe nitrogen fixation

A
  • When nitrogen gas in the atmosphere is turned into nitrogen-containing compounds
  • Carried out my mutualistic bacteria in the root nodules of plants
142
Q

Describe the relationship between nitrogen fixing bacteria and plants

A

The mutualistic bacteria live in the root nodules and convert nitrogen gas into nitrogen compounds. They provide the plants with nitrogen compounds and in exchange the plant provides them with carbohydrates

143
Q

Describe ammonification

A
  • When nitrogen compounds from dead organisms are turned into ammonia by saprobionts, which goes on to form ammonium ions
  • Animal waste (urine + faeces) also contains nitrogen compounds
144
Q

Describe ammonification

A

When nitrogen compounds from dead organisms or Animal waste (urine + faeces) are turned into ammonia by saprobionts, which goes on to form ammonium ions

145
Q

Describe denitrification

A

When nitrates in the soil are converted into nitrogen gas by denitrifying bacteria, this happens in anaerobic conditions e.g in waterlogged soils

146
Q

Why does denitrification happen in waterlogged soils?

A

Because there’s no oxygen and denitrification happens in anaerobic conditions

147
Q

What 2 ways does nitrogen fixing occur?

A
  1. Nitrogen fixing bacteria

2. Lightning

148
Q

What molecules do plants and animals need phosphorus to make?

A

Phospholipids, ATP and DNA/RNA

149
Q

Where is phosphorus found?

A

In rocks and dissolved in the oceans in the form of phosphate ions

150
Q

Describe the phosphorus cycle (6 stages)

A
  1. Phosphate ions in the rocks are released into the soil by weathering
  2. Phosphate ions are taken into the plant through the roots, mycorrhizae increase the rate at which phosphorus can be assimilated
  3. Phosphate ions are transferred through the food chain as animals eat plants and in turn eaten by other animals
  4. When plants and animals die (or from faeces and urine), saprobionts are involved in breaking down the organic compounds, releasing phosphate ions into the soil for assimilation by plants.
  5. Weathering of rocks also releases phosphate ions into seas, lakes and rivers . This is taken up by aquatic producers e.g algae and passed along the food chain to birds
  6. Guano, the faeces of sea birds has a high conc. of phosphate ions. It returns a significant amount of phosphate ions to the soil - often used as a natural fertiliser
151
Q

What are mycorrhizae?

A

Mycorrhizae are associations between certain types of fungi and the roots of plants.

152
Q

Describe how the fungi mycorrhizae help the plant

A
  • The fungi increase the SA of the plants roots, for the absorption of water and minerals.
  • They help in the uptake of scarce ions e.g phosphate
  • The mutualistic relationship between the plant and fungi: plant gets water and nutrients and fungi gets organic compounds e.g glucose
153
Q

Why are nutrients lost when crops are harvested?

A
  • Crops take in minerals from the soils when they grow
  • When crops are harvested they’re removed from the field rather than being allowed to die and decompose
  • This means that the mineral ions they contain are not returned to the soil by decomposers in the nitrogen/ phosphorus cycles
154
Q

Why are minerals lost from the ecosystem when animals or animals products are removed?

A

Phosphates and nitrates are lost:

  • Animals eat grass/ plants, taking in their nutrients
  • When they are taken elsewhere for slaughter/ transferred to a different field, the nutrients aren’t replaced through their remains of waste products
155
Q

What are added to the soil to replace lost nutrients?

A

Fertilisers

156
Q

What 2 types of fertilisers are there?

A

Natural and artificial

157
Q

Describe natural fertilisers

A
  • Made from organic matter

- Include manure, compostable vegetables, crop residues and sewage sludge

158
Q

Describe artificial fertilisers

A
  • Made from inorganic matter (from rocks)
  • They contain pure chemicals (e.g ammonium nitrate)
  • In the form of powders or pellets
159
Q

What can adding more fertilisers than plants need/ are able to use at a particular time lead to?

A

Leaching into waterways

160
Q

What is leaching?

A

When water-soluble compounds (e.g nitrates) in the soil are washed away, by rain or irrigation systems. They’re often washed into nearby ponds or rivers

161
Q

When is leaching more likely to occur?

A

When fertiliser is applied before heavy rainfall

162
Q

Describe the ions in artificial fertilisers, what does this mean in terms of leaching?

A

The inorganic ions are relatively soluble, means that excess minerals that are not used immediately are more likely to leach into waterways

163
Q

Describe the ions in natural fertilisers, what does this mean in terms of leaching?

A
  • Nitrogen and phosphorus are still contained in organic molecules that need to be decomposed by microorganisms before they can be assimilated by plants. - Means that their release into the soil for uptake by plants is more controlled, leaching is less likely
164
Q

Is the leaching of phosphates more or less likely than the leaching of nitrates? Why?

A
  • The leaching of phosphates is less likely than the leaching of nitrates
  • Because phosphates are less soluble in water
165
Q

Describe the process of eutrophication (5 stages)

A
  1. Mineral ions leached from fertilised fields stimulate the rapid growth of algae in nearby ponds and rivers
  2. Large amounts of algae block light from reaching the plants below
  3. Eventually the plants below die because they are unable to photosynthesise
  4. Bacteria feed on the dead plant matter. The increased numbers of bacteria reduce the O2 conc. in the water by carrying out aerobic respiration
  5. Fish and other aquatic organisms (that respire aerobically) eventually die because the conc. of dissolved O2 in the water is too low

Biology A1 & A2 (19 decks)

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