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AQA A Level Biology > Energy Transfer and Nutrient cycles > Flashcards

Energy Transfer and Nutrient cycles Flashcards

1
Q

Abiotic

A

Non-living

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2
Q

Biotic

A

Living

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3
Q

Some glucose is used for growth in respiration whilst the rest of the glucose is used…

A

to make other biological molecules such as cellulose

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4
Q

What makes up a plant’s biomass?

A

The biological molecules that the glucose that isn’t used in respiration is used to make

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5
Q

What is biomass?

A

The mass of living material and the chemical energy stored in the plant

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6
Q

What are the units of measuring biomass?

A

Mass of carbon the organism contains/dry mass of its tissue per unit area

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7
Q

What is dry mass?

A

Mass of the organism with the water removed

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8
Q

Why do we used dry mass as a measure of biomass over using wet mass?

A

Water content varies

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9
Q

How do you measure a sample of dry mass?

A

Dry a sample of the organism - in an oven at 100 degrees celcius
Weigh samples at regular intervals
Once constant, all water has been removed
(ms. Weigh and heat
Until mass is constant)

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10
Q

How do you work out the mass of carbon present?

A

Usually 50% of the dry mass

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11
Q

How can you work out the dry mass of the total population?

A

Work out dry mass for one organism, then scale up the result to give dry mass of total population or the are being investigated.

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12
Q

What are the typical units for dry mass?

A

kg m-2

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13
Q

What is calorimetry?

A

Where you can estimate the amount of chemical energy stored in biomass by burning the biomass in a calorimeter.

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14
Q

Using calorimtery, what tells us how much chemical energy is in the biomass?

A

The amount of heat given off tells you how much energy is in it

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15
Q

Describe the process of calorimetry.

A

A sample of dry biomass is burnt and the energy released is used to heat a known volume of water. The change in temperature of the water is used to calculate the chemical energy of the dry biomass.

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16
Q

Name the 7 components of a calorimeter?

A

Stirrer, thermometer, Water, Combustion chamber, Dry sample of biomass, Ignition box, wires connecting sample to ignition box.

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17
Q

What is gross primary production?

A

The total amount of chemical energy converted from light energy by plants in a given area.

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18
Q

What is respiratory loss?

A

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

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19
Q

What is net primary production? (Give three different uses of it)

A

The remaining chemical energy after respiratory losses have been taken into account. NPP is the energy available to the plant for growth and reproduction. NPP is also the energy available to organisms at the next stage in the food chain.

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20
Q

Give the equation that links GPP, R and NPP

A

NPP = GPP - R

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21
Q

What can primary productuon often be expressed as? Give an example of this.

A

A rate. total amount of chemical energy in a given area in a given time

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22
Q

What are the typical units for the rate of primary production (primary productivity)?

A

kJ ha-1 yr-1 or kJ m-2 yr-1

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23
Q

When primary production is expressed as a rate - what is it called?

A

Primary productivity

24
Q

How do consumers get energy? Give two ways

A

By ingesting plant material or animals that have eaten plant material

25
Q

Why is not all the chemical energy stored in a consumers’ food available to the next trophic level?

A

Some are indegestible - so egested as faeces, the chemical energy stored is lost to the environment
Some energy is lost to the environment through respiration or excretion of urine
Some food is not consumed e.g plant roots, bones

26
Q

What is the net production?

A

The energy that is left after all of the losses to the environment, or some not being consumed. It is the energy available to the next trophic level.

27
Q

What formula do you use to calculate the net production?

A

N = I - (F+R)

28
Q

In the formula used to calculaye the net production what do the letters: N,I,F,R stand for?

A

N = net primary production
I = chemical energy in ingested food
F = chemical energy lost in faeces + urine
R = energy lost through respiration

29
Q

What can the net production of consumers also be called?

A

Secondary production

30
Q

What is the equation to calculate how efficient energy transfer is between one trophic level and the next?

A

% efficiency of energy transfer = ( net production of trophic level / net production of previous trophic level ) x 100

31
Q

What happens to energy transfer as you move up a food chain? And why is this?

A

energy transfer usually becomes more efficient, because plants contain more indigestible matter than animals

32
Q

Majority of bacteria and fungi are?

A

Saprobionts

33
Q

What two things do saprobionts do?

A
  1. Feed on remains of dead plants + animals and their waste, breaking them down. They are decomposers and it allows important chemical elements to be recycled
  2. Secrete enzymes + digest food through extracellular digestion, during this process organic molecules are broken down into inorganic ions
34
Q

What is extracellular digestion?

A

Where saprobionts digest their good externally and then absorb the nutrients they need

35
Q

What is saprobiotic nutrition?

A

When saprobionts obtain nutrients from dead organic matter and animal waste using extracellular digestion

36
Q

What are mycorrhizae?

A

The symbiotic relationships that some fungi form with the roots of plants

37
Q

Describe how mycorrhizae is a symbiotic relationship?

A

The fungi are made up of long thin strands, called hyphae. These connect to the plant’s roots which greatly increases the surface area of the plant’s root system - this helps the plant to absorb ions from the soil that are usually scarce e.g phosphorus. Hyphae also increase uptake of water by the plant, in return, the fungi obtain organic compounds e.g. glucose

38
Q

Why do plants and animals need nitrogen?

A

To make proteins and nucleic acids (DNA, RNA)

39
Q

What does the nitrogen cycle show?

A

How nitrogen is converted into a usable form and then passed on between different living organisms and the non-living environment.

40
Q

What does the entire nitrgoen cycle consist of?

A

Food chains (nitrogen is passed on when organisms are eaten) and four different processes that involve bacteria: nitrogen fixation, ammonification, nitrification and denitrification

41
Q

What happens during nitrogen fixation?

A

It is when nitrogen gas is turned into nitrogen-containing compounds. Biological nitrogen fixation is carried out by bacteria e.g. Rhizobium which converts nitrogen –> ammonia –> ammonium ions in solution which can be used by plants

42
Q

Where is rhizobium found and how does it help with nitrogen fixation? (describe the mutualistic relationship)?

A

In the root nodules of leguminous plants (peas, beans, clover) and they form a mutualistic relationship with the plant as they provide the plant with nitrogen containing compounds and the the plant provides them with carbohydrates.

43
Q

Give a summary of nitrogen fixation:

A

Nitrogen gas –> nitrogen containing compounds

44
Q

What type of bacteria is rhizobium?

A

Nitrogen fixing bacteria

45
Q

What happens during ammonification?

A

This is when nitrgoen compounds from dead organisms are turned into ammonia by saprobionts. They go on to form ammonium ions. This same process happens with the nitrogen compounds within urine + faeces

46
Q

Give a summary of ammonification?

A

Nitrogen compounds in dead organisms + waste –> ammonia (by saprobionts) –> ammonium ions

47
Q

What happens during nitrification?

A

Ammonium ions in soil turned into nitrogen compounds which can be used by plants (nitrates)
Nitrosomonas changes ammonium ions –> nitrites
Nitrobacter changes nitrites –> nitrates

48
Q

Give two examples of nitrifying bacteria:

A

Nitrosomonas
Nitrobacter

49
Q

What happens during denitrification?

A

When nitrates in soil are converted into nitrogen gas by denitrifying bacteria, happens under anaerobic conditions e.g. waterlogged soil
The denitrifying bacteria use nitrates in the soil to carry out respiration which produces nitrogen gas

50
Q

Give an example of denitrifying bacteria?

A

Pseudomonas aeruginosa

51
Q

Summarise denitrification:

A

Nitrates –> nitrogen gas due to lack of oxygen, nitrates are used as respiratory sibstrate instead which produces nitrogen gas

52
Q

Why do organisms need phosphorus?

A

Make biological molcules such as phospholipids, DNA, ATP

53
Q

Where are phosphate ions found?

A

Dissolved in oceans

54
Q

Where is phosphorus found?

A

in rocks

55
Q

Show the 11 summarised points of the phosphorus cycle:

A

Rocks (from soil) –> sea/lake/river –> algae + other primary producers –> fish –> birds –> guano –> soil –> plants* –> animals* –> faeces + urine –> soil
*decaying organisms –> soil

56
Q

In the phosphorus cycle, what puts phosphorus into the soil?

A

Decaying organisms, rocks, guano, faeces + urine

57
Q

Now describe the phosphorus cycle:

A

PO43- are released from rocks into soil by weathering
PO43- taken into plants through roots - mycorrhizae greatly increase the rate at which phosphorus can be assimilated, PO43- are transferred through the food chain, PO43- are lost from animals during excretion, saprobionts break down the organic compounds in dead organic matter –> releasing PO43- into soil for assimilation by plants, these microorganisms also release the PO43- from urine + faeces
Weathering of rocks also releases the ions into sea/lakes/rivers –> taken up by aquatic producers (ALGAE) + passed down chain to birds (through fish) –> waste from sea birds holds a high proportion of PO43-
Guano returns a significant amount of PO43- to soils - especially coastal areas and guano is often used as a natural fertiliser

AQA A Level Biology (19 decks)

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