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AQA A-level Biology > Topic 5: Energy And Ecosystems > Flashcards

Topic 5: Energy And Ecosystems Flashcards

1
Q

What are producers?

A

Photosynthetic organisms that gain energy from light

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2
Q

What are consumers?

A

Organisms that obtain energy from feeding on other organisms

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3
Q

What are primary consumers?

A

Animals that feed on producers

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4
Q

What are secondary consumers?

A

Animals that eat primary consumers

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5
Q

What do tertiary consumers eat?

A

Secondary consumers

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6
Q

what are Saprobionts?

A

Organisms that break down the organic molecules in dead organisms

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7
Q

Examples of Saprobionts

A

Fungi and bacteria

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8
Q

What is a food chain?

A

A sequence of organisms in which each is the food for the next member of the chain

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9
Q

What is each level of a food chain known as?

A

A Trophic level

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10
Q

What is a food web?

A

The linking together of food chains in a habitat

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11
Q

What is a trophic level?

A

Hierarchical levels in an ecosystem
As the trophic levels in a food chain increase, less food and energy available

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12
Q

Are animals confined to one tropic level?

A

No, many feed on different trophic levels because the eat both animals and plants

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13
Q

What is biomass?

A

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

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14
Q

How is the biomass of an organism produced?

A

Biological molecules= biomass. The carbohydrates synthesised by plants that aren’t used for respiratory substances ( the majority are) are used in a plant to make biological molecules

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15
Q

What is the difference between fresh biomass and dry biomass?

A

Fresh biomass is the mass of the whole organism recorded whereas dry biomass is the mass of carbon

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16
Q

What are the advantages and disadvantages of measuring fresh biomass?

A

+ it is easy to weigh
- methods can be made unreliable by different volumes of water in the fresh biomass

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17
Q

How is dry biomass obtained?

A
  • heating material in an oven just below 100oC to remove the water
  • reweigh until there is no mass change which indicates that all the water has been removed
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18
Q

What are the advantages of and disadvantages of measuring the dry biomass?

A

+ it is more reliable
- the organism would be killed
- only a small sample would be measured
Sample may not be representative of the whole organism

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19
Q

What are the units for biomass from a terrestrial ecosystem?

A

Dry mass per given area in a given time period

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20
Q

What are the units for biomass from an aquatic ecosystem?

A

Dry mass per given volume in a given time

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21
Q

What is bomb calorimetry?

A

How the chemical energy store in dry biomass can be calculated

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22
Q

How is bomb calorimetry done?

A
  • A sample of dry material is weighed and burned in a sealed container called a bomb
  • the bomb is in a water bath and the heat from the combustion inside causes a small rise in the waters temperature
23
Q

What is the energy released from the mass of burnt biomass calculated in?

A

kJ kg^-1

24
Q

How can you calculate the energy released from a mass of burnt biomass?

A

Knowing the volume of water used, recording the temperature increase, knowledge of how much hear is needed to raise the temperatures of 1g of water by 1oC

25
Q

How much solar energy do plants convert to biomass?

A

Between 1 and 3 %

26
Q

Why isn’t all the light reaching a plant converted to biomass?

A

15% is reflected from the leafs surface because not all wavelengths can be absorbed in photosynthesis
30% is transmitted straight through the plant, completely misses the chlorophyll
50% of light energy absorbed is lost as heat
There may be other factors affecting the rate of respiration e.g. CO2

27
Q

What does GPP stand for?

A

Gross Primary production

28
Q

What is gross primary production (GPP)?

A

The total quantity of chemical energy stored in a plants biomass, in a given area/volume in a given time

29
Q

What does NPP stand for?

A

Net primary product

30
Q

What is the net primary product (NPP)?

A

The chemical energy stored in a plants biomass after respiration losses to the environment have been taken into account

31
Q

What is the equation for Net production in producers?

A

NPP=GPP-R
R= respiration losses

32
Q

What is the NPP available to?

A

Plant growth and reproduction
Also to other trophic levels in the ecosystem e.g. consumers & decomposers

33
Q

What are they units for NPP or GPP

A

kJ m^-2 year^-1
A unit of energy per area or volume per unit of time

34
Q

What is primary productivity?

A

Chemical energy stored in plants/producers as biomass

35
Q

What is secondary productivity?

A

Consumers convert chemical energy in food into biomass

36
Q

What is primary and secondary is measured in?

A

As biomass in a given area in a given time
kJ ha^-1 year^-1

37
Q

What happens to energy between trophic levels/ where does it go?

A
  1. Heat is produced in metabolic reactions e.g. respiration
  2. Growth and repair of tissues
  3. Excretion of urine and faeces
38
Q

How efficient are energy transfers between organisms?

A
  • > 10% of NPP in plants can be used by primary consumers for growth
  • secondary/tertiary are slightly more efficient & transfer- 20% energy available from prey to predators
39
Q

What are the reasons for low %s of energy transfers?

A
  • some parts of the organism aren’t consumed e.g. bones
  • some parts can be consumed but not digested e.g. cellulose is lost in faeces
  • some energy is lost in excretory materials
  • some is lost as heat in respiration
40
Q

What organisms have the highest heat loss and why?

A

Mammals and birds as they are endothermic & have a high body temp so need more energy to maintain such

41
Q

What is the equation for the net production in consumers?

A

N= I - (F+R)

42
Q

What does ‘N’ stand for in the equation for the net production in consumers?

A

N= net production of consumers

43
Q

What does ‘I’ stand for in the equation for the net production in consumers?

A

I= the chemical energy stored in digested food

44
Q

What does ‘F ’stand for in the equation for the net production in consumers?

A

F= chemical energy lost to the environment in faeces and urine

45
Q

What does ‘R ’ stand for in the equation for the net production in consumers?

A

Respiratory losses to the environment

46
Q

What is the energy available at each trophic level usually measured in?

A

Kilojoules per square metre per year

47
Q

How do you calculate the efficiency of energy transfers?

A

Energy transfer= energy available after the transfer/ energy available before the transfer x 100

48
Q

In what ways can farming practices increase the efficiency of energy transfers?

A

Slaughtering whilst still growing/before maturity
Feed on a concentrate or controlled diet
Restrict their movement
Keep inside a shelter or inside with heating
Use genetic selection/ selective breeding

49
Q

Why is slaughtering animals before maturity a farming practice that can increase the efficiency of energy transfer ?

A

More energy is transferred to biomass/tissue production

50
Q

Why is feeding animals on a controlled diet a farming practice that can increase the efficiency of energy transfer ?

A

There is a lower proportion of food containing energy lost in faeces

51
Q

Why is restricting the movement of animals a farming practice that can increase the efficiency of energy transfer ?

A

Less respiratory loss to the environment/ less energy is used

52
Q

Why is keeping animals inside a shelter(with heating) a farming practice that can increase the efficiency of energy transfer ?

A

Less heat loss to the environment, reducing the temperature gradient
No predators

53
Q

Why is selective breeding a farming practice that can increase the efficiency of energy transfer ?

A

Genes for a higher productivity can be selected

54
Q

Why might all the light energy that reaches them, not be used by producers in photosynthesis?

A
  • the light is reflected off the leaf
  • the light misses the chlorophyll
  • the light is the wrong wavelength
  • the plant is respiring a lot so less biomass, heat energy is also lost

AQA A-level Biology (25 decks)

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