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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?

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
How much solar energy do plants convert to biomass?
Between 1 and 3 %
26
Why isn’t all the light reaching a plant converted to biomass?
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
What does GPP stand for?
Gross Primary production
28
What is gross primary production (GPP)?
The total quantity of chemical energy stored in a plants biomass, in a given area/volume in a given time
29
What does NPP stand for?
Net primary product
30
What is the net primary product (NPP)?
The chemical energy stored in a plants biomass after respiration losses to the environment have been taken into account
31
What is the equation for Net production in producers?
NPP=GPP-R R= respiration losses
32
What is the NPP available to?
Plant growth and reproduction Also to other trophic levels in the ecosystem e.g. consumers & decomposers
33
What are they units for NPP or GPP
kJ m^-2 year^-1 A unit of energy per area or volume per unit of time
34
What is primary productivity?
Chemical energy stored in plants/producers as biomass
35
What is secondary productivity?
Consumers convert chemical energy in food into biomass
36
What is primary and secondary is measured in?
As biomass in a given area in a given time kJ ha^-1 year^-1
37
What happens to energy between trophic levels/ where does it go?
1. Heat is produced in metabolic reactions e.g. respiration 2. Growth and repair of tissues 3. Excretion of urine and faeces
38
How efficient are energy transfers between organisms?
- >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
What are the reasons for low %s of energy transfers?
- 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
What organisms have the highest heat loss and why?
Mammals and birds as they are endothermic & have a high body temp so need more energy to maintain such
41
What is the equation for the net production in consumers?
N= I - (F+R)
42
What does ‘N’ stand for in the equation for the net production in consumers?
N= net production of consumers
43
What does ‘I’ stand for in the equation for the net production in consumers?
I= the chemical energy stored in digested food
44
What does ‘F ’stand for in the equation for the net production in consumers?
F= chemical energy lost to the environment in faeces and urine
45
What does ‘R ’ stand for in the equation for the net production in consumers?
Respiratory losses to the environment
46
What is the energy available at each trophic level usually measured in?
Kilojoules per square metre per year
47
How do you calculate the efficiency of energy transfers?
Energy transfer= energy available after the transfer/ energy available before the transfer x 100
48
In what ways can farming practices increase the efficiency of energy transfers?
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
Why is slaughtering animals before maturity a farming practice that can increase the efficiency of energy transfer ?
More energy is transferred to biomass/tissue production
50
Why is feeding animals on a controlled diet a farming practice that can increase the efficiency of energy transfer ?
There is a lower proportion of food containing energy lost in faeces
51
Why is restricting the movement of animals a farming practice that can increase the efficiency of energy transfer ?
Less respiratory loss to the environment/ less energy is used
52
Why is keeping animals inside a shelter(with heating) a farming practice that can increase the efficiency of energy transfer ?
Less heat loss to the environment, reducing the temperature gradient No predators
53
Why is selective breeding a farming practice that can increase the efficiency of energy transfer ?
Genes for a higher productivity can be selected
54
Why might all the light energy that reaches them, not be used by producers in photosynthesis?
- 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 (32 decks)

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