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Biology Unit 4 > Energy And Ecosystems > Flashcards

Energy And Ecosystems Flashcards

1
Q

What is bioaccumulation?

A

When the concentration of pesticide builds up in a food chain at each stage

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2
Q

What is a tropic level?

A

Each stage in a food chain

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3
Q

What are decomposers?

A

Bacteria and fungi that break down dead organisms

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4
Q

How much of the sun’s energy is available to plants?

A

1-3%

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5
Q

Why isn’t most of the sun’s energy used in photosynthesis?

A

Over 90% reabsorbed by the atmosphere or reflected back by clouds and dust

Not all wavelengths of light can be absorbed

Light may not fall on chlorophyll molecule

Photosynthesis is limited by other factors eg co2

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6
Q

What is gross production?

A

Total quantity of energy the plants in a community convert to organic matter

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7
Q

What is net production?

A

Rate at which plants in a community store energy

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8
Q

What is the net production equation?

A

Net production = gross production - respiratory loss

Aka
Stored stuff = photosynthesis - energy lost

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9
Q

Why is a lower percentage of energy transferred at each stage?

A

Some of organism not eaten

Some parts eaten can’t be digested (so lost in faeces)

Some energy lost in excretion eg urine

Some energy lost in heat

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10
Q

What does inefficient transfer of energy between tropic levels explain?

A

Why food chains are usually short

Why higher tropic levels have less biomass

Amount of energy stored at each level is less as moves up chain

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11
Q

Why are secondary and tertiary consumers more efficient than primary consumers at transferring available energy from prey into their own bodies?

A

Primary consumers usually eat more stuff that can’t be fully digested so they produce more faeces thus less energy is absorbed

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12
Q

What is the energy transfer equation?

A

Energy transfer = energy available after transfer divided by energy available before transfer x100

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13
Q

What is the percentage efficiency equation?

A

Same as energy transfer

Energy available after divided by energy available before x100

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14
Q

What is biomass?

A

The amount of living tissue (without water)

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15
Q

More energy is retained in the organism if:

A

Animal cold blooded (not as much needed to maintain body temperature)

Animal is herbivore (doesn’t need as much energy to obtain food)

Animal is large (small surface to volume ratio so looses less energy as heat)

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16
Q

What is detritus

A

Animals that eat dead organisms

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17
Q

Why is there a smaller biomass in winter

A

Plants don’t grow as much in winter

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18
Q

Why are biomass pyramids sometimes not pyramids

A

If taken over a season rather than a whole year

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19
Q

Problems with using number pyramids to describe food chains

A

Doesn’t take into account size (1 tree and 1 fly the same)

Number so great of one species that it’s impossible to represent on same scale as the other species (1 tree and 1 million flies)

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20
Q

Why would you use pyramids of biomass

A

Reliable

Gives quantitative description

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21
Q

Strengths and weaknesses of using fresh mass (biomass)

A

Easier to assess

Unreliable because varying amounts of water present

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22
Q

Strengths and weaknesses of using dry mass (biomass)

A

More reliable as no water

Organisms must be killed
Since they must be killed, only a small sample can be taken. This means sample may not be representative

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23
Q

What is biomass measured in

A

Gm-2

Grams per metre

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24
Q

What is biomass measured in if the sample is a volume

A

Gm-3

Grams per cubic metre

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25
What is the usual given area and period of time for pyramids of energy if one is not given
Per metre per year
26
Why do pyramids of energy give more reliable results than pyramids of biomass
2 organisms may have same dry mass but store different amounts of energy Fat stored twice as much energy as carbohydrate Eg 1 fat = 2 units energy 1 carbohydrate = 1 unit energy
27
What is energy measured in
KJm-2y-1
28
Explain why the productivity of an agricultural ecosystem is greater than that for a natural ecosystem
Additional energy put in to remove other species. This reduces competition for light etc. also reduces disease & destroys pests All these increase photosynthesis In turn this increases productivity
29
How farmers maximise production
``` Monoculture Fertiliser Pesticide Crop rotation (but old method) Intensive livestock rearing ```
30
Benefits of monoculture
Faster harvesting | Reduces plant competition
31
What is an agricultural ecosystem
Domesticated animals and plants used to produce food for mankind
32
What is organic fertiliser
Animal waste
33
When is synthetic fertiliser best to use
As long as it doesn't rain | If it rains, it'll all wash away and be waste of money
34
What is agriculture about and why is this a problem
About simplifying food webs to allow more energy to be supplied to humans Problem = bad effect on other organisms in the food web
35
What is the 2 main differences between ecosystems
Energy input Productivity
36
How is additional energy input in agricultural ecosystems to ensure maximum growth
Food (people work on farm expend energy as they work) Fossil fuels (fuel used to produce and apply fertilisers and pesticides etc)
37
What are pests
Organisms growing or living where we don't want them to
38
What are pesticides
Poisonous chemicals that kill pests
39
What does molluscicides target
Snails/slugs
40
What do herbicides target
Weeds
41
What do fungicides target
Fungi
42
What do insecticides target
Insects
43
How do systematic pesticides work
They're taken in by the plant and they enter the insects when they feed on the plant
44
What legal standards must pesticides meet
Specific - only hits target No accumulation in food chain Able to biodegradable
45
What things other than legal standards must a pesticide be in order to be effective
Cost effective = cheap to make Biodegradable but not too fast as needs a good shelf life
46
Problems with pesticides
Insecticides kill useful organisms as well as target Resistance can occur through natural selection Some bioaccumulation occurs Herbicides can remain in soil for long time then taken up by crops and humans Pesticides persisting in environment for many years since slow speed of degrading
47
Alternative methods to pesticides
Remove damaged crop that harbours the pests Create physical barriers (plants that draw them away from crop) Covering soil with mulching to prevent light reaching weeds Intercropping (2 crop 1 field) so provides conditions to biologically control pests
48
What is biological control
Using natural predators or parasites to control pest population without eradicating them. Instead of using pesticides
49
Advantages of using biological control
Pests don't usually develop resistance (can develop resistance to pesticides) More specific target than pesticides Once introduced, no need to re-introduce later (pesticides need repeated application)
50
Disadvantages of biological control
Not as fast acting as pesticides The organism may itself become a pest
51
Examples of biological control
Predator of pest Herbivore of a pest plant Parasite of pest Use pheromones (sex hormones) to attract them so they're trapped and destroyed Introduce sterile mate - reduced number that successfully breed
52
What does integrated control involve
Biological agents if necessary Pesticides used as last resort if population out of control Good soil irrigation Species well suited to area Crop rotation good Good treatment & storage of final crop Manage environment to provide suitable habitat
53
What is integrated pest-control system also known as
Integrated crop management
54
What is the aim of integrated pest-control system
Integrate all forms of pest control rather than rely on one type
55
How do pests reduce productivity
Compete with crop plants for light etc This is limited supply so if taken my pest there's less for crop It may become limiting factor for photosynthesis so reduced productivity
56
What is the problem of balancing cost of pest control with its benefit
Farmers need to produce cheap food for us but still make a living. They also need to try conserve natural resources for the future
57
What is the aim of intensive rearing of domesticated livestock?
To produce maximum yield at the lowest possible cost
58
How does keeping animals in a small space ensure energy conversion is made efficient
Little movement so less energy in muscle contraction Environment warm so less energy into heat Feeding controlled so received optimum food for maximum growth Predators excluded so no loss to other organisms in food web
59
Other than keeping animals in a small space, how else could you improve the energy conversion rate?
Using hormones to increase growth rate Selective breeding animals (so produce varieties that are more efficient at converting food they eat into body mass)
60
What are the main features of intensive rearing?
``` Low cost Efficient energy conversion Quality of food Use of space Use of drugs Animal welfare Safety Pollution Reduced genetic diversity Use of fossil fuels ```
61
What is the economic issue of intensive rearing of domesticated animals?
We want food at a low price which has created competitive market where farmers turn to intensive rearing in order to cut costs
62
What is the environmental issue with intensive rearing of domesticated animals?
There's is a reduction in species diversity Eg monoculture fields and use to pesticides

Biology Unit 4 (14 decks)

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