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Biology Unit 4 > Energy And Ecosystems > Flashcards

Energy And Ecosystems Flashcards

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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
Q

What is the usual given area and period of time for pyramids of energy if one is not given

A

Per metre per year

26
Q

Why do pyramids of energy give more reliable results than pyramids of biomass

A

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
Q

What is energy measured in

A

KJm-2y-1

28
Q

Explain why the productivity of an agricultural ecosystem is greater than that for a natural ecosystem

A

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
Q

How farmers maximise production

A 
Monoculture 
Fertiliser
Pesticide
Crop rotation (but old method)
Intensive livestock rearing
30
Q

Benefits of monoculture

A

Faster harvesting

Reduces plant competition

31
Q

What is an agricultural ecosystem

A

Domesticated animals and plants used to produce food for mankind

32
Q

What is organic fertiliser

A

Animal waste

33
Q

When is synthetic fertiliser best to use

A

As long as it doesn’t rain

If it rains, it’ll all wash away and be waste of money

34
Q

What is agriculture about and why is this a problem

A

About simplifying food webs to allow more energy to be supplied to humans

Problem = bad effect on other organisms in the food web

35
Q

What is the 2 main differences between ecosystems

A

Energy input

Productivity

36
Q

How is additional energy input in agricultural ecosystems to ensure maximum growth

A

Food (people work on farm expend energy as they work)

Fossil fuels (fuel used to produce and apply fertilisers and pesticides etc)

37
Q

What are pests

A

Organisms growing or living where we don’t want them to

38
Q

What are pesticides

A

Poisonous chemicals that kill pests

39
Q

What does molluscicides target

A

Snails/slugs

40
Q

What do herbicides target

A

Weeds

41
Q

What do fungicides target

A

Fungi

42
Q

What do insecticides target

A

Insects

43
Q

How do systematic pesticides work

A

They’re taken in by the plant and they enter the insects when they feed on the plant

44
Q

What legal standards must pesticides meet

A

Specific - only hits target

No accumulation in food chain

Able to biodegradable

45
Q

What things other than legal standards must a pesticide be in order to be effective

A

Cost effective = cheap to make

Biodegradable but not too fast as needs a good shelf life

46
Q

Problems with pesticides

A

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
Q

Alternative methods to pesticides

A

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
Q

What is biological control

A

Using natural predators or parasites to control pest population without eradicating them. Instead of using pesticides

49
Q

Advantages of using biological control

A

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
Q

Disadvantages of biological control

A

Not as fast acting as pesticides

The organism may itself become a pest

51
Q

Examples of biological control

A

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
Q

What does integrated control involve

A

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
Q

What is integrated pest-control system also known as

A

Integrated crop management

54
Q

What is the aim of integrated pest-control system

A

Integrate all forms of pest control rather than rely on one type

55
Q

How do pests reduce productivity

A

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
Q

What is the problem of balancing cost of pest control with its benefit

A

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
Q

What is the aim of intensive rearing of domesticated livestock?

A

To produce maximum yield at the lowest possible cost

58
Q

How does keeping animals in a small space ensure energy conversion is made efficient

A

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
Q

Other than keeping animals in a small space, how else could you improve the energy conversion rate?

A

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
Q

What are the main features of intensive rearing?

A 
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
Q

What is the economic issue of intensive rearing of domesticated animals?

A

We want food at a low price which has created competitive market where farmers turn to intensive rearing in order to cut costs

62
Q

What is the environmental issue with intensive rearing of domesticated animals?

A

There’s is a reduction in species diversity

Eg monoculture fields and use to pesticides

Biology Unit 4 (14 decks)

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