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Biology > Section 5- Energy and ecosystems > Flashcards

Section 5- Energy and ecosystems Flashcards

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1
Q

How is most energy lost?

A

Lost as heat

Leaves the environment as thermal energy

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2
Q

How is the energy content of organisms measured?

A

Measuring dry biomass

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3
Q

Why is dry biomass used to measure the energy content of organisms?

A

There is no energy in water

Water content of an organism can vary

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4
Q

What is used to measure energy content of organisms?

A

Calorimeter

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5
Q

What is an autotroph?

A

Plants

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6
Q

What is a heterotroph?

A

Organism that gets energy from other organsisms

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7
Q

How do you calculate energy efficiency?

A

Net production of trophic level
/Total energy of previous trophic level
x100

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8
Q

How is the Net production (N) calculated in heterotrophs?

A

N = I - (F + R)

I = Energy ingested 
F = Losses in faeces
R = Losses in respiration
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9
Q

How is the Net Primary Product (NPP) calculated in autotrophs?

A

NPP = GPP - R

GPP = gross primary production
R = respiration losses
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10
Q

Suggest how the efficiency of energy transfer in cattle could be improved?

A

Keep the cattle in sheds

Less energy used in movement

Less energy used in keeping warm

More energy available for growth

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11
Q

What is the nitrogen cycle?

A

Cycling of nutrients including nitrogen involved saprobiotic micro-organisms

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12
Q

What does saprobiotic mean?

A

Digesting extracellularly

Release enzymes, digestion occurs outside of the cell and the digested products are absorbed

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13
Q

What is ammonification and nitrification in the nitrogen cycle?

A

Dead organic matter contains nitrogen in proteins, DNA, RNA and ATP

Nitrogen is also found in urea and faeces

Bacteria will convert nitrogen into:
Ammonia -> nitrite -> nitrate

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14
Q

What is nitrogen fixation?

A

Nitrogen fixing bacteria take nitrogen gas and convert it to ammonia or nitrates

Many bacteria live in root nodules of leguminous plants

Bacteria makes nitrates for the plant which provides glucose and amino acids for the bacteria

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15
Q

What do mycorrhizae do in the nitrogen cycle?

A

Fungi which grow on roots of many plants

Extend the roots further into the soil and across a wider area

Provides plants with greater surface area for absorbing nutrients and water

Fungi get a source of glucose from the plant

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16
Q

What is denitrification?

A

Occurs when the soil becomes anaerobic (water-logged)

Denitrifying bacteria removes oxygen from nitrates for respiration

Releases nitrogen as nitrogen gas

-Quickly makes soil fertile

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17
Q

What is assimilation in the nitrogen cycle?

A

Uptake of ammonium ions and nitrates by plant roots and their incorporation into plant protein and nucleic acids

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18
Q

What are 2 reasons for the stunted growth of plants in a field?

A

Lack of nitrates due to denitrification

Little oxygen for respiration to provide energy for active transport

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19
Q

Why are composts rich in cellulose likely to be poor in nitrogen-containing ions?

A

Cellulose doesn’t contain nitrogen, neither do decomposed products

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20
Q

What is eutrophication?

A

When excess nitrates and phosphates are leached (washed) from soil into rivers and lakes, algal bloom occurs

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21
Q

What is the problem with eutrophication?

A

Algal bloom blocks light from reaching photosynthetic aquatic organisms, leading to their death

Decomposers use up oxygen in water, leading to death of aerobic animals

Only anaerobic bacteria survives- water becomes stagnant

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22
Q

What are the stages of the phosphorus cycle?

A
  1. Weathering
  2. Runoff
  3. Assimilation
  4. Decomposition
  5. Uplift
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23
Q

Why is the phosphorus cycle a slow process?

A

Phosphorus has no gas phase

No atmospheric cycle

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24
Q

What happens during weathering and runoff in the phosphorus cycle?

A

Phosphate compounds from sedimentary rocks leach into surface water and soil

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25
Q

What happens during uplift in the phosphorus cycle?

A

Sedimentary layers from oceans are brought up to land over many of years

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26
Q

What are the 4 main stages of the nitrogen cycle?

A
  1. Nitrogen fixation
  2. Ammonification
  3. Nitrification
  4. Denitrification
27
Q

Why can’t organisms use nitrogen directly from the atmosphere?

A

N2 is very stable due to strong covalent triple bonds

28
Q

How can the risk of eutrophication be reduced?

A

Use phosphate-free detergent

Pumping nutrient-enriched sediment out of water

Sewage treatment marshes on farms

29
Q

What are 2 environmental issues caused by the use of fertilisers?

A

Eutrophication- algal bloom causes water sources being putrid

Leaching- nitrates dissolve in rainwater and runoff into water sources

30
Q

What are the 2 categories of fertilisers?

A

Organic- decaying organic matter & animal waster

Inorganic- minerals from rocks, usually containing nitrogen, phosphorus, potassium

31
Q

What are the advantages of planting a different crop on the same field each year?

A

Different crops use different proportions of certain ions

Different crops have different pathogens

Nitrogen-fixing crops make soil more fertile

32
Q

How do plants use the sugars from photosynthesis?

A

Primarily as respiratory substrates

To synthesise other biological molecules

33
Q

What is biomass?

A

Total dry mass of tissue or mass of carbon measured over a given time in a specific area

34
Q

What is gross primary production?

A

Total chemical energy in plant biomass within a given volume or area

35
Q

What is net primary productivity?

A

Total chemical energy available for plant growth, reproduction and energy transfer to other trophic levels after respiratory losses

36
Q

Why is most of the suns energy not converted to organic matter?

A

Most absorbed by atmosphere or reflected by clouds

Photosynthetic pigments cannot absorb some wavelengths of light

Not all light falls directly on a chlorophyll molecule

Lost as heat during respiration/ photosynthesis

37
Q

Why does biomass decrease along a food chain?

A

Energy lost in nitrogenous waste and faeces

Some of organisms not consumes

Energy lost to surroundings as heat

38
Q

What are some common farming practices used to increase efficiency of energy transfer?

A

Exclusion of predators

Artificial heating

Restriction of movement

Feeding is controlled at the optimum

39
Q

What are 2 nitrogen-containing molecules that are found in plants and animals?

A

DNA

ATP

40
Q

What is the role of microorganisms in nitrogen fixation?

A

Converts nitrogen gas to ammonia ions

41
Q

What is the role of microorganisms in denitrification?

A

Converts ammonia ions into Nitrogen gas

42
Q

What are 2 advantages of using treated sewage sludge on farmland, rather than inorganic fertilisers?

A

Improves soil quality

Ensures it is anaerobic

Cheaper for farmers to use it

43
Q

Why is there no build-up of phosphate ions when they enter chloroplasts?

A

Used in phosphorylation of ATP in the light-dependent reaction

Catalysed by ATP synthase

44
Q

What do the arrows in a food web show?

A

The direction of energy flow

45
Q

What is the general name to describe the bacteria and fungi that will break down death matter?

A

Saprobionts/ decomposers

46
Q

What are 3 reasons for the small percentage of energy transferred at each trophic level?

A

Some of the organism is not eaten

Some parts are not digested and so are lost as faeces

Some energy is lost as excretory materials

Some energy is lost as heat

47
Q

Why do most food chains rarely have more than four trophic levels?

A

After 4 trophic levels there is insufficient energy to support a large enough breeding population

48
Q

Why does biomass show little increase after 100 years?

A

Net productivity = gross productivity - respiratory loss

Decrease in gross productivity

49
Q

Why does gross productivity decrease as woodland matures?

A

Less light = more competition for light

Reduced photosynthesis

50
Q

How do nitrogen-containing substances get into a lake from a field?

A

Runoff

51
Q

How is nitrogen taken up by plant roots?

A

Uptake by roots involves active transport

Requires ATP

52
Q

How does the presence of nitrates in a lake eventually lead to the death of fish? [4]

A

Algal bloom

Blocks light = less photosynthesis

Plants die

Less oxygen for fish

53
Q

What is the role of microorganisms in producing nitrates from the remains of dead organsisms?

A

Saprobiotic break down dead material

Ammonium -> nitrite -> nitrate

By nitrifying bacteria

54
Q

What is leaching?

A

Fertiliser dissolves in soil water

55
Q

What are mycorrhizae and how do they benefit many plants?

A

Fungi that live in close association with plant roots

Increase water uptake

56
Q

How does hedge removal result in the removal of nitrogen-containing compounds?

A

Leaching of nitrates

57
Q

Why are leguminous plants important in succession?

A

Able to grow in nitrate poor soil

It will provide more nitrate when it dies
- these can be used by other species

58
Q

What happens to the energy reaching producers that is not converted to growth?

A

Lost to surroundings as heat

Reflected off the plant

59
Q

Why would percentage energy transfer between producers and primary consumers be less than the transfer between primary consumers and secondary consumers?

A

Producers have cell walls

Difficult to digest

Much cannot be eaten

60
Q

What are 2 disadvantages of using biological pest control?

A

Risk of migration

Slow to work

May eat crop

61
Q

What is a way in which nitrogen in the air can be converted directly into nitrate ions?

A

Lightning

62
Q

Why might farmers grow plants containing root nodules on fields during periods when crop plants are not growing?

A

Nodules contain nitrogen-fixing bacteria

Increase amount of nitrogen containing compounds, increases amount of nitrogen available for next crop to use

63
Q

What is one source of phosphate in a lake?

A

Fertilisers, detergents, sewage, faeces

64
Q

Explain how a change in the phosphate concentration in a lake may have resulted in a decrease in fish population? [6]

A

Increased phosphate causes algal bloom

Plants cover surface, blocking light so plants underneath die - causes increase in decomposers

Decomposers use up oxygen in respiration

Plants unable to photosynthesise so less oxygen produced

Biology (25 decks)

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