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Biology - Unit 5 > Chapter 13 - Energy and Ecosystems > Flashcards

Chapter 13 - Energy and Ecosystems Flashcards

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1
Q

What is the source of energy for an ecosystem?

A

Sunlight

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2
Q

Define biomass

A

Total dry mass of living material measured in specific area or over a given time period. Measured in grams per m2 or m3

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3
Q

Define producers

A

Plants that perform photosynthesis and use light to make biological molecules

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4
Q

Define consumers

A

Organisms that obtain their energy by feeding on other organisms as they cannot make biological molecules from sunlight. Two types: primary and secondary

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5
Q

Distinguish between primary and secondary consumers

A

Primary are first consumers in the chain that feed on producers
Secondary consumers feed on primary consumers

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6
Q

Define saprobionts

A

Also known as decomposers/ Organisms that break down complex materials in dead organisms to simples ones. They include bacteria and fungi and perform saprobiotic decomposition

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7
Q

What is a food chain?

A

Chain describing feeding relationship where producers eaten by consumers etc. Each stage is called a trophic level

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8
Q

How can the chemical energy in dry biomass be estimated?

A
  • Bomb calorimetry
  • Dry material weighed then burnt in oxygen surrounded by water
  • Specific heat capacity used
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9
Q

Why do producers need biological molecules?

A
  • Glucose for respiration and make starch/glucose
  • Amino acids for proteins
  • Fatty acid + Glycerol for triglyceride and membranes
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10
Q

Why do consumers need biological molecules?

A
  • Glucose for respiration and store glycogen
  • Amino acids for proteins
  • Fatty acid + Glycerol for triglyceride, insulation and membranes
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11
Q

Why do decomposers need biological molecules?

A
  • Glucose for respiration
  • Amino acids for proteins
  • Fatty acid + Glycerol for membranes
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12
Q

How much energy is harnessed from the sun by producers?

A

1% - 3%

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13
Q

Why is most of the suns energy not converted into organic matter by producers?

A
  • 90% reflected back into space
  • Not all wavelengths of light absorbed
  • Light does not fall on chlorophyll molecule
  • Limiting factors such as low CO2
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14
Q

What is gross primary production?

A

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

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15
Q

Give the equation for net primary production in plants

A

Gross primary production MINUS respiratory losses

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16
Q

What are the reasons for low energy transfer between trophic levels?

A
  • Some of organism not consumed
  • Some parts consumed by not digestible so lost if faeces
  • Some lost in excretory materials
  • Energy lost as heat from respiration
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17
Q

What is the equation for the net production of consumers?

A 
N = I - (F+R)
N = net production
I = Chemical energy of ingested food
- F = Energy lost in p=faeces
R = Energy lost in respiration
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18
Q

Inefficiency of energy transfer in trophic levels explains what?

A
  • Max four or five trophic levels
  • Total biomass less at higher trophic levels
  • Total amount of energy available less as trophic levels progress
19
Q

What is the percentage efficiency equation for energy transfer?

A

Energy available after transfer divided by energy available before transfer multiplied by 100

20
Q

How much energy is transferred from producer to consumer?

A

10%

21
Q

How much energy is transferred from consumer to consumer?

A

20%

22
Q

Why is energy transfer high between consumers?

A

Consumers more edible and digestible whereas producers made up of cellulose

23
Q

Describe the path taken by nutrients

A
  • Nutrient taken up by producers
  • Producer incorporates nutrient into complex molecule
  • Consumer eats producer and nutrients
  • Passes along food chain
  • When consumer dies, saprobiotic decomposition occurs releasing nutrients
24
Q

Summarise the WHOLE nitrogen cycle

A
  • Nitrogen in atmosphere as gas N2
  • Plants can only absorb NO3-
  • N2 converted into ammonium ions NH4+ by nitrogen fixation by nitrogen fixing bacteria (mutualistic in roots of leguminous plants or free living in soil)
  • NH4+ converted into NO3- ions by nitrification by nitrifying bacteria
    where NH4+ oxidised into NO2- then oxidised into NO3-
  • NO3- absorbed by plants to make AA/proteins
  • Consumers eat plant to obtain AA
  • Organic material broken down by saprobiotic decomposers releasing NH4+ into soil (ammonification)
  • Nitrate ions (NO3-) converted back into N2 gas by denitrification by denitrifying bacteria
  • Denitrifying bacteria work in anaerobic conditions e.g waterlogged fields
25
Q

Why do organisms need phosphorus substances?

A
  • Phospholipids
  • DNA
  • ATP
26
Q

Summarise the WHOLE phosphorous cycle

A
  • Phosphorous present in sedimentary rock as phosphate ions PO4 3-
  • Sedimentary rock erodes leaving soil with PO4 3-
  • Plants absorb PO4 3- to make phospholipid/DNA/ATP
  • Consumer eats plants
  • Saprobiotic decomposers releases PO4 3- back into soil
  • Mycorrhize fungi in roots of plants support uptake of scarce materials such as phosphate ions by increasing SA and acting like a sponge
27
Q

What is an agricultural ecosystem?

A
  • Farming ecosystems

- Grows crops and raise animals

28
Q

How are crops intensively farmed for high yield?

A
  • Suitable location with lots of water, sunlight and minerals
  • Clear area of plant and animals (deforestation removes competition and pests)
  • Selectively breed crop
  • Greenhouse for high levels of light, CO2 and temperature
  • Water by irrigation
  • Fertilisers
  • Control pests
  • Crop rotation ensure mineral levels do not deplete
  • Ploughing to add air spaces, bacteria involved in nutrient cycles can aerobically respire
29
Q

Distinguish between natural and artificial fertilisers

A 
Natural = Dead/decaying remains
Artificial = Mined from rocks and applied in appropriate balance
30
Q

What are pests?

A

Organisms that harm plants/crops as they compete/eat or disease the plant

31
Q

What are the two ways that pests can be controlled?

A

Pesticides or biological control

32
Q

What are pesticides?

A

Chemical sprays that kill the pest

33
Q

What are the advantages and disadvantages of pesticides?

A

Advantages:
Fasting acting and can control area covered
Disadvantages:
Non-specific and nonbiodegradable so bioaccumulation occurs
Pests may be resistant
Reapplication

34
Q

What is biological control?

A

Using predators or parasites to control the pest

35
Q

What are the advantages and disadvantages of biological control

A 
Advantages:
Specific
No bioaccumulation
No resistance and no reapplication
Disadvantages:
Slow acting
May become pest
Cannot control area covered
36
Q

What is bioaccumulation?

A

Pesticides not biodegradable so remain in organisms tissues. Accumulate along food chain up trophic levels and toxic to consumers on high trophic levels

37
Q

What three minerals do fertilisers provide?

A

Nitrate for AA
Phosphate for DNA/ATP and phospholipids
Magnesium for chlorphyll

38
Q

Debate natural and artificial fertilisers

A

Natural has reduced risk of eutrophication but slower release
Artificial has faster release but more risk of eutrophication and lowers water potential of soil

39
Q

What is the benefit of ploughing?

A

Aerates soil increasing air spaces supporting aerobic respiration (more nitrogen fixation and less denitrifying bacteria)

40
Q

Summarise eutrophication

A
  • Large amounts of fertilisers
  • Leaching into water sources
  • Builds up in ponds
  • Increased algae growth (algae bloom)
  • Prevents light reaching bottom of water
  • Plants do not photosynthesis so die
  • Saprobiotic decomposers use oxygen in water from respiration
  • Fish die
41
Q

How do the four ways of crop farming affect the environment?

A

Deforestation reduces species/plant diversity and less habitats/food
Monoculture depletes nutrients
Selective breeding reduces genetic diversity
Pollution causes bioaccumulation and eutrophication

42
Q

What five ways can we reduce the impact of crop farming?

A

Native trees for species diversity
Hedgerows for species diversity
Polyculture and crop rotation to prevent depletion of nutrients
Wild crops maintain genetic diversity
Biological control and natural fertiliser

43
Q

How are animals reared in farming?

A
  • Selectively bred
  • Pre digested food with antibiotics and vaccines
  • Hormones
  • Restricted movement and kept warm

Biology - Unit 5 (4 decks)

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