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Biology - Topic 5 > energy cycles > Flashcards

energy cycles Flashcards

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1
Q

Producers

A

Plants
- produce their own carbohydrates from carbon dioxide (autotrophs)
- start of a food web

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2
Q

Energy transfer between trophic levels

A
  • Biomass and its stored energy is transferred through trophic levels very inefficiently
  • most energy is lost due to respiration and excretion
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3
Q

Consumers

A

Heterotrophs that cannot synthesise their own energy
- obtain chemical energy through eating

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4
Q

Why is dry mass a representative measure of biomass

A
  • Water content in tissues varies
  • heating until constant mass allows standardisation of measurements
  • for comparison
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5
Q

Biomass

A

Measured in terms of:
- mass of carbon
- dry mass of tissue per given area

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6
Q

How is dry mass of tissue estimated

A
  • Sample of organism dried in oven below 100C (avoiding combustion + loss of biomass)
  • sample reweighed at regular intervals
  • all water removed when mass constant
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7
Q

Calorimetry

A

Laboratory method used to estimate chemical energy stored in dry biomass

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8
Q

Calorimetry method

A

Sample of dry biomass is burnt
- energy released used to heat known volume of water
- change in temperature of water used to calculate chemical energy

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9
Q

Calculating net primary production

A

NPP = GPP - R
R = respiratory losses to the environment

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10
Q

Gross primary production

A
  • Chemical energy stored in plant biomass, in a given area / volume
  • total energy resulting from photosynthesis
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11
Q

Net primary production

A
  • Chemical energy stored in plant biomass after respiratory losses
  • available for plant growth and reproduction - create biomass available to other trophic levels
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12
Q

Calculating net production of consumers (N)

A

N = I - (F + R)
I = chemical energy store in ingested food
F = chemical energy store in faeces / urine
R = respiratory losses

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13
Q

Units of productivity rates

A

kJ Ha-1 year-1
kJ is the unit for energy

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14
Q

Why is productivity measured per area

A

Per hectare (for example) is used because environments vary in size
- standardises results so environments can be compared

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15
Q

Why is productivity measured per year

A
  • More representative of productivity
  • takes into account effects of seasonal variation (temperature) on biomass
  • environments can be compared with a standardised amount of time
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16
Q

Why is energy transfer inefficient from sun -> producer

A
  • Wrong wavelength of light - not absorbed by chlorophyll
  • light strikes non- photosynthetic region (bark)
  • light reflected by clouds / dust
  • lost as heat
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17
Q

Why is energy transfer inefficient after producers

A
  • Respiratory loss - energy used for metabolism (active transport)
  • lost as heat
  • not all plant / animal eaten (bones)
  • some food undigested (faeces)
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18
Q

Farming practices to increase energy transfer for crops

A
  • Simplifying food webs to reduce energy / biomass
  • herbicides kill weeds -> less competition
  • fungicides reduce fungal infections
  • results in more energy used to create biomass
  • fertilisers such as nitrates to promote growth
19
Q

Farming practices to increase energy transfer for animals

A
  • Reducing respiratory losses (more energy to make biomass)
  • restrict movement
  • keep warm
  • slaughter animal when young (most energy used for growth)
  • selective breeding to produce breeds with higher growth rates
20
Q

Saprobionts

A
  • Feed on remains of dead organisms and their waste products (faeces / urea) and break down organic molecules
  • secrete enzymes for extracellular digestion
21
Q

Mycorrhizae

A
  • Symbiotic relationship between fungi and roots of plants
  • fungi act as extensions of roots
  • increase surface area of system - increasing rate of absorption
  • mutualistic relationship as plants supply fungi with carbohydrates
22
Q

Importance of nitrogen to organisms

A

Used to create
amino acids / proteins
DNA
RNA
ATP

23
Q

Nitrogen cycle stages

A

Nitrogen fixation
nitrification
denitrification
ammonification

24
Q

Nitrogen fixation

A
  • Nitrogen fixing bacteria break triple bond between two nitrogen atoms in nitrogen gas
  • fix this nitrogen into ammonium ions
24
Q

Nitrogen fixing bacteria

A
  • Fix nitrogen gas into ammonium ions
  • free living in soil
  • or form mutualistic relationship on root nodules of leguminous plants
  • give plants N in exchange for carbohydrates
25
Q

Nitrification

A
  • Ammonium ions in soil are oxidised to nitrite ions
  • nitrite ions are oxidised to nitrate ions
  • by nitrifying bacteria
26
Q

Denitrification

A
  • Returns nitrogen in compounds back into nitrogen gas in atmosphere
  • by anaerobic denitrifying bacteria
27
Q

Ammonification

A
  • Proteins / urea / DNA can be decomposed in dead matter and waste by saprobionts
  • return ammonium ions to soil - saprobiotic nutrition
28
Q

Importance of phosphorous

A

Used to create:
DNA
RNA
ATP
phospholipid bilayers
RuBP / GP/ TP

29
Q

Fertilisers

A
  • Replace nutrients (nitrates and phosphates) lost from an ecosystem’s nutrient cycle when:
  • crops are harvested
  • livestock removed
  • can be natural (manure) or artificial (inorganic chemicals)
30
Q

Natural fertilisers advantages

A
  • Cheaper than artificial fertilisers
    often free if farmer has own
    animals - recycle manure
  • organic molecules have to be broken down first by saprobionts so leaching less likely
31
Q

Artificial fertilisers advantages

A
  • Contain pure chemicals in exact proportions
  • more water-soluble, so more ions dissolve in water surrounding soil.
  • higher absorption
32
Q

Leaching

A

When water-soluble compounds are washed away into rivers / ponds
- for nitrogen fertilisers, this can lead to eutrophication

32
Q

Artificial fertilisers disadvantages

A
  • High solubility means larger quantities can leach away with rain - risking eutrophication
  • reduce species diversity as favour plants with higher growth rates e.g., nettles
32
Q

Natural fertilisers disadvantages

A

Exact minerals and proportions
cannot be controlled

33
Q

Eutrophication

A

When nitrates leached from fields stimulate growth of algae
- algal bloom
- can lead to death of aquatic organisms

34
Q

How does eutrophication lead to death of aquatic organisms?

A
  • Algal bloom creates blanket surface of water blocking light
  • plants cannot photosynthesize and die
  • aerobic bacteria feed and respire on dead plant matter
  • eventually, aquatic organisms die due to lack of dissolved oxygen in water
35
Q

Mutualistic relationships

A

A type of symbiotic relationship where all species involved benefit from their interactions

36
Q

Role of saprobionts in nitrogen cycle

A

They use enzymes to decompose proteins/DNA/RNA/urea
- releasing ammonium ions

37
Q

what are the 4 steps of the phosphorous cycle?

A
  1. Ions released
  2. Absorption
  3. Consumers
  4. Organic matter
38
Q

step 1 of the phosphorous cycle

A

Phosphate ions are released as sedimentary rock erodes
- ions transferred to soil,lakes,rivers etc.

39
Q

step 2 of the phosphorous cycle

A

Plants absorb phosphate ions through their roots assisted by mycorrhizae
- mutually beneficial relationship

40
Q

step 3 of the phosphorous cycle

A

consumers eat plants that now contain phosphate materials

41
Q

step 4 of the phosphorous cycle

A

animal dies/ animal’s waste/ dead plants decompose
saprobionts break down the organic matter
phosphate ions released back to the soil

Biology - Topic 5 (2 decks)

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