Topic 20: Planetary Health

Question 1

Describe the role of autotrophs in Carbon cycle

Answer 1

• Self-feeder or self-sustained
• Convert inorganic C in CO2 → organic C for nutrients → Sinks for CO2
• Photoautotrophs (light as energy source)
  e.g Algae - does photosynthesis CO2 + H2O + light → sugars + O2
• Chemoautotrophs (chemical energy source)
  e.g Methanogens (archea) - use H2 as energy source; stricly anaerobic as O2 can kill them
  + Oxygen-free habits
  + CO2 + H2 → CH4 + sugars (ancient metabolism pathway before O2 in atm)
  + Sink for CO2 but source of CH4 → BAD

Question 2

Describe the role of heterotrophs in Carbon cycle (general)

Answer 2

“Other-feeder”; sources of CO2 → generally bad for climate

Question 3

Describe the role of methanotrophs in Carbon cycle

Answer 3

• CH4 as energy and carbon source → produce CO2
• Have methane monooxygenase enzyme with broad substrate range → able to oxidize other substance beside CH4
• Source of CO2, but sink for CH4 → good

Question 4

Describe the role of decomposers and pollutant degraders in Carbon cycle

Answer 4

• Decomposers: break down dead cells to recycle carbon back to the cycle as CO2 and acquire nutrients from that
• Pollutant degraders: grow on hydrocarbons as energy and carbon source → remediate pollutants - bioremediation
  + Methanotrophs can also degrade other pollutants → 1 example of pollutant degrader
  + Microbes clean up pollutants - especially those from fossil fuels, which were fossilized from dead matter; oxidizing organic C → CO2
  + Special enzymes to degrade large hydrocarbons like alkanes, alkenes and aromatic C

Question 5

Identify and describe some auto- and heterotrophs symbiosis

Answer 5

• Coral: loose symbiosis
  + Coral: primary producers, heterotrophs → need external source of food
  - acquires sugars from algae → CO2
  - provides algae with essential nutrients like N, P, S, etc.
  + Algae: autotrophs → CO2 + light → sugars for coral
• Lichen: primary producers in terrestial environment; photosynthetic but not plant
  + Fungus: heterotrophs
  - Anchor for algae
  - Feed algae with inorganic nutrients and moisture
  + Algae: autotrophs

Question 6

Describe the role of predators microbes in Carbon cycle

Answer 6

• Include: ciiliates, flagellas, and amoeba
• Not all protists are predators; some are:
  + Detritivores: eat dead or decomposing matter → digest internally to gain nutrients
  + Photosynthetic: different from in plants