2.2 Energy and biomass in ecosystemsIB Environmental Systems and Societies HL: Flashcards
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State the first law of thermodynamics.
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- State the first law of thermodynamics.
- Energy can be transformed from one form to another but cannot be created or destroyed.
- State the second law of thermodynamics.
- Energy transformations are inefficient; some energy is lost, mostly as heat.
- What does photosynthesis do to energy?
- Converts light energy into chemical energy in glucose, some stored as biomass.
- Why is energy lost along a food chain?
- Respiration (heat), uneaten parts, egestion and death; limits the number of trophic levels.
- Define gross and net productivity.
- GP is the total gain in biomass; NP is GP minus losses from cellular respiration.
- How is the biomass of a trophic level measured?
- Collect samples and dry them, then measure the mass.
- Name three non-biodegradable pollutants.
- PCBs, DDT and mercury.
- Distinguish bioaccumulation and biomagnification.
- Bioaccumulation: build-up in one organism. Biomagnification: increasing concentration at each trophic level.
- Why do microplastics matter for pollutants?
- They absorb non-biodegradable pollutants, which increases their transmission in food chains.
- (HL) Distinguish autotrophs and heterotrophs.
- Autotrophs make carbon compounds from inorganic sources; heterotrophs obtain them from other organisms.
- (HL) Distinguish photoautotrophs and chemoautotrophs.
- Photoautotrophs use light; chemoautotrophs use energy from exothermic inorganic reactions (chemosynthesis).
- (HL) Define maximum sustainable yield.
- The net primary or net secondary productivity of a system.
- (HL) Why are sustainable yields higher at lower trophic levels?
- Net productivity is greater at lower levels because energy is lost at each transfer.
- (HL) Define ecological efficiency.
- The percentage of energy received by one trophic level that is passed on to the next.
- (HL) What happens to entropy as biomass passes through ecosystems?
- It increases (second law).
Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).