Explain the processes by which light energy is converted into chemical energy.

Describe how energy flows through and is used by organisms in ecosystems.

a. plants/producers/autotrophs convert light to chemical energy by photosynthesis

b. chlorophyll/photosynthetic pigments absorb light

c. electrons are excited/raised to higher energy level

d. excited electrons pass along chain of electron carriers

e. energy from electrons used to pump protons across thylakoid membrane/into thylakoid space

f. chemiosmosis/proton gradient used to make ATP

g. ATP synthase generates ATP

h. pigments arranged in photosystems

i. electrons from Photosystem II flow via the electron chain to Photosystem I

j. electrons from Photosystem I are used to reduce NADP

k. ATP and reduced NADP used in the light independent reactions/Calvin cycle

l. carbohydrate/glucose/carbon compounds produced containing energy

Award marking points for any point made on a clearly annotated diagram.

a. producers/plants/autotrophs obtain energy from light/sun/inorganic sources

b. food contains energy / energy passed in the form of food/carbon compounds (along food chains/between trophic levels)

c. consumers obtain energy from other organisms/from previous trophic level 

This mark point distinguishes consumers from producers.

d. energy released (in organisms) by (cell) respiration 

Reject energy used in respiration.

e. ATP produced

f. energy/ATP used for biosynthesis/movement/active transport/other valid use of ATP

g. less energy available / energy lost at each trophic level