Practise IB Biology SL 4.1.3 by distinguishing autotrophic and heterotrophic nutrition and explaining how early bacteria contributed to an oxygen-rich atmosphere.
There is evidence that prokaryotes were responsible for changes in the atmospheric gases 3.5 billion years ago. Outline the role of bacteria in producing an oxygen-rich atmosphere.
early prokaryotes were anaerobic/did not require oxygen;
b. population increased / shortage of food;
c. photosynthetic bacteria/cyanobacteria evolved;
d. produced/released oxygen (into the atmosphere);
e. by splitting water molecules/photolysis/photosynthesis;
f. concentration of oxygen built up over time / conditions changed from reducing to oxidizing;