The oxygen revolution changed Earth's environment dramatically. Which of the following took advantage of the presence of free oxygen in the oceans and atmosphere? a. the evolution of cellular respiration, which used oxygen to help harvest energy from organic molecules b. the persistence of some animal groups in anaerobic habitats c. the evolution of photosynthetic pigments that protected early algae from the corrosive effects of oxygen d. the evolution of chloroplasts after early protists incorporated photosynthetic cyanobacteria

Key Concepts

Cellular Respiration

Cellular respiration is a metabolic process that converts biochemical energy from nutrients into adenosine triphosphate (ATP), using oxygen in aerobic organisms. This process allows cells to efficiently harvest energy from organic molecules, which became possible with the rise of free oxygen in the environment during the oxygen revolution.

Anaerobic Habitats

Anaerobic habitats are environments where oxygen is absent or in very low concentrations. Some organisms, particularly certain bacteria and archaea, thrive in these conditions by utilizing alternative metabolic pathways that do not require oxygen, allowing them to persist despite the increasing levels of oxygen in the atmosphere.

Photosynthetic Pigments

Photosynthetic pigments are molecules that absorb light energy for photosynthesis, allowing organisms like algae to convert light into chemical energy. The evolution of these pigments was crucial for early photosynthetic organisms to survive in an oxygen-rich environment, as they provided protection against the potentially harmful effects of reactive oxygen species.