Oxygen cycle The cycling of oxygen between the biotic and abiotic components of the environment (see biogeochemical cycle). ... In the process of respiration oxygen is taken in by living organisms and released into the atmosphere, combined with carbon, in the form of carbon dioxide.
Answer:
the first wave of extinction may be related to rapid cooling at the end of the Ordovician Period, and the second phase is widely regarded as having been caused by the sea-level fall associated with the glaciation.
The main form is carbon dioxide and methane
Plant cells have a cell wall, but animals cells do not. Cell walls provide support and give shape to plants. Plant cells have chloroplasts, but animal cells do not.
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