sentence: Most nitrogen fixation is done by micro-organisms called bacteria.
sentences_before: Nitrogen is needed for life. In plants, nitrogen is needed for photosynthesis and growth.
sentences_after: In these roots, they make ammonia for the plant and the plant gives them carbohydrates. Other plants take nitrogen compounds out of the soil through their roots. All nitrogen in animals comes from eating plants.
concept_name: nitrogen fixation
headings: Nitrogen cycle
categories: Ecology