For each of the following statements that is true, write “true” in the blank. For each statement that is false, write the word(s) that should be substituted for the underlined word(s) to make the statement correct.
__________ Most cyanobacteria form heterocysts in which nitrogen fixation occurs.

Verified step by step guidance

1. Step 1: Understand the key terms in the statement. 'Cyanobacteria' are a group of photosynthetic bacteria, and 'heterocysts' are specialized cells that some cyanobacteria form to fix nitrogen under aerobic conditions.
2. Step 2: Recall that not all cyanobacteria form heterocysts. Only certain filamentous cyanobacteria, such as those in the genus Anabaena, develop heterocysts for nitrogen fixation.
3. Step 3: Analyze the statement: 'Most cyanobacteria form heterocysts in which nitrogen fixation occurs.' Since only some cyanobacteria form heterocysts, the word 'Most' is inaccurate.
4. Step 4: Determine the correct substitution. Replace 'Most' with 'Some' to accurately reflect that only some cyanobacteria form heterocysts for nitrogen fixation.
5. Step 5: Conclude that the corrected statement should read: 'Some cyanobacteria form heterocysts in which nitrogen fixation occurs.'

Key Concepts

Cyanobacteria

Cyanobacteria are photosynthetic bacteria that produce oxygen and are found in various aquatic and terrestrial environments. They play a crucial role in nitrogen and carbon cycles and can form specialized cells called heterocysts for nitrogen fixation.

Heterocysts

Heterocysts are thick-walled, specialized cells formed by some filamentous cyanobacteria under nitrogen-limiting conditions. These cells provide an anaerobic environment necessary for the enzyme nitrogenase to fix atmospheric nitrogen into ammonia.

Nitrogen Fixation

Nitrogen fixation is the biological process of converting atmospheric nitrogen (N2) into ammonia (NH3), a form usable by living organisms. This process is catalyzed by the enzyme nitrogenase, which is sensitive to oxygen and thus occurs in specialized cells like heterocysts.