Which nutrients often limit the distribution and abundance of photosynthetic organisms?

• A. Nitrogen and phosphorus
• B. Sodium and chloride
• C. Calcium and magnesium
• D. Iron and copper

Answer: (A)

Verified step by step guidance

1. Understand the role of nutrients in photosynthesis: Photosynthetic organisms, such as plants and algae, require specific nutrients to grow and perform photosynthesis effectively. These nutrients are often referred to as limiting factors because their availability can restrict the growth and abundance of these organisms.
2. Identify the key nutrients involved in photosynthesis: Nitrogen and phosphorus are essential macronutrients for photosynthetic organisms. Nitrogen is a critical component of chlorophyll and amino acids, while phosphorus is vital for energy transfer through molecules like ATP and for the formation of DNA and RNA.
3. Consider the other nutrient options: Sodium and chloride, calcium and magnesium, and iron and copper are also important for various biological processes, but they are not typically the primary limiting factors for photosynthetic organisms. For example, iron is important for electron transport in photosynthesis, but it is not as universally limiting as nitrogen and phosphorus.
4. Relate nutrient limitation to ecosystems: In many ecosystems, nitrogen and phosphorus are often in short supply relative to the demand by photosynthetic organisms. This is why fertilizers commonly contain these nutrients to enhance plant growth.
5. Conclude the reasoning: Based on the ecological importance and biochemical roles of nitrogen and phosphorus, these two nutrients are most often the limiting factors for the distribution and abundance of photosynthetic organisms.