The evolution of complex multicellularity in eukaryotes __________.

• A. required the evolution of photosynthesis in all multicellular organisms
• B. occurred independently in several different lineages, such as animals, plants, and fungi
• C. happened only once in the common ancestor of all eukaryotes
• D. was driven solely by the presence of mitochondria

Answer: (B)

Verified step by step guidance

1. Understand the concept of complex multicellularity: Complex multicellularity refers to organisms composed of multiple cells that work together in a coordinated manner, often with specialized functions. This is distinct from simple multicellularity, where cells may aggregate but lack specialization.
2. Analyze the role of photosynthesis: Photosynthesis is not a requirement for all multicellular organisms. While it is essential for plants and some protists, animals and fungi do not rely on photosynthesis for their multicellularity.
3. Examine the evolutionary history of eukaryotes: Complex multicellularity evolved independently in different eukaryotic lineages, such as animals, plants, and fungi. This indicates that it did not happen only once in a common ancestor of all eukaryotes.
4. Consider the role of mitochondria: While mitochondria are crucial for energy production in eukaryotic cells, the evolution of complex multicellularity was not solely driven by their presence. Other factors, such as cell signaling, adhesion, and gene regulation, played significant roles.
5. Conclude that complex multicellularity evolved independently in several lineages: Based on the evidence, the correct answer is that complex multicellularity occurred independently in different eukaryotic groups, such as animals, plants, and fungi.