In the domain Eukarya, how do fungi obtain energy and carbon?

• A. They are mixotrophs that primarily generate energy by consuming bacteria through phagocytosis.
• B. They are heterotrophs that secrete enzymes to digest organic matter externally and then absorb the nutrients.
• C. They are photoautotrophs that use chlorophyll to perform photosynthesis.
• D. They are chemolithoautotrophs that oxidize inorganic compounds and fix $C_{\mathrm{O}}2$.

Answer: (B)

Verified step by step guidance

1. Understand the nutritional modes of organisms: autotrophs produce their own organic molecules from inorganic sources, while heterotrophs obtain organic molecules by consuming other organisms or organic matter.
2. Recognize that fungi belong to the domain Eukarya and are not photosynthetic, so they do not use chlorophyll or perform photosynthesis like photoautotrophs.
3. Recall that fungi are not chemolithoautotrophs; they do not oxidize inorganic compounds to fix carbon dioxide.
4. Know that fungi obtain energy and carbon by secreting enzymes into their environment to break down complex organic materials externally, a process called extracellular digestion.
5. After digestion, fungi absorb the resulting smaller organic molecules directly through their cell walls, making them heterotrophs that rely on external digestion and absorption.