Final answer:
Volvox are autotrophs since they are composed of photosynthetic algae that convert inorganic carbon dioxide into organic carbon compounds, a process characteristic of autotrophic organisms.
Step-by-step explanation:
Volvox are autotrophs, meaning they can produce their own food through photosynthesis. This can be deduced from the description that each Volvox is made up of between 1,000 to 3,000 photosynthetic algae. These algae are capable of converting inorganic carbon dioxide (CO₂) into organic carbon compounds, a typical characteristic of autotrophs. Furthermore, they are found to be grouped together into a spherical formation and possess eyespots, which allow them to swim towards light, an adaptation typically associated with photosynthetic organisms seeking out light to power their photosynthesis.
While it is noted that some related organisms may require B vitamins, reflecting a heterotrophic ancestry, or even exhibit mixotrophy, the description of Volvox indicates that they are predominantly autotrophic, obtaining carbon and other elements in inorganic form from their environment and converting these into organic compounds necessary for life.