Question

Photosynthetic euglenoids are:

• A. Obligate autotrophs
• B. Facultative heterotrophs
• C. Facultative autotrophs
• D. Obligate heterotrophs

Answer 1

The correct option is B

Explanation of the correct answer:

1. Facultative autotrophs are basically heterotrophs which also have chlorophyll and make food through photosynthesis.

2. Euglena is basically a heterotroph, but it also has chlorophyll and on the availability of light and in the absence of organic food source and turn into autotroph.

3. But they are not obligate autotrophs.

4. Photosynthetic euglenoids lose their chlorophyll when they grow in the dark and obtain nutrients heterotrophically from organic matter.

Explanation of the incorrect answers:

Option A:

1. Obligate autotrophs are completely autotrophs and do not have the ability to become heterotrophs at all.

Option C:

1. Obligate heterotrophs are completely dependent on heterotrophic mode of nutrition and can not live if the food availability is over in the surrounding.
2. But Euglena can switch into autotrophic mode when required.

Option D:

1. Facultative heterotrophs are basically autotrophs but can switch into heterotrophs when required.

2. But the basic mode of nutrition in Euglena is heterotrophic.

Final answer: Photosynthetic euglenoids are facultative autotrophs.