Question

Which one of the following animals come under the micro animals? A. Squirrels
B. Beetles
C. Mice
D. Protozoa
Choose the correct answer from the options given below:

• (A) only
• (B) only
• (D) only
• (C) and (D)

Hint:

Tardigrades (water bears) are famous micro-animals that can survive extreme conditions including space vacuum.

Answer 1

The Correct Option is C

Micro animals: Typically <1 mm
Protozoa (unicellular eukaryotes)
Rotifers, tardigrades
Other options:
Squirrels: Macroscopic rodents
Beetles: Insects (macrofauna)
Mice: Small mammals but macroscopic

Answer 2

Size-classification approach:
Soil and ecological fauna are conventionally grouped by body size: microfauna are generally under about 0.2 mm and include organisms such as protozoa, nematodes and rotifers; mesofauna range roughly from 0.2 mm to 2 mm; and macrofauna, visible to the naked eye without magnification, include organisms larger than about 2 mm.
Applying this scale, squirrels and mice are vertebrates several centimetres in size, placing them firmly in the macrofauna category, and beetles, being insects several millimetres to a couple of centimetres long, also fall under macrofauna. Protozoa, being unicellular and microscopic, are the only organisms among the four that satisfy the microfauna size class.
This confirms that only Protozoa qualifies as a micro animal.