Question

Which of the protozoan is considered as a connecting link between plants and animals?
A. Entamoeba
B. Paramoecium
C. Euglena
D. Monocystis

Answer 1

Hint: Protozoa or protozoans are the microscopic groups of unicellular eukaryotes. The connecting link is an organism that has characters of two different groups of organisms. For example, a duck-billed platypus has characters of both mammals and reptiles, so it is a connecting link between mammals and reptiles.

Complete answer:
The protozoan which is considered as the connecting link between plants and animals is Euglena.
Because Euglena has characteristics of both animals and plants.
The Plant character present in euglena is the chloroplast. With the help of chloroplasts, they perform photosynthesis.
Animal character is that the cell wall is absent in euglena. When the light is absent, they are composed of a structure known as a flagellum, these are used to get food and thus, perform heterotrophic nutrition.
Entamoeba is a parasite and causes the disease Amebiasis.
Paramecium is a single cell ciliate.
Monocystis is the parasite and genus of a cephaline gregarine.

Hence, the correct answer is option C.

Additional Information:
> Euglena is a eukaryotic unicellular flagellate.
> It lives in saltwater and freshwater.
> Euglena causes serious tissue and blood diseases.
> Reproduce by the asexual mode by binary fission.

Note:
Euglena resembles both animals and plants. Euglena is phytoflagellate due to the presence of both chloroplast and flagella. Motility and predation are the animal behaviours possessed by Euglena. The presence of chloroplasts is a plant characteristic with the help of which it performs photosynthesis and prepares food. They are both heterotrophic(in sunlight) and autotrophic(in dark). Euglena is both helpful and harmful. Diseases caused by Euglena are passed to humans by biting flies.
The shape and size of protozoans vary differently from Amoeba to Paramecium. Amoeba, Euglena, Paramecium, and Trypanosoma are some examples of protozoans.