Question

What is locomotion in protozoa?

Answer 1

Hint: All the single celled, eukaryotic organisms are protozoans. Most of the protozoans have heterotrophic modes of nutrition. They depend on the autotrophs. Some of them also have an autotrophic mode of nutrition and they are referred to as mixotrophs. Their shape and size varies greatly.

Complete answer:
Protozoans have diverse modes of locomotion and they can be broadly divided into three groups :
Flagellar Movement
Ciliary Movement
Amoeboid Movement
1. Flagellar Movement: It is found in some stages in the life cycle of certain amoeba including vegetative phase of some genera. Eukaryotic flagellum is a membrane bound, whip-like structure found not only in protozoans but also in some animals as well.
The structure of flagella contains a cylinder (axoneme) surrounded by a cross bridge structure with the nine pairs of microtubules. This is known as the 9+2 arrangement.
2. Ciliary Movement: Ciliates have more number of beating flagella which generate power and speed in viscous medium. Structure of cilia is identical to flagella but is small in size. Types of flagella arranged in closely aligned longitudinal rows are known as kineties.
Effective stroke of cilia is planar, but the recovery stroke of cilia is out to the side thereby forming a three dimensional movement. It performs work against the viscous force of water in both effective and recovery strokes.
3. Amoeboid Movement: This movement is achieved by pseudopodia which is formed by the extension of cytoplasm in the organism. This process is visible under the light microscope as movement of granules in the organism. Basic locomotory organism is pseudopodium. Flow of cytoplasm provides the momentum necessary to propel the organism further in its direction of movement.

Note:
All the single celled, eukaryotic organisms come under the category of protozoans. Most of them have heterotrophic mode of nutrition while some of them have autotrophic mode also. There are three major forms of movement in protozoans which are Flagellar, Ciliary ,and Amoeboid.