Mention the mode of reproduction used by – A. Amoeba B. Planaria
Hint:Amoeba and Planaria both are simple organisms that reproduce by asexual reproduction. These include several processes like fission, budding, fragmentation, vegetative propagation, parthenogenesis etc.
Complete answer- To begin this answer we first need to know about asexual reproduction. Asexual reproduction involves the production of genetically identical offspring from a single parent. Amoeba develops its offspring through the process of binary fission. In this process the plane of the cytoplasmic division passes through any direction. This reproduction process involves mitosis only and as a result offspring produced are identical to the parent and also to each other. Fission also involves various process according to the plane of fission such as – Transverse binary fission - In this plane of cytoplasmic division coincides with the transverse axis of individuals as in Paramecium. Longitudinal binary fission- The plane of cytoplasmic division coincides with the longitudinal axis of the individual as in Euglena and Vorticella. Multiple fission – In this the nucleus divides several times by mitosis to produce many nuclei, without involving any cytokinesis. Later, each nucleus gathers a small amount of cytoplasm around it and the mother individual splits into many daughter cells. For e.g., Amoeba and Plasmodium. So Amoeba in most of the cases reproduce through binary fission but under the shortage of food it performs multiple fission. Planaria reproduces through a process known as fragmentation. In this, the body of the parent breaks into discrete pieces, each of which produces an offspring. This capability of generating an entire new individual from a fragment of tissue is called regeneration.
Note: While in animals and other simple organism the term asexual is used for plants the term vegetative propagation is in common use. Planaria can also reproduce through transverse binary fission.