Question

Why is mitosis used in organisms? List three reasons for multicellular organisms.

Answer 1

Ans. Significance of Mitosis:

#I. Tissue repair and replenishment: Cell replenishment in multicellular organisms is a result of mitosis. The cells lost during normal functioning of the body or would or infection is generally replenished by specialized body cells. Some cells in the body, called pluripotent stem cells are capable of producing different types of cells. For example, hematopoietic stem cell replenishes all types of blood cells in body. Mitosis is also responsible for tissue repair and wound-healing.

#II. Growth & Development: The development of zygote into multicellular organism consisting of hundreds of different type of cells is also a result of asymmetric cell division. A plant cell, under optimum laboratory conditions, can form the whole new plant through mitosis. The capacity of a cell to form whole new organism is called totipotency. In multicellular animals, the zygote preserves this capacity. Increase in body size of multicellular organism (say, animals, pants) is due to increase in cell number in the body after mitosis.

#III. Asexual reproduction: Several eukaryotes reproduce asexually through mitosis. Many fungi and algae produce spores through mitosis. Vegetative propagation (in plants), parthenogenesis (in some ants, bees, wasps and many plants) and fragmentation (in filamentous algae, lichens, sea stars, etc.) among other asexual reproduction methods occur through mitosis.

#IV. Regeneration: The capacity of an organism to re-grow lost body parts is called regeneration. The parent cells produce new cells through mitosis to form new body parts. Planarians (Flatworms in class Turbellaria) and sea cucumber (Echinoderms, Class Holothuroidea) have the capacity of complete regeneration i.e. capacity to develop into new individuals from each pieces they are sliced into. Some animals have partial regeneration capacity i.e. they can only re-grow specific lost parts but don’t form new individuals from pieces they’re sliced into. Lizard (autotomy i.e. shredding of tail follows its regeneration), axoloti (Ambystoma mexicanum commonly known as Mexican salamander or Mexican walking fish) and sea star (Echinoderm) show partial regeneration.