Gunpreet, Subject matter expert at Edumarz
Answer: Reproduction is the process by which organisms produce their offsprings to propagate their species. Reproduction occurs in every organism whether it is a unicellular or multicellular organism, however the mode of reproduction varies in them.
Reproduction in unicellular organisms: Unicellular organisms reproduce asexually. Asexual reproduction is a type of reproduction in which only one parent is required and there is no fusion of gametes thus, the number of chromosomes remains the same.
Different means of asexual reproduction in single cell organisms are binary fission (Amoeba), multiple fission (Plasmodium) fragmentation (Spirogyra), regeneration (Planaria) and budding (Hydra).
Reproduction in multicellular organisms: Multicellular organisms reproduce by both asexual and sexual means.
Different methods of asexual reproduction in multicellular organisms are vegetative propagation and spore formation. Plants propagate vegetatively by roots, stem or leaves into new plants. This method is used in layering or grafting to grow many plants such as sugarcane, roses, or grapes. While simple multicellular organisms such as Rhizopus reproduce by spore formation in unfavourable conditions. Spores are covered by thick walls to protect them in harsh conditions. When spores come into contact with a moist surface, they begin to grow.
Sexual reproduction occurs in flowering plants and higher animals which requires male and female parents and fusion of two haploid gametes to form a diploid zygote. Thus offspring acquire characters of both parents.