Which one of the following groups of animals reproduces only by...

In Ctenophores, asexual reproduction is absent. They are monoccious and fertilization is external. In cnidaria, asexual reproduction by budding is seen in polyp forms, and sexual reproduction in medusae forms. In protozoan, asexual reproduction occurs by fission, budding, etc. and sexual reproduction by conjugation and syngamy. In porifera ascxual reproduction occurs by gemmule formation. Related Theory Ctenophores are free-swimming. marine, solitary, pelagic animals with no polymorphism and no attached stages were found. They have a pair of long, solid, retractile tentacles and lack nematocysts. They have special adhesive and sensory cell i.e., colloblasts or lasso cells present in tentacles which helps in food capture. They are monoecious (hermaphrodite); gonads are endodermal situated on walls of digestive canals and development is direct with characteristic cydippid larva and lack asexual reproduction and alternation of generation. Regeneration and paedogenesis are common in them. Eg. Pleurobrachia, Hormiphora, Ctenoplana, Coeloplana.