Question

Which of the following can show self fertilization?
A. Earthworm
B. Liver fluke
C. Fish
D. Roundworm

Answer 1

Hint: Fertilization is a process that involves the fusion of haploid gametes, sperm and egg to form the diploid zygote. Self fertilization also known as selfing is a process of fertilization of male and female gametes of the same organism that is either haploid, diploid or polyploid.

Complete answer:
- Selfing is considered as the extreme degree of inbreeding. Self fertilization occurs in the bisexual organisms among many unicellular organisms as well as multicellular organisms especially in invertebrates and in most of the flowering plants, protozoans etc.
- Liver fluke belongs to the group of parasitic trematodes that comes under the phylum Platyhelminthes. Basically they are the liver parasites that are found in various mammals including human beings.
- The scientific name of liver fluke is Fasciola hepatica. Adult liver flukes are hermaphroditic. They can undergo both self fertilization and cross fertilization.
- During selfing, the sperm enters the uterus of the same liver fluke through female genital pore. The fertilization of egg takes place in the distal part of the oviduct.

Therefore, the correct answer is (B) Liver fluke.

Additional information:
- Earthworm: They are hermaphroditic and undergo cross fertilization. During copulation, the two worms exchange the sperm cells and the fertilization occurs outside the body of the earthworm but inside the protection of the slime tube.
- Fish: Most of the pieces of fish undergo external fertilization. They are oviparous. The eggs are laid and the embryo is developed outside the body of the fish.
- Roundworm: Roundworms have both hermaphroditic and gender specific species. Sexual reproduction is the dominant mode of reproduction. Fertilization takes place between male and female in gender specific species.

Note: Alike liver fluke, roundworms are parasitic and also have hermaphroditic species. Such species of roundworms undergo self fertilization to form an egg; example nematode. Self fertilization commonly occurs in animals that have restricted mobility or immobile organisms. Internal fertilization is a process where fertilization takes place inside the body of an organism whereas self fertilization is the process of fertilization of male and female gametes of the same organism.