Question

Which of the following statements about animals that utilise external fertilisation is incorrect?
A. They are divided equally between terrestrial and aquatic species.
B. Many produce large numbers of gametes to ensure successful reproduction.
C. The behaviours associated with mating are often highly synchronised.
D. The probability of any one egg being fertilized and developing into an adult can be low.

Answer 1

Hint: Commonly seen in aquatic animals is external fertilisation. In order to assure a high success rate of fertilisation, animals undergoing external fertilisation often lay a large number of eggs.

Complete Step by Step Answer:
In the process of fertilisation, sperm and an egg combine to create a zygote. Internal and external fertilisation are the two forms of fertilisation. An external female body is where external fertilisation occurs. The female deposits a lot of eggs whenever a male and female animal comes close to one another. Since these eggs are typically fragile, a jelly coating binds them together and protects them. The male will now release sperms into the water, each of which will swim to the egg. Fertilization takes place when the sperm and egg combine. Common examples of aquatic animals that undergo this type of external fertilisation are fish. Frogs can reproduce externally as well. A frog releases its sperm and eggs into the water. Frogs spend their larval stage in the water and their adult stage on land.

Hence, the correct option is A. They are divided equally between terrestrial and aquatic species.

Note: When an animal uses external fertilisation to reproduce, the embryo develops inside the egg, which is housed outside the female body. The eggs will hatch after an embryo has grown fully. Furthermore, in cases where the egg and sperm are unable to fuse together for fertilisation, external fertilisation can also be intentionally carried out in humans. In-vitro fertilisation is the term used to describe this kind of external human fertilisation.