Sentence examples for internal fertilisation from inspiring English sources

"Now we know that internal fertilisation is the general condition for placoderms, and is the most primitive type of reproduction for vertebrates," she added.

The discovery of such ancient copulation means that sex with internal fertilisation evolved early on in the history of vertebrates but was then lost, with fish reverting back to spawning in water, and then evolved again in a different way.

"We've defined the point in evolution when the origin of internal fertilisation in all animals began and that's a really big step," said Long. "In terms of evolution, this is the very earliest act of copulation that we know of".

Zerina Johanson, a co-author on the paper and researcher at the Natural History Museum in London, said: "Previously we showed that many placoderms had internal fertilisation – males transferring sperm into females, where eggs or embryos developed – but we lacked information from the Antiarchi, currently accepted as the most primitive group of placoderms".

This great variation has to be properly understood before we can know the true diversity of the group". Ecologically, because stingrays have internal fertilisation and reproduce slowly compared to many freshwater fishes, they are more easily threatened by environmental degradation or illegal harvesting by the aquarium industry.

Internal fertilisation does mean that you have to woo a mate, which is time consuming, but, though many of those species that have gone down the external route do not bother and do their thing in crowds, others (sticklebacks, for example) are just as picky as any human.

One way of avoiding the logistical problems posed by internal fertilisers is to instead examine the relative effects of multiple mating and genetic in organisms with external fertilisation [2], [23].

In mammals with internal fertilization sperm chemotaxis is also a critical component of the fertilisation process, but here chemotactic responses depend on G protein coupled chemoreceptors.

This variation is largely unexplained, but is thought to be determined by three factors: (i) phylogeny [2]; (ii) mode of fertilisation (internal vs external [3]); and (iii) post-copulatory sexual selection i.e., sperm competition and cryptic female choice [4].

In about 90% of all species, fertilisation is internal.

In caecilians, fertilisation is internal, the male extruding an intromittent organ, the phallodeum, and inserting it into the female cloaca.