Virgin Birth?

[joeactor]

Hmmm...

Apparently some sharks can reproduce asexually!

Sex-free shark birth startles scientists, and worries them

Hail Mary, full of teeth?

JoeActor

[tacoma_kyle]

Hmmm, thats interesting.

Hows there a genetc disadvantage? I was confused on that.

[joeactor]

Hmmm, thats interesting.
Hows there a genetc disadvantage? I was confused on that.

If I understood correctly, by only having one parent, genetic diversity is sacrificed.  When an species lacks genetic diversity, a new disease can more easily wipe them out...

Not a Scientist, but I play one on the internet,
JoeActor

[tacoma_kyle]

Ahhh...Makes sense.

[brainshmain]

Also sharks are usually pretty solitary creatures, so it would be beneficial to be able to reproduce while miles away from other members of their own species.

[McQ]

Also sharks are usually pretty solitary creatures, so it would be beneficial to be able to reproduce while miles away from other members of their own species.

That depends on the species of shark, though, and Hammerheads are pretty social, for sharks. That kind of came as a surprise to me because of the species involved.

[Squid]

Hmmm, thats interesting.

Hows there a genetc disadvantage? I was confused on that.

Birth by parthenogenesis is not unheard of in animals such as lizards and fish - a shark is a cartilaginous fish - however, this is the first positively identified case in cartilaginous fishes.  There is a decidedly marked disadvantaged to such reproduction as the offspring carry only the genetic material inherited from their mother - there is no contribution from another parent and therefore limits the genetic diversity.  While they will still have the variation produced by crossing over during meiosis of the gametes - the variation is still limited because of the process of an egg basically fertilizing itself in automictic parthenogenesis which is the specific type mentioned in the article (which I have if anyone is interested).

With sexual reproduction you get a larger variation in the population and therefore more raw material for natural selection to work upon.  Less variation - the less probability a population has of survival, especially in the face of rapid environmental changes such as climate change.

A funny side bar - parthenogenesis is not seen in mammals.  However, there are still people who run about saying that because of the recent documented cases of a shark and a komodo dragon giving birth asexually that it somehow supports the virgin birth in the bible - as Penn & Teller would say - Bullshit!  And also it's reasons like that which lead me to push science literacy so much.

[skeptigirl]

Hmmm, thats interesting.

Hows there a genetc disadvantage? I was confused on that.

A single parent is OK if you multiply fast enough like bacteria or viruses. In those cases mutations are frequent enough that should the environment change, a mutation might occur in time to evolve an adaptation.

With slower reproducing organisms, sexual reproduction developed because it  increased the rate of change making adaptation to the changing environment fast enough.

In addition, bacteria and viruses actually have a few other mechanisms for exchanging genetic material. So a bacteria can develop a drug resistant genetic change and that gene can actually be transferred to different organisms by a number of different ways.

With multi-celled slower reproducing organisms, there has also been a survival advantage for diversity. The result is there is a lot of variability within species' genomes. When a threat emerges like a pandemic, the genes that provide resistance are already there. Those genes get selected and amplified as the pandemic survivors reproduce. Soon the population recovers and now many members of the species have resistance. The pandemic subsides.

If a mutation had to come along after the species threat began, it probably wouldn't happen fast enough in conditions such as a pandemic. So those mutations are quietly waiting in the wings so to speak, for their day in the Sun.

[skeptigirl]

I love the jokes about the Jesus Shark and of course they are still waiting for the resurrection. The poor thing was apparently eaten before it had a chance to grow up.