dougalbod

'Hunger' is a physiological response which is thought to be managed by a combination of hormones, in aprticular Ghrelin (http://en.wikipedia.org/wiki/Ghrelin) and Leptin (http://en.wikipedia.org/wiki/Leptin).

How our bodies recognise a need for specific minerals/vitamins - I'm not sure, it could simply be a learned response?

re : diabetes - I think the dizziness is a direct result of low glucose levels, but I'm not certain how this works. Oxygen transport does not rely on active transport - it's a simple diffusion process so I don't think that glucose levels will have a direct impact.

Dougal

This is a really good question. I'll try and offer some suggestions when I've had some time to think about it more.

Dougal

I find myself a bit confused with the terminology: "adaptive" and "random" genomic change.

 

Is there a significant difference that I'm missing, or are they classed simply as a change that offered an adaptive facet, and a change that did not?

Hi Jill

There is evidence to suggest that when organisms are subject to environmental stress their mutation rate increases. If such a mutation is adaptive towards the stress then it is an 'Adaptive Mutation'.

http://www.micab.umn.edu/current/adaprev01.pdf

Dougal

REPLY: Bacteria [ also asexual organisms ] have three known methods of exchanging partial DNA material. Perhaps amoebae have developed some simullar methods. I`ll give you a website that describes these processes : http://www.slic2.wsu.edu:82/hurlbert/micro101/pages/chap9.html . I am not saying this is what amoebae do,only offering it as a possibility. ...Dr.Syntax

Hi Dr.Syntax, thanks for trying to help but...

I get 'access denied' for this website....

Dougal

Merged post follows:

See

• H. Urushihara, "Cultivation, spore production, and mating" Methods Mol Bio (2006) 346:113-24, which mentions sexual reproduction in Dictyostelium (the slime mold amoeba); and
  
• H. Urushihara et al., "Genes involved in Dictyostelium discoideum sexual reproduction" Eur J Cell Biol (2006) 85:961-68.
  

THanks GDG, I've only had a chance to look at one of these so far, but it looks interesting.

The information I've been able to put together suggests that amoeba are normally haploid, but form a diploid zygote - presumably by nuclear fusion - but details on this seem sparse.

I've also got intersted in slime moulds, but I'll start a new topic when I work out what I need to ask about them:-)

Dougal

I realise that amaoba reproduce asexually! However I've heard about some research that suggests that they do exchange genetic material but nobody seems to know how. I was wondering if anybody had further information??

Hi All

Does anybody know of the mechanism of, or any evidence of, sexual reproduction in amoeba?

ta

Dougal

While the average speed of 'male' vs 'female' sperm may be a factor it's far too simplistic to think that this by itself is the cause of an imbalance in the gender of offspring. If there are more male offspring than female then their is a selective advantage to producing offspring of the less common gender.

As Mr Skeptic said, males (at least for humans and I guess for many other mammal species) have a higher mortality rate before reaching sexual maturity. This does seem like a better reason for the gender imbalance at birth.

Does anybody know of a species where the imbalance is more significant? - I know social insects produce far more males than females but they have weird genetics -

My guess is that for most species the a 50:50 balance (more or less ) is maintained.

Dougal