[leeds laura (OP)]

i recently was having a discussion with some fellow peers and got onto the subject of random facts! from this, a few questions emerged and the challenge is...can you answer any of them!!?? they are all loosely science based so i thought you would be the best people for the job...here goes...

1. is the sky blue because it reflects the sea?

2. how do cats purr?

3. why are babies nails so sharp?

4. why do people have eye colour?

5. why do men have nipples?

6. if you chop a worm in half, do both ends live?

7. why do you never see baby squirrels?

thank you for your time and any light you can shed!

[ukmicky]

Hi laura and welcome

quote:1. is the sky blue because it reflects the sea?

NO but the sea is blue when it reflects the blue sky and the sky is blue because of Rayleigh scattering. Molecules in the atmosphere scatter the  blue part of the spectrum from the sun more than they scatter red light. The visible colours of the spectrum which you can see if you send light through a prism are    R O Y  G B I V .

The high frequency short wavelength part of the spectrum from green to violet are scattered more than the red to yellow low frequency  long wavelength part.
At sunset we see orange and red because the blue light has been scattered from our line of sight.

 

quote:2. how do cats purr?

dont know
 

quote:3. why are babies nails so sharp?

Mainly because they are very very thin and therefore sharp and also because there's nothing in the womb which can wear them  down and blunt them .

 

quote:4. why do people have eye colour?

Good question which i dont know

 

quote:5. why do men have nipples?

Because men start off life in the womb as females

 

quote:6. if you chop a worm in half, do both ends live?

No

 

quote:7. why do you never see baby squirrels?

You do its just that they grow quickly and when they leave the drey (squirrel home) they already look like there adult counterparts, just a little bit smaller
 

quote:thank you for your time and any light you can shed!

No problem[]

Michael

[DoctorBeaver]

quote:Because men start off life in the womb as females

Is that your final answer? Are you sure you don't want to retract?

[Ophiolite]

quote:Originally posted by DoctorBeaver

quote:Because men start off life in the womb as females

Is that your final answer? Are you sure you don't want to retract?

Doctor Beaver, are you disputing this? The simple, some might say simplistic, consensus view is that all mammals begin in utero as females. Male characteristics become imposed about half way through the gestation period. In the absence of the hormonal influences, induced by the genetic make up of the fetus, that would convert the fetus to a male, it remains female.

This is well summarised here: http://www.gfmer.ch/Books/Reproductive_health/Human_sexual_differentiation.html

The first paragraph from this source captures the essence of the idea:

Fetal sexual differentiation is a very complicated series of events actively programmed, at appropriate critical periods of fetal life, which involves both genetic and hormonal factors leading to the sexual dimorphism observed at birth. Sexual differentiation is achieved at midgestation. Genetic factors and hormonal factors will alternate in this chain of programmed transformations of the primary gonads, the internal sex structures and the external genitalia. Sex chromosomes promote the development and the differentiation of the primary gonad but the decisive influences are the presence or absence of testosterone and of antimüllerian hormone production by the testis. Femaleness results from the absence of any masculinizing genetic factor or hormone acting during the critical period of differentiation. Brain and hypothalamic sexual identities are mainly acquired during postnatal life. Gender and behaviour identities are markedly influenced by psychosocial imprinting.

[DoctorBeaver]

Yes, I am disputing that. When the eggis 1st fertilised it is asexual. As noted in your precis, various factors change & alternate during gestation... that, I am not arguing with. But Michael's statement that all males start off as females is inaccurate as before any gender differentiation occurs, the egg is of no identifiable sex. So for both sexes the path is asexual-->female. Males then develop from this female phase by the methods you outllined.

 

quote:Brain and hypothalamic sexual identities are mainly acquired during postnatal life. Gender and behaviour identities are markedly influenced by psychosocial imprinting

That is also open to dispute. As noted by Baron-Cohen et al (2001) "Results showed that the male infants [neonates] showed a stronger interest in the physical-mechanical mobile whilst the female infants showed a stronger interest in the face. The results of this research clearly demonstrate that sex differences are in part biological in origin."

Fantz (1963), and Johnson & Morton (1991) drew the same conclusions, but their studies were based on a much smaller test group.

[Ophiolite]

Clearly the egg is asexual, since it is a single cell. That was why I emphasised "Male characteristics become imposed about half way through the gestation period."
I was also careful to note that this view was a simple, if not simplistic one. Since the fetus will develop as a female unless maleness is 'imposed' it is not unreasonable to say that we begin as females.
Perhaps we are merely arguing semantics. (Although, I have always found the dismissive 'merely semantics' to be quite annoying.)

I hesitated to include the last two sentences of the quoted paragraph. It was not relevant to my central point, nor in line with my own views. However, I did not wish to appear to be editing source material.

[ukmicky]

HMMM i forgot about the egg stage [].  


So this is what happens.

we start out in life as an asexual blob of genderless cells, and then as if that's not bad enough mother nature then comes along, kicks us in the bollocks and turns us into females with clitorises and nipples (what a bitch) []

However  if like me and your one of the lucky ones in a complte turn of fate she then decides that there's room for improvement and turns us in to men. []NICE

i'm glad mother nature not very good at her job though overwise she may not have forgotten to remove the nipple's, and that would just look silly[]





Michael

[JimBob]

quote:Originally posted by ukmicky

HMMM i forgot about the egg stage [].  


So this is what happens.

we start out in life as an asexual blob of genderless cells, and then as if that's not bad enough mother nature then comes along, kicks us in the bollocks and turns us into females with clitorises and nipples (what a bitch) []

However  if like me and your one of the lucky ones in a complte turn of fate she then decides that there's room for improvement and turns us in to men. []NICE

i'm glad mother nature not very good at her job though overwise she may not have forgotten to remove the nipple's, and that would just look silly[]





Michael

[V][V][V][V][V] DARN!

I have been operating under the assumption that two haploid cells came together (rare event in my experience, I usually come first)[] and this resulted in an egg which had either two X chromosomes or an X chromosome and a Y chromosome, thus determining gender. I must be geting REALLY old to have missed out on my gender-bending stage.

The embryo may LOOK female but genetically there is never any question as to gender.

Jim []

[Ophiolite]

There is a question about its gender if the hormones etc don't kick in as 'designed'. (Completely off-topic, it is very refreshing to find no ID propagandists strutting their stuff on this forum. Or did I join while they are all at summer camp in Oz?)

[DoctorBeaver]

quote:we start out in life as an asexual blob of genderless cells, and then as if that's not bad enough mother nature then comes along, kicks us in the bollocks and turns us into females with clitorises and nipples (what a bitch)

erm... aren't you forgetting something? At that stage we wouldn't have any bollocks to kick! [)]

[DoctorBeaver]

I suppose it could be said that ova are female as there are no Y chromosomes in them. But as the chromosomes are not paired, gender identity is pretty much irrelevant.
Eggs always contain an X chromosome but a sperm can contain either an X or a Y. If the sperm contains an X chromosome the child will be female whereas a Y chromosome in the sperm will result in a male.
Then, just to complicate matters, you get hermaphrodites (to which, I believe, Ophiliote's post was referring). I'm not even going to go there! [|)]

[another_someone]

Not just hermaphrodites.

http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=300068

quote:
The androgen insensitivity syndrome is an X-linked recessive disorder in which affected males have female external genitalia, female breast development, blind vagina, absent uterus and female adnexa, and abdominal or inguinal testes, despite a normal male (2A + XY) karyotype. Partial androgen insensitivity results in hypospadias and micropenis with gynecomastia

People who are XY, but externally almost indistinguishable from XX (but with some internal vestige of XY organs, and incomplete internal development of XX organs).

George

[Monox D. I-Fly]

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">6. if you chop a worm in half, do both ends live?<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">No

Huh? I think some worms do (though not all). Can't planaria, earthworm, and tapeworm live after being chopped in half? Though the latter two can't if by "half" you mean divided to its left and right part.