Chordates Q

[osimsDDS]

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The function of the notochord is to:
a) form the placenta in placental mammals
b) form the vertebrae in higher chordates
c) form the central nervous system in higher chordates
d)form the umbilical cord in placental mammals
e)provide body support in lower chordates

there is an obvious answer, however, how come the answer can not be choice B also, is it because the notochord does not directly form the vertebrae...is it the mesodermal cells that lie close to the notochord that develop into the vertebrae in higher chordates??? thanks

 

[klutzy1987]

Hmm
http://en.wikipedia.org/wiki/Notochord
The notochord does develop into (gets replaced by) the vertebrate column in upper chordates. I dunno.

 

[Glycogen]

The function of the notochord is to:
a) form the placenta in placental mammals
b) form the vertebrae in higher chordates
c) form the central nervous system in higher chordates
d)form the umbilical cord in placental mammals
e)provide body support in lower chordates

there is an obvious answer, however, how come the answer can not be choice B also, is it because the notochord does not directly form the vertebrae...is it the mesodermal cells that lie close to the notochord that develop into the vertebrae in higher chordates??? thanks

Osims,I think if we are talking about notochord itself and it's primary function then the only answer will be e because notochord is present in all chordate but if we consider it as a vertebrae in higher chordates then it won't be it's primary function b/c vertebrae is not present in all chordate like invertebrate chordate.Notochord is present in the adult of some invertebrate.

 

[osimsDDS]

Osims,I think if we are talking about notochord itself and it's primary function then the only answer will be e because notochord is present in all chordate but if we consider it as a vertebrae in higher chordates then it won't be it's primary function b/c vertebrae is not present in all chordate like invertebrate chordate.Notochord is present in the adult of some invertebrate.

right but the answer choice for B says it forms into the vertebrae in higher chordates, meaning those that are vertebrates...the lower chordates are considered invertebrates like tunicate,amphioxus, etc...

I just think the notochord itself DOES NOT give rise to the vertebrae in vertebrate chordates, its the mesodermal cells adjacent to the notochord in development, but im not 100% sure

 

[HoangDDS]

I thought the obvious answer was B. I am still not too sure why it's E over B.

 

[Thundercatz]

So the answer choice is E? I would of picked B. Many I am stressing out now......

 

[HoangDDS]

So I'm thinking its E over B because the notochord, in all chordates, becomes the internal support structure for the body. But only in higher chordata that the notochord forms the veteberal column.

 

[futuredent22]

What's the source of that question? It is definitely one that, in a testing situation, would make me pause and curse at the testmaker for giving two seemingly right answers and making me pick which one is best.

I think the best answer is E because the actual funtion or purpose of the notochord, the reason that it evolved, was to provide body support. In vertebrate, they have evolved a further adaptation of the notochord, but I don't think its right to say that the actual function of the notochord is to make the vertebra. I think you would say the notochord gives rise to the vertebrae.

Thats just my biased hindsight view, after knowing the correct answer is E

 

[HoangDDS]

oops, sorry. Glycogen already said that. So...nm! =)

 

[Glycogen]

Ok I think I got it.
From campbell:

Notochord,provides skeleton support throughout most of the length of the animal.The notochord persists in the adult of some invertebrate chordates and primitive vertebrae.However in most vertebrae a more complex,jointed skeleton develops and the adult retaine only remnants of the embryonic notochord.

I would choose B myself if I had this on the test but after reading this E is right .I think the Q is very confusing.But,I guess when asking about notochord we have to pick lower chordates.

 

[osimsDDS]

yea its what i thought, the answer is E and let me tell you why its not B...straight from the book answer explanation:

The notochord gives support in lower chordates while in higher chordates the nearby cells of the mesoderm give rise to the vertebrae...

so basically its not the notochord in higher chordates that give rise to the vertebrae its the adjacent mesodermal cells...i think in schaum's it outlines it pretty well...basically there are cells very close to the notochord on the outside surrounding the notochord that give rise to vertebrae in higher chordates

hope that helps...

 

[td4azklz]

The function of the notochord is to:
a) form the placenta in placental mammals
b) form the vertebrae in higher chordates
c) form the central nervous system in higher chordates
d)form the umbilical cord in placental mammals
e)provide body support in lower chordates

there is an obvious answer, however, how come the answer can not be choice B also, is it because the notochord does not directly form the vertebrae...is it the mesodermal cells that lie close to the notochord that develop into the vertebrae in higher chordates??? thanks

____________________________________________________________
So, what was the right answer?

 

[PooyaH]

I picked E...Notochord remains in higher chordata, but it becomes spinal column which is made of of bone and not as flexible anymore!

 

[osimsDDS]

the answer is E, but were arguing why B is not correct...haha

 

[HoangDDS]

yea its what i thought, the answer is E and let me tell you why its not B...straight from the book answer explanation:

The notochord gives support in lower chordates while in higher chordates the nearby cells of the mesoderm give rise to the vertebrae...

so basically its not the notochord in higher chordates that give rise to the vertebrae its the adjacent mesodermal cells...i think in schaum's it outlines it pretty well...basically there are cells very close to the notochord on the outside surrounding the notochord that give rise to vertebrae in higher chordates

hope that helps...

ahhhhh, thanks. That helps.

 

[Glycogen]

basically there are cells very close to the notochord on the outside surrounding the notochord that give rise to vertebrae in higher chordates

hope that helps...[/quote]
So,can we consider that as a result on induction then!?

 

[flycd05]

So I'm thinking its E over B because the notochord, in all chordates, becomes the internal support structure for the body. But only in higher chordata that the notochord forms the veteberal column.

so doesn't that mean that both E and B are true? The notochord is support in all chordates (higher and lower) but only in higher does it form the vertebrate column...am i missing something b/c it seems that both choices E and B are true according to this explanation?

 

[PooyaH]

Yeah it is kinda vague!

 

[klutzy1987]

reason why theyre saying B is false is because it is actually the mesoderm cells that give rise to the vertebrate no the notochord directly.

 

[harrygt]

I think B and E are both correct. Notochord DOES form the vertebrae in higher chordates.

 

[klutzy1987]

I think B and E are both correct. Notochord DOES form the vertebrae in higher chordates.

Thats what i said but the source says the answer is E so unless its kaplans i dunno what to say.

 

[Mstoothlady2012]

The answer is clearly E. Remember neural tube forms the CNS, notocord only plays a part in it. Notocord secretes something that induces neural plate to form a groove and form neural tube, which will later on form the CNS (brain + spinal cord).

I don't think question is confusing at all....

 

[td4azklz]

The answer is definitely E....

here's the reason why http://www.wisegeek.com/what-is-a-notochord.htm
🙂

 

[osimsDDS]

hmm just to throw something in there, i also think there is an inductive process that occurs between the notochord and mesoderm cells adjacent to the notochord in higher chordates...i believe the inductive process basically induces tissue (mesodermal tissue adjacent to the notochord) to start developing into the vertebrae (specialization of tissue)..i remember reading this somewhere but totally for and it just clicked haha

 

[Mstoothlady2012]

hmm just to throw something in there, i also think there is an inductive process that occurs between the notochord and mesoderm cells adjacent to the notochord in higher chordates...i believe the inductive process basically induces tissue (mesodermal tissue adjacent to the notochord) to start developing into the vertebrae (specialization of tissue)..i remember reading this somewhere but totally for and it just clicked haha

you sure mesodermal cells? should be ectodermal cells. Ectoderm forms CNS not mesoderm.

 

[yakuza]

This question comes straight out of Cliff's huh?

Here's what the actual book says about notochords

Notochord: Cells along the dorsal surface of the mesoderm germ layer form the notochord, a stiff rod that provides support in lower chordates. The vertebrae of higher chordates are formed from nearby cells in the mesoderm.

 

[Mstoothlady2012]

This question comes straight out of Cliff's huh?

Here's what the actual book says about notochords

Notochord: Cells along the dorsal surface of the mesoderm germ layer form the notochord, a stiff rod that provides support in lower chordates. The vertebrae of higher chordates are formed from nearby cells in the mesoderm.

read 3 more lines under it.

 

[yakuza]

read 3 more lines under it.

It looks fine to me, unless I'm missing something here

 

[osimsDDS]

you sure mesodermal cells? should be ectodermal cells. Ectoderm forms CNS not mesoderm.

in the question were talking about the notochord not the neural tube...the cells adjacent to the notochord are mesodermal and form the vertebrae in higher chordates while the cells of the neural tube form the CNS of the spinal cord which are derived from the ectoderm...what your saying is correct but it does not pertain to the question asked...

 

[Mstoothlady2012]

in the question were talking about the notochord not the neural tube...the cells adjacent to the notochord are mesodermal and form the vertebrae in higher chordates while the cells of the neural tube form the CNS of the spinal cord which are derived from the ectoderm...what your saying is correct but it does not pertain to the question asked...

aha!! you are right! sorry all this time I was mixing up vertebrae and spinal cord lol. Anyways either way yes notocord doesn't form any of those. Notocord induces mesodermal cells to form vertebrae and induces neural plate to form neural tube which forms CNS. Sorry again!😀