research about starfish

[Priya]

I would like to have anwers on the following questions:

1. What sort of mouth of mouthparts has it to capture its food

2. What sense organs does it have to locate its food

3. Does it have the same food for all its life

4. Does it change in appearance or behaviour during its breeding season

5. How many youg does a pair of these animals produce in a year

 

i urgently need this anwers to do my assignment

[ecoli]

Just so you know, the PC term for them is now Sea Stars, because they aren't really fish.

 

http://oceanlink.island.net/oinfo/biodiversity/seastars.html

http://en.wikipedia.org/wiki/Starfish

[daneeka]

... but a startfish is probably closer to a fish than a seahorse is to a horse.

[ecoli]

... but a startfish is probably closer to a fish than a seahorse is to a horse.

 

True, but a seastar *may* be more closely related to a horse than a seahorse. (not entirely sure about that, but they're both deuterostomes, while a sea horse is a protostome.)

[Mokele]

Um, that's all backwards.

 

A seahorse is a fish, and therefore shares a common ancestor with the horse about 370 mya. The starfish, on the other hand, is a totally different phylum, and has not shared a common ancestor with fish, horses, or any other vertebrate for 530 my.

 

So technically, a sea-horse is more closely related to a horse than a star-fish is related to a fish.

 

Also, fish (including seahorses), all other vertebrates, echinoderms, and an odd phylum called the Chaetognathes are all deuterostomes.

 

Mokele

[ecoli]

Also, fish (including seahorses), all other vertebrates, echinoderms, and an odd phylum called the Chaetognathes are all deuterostomes.

 

Yep, of course that's right. I guess I had a brain fart or something.

[daneeka]

Hah, nice. But while, on a phylogenetic basis, a sea horse is closer to a horse than a sea star is to a fish, such relatedness is irrelevant in assigning commmon names to present taxa because common names are rarely based on phylogenies. The point is that calling a starfish a starfish is not erroneous, and anyone suggesting a common name change based on systematics is just being unessarily pedantic, because anyone interested in a species' taxonomy would use the binomial anyway.