question about CaCO3

[nicz888]

---

Members don't see this ad.

question out of Kaplan pratice test

which of the following possess exoskeletons made of calcium carbonate?

a. Lobsters
b. Insects
c. Snails
d. Scorpions
e. Spiders

the answer choice was c
but i disagree because a,b are true as well.

why?

 

[iwannabadentist]

Don't A and B, which are arthropods, have an exoskeleton made up of chitin?
🙂

 

[whc235]

uhhh i think snail has..a mantle or something.. and that's made of calcium carbonate.. the rest of the choices are all made of chitin in their exoskeleton.

 

[PooyaH]

Don't A and B, which are arthropods, have an exoskeleton made up of chitin?
🙂

👍

Arthropods possess chitinous exoskeletons while Mollusca (such as snails) have calcareous exoskeletons.

 

[nicz888]

i am confuse

here

Arthropods are characterized by their jointed limbs and cuticles, which are mainly made of α-chitin; the cuticles of crustaceans are also biomineralized with calcium carbonate.

and

Molluscs have such a varied range of body structures that it is difficult to find defining characteristics that apply to all modern groups. The two most universal features are a mantle with a significant cavity used for breathing and excretion, and the structure of the nervous system. As a result of this wide diversity, many textbooks base their descriptions on a hypothetical "generalized mollusc". This has a single, "limpet-like" shell on top, which is made of proteins and chitin reinforced with calcium carbonate, and is secreted by a mantle that covers the whole upper surface

so?

 

[whc235]

Well im looking at my bio book this is how i interpreted it..

cuticle of arthropods = their exoskeleton.. and is made of chitin and protein
a layer over the cuticle = not the exoskeleton.. is the Calcium carbonate.

 

[dl9006]

lol i don't think you can argue with facts

just memorize it

everything there is a member of arthropod family except c