question about CaCO3

[nicz888]

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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