Which one of the following statements regarding the origin of metazoans has the most support?
A) The choanoflagellates share features with the sponges,like having collars of microvilli surrounding a flagellum and being colonial.These shared features suggest a link to at least one metazoan lineage.
B) Metazoans are derived from many separate lineages of unicellular organisms.
C) Ancient metazoans,similar to members of the phylum Placozoa,have been ruled out as ancestral metazoans.
D) Modern sponges have a genetic makeup that reflects their ancestral status.The origin of the metazoa is problematic.Morphological and functional similarities of sponges to choanocytes suggest a possible origin of that metazon lineage,however,the sponge genome is quite complex with more modern features.Placozoans have genetic features that suggest they may reflect the primitive state.
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Q8: The most complex and the most common
Q9: The structural protein found in all sponges
Q10: The modified cells of sponges that form
Q11: Flagellated canals of syconoid sponges form by
Q12: Cells that move about in the mesohyl,digest
Q14: The extracellular matrix found in sponges is
A)spongin.
B)collagen.
C)pinacoderm.
D)mesohyl
Q15: Specialized archaeocytes that secrete spicules are
A)collencytes.
B)sclerocytes.
C)choanocytes.
D)spongocytes.
E)lophocytes.Archaeocytes may
Q16: A sponge feeds by
A)using a net and
Q17: The simplest of canal systems is found
Q18: The order in which a drop of
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