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.
F) None of the above
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A) Asconoid sponges were derived from syconoid ancestors.
B) Leuconoid sponges were derived from syconoid ancestors.
C) Syconoid sponges were derived from leuconoid ancestors.
D) Syconoid sponges were derived from asconoid ancestors.
E) Leuconoid sponges were derived from asconoid ancestors.Syconoid sponges may have evolved through an asconoid body plan.All syconoid sponges,however,do not share a common ancestor.This transition to the syconoid stage may have occurred more than once.
G) A) and D)
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A) Origin of the metazoa has been clearly elucidated and involves ancestry from a colonial flagellate stock.
B) Metazoans are derived twice.One lineage involves a colonial flagellate stock,and the other lineage involves placozoan-like ancestors.
C) Metazoans arose from a multinucleate ciliate where cell boundaries eventually formed around each nucleus.
D) Placozoans may be similar to the single ancestral state.Features like their small nuclear genome and their large mitochondrial genome are features that may be derived from a common ancestor shared with some animal outgroups.The nuclear and mitochondrial genomes of the Placozoa suggest ancestry with animal outgroups.
F) None of the above
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A) the Devonian period or "age of fishes."
B) the early time of anaerobic prokaryotes.
C) the Cambrian period and probably earlier.
D) the time of the first prokaryotes but the sponges left no fossil evidence for lack of hard parts.Ancestral members of the phylum Porifera arose at least by the early Cambrian period and probably into Precambrian times.Later evolution resulted in diversification into the classes present today.
F) None of the above
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A) amoebocytes.
B) pinacocytes.
C) choanocytes.
D) spicules.
E) spongin.Spicules are supportive,calcareous structures in the body wall of many sponges.
G) B) and D)
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A) archaeocytes.
B) pinacocytes.
C) choanocytes.
D) spongocytes.
E) lophocytes.Sponge cells are specialized for specific functions.Archaeocytes are found in the mesohyl and phagocytize particles at the pinacoderm.They also receive food particles from choanocytes and may be specialized for other functions.
G) A) and E)
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A) They are sessile filter feeders
B) Their body wall has two incipient "cell layers"
C) Their flagellated collar cells move water
D) Water enters through the osculum
E) Amoeboid cells digest food and make skeletal fibers and gametes Water exits a sponge through the osculum.
G) A) and B)
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A) sharing food produced by symbiotic algae in their diffuse tissues.
B) gliding over their food,secreting enzymes,and absorbing products.
C) filtering food that moves through them in tiny pores.
D) taking food in through a ventral tube,digesting it,and expelling wastes back out the tube.
E) taking food in through a central tube,digesting it,and moving wastes out the anus.Placozoans lack organs,including digestive organs.They secrete digestive enzymes as they glide over their food.Products of digestion are absorbed by the ventral epithelium.
G) B) and D)
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A) Silica is washed away and the calcium carbonate remains
B) Spongin spicules are washed away and the silky silica remains
C) The choanocytes and amoebocytes are softer
D) Bath sponge support is provided primarily by spongin proteins
E) All of the choices are correct Spongin is a soft protein present in the body wall of bath sponges.Bath sponges lack calcareous or siliceous spicules.
G) A) and B)
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