Deck 12: Sponges and Placozoans

Question 1

Which one of the following statements regarding metazoan origins is true?

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.

Answer 1

C

Question 2

Specialized archaeocytes that secrete spongin are

A)collencytes.
B)sclerocytes.
C)choanocytes.
D)spongocytes.
E)lophocytes.Spongocytes are archeocytes specialized for secreting spongin.

Answer 2

D

Question 3

The sponges date back to

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.

Answer 3

C

Question 4

The outer thin,flat,epithelial-like cells that cover the outside and some inside surfaces of sponges,are

A)amoebocytes.
B)pinacocytes.
C)choanocytes.
D)spicules.
E)spongin.Pinacocytes line the outer surface of the body wall of sponges.They may ingest food by phagocytosis and many are contractile to help regulate water flow.

Question 5

Cells responsible for water flow and capture of some particles are the

A)myocytes.
B)archaeocytes.
C)choanocytes.
D)pinacocytes.
E)lophocytes.Choanocytes are responsible for water flow and capture of some food particles.

Question 6

Calcareous or siliceous elements of the sponge body wall provide support.These elements are called

A)amoebocytes.
B)pinacocytes.
C)choanocytes.
D)spicules.
E)spongin.Spicules are supportive,calcareous structures in the body wall of many sponges.

Question 7

Specialized archaeocytes that secrete large quantities of collagen are

A)collencytes.
B)sclerocytes.
C)choanocytes.
D)spongocytes.
E)lophocytes.Lophocytes are archeocytes specialized for secreting collagen.

Question 8

The most complex and the most common body form of sponges is found in the

A)asconoids.
B)leuconoids.
C)syconoids.Leuconoid sponges include the largest,most common,and most complex sponges.

Question 9

The structural protein found in all sponges is

A)elastin.
B)collagen.
C)gorgonin.
D)spiculin.
E)None of the choices is correct Collagen is a connective protein common to all sponges.

Question 10

The modified cells of sponges that form circular bands and provide just a little constriction to control water flow are

A)amoebocytes.
B)choanocytes.
C)spicules.
D)myocytes.Myocytes are modified pinacocytes and constrict to regulate water flow.

Question 11

Flagellated canals of syconoid sponges form by evagination of the body wall and these sponges often develop through a simple vase-like stage.Which of the following is a logical hypothesis based on this evidence?

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.

Question 12

Cells that move about in the mesohyl,digest particles,and may specialize for other functions are the

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.

Question 13

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.

Question 14

The extracellular matrix found in sponges is

A)spongin.
B)collagen.
C)pinacoderm.
D)mesohyl or mesenchyme.The gelatinous extracellular matrix,called mesohyle or mesenchyme,contains fibrils,skeletal elements and ameboid cells.

Question 15

Specialized archaeocytes that secrete spicules are

A)collencytes.
B)sclerocytes.
C)choanocytes.
D)spongocytes.
E)lophocytes.Archaeocytes may be specialized as sclerocytes,which secrete spicules.

Question 16

A sponge feeds by

A)using a net and a current that sweeps food particles through it.
B)squeezing the spongocoel cavity to suck debris in and out through the osculum.
C)beating the flagella of collar cells to form a current;food is absorbed by collar cells.
D)beating the flagella of collar cells to form a current from osculum to pores;food is engulfed by amoebocytes in the central cavity of the sponge.Beating of flagella of collar cells creates water currents that circulate water through the body of a sponge.Water currents bring microscopic food particles into the canal system of a sponge.Food particles are filtered by collar cells.

Question 17

The simplest of canal systems is found in the

A)asconoids.
B)leuconoids.
C)syconoids.The asconoid sponge body form is the simplest of the sponge body forms.Larger,more complex sponge body forms are syconoid and leuconoid.

Question 18

The order in which a drop of ink would pass by the structures in an ascon sponge is

A)spongocoel-ostia-osculum.
B)osculum-spongocoel-ostia.
C)osculum-ostia-spongocoel.
D)ostia-spongocoel-osculum.
E)ostia-osculum-spongocoel.The pathway for water moving through the simplest sponge body form is ostia-spongocoel-osculum.In sycon sponges incurrent and radial canals are present.In leucon sponges the spongocoel is often absent.

Question 19

Concerning producing larger organisms without cellular differentiation,

A)nature has never evolved larger organisms because it would never work.
B)nature has evolved larger unicellular organisms but they are rare and have surface-to-volume limitations.
C)this has never occurred since the ancestral cell was small.
D)the more derived the organism,the more differentiated and the smaller the cell size.
E)the more primitive the organism,the smaller the cell size.Larger size and complexity is accomplished through multicellularity.A workable surface-to-mass ratio in an increasingly large single cell cannot be maintained.

Question 20

Which statement about adult sponges is false?

A)Their bodies are aggregations of one cell type.
B)They do not have a mouth.
C)Their bodies are usually asymmetrical.
D)Their apparently simple structure is deceptive.Sponge bodies are aggregates of many cell types.Even though they lack mouths and other features of more complex animals,their apparent simplicity is deceptive.

Question 21

Which of the following statements about sponges is NOT correct?

A)Larvae are ciliated and swim to new locations
B)Sponges are classified by spicule type and material
C)Sponges comprise a sister group to all other animals
D)Sponges share few characteristics with other animals
E)Sponge cells can transform from one cell type to another,a trait not seen in other kinds of animals Sponges share many characteristics with other animals including the following: common adhesion proteins,a common blastula embryonic stage,and common cell signaling proteins.

Question 22

If a sponge is fragmented and cells are dissociated from one another,the cells will

A)reproduce sexually.
B)die from being separated.
C)form spicules in the pattern of the cloth.
D)reorganize their structure and function,and clumps of isolated cells will form a new sponge.Sponges have remarkable powers of regeneration from fragments of an organism and can undergo somatic embryogenesis when cells are dissociated into clumps of cells.

Question 23

Out of all metazoans,members of __________________ have the smallest nuclear genome but the largest mitochondrial genome.

Question 24

The unique feature of sponge development in members of the class Calcarea is the amphiblastula which

A)produces new buds.
B)generates gemmules.
C)determines the types of spicules produced.
D)turns inside out during its development.
E)controls the process of regeneration.The amphiblastula is a developmental stage in members of the class Calcarea.It is also present in a few members of the class Demospongia.

Question 25

The demosponges

A)constitute only a small number of species.
B)are mostly marine but include the freshwater sponges.
C)have the asconoid-type canal system.
D)are referred to as calcium or chalk sponges.
E)form the most beautiful glass spicule patterns.Members of the class Demospongia are the most common sponges.Most are large,leuconoid sponges.

Question 26

Molecular data support the hypotheses that metazoans have a single origin or are _________________.

Question 27

Which of the following statements about sponges is NOT correct?

A)Sponges lack nerve fibers
B)Sponges lack fully developed muscle fibers
C)Ameboid cells capture food particles from the water
D)Sponges reproduce asexually by budding or by regeneration from a small piece
E)If a sponge is fragmented and cells dissociate,cells undergo somatic embryogenesis and clumps of cells can form a new organism Choanocytes create water currents,capture food,and pass food on to ameboid cells.

Question 28

Which is NOT a trait of sponges?

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.

Question 29

The water outlet in sponges is known as a/an __________________.

Question 30

In most sponges,the free-swimming larva produced by sexual reproduction is called a(n)

A)bud.
B)gemmule.
C)apopyle.
D)parenchymula.
E)plasmodium.Parenchymula larvae are free-swimming larval stages that are the result of sexual reproduction and that are found in the development of most sponges.Gemmules are internal buds formed by a type of asexual reproduction in freshwater sponges and some marine sponges.

Question 31

Why are bath sponges so soft?

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.

Question 32

The tough protein fibers sometimes found in sponge skeletons are of a substance called _____________.

Question 33

The largest impact that the loss of sponges would have on the environment would be

A)collapse of most food chains.
B)extinctions of other species that are symbionts of sponges.
C)alteration of ocean currents.
D)alteration of gases in water and the atmosphere.
E)loss of filtration.Large sponges can filter up to 1,500 liters of water each day.Loss of this filtering would adversely affect water quality in marine habitats.

Question 34

The minute,needle-like structures that act as a skeletal support system in sponges are called _________________.

Question 35

Placozoans feed by

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.

Question 36

The flagellated cells embedded in the mesohyl of a sponge are called ___________________.Choanocytes line the spongocoel and flagellated chambers of sponges.They propel water through a sponge and filter food from the water.

Question 37

Which of the following is NOT found in at least some sponges?

A)Spicules of calcium carbonate
B)Spicules of silica
C)Spicules of fibrous protein
D)Spongin,a fibrous protein Skeletal elements of sponges include calcareous and siliceous spicules and the protein,spongin.

Question 38

Reproduction in at least some sponges is

A)asexual by budding.
B)asexual by gemmules.
C)sexual with both male and female sex cells in one individual.
D)asexual by fragmentation.
E)All of the choices are correct Sponges reproduce sexually and asexually.Specific reproductive mechanisms are group specific and may involve one or more of the methods described in this question.

Question 39

Placozoans

A)are flat,plate-like animals with no symmetry.
B)are probably advanced mesozoans.
C)have calcareous spicules.
D)have three germ layers.Placozoans lack symmetry and any organs,muscular,and nervous tissues.Their dorsal and ventral epithelial layers may be ectodermal and endodermal tissue layers,thus some zoologists consider placozoans to be diplobastic.

Question 40

In glass sponges,archaeocytes fuse their pseudopodia to form a

A)bud.
B)spongin network.
C)micropyle.
D)leuconoid framework.
E)trabecular reticulum.Hexactinellid sponges possess a unique syncytial body wall.All cells fuse into a single,multinucleate syncytum called the trabecular reticulum.

Question 41

New evidence suggests that the calcarea belong to a clade separate from other sponges.Discuss the evidence upon which this idea is based.

Question 42

Explain the unique attributes of hexactinellids as compared to other sponges.

Question 43

Describe the characteristics of the Phylum Porifera.Which of those characteristics support the contention that the sponges are the basal group of the Animal kingdom?

Question 44

About 95% of the sponges belong to the class __________.

Question 45

Deep-sea sponges with six-rayed siliceous spicules and a trabecular reticulum belong to the ______________.Hexactinellids are sponges with six-rayed spicules and a trabecular reticulum.

Question 46

About 80% of particulate organic carbon in the marine environment is in the form of the smallest particles that sponges can consume,and phagocytosis of these particles is carried out by the ____________.Choanocytes create water currents and filter particulate food matter from the water.

Question 47

The simplest body plan of sponges is ____________,and the plan characterized by flagellated canals is leuconoids.

Question 48

All digestion in sponges is intracellular and is carried out by the ____________________.

Question 49

Sponge beds have been heavily "fished" for bath sponges and in other cases pollution or an imbalance in organisms has devastated other sponge beds.What is the likely overall consequence of this in the ocean environment?

Question 50

There are a few marine sponges that are large enough that a small person could crawl inside.Would you have to worry about your tissues being digested?

Question 51

Internal buds of freshwater sponges that can withstand adverse conditions are ____________________.Gemmules are found in freshwater and a few marine sponges.They are internal buds that withstand harsh environmental conditions.

Question 52

Explain the concept of monophyly as it applies to the animals.How do the relationships of placozoans and poriferans,as explained in this chapter,contribute to our understanding of the base of the animal tree shown on the inside cover of the book?

Question 53

Thin,epithelial-type cells covering the outer surface of sponges are the ________________.