31. Invertebrates

Porifera and Cnideria

An introduction to cnidarians.

 This phylum has more species than any other phylum. 

 No. The phylum Arthropoda has more species than any other phylum. 

 All cnidarians except corals are in the medusa stage. 

 No. The life cycles of many cnidarians alternate between a feeding polyp and a reproductive medusa. 

 The bodies of cnidarians are bilaterally symmetrical and show cephalization. 

 No. The bodies of cnidarians are radially symmetrical and show no cephalization. 

 All of the listed responses are correct. 

 No. Only one of the statements is correct. 

 The bodies of its members are organized around a gastrovascular cavity. 

Think about the structure of the two body plans found in cnidarians.

Which of the following is true about the phylum Cnidaria?

 Sponges; Urochordata; scraping away organic films covering the rocks on which they grow 

 No. Urochordates are a chordate subphylum. 

 Leeches; Porifera; filtering tiny particles from water passing through their bodies 

 Bivalves; Annelida; killing small animals with electric shock 

 No. Bivalves are molluscan suspension feeders. 

 No. One of the other choices is correct. 

 Sea anemones; Cnidaria; using stinging cells to capture small animals that venture too close to them 

This group has special cells called cnidocytes.

__________ are members of the phylum __________ and feed by __________.

Short Video: Jelly Swimming

 No. This statement is true, but there is a better response. 

 They consist of two layers of cells with a noncellular gelatinous layer between them. 

 They have holes, or pores, in specialized cells, through which water enters. 

 None of the listed responses is correct. 

 No. At least one of the traits listed is characteristic of sponges. 

Sponges are the least complex animals.

Which of the following is/are characteristic of sponges?

 No. Sponges do not exhibit this degree of complexity. 

 No. Sponges lack a cavity in which digestion could take place. 

How do sponges spread into new regions?

Which of the following features is characteristic of the poriferan (sponge) body plan or life history?

the ability to make organic compounds from CO2 and water

Sponges lack __________.

5.5.4 Distinguish between Porifera, Cnidaria, Platyhelminthes, Annelida, Mollusca and Arthropoda

 No. Lining the inside of a spongocoel are flagellated choanocytes, which trap food particles. Nematocysts are stinging capsules that function in defense and in the capture of prey. 

 No. Neither of these types of animals can "see." Lining the inside of a spongocoel are flagellated choanocytes, which trap food particles. Nematocysts are stinging capsules that function in defense and in the capture of prey. 

Cnidocytes contain nematocysts that can be used in defense and/or feeding.

The choanocyte of a sponge and the nematocyst of a cnidarian both function in __________.

Short Video: Hydra eating Daphnia

Which of these choices is an example of homology (similarity due to common ancestry)?
a. suspension feeding in sponges and clams
b. ectoparasite lifestyle in aphids and ticks
c. cnidocytes (stinging cells) in jellyfish and sea anemones
d. radial symmetry in cnidarians and echinoderms

 No. All cnidarians, including coral, are predators. 

 Absorption of predigested food from their prey 

 Dinoflagellates (photosynthetic protists that live in the coral's tissues) 

 No. However, some corals do harbor photosynthetic endosymbionts. 

Corals are cnidarians.

Through what means do coral animals capture their food?

Phylum Cnidaria  - General Characteristics

Unit 14 - Sponges & Cnidaria

Which of these characteristics does not apply to cnidarians?
a. are diploblastic
b. possess a gastrovascular cavity with one opening
c. undergo metamorphosis
d. have a central nervous system

Phylum Cnidaria-Characteristics and Examples

 scraping bacteria and algae from hard substrates 

 No. Sponges lack the anatomy to do this. 

 paralyzing small crustaceans with stinging cells 

 No. Sponges do not have paralyzing structures. 

 absorbing nutrients from the guts of their hosts 

 No. Some sponges do harbor photosynthetic endosymbionts, but they still obtain the bulk of their nutrition from suspension feeding. 

Sponges move large amounts of water through the sides of their bodies.

Sponges feed by __________.

 No. Water that has been drawn into a sponge's central cavity exits via the osculum. 

 No. Sponges do not have a gastrovascular cavity. 

 No. The spongocoel is the central cavity of a sponge into which water flows and from which food is captured. However, food is not digested here. 

 No. Sponges do not have a gastrointestinal tract. 

How are tough skeletal fibers manufactured within the mesohyl?

Some digestion in sponges takes place in the __________.

 No. This is neither the motile nor the sessile stage referred to in this question. 

 No. The medusa is not an attached form. 

 No. This is a part of a cnidarian's body. 

Adult jellies ("jellyfish") exist in the medusa stage.

Some cnidarians go through both a motile stage and a sessile (attached) stage during their life cycle. The attached stage is called a(n) __________.

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