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Sponges, Cnidarians, and CtenophoresChapter 33
Table of Contents
Section 1 Porifera
Section 2 Cnidaria and Ctenophora
Section 1 PoriferaChapter 33
Objectives
• Describe the basic body plan of a sponge.
• Describe the process of filter feeding in sponges.
• Contrast the processes of sexual and asexual reproduction in sponges.
Section 1 PoriferaChapter 33
Body Plan of Sponges
• The phylum Porifera is made up of sponges.• Sponges are sessile invertebrates that have no true tissues or
organs. The simplest sponges are shaped like hollow cylinders.• The body wall of a sponge is composed of two layers of cells
that are separated by a jellylike substance called mesohyl.• Choanocytes in the interior layer draw water through the ostia
that penetrate the body wall. The water leaves through the osculum.
• The body is supported by a skeleton made of spongin, spicules, or both.
Chapter 33
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Visual Concept
Sponges
Section 1 Porifera
Chapter 33
Structure of a Sponge
Section 1 Porifera
Chapter 33
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Visual Concept
Parts of a Sponge
Section 1 Porifera
Chapter 33
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Collar Cells
Section 1 Porifera
Section 1 PoriferaChapter 33
Feeding and Digestion in Sponges
• Sponges feed by filtering small organisms and organic matter out of the water that passes through their body. This is called filter feeding.
• Nutrients are distributed through the body by amoebocytes, cells which crawl about within the body wall.
Chapter 33
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Feeding Habits of Sponges
Section 1 Porifera
Section 1 PoriferaChapter 33
Reproduction in Sponges
• Sponges can reproduce both asexually and sexually.• They reproduce asexually through:
– producing buds or gemmules– regeneration of missing parts
• They reproduce sexually through the joining of egg and sperm.
• Most sponges are hermaphrodites, which can produce both eggs and sperm.
Chapter 33
Sexual Reproduction in Sponges
Section 1 Porifera
Chapter 33
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Visual Concept
Reproduction in Sponges
Section 1 Porifera
Chapter 33
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Gemmules
Section 1 Porifera
Section 2 Cnidaria and CtenophoraChapter 33
Objectives
• Describe the basic body plan of a cnidarian.
• Summarize how cnidarians feed.
• Describe the nervous system of cnidarians.
• Identify and give examples of the four classes of cnidarians.
• Describe the common characteristics of ctenophores.
Section 2 Cnidaria and CtenophoraChapter 33
Body Plan of Cnidarians
• Animals in the phylum Cnidaria are radially symmetrical aquatic invertebrates that are more complex than the sponges. They have tissues and a few simple organs.
• The cnidairan body is either a sessile polyp or a swimming medusa. Some cnidarians alternate between both types during their life cycles.
• The body of a cnidarian consists of two cell layers:– an outer epidermis – an inner gastrodermis
• The layers are separated by the mesoglea.• The gastrovascular cavity has a single opening (the mouth)
surrounded by tentacles.
Section 2 Cnidaria and CtenophoraChapter 33
Feeding and Defense in Cnidarians
• Cnidarians have cells called cnidocytes.• Each cnidocyte contains a nematocyst.• When a cnidocyte is stimulated, its nematocyst ejects
a filament that can paralyze or ensnare prey.
Nervous System in Cnidarians• The cnidarian nervous system is a diffuse web of
interconnected nerve cells called a nerve net.
Section 2 Cnidaria and CtenophoraChapter 33
Classification of Cnidarians
The four classes of cnidarians are:• Class Hydrozoa
– This class includes Obelia, man-o-war, and the hydra.– Hydrozoans may live as polyps, medusae, or mixed colonies.
• Class Cubozoa– This class includes box jellies.– Cubozoans spend most of their lives as medusae.
• Class Scyphozoa– This class includes jellyfish.– Scyphozoans spend most of their lives as medusae.
• Class Anthozoa– This class includes sea anemones and corals.– Anthozoans live only as polyps.
Chapter 33
Reproduction in Obelia
Section 2 Cnidaria and Ctenophora
Chapter 33
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Movement of Hydra
Section 2 Cnidaria and Ctenophora
Chapter 33
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Reproduction in Hydras
Section 2 Cnidaria and Ctenophora
Chapter 33
Reproduction in Aurelia
Section 2 Cnidaria and Ctenophora
Chapter 33
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Reproduction in Jellyfish
Section 2 Cnidaria and Ctenophora
Chapter 33
Comparing Medusa and Polyp Bodies
Section 2 Cnidaria and Ctenophora
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Visual Concept
Chapter 33
Coral Reefs
Section 2 Cnidaria and Ctenophora
Section 2 Cnidaria and CtenophoraChapter 33
Phylum Ctenophora
• Animals in the phylum Ctenophora are known as ctenophores and often called comb jellies.
• Ctenophores move through the water by beating the cilia that occur in eight rows on the outside of their body.
• Ctenophores capture prey with a sticky substance secreted by their colloblasts.
• An apical organ at one end of the body enables ctenophores to sense their orientation in the water.
• Most ctenophores are hermaphroditic.• Many ctenophores have bioluminescence.
Chapter 33
Two Cnidarian Body Forms
Section 2 Cnidaria and Ctenophora
Chapter 33
Cnidarian Body Plan
Section 2 Cnidaria and Ctenophora
Chapter 33
Exploration of a Cnidarian
Section 2 Cnidaria and Ctenophora
Chapter 33
Development of Cnidarian Embryo
Section 2 Cnidaria and Ctenophora
Chapter 33
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Characteristics of Cnidarians
Section 2 Cnidaria and Ctenophora
Chapter 33
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Visual Concept
Cnidocyte
Section 2 Cnidaria and Ctenophora
Chapter 33
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Visual Concept
Types of Cnidarians
Section 2 Cnidaria and Ctenophora