Transcript Chapter 33 Sponges, Cnidarians, and Ctenophores Table of Contents Section 1 Porifera Section 2 Cnidaria and Ctenophora.

Chapter 33
Sponges, Cnidarians, and
Ctenophores
Table of Contents
Section 1 Porifera
Section 2 Cnidaria and Ctenophora
Chapter 33
Section 1 Porifera
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.
Chapter 33
Section 1 Porifera
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
Section 1 Porifera
Sponges
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Chapter 33
Section 1 Porifera
Structure of a Sponge
Chapter 33
Section 1 Porifera
Parts of a Sponge
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Chapter 33
Section 1 Porifera
Collar Cells
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Chapter 33
Section 1 Porifera
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
Section 1 Porifera
Feeding Habits of Sponges
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Chapter 33
Section 1 Porifera
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
Section 1 Porifera
Sexual Reproduction in
Sponges
Chapter 33
Section 1 Porifera
Reproduction in Sponges
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Chapter 33
Section 1 Porifera
Gemmules
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Chapter 33
Section 2 Cnidaria and
Ctenophora
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.
Chapter 33
Section 2 Cnidaria and
Ctenophora
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.
Chapter 33
Section 2 Cnidaria and
Ctenophora
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.
Chapter 33
Section 2 Cnidaria and
Ctenophora
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
Section 2 Cnidaria and
Ctenophora
Reproduction in Obelia
Chapter 33
Section 2 Cnidaria and
Ctenophora
Movement of Hydra
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Chapter 33
Section 2 Cnidaria and
Ctenophora
Reproduction in Hydras
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Chapter 33
Section 2 Cnidaria and
Ctenophora
Reproduction in Aurelia
Chapter 33
Section 2 Cnidaria and
Ctenophora
Reproduction in Jellyfish
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Chapter 33
Section 2 Cnidaria and
Ctenophora
Comparing Medusa and Polyp Bodies
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Chapter 33
Coral Reefs
Section 2 Cnidaria and
Ctenophora
Chapter 33
Section 2 Cnidaria and
Ctenophora
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
Section 2 Cnidaria and
Ctenophora
Two Cnidarian Body Forms
Chapter 33
Section 2 Cnidaria and
Ctenophora
Cnidarian Body Plan
Chapter 33
Section 2 Cnidaria and
Ctenophora
Exploration of a Cnidarian
Chapter 33
Section 2 Cnidaria and
Ctenophora
Development of Cnidarian Embryo
Chapter 33
Section 2 Cnidaria and
Ctenophora
Characteristics of Cnidarians
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Chapter 33
Section 2 Cnidaria and
Ctenophora
Cnidocyte
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Chapter 33
Section 2 Cnidaria and
Ctenophora
Types of Cnidarians
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