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Questions and Answers
What is the primary function of the micropyle in the context of gemmules?
What is the primary function of the micropyle in the context of gemmules?
Which type of sponges are characterized as viviparous?
Which type of sponges are characterized as viviparous?
What environmental conditions can gemmules withstand?
What environmental conditions can gemmules withstand?
In which reproductive method do all sponges have the ability to participate?
In which reproductive method do all sponges have the ability to participate?
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What occurs during the mass population event of Oviparous sponges?
What occurs during the mass population event of Oviparous sponges?
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Which characteristic distinguishes oviparous sponges from viviparous ones?
Which characteristic distinguishes oviparous sponges from viviparous ones?
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What type of chamber contains choanocytes that produce sperm in viviparous sponges?
What type of chamber contains choanocytes that produce sperm in viviparous sponges?
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What is the role of nurse cells in the reproduction of Oviparous sponges?
What is the role of nurse cells in the reproduction of Oviparous sponges?
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What is a characteristic feature of the flagellated larvae produced by viviparous sponges?
What is a characteristic feature of the flagellated larvae produced by viviparous sponges?
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Which cell type forms the outer layer of the sponge body?
Which cell type forms the outer layer of the sponge body?
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What is unique to the leuconoid canal system compared to other canal systems in sponges?
What is unique to the leuconoid canal system compared to other canal systems in sponges?
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Which statement about the syconoid canal system is true?
Which statement about the syconoid canal system is true?
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What process do archaeocytes undergo during asexual reproduction to form gemmules?
What process do archaeocytes undergo during asexual reproduction to form gemmules?
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What is the primary function of choanocytes in sponges?
What is the primary function of choanocytes in sponges?
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Which type of canal system is most common in sponges?
Which type of canal system is most common in sponges?
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What role do sclerocytes play in sponge anatomy?
What role do sclerocytes play in sponge anatomy?
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What type of sponge canal system would you expect to have numerous small oscula?
What type of sponge canal system would you expect to have numerous small oscula?
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In sponges, what is the gelatinous matrix called that supports the cell types?
In sponges, what is the gelatinous matrix called that supports the cell types?
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Which of the following cell types is involved in the ingestion process in sponges?
Which of the following cell types is involved in the ingestion process in sponges?
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What defining characteristic distinguishes cnidarians from other animal phyla?
What defining characteristic distinguishes cnidarians from other animal phyla?
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How many germ layers are present in cnidarians?
How many germ layers are present in cnidarians?
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Which of the following structures is responsible for the stinging reaction in cnidarians?
Which of the following structures is responsible for the stinging reaction in cnidarians?
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What type of symmetry do cnidarians display?
What type of symmetry do cnidarians display?
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What is the function of the gastrovascular cavity in cnidarians?
What is the function of the gastrovascular cavity in cnidarians?
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Which group of organisms are classified as eumetazoans, alongside cnidarians?
Which group of organisms are classified as eumetazoans, alongside cnidarians?
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Which of the following is a feature of the polyp form in cnidarians?
Which of the following is a feature of the polyp form in cnidarians?
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Which type of organism does NOT belong to the same cellular organization as cnidarians?
Which type of organism does NOT belong to the same cellular organization as cnidarians?
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The ancestral metazoan is represented by which type of organism?
The ancestral metazoan is represented by which type of organism?
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What type of organism is characterized by a gastrovascular cavity with a single opening?
What type of organism is characterized by a gastrovascular cavity with a single opening?
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Study Notes
Introduction
- Two body forms: polyp and medusa
- Two germ layers: ectoderm and endoderm
- Radial symmetry
- Gastrovascular cavity (enteron) with a single opening, surrounded by tentacles
- Cnidocytes contain cnidae
Phylum Porifera - Sponges
- Polymorphic organisms: sponges
- Cell types: porocytes, archaeocytes, pinacocytes, sclerocytes, and choanocytes
Canal Systems
- Three major canal system types: asconoids, syconoids, and leuconoids
Asconoids
- Flagellated spongocoels: water flows through the spongocoel
- Osculum: a single excurrent canal
- Ostia: many small incurrent canals
- Porocytes: cells that allow water to pass through the body wall
- Choanocytes: flagellated cells lining the spongocoel that create water currents
- Pinacocytes: flattened cells that line the outer surface of the sponge
Syconoids
- Flagellated canals: water flows through canals
- Prosopyle: openings that connect the incurrent canals to radial canals
- Choanocyte canals (radial canals): canals lined with choanocytes
- Apopyle: opening that connects the radial canal to the spongocoel
- Spongocoel: central cavity that is not lined with choanocytes
Leuconoids
- Flagellated chambers: water flows through chambers lined with choanocytes
- No spongocoel
- Often have more than one osculum
Reproduction
- All sponges reproduce asexually and sexually
Asexual Reproduction
- Gemmules:
- Archaeocytes cluster together inside the sponge and phagocytose other cells to store nutrients
- Cells on the outer perimeter secrete a thick protective covering of spongin with microsclere (capsule)
- Fragmentation: a piece of the sponge breaks off and grows into a new sponge
- Budding: a small outgrowth on the sponge grows into a new sponge
Sexual Reproduction
- Viviparous sponges: Usually monoecious
- Sperm formed from choanocytes (spermatocysts = special flagellated chamber) and released to the environment
- Eggs formed from archaeocytes (sometimes choanocytes), distributed throughout mesohyl
- Parenchymula: flagellated larvae
- Oviparous sponges: Usually dioecious
- Release egg and sperm to the environment (usually a mass population event at one time of the year)
- Fertilization and development occur in the environment
- Eggs with nurse cells snag sperm of other individuals and soon become negatively buoyant and sink
Gemmule
- It is a well developed system for freshwater sponges.
- The habitat is prone to seasonal freezing and periodic dessication.
- A gemmule can withstand dessication, freezing temperatures, and low oxygen.
- When environmental conditions are favorable, archaeocytes leave the gemmule through the micropyle (opening in the gemmule) and differentiate into a new individual.
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