Invertebrates: Parazoa and Eumetazoa

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Questions and Answers

What is a defining characteristic of sponges in the phylum Porifera?

Symmetrical body structure

Presence of true tissues and organs

Ability to move freely in the water

Absence of a nervous system (correct)

Which reproductive method is NOT associated with sponges?

Fragmentation

Sexual reproduction with flagellated larvae

Binary fission (correct)

Asexual reproduction by budding

What structure allows water to flow out of a sponge?

Canals

Osculum (correct)

Pores

Spongocoel

Which of the following describes the body structure of sponges?

Asymmetrical body with two cell layers Signup and view all the answers

What type of organism are sponges classified under?

Parazoa Signup and view all the answers

Which of the following statements about sponge skeletal structure is true?

Composed of collagen and other materials like siliceous spines Signup and view all the answers

How does a sponge obtain nutrition?

Through intracellular digestion Signup and view all the answers

Which statement best describes the habitat of sponges?

Most are marine and some live in freshwater Signup and view all the answers

What is the primary function of porocytes in asconoid sponges?

To form incurrent pores Signup and view all the answers

Which canal system type features a spongocoel lined entirely by choanocytes?

Asconoid Signup and view all the answers

What differentiates leuconoid sponges from asconoid and syconoid types?

Additional folding of the choanoderm Signup and view all the answers

What role do choanocytes play in the sponge's aquiferous system?

Generating water flow Signup and view all the answers

How do syconoid sponges differ from asconoid sponges in structure?

They possess a thicker mesohyl and more complex folding Signup and view all the answers

What is the function of the apopyle in syconoid sponges?

To channel water into excurrent canals Signup and view all the answers

What characterizes the leuconoid canal system's flagellated surfaces?

They are large in number but small in size due to subdivision Signup and view all the answers

Which of the following statements is true about the dermal pores in syconoid sponges?

They consist of more than one cell Signup and view all the answers

What is the main function of porocytes in sponges?

To regulate water circulation Signup and view all the answers

What type of cells are choanocytes primarily responsible for?

Creating a flow of water and trapping food Signup and view all the answers

Gemmules serve which function in sponges?

To survive harsh conditions Signup and view all the answers

Which of the following components primarily contributes to the fibrous skeletal structure of a sponge?

Collagen fibrils (spongin) Signup and view all the answers

How do most sponges reproduce sexually?

Via cross-fertilization of gametes Signup and view all the answers

Which statement about archaeocytes is correct?

They digest food and distribute nutrients Signup and view all the answers

Which type of spicules are primarily made of calcium carbonate?

Limestone spicules Signup and view all the answers

What is a key feature of sponge asexual reproduction?

Regeneration from broken fragments Signup and view all the answers

Study Notes

Classification of Invertebrates

Kingdom Animalia consists of Parazoa and Eumetazoa
Parazoa includes Phylum Porifera, which encompasses sponges
Eumetazoa includes animals with true tissues and organs

Characteristics of Phylum Porifera

Approximately 9,000 sponge species, ranging from 1 cm to 2 m in height; primarily marine, with about 100 freshwater species
Multicellular organisms lacking true tissues and organs, with various differentiated cell types
Body structure resembles a sac with pores, canals, and chambers for water transport
Water enters through pores into the spongocoel and exits via the osculum
More complex sponges feature branched canals and multiple oscula

Sponge Body Structure

Body is asymmetrical with two cell layers: outer epidermis and inner endoderm, separated by mesenchyme (mesohyl)
Mesenchyme contains skeletal elements and cells like archaeocytes and amebocytes

Key Cell Types in Sponges

Pinacocytes: Thin cells covering the sponge's surfaces
Porocytes: Regulate water flow via contractile tubes
Amebocytes (archaeocytes): Digest food and distribute nutrients
Choanocytes (collar cells): Flagellated cells creating water flow and capturing food particles

Sponge Skeletal Structure

Skeleton can be fibrous (collagen spongin) or rigid (calcareous or siliceous spicules)
Silica spicules: Glass-like structures
Limestone spicules: Composed of calcium carbonate

Reproduction in Sponges

Most sponges are hermaphrodites, producing both sperm and eggs
Sexual reproduction involves gametes from choanocytes or amebocytes, with cross-fertilization and development of flagellated larvae
Asexual reproduction occurs through regeneration and budding from broken fragments

Surviving Harsh Conditions

Gemmules: Specialized structures containing food and amebocytes, can survive extreme temperatures
Gemmules can develop into adult sponges when conditions improve

Canal Systems in Porifera

Sponges have a simple water canal system with tiny openings (ostia) for water intake and larger openings (oscula) for water release
Three types of canal systems:
- Asconoid: Simplest form with continuous spongocoel lined by choanocytes
- Syconoid: Features simple folding, with distinct choanocyte chambers
- Leuconoid: Most complex, with highly subdivided chambers for increased flagellated surface area

Water Flow Through Sponges

Water flow mechanisms are essential for feeding, as sponges are suspension feeders, trapping particles from the water passing through their systems

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Description

Explore the fascinating world of invertebrates, focusing on Parazoa such as Porifera and the structures of Eumetazoa. This quiz covers categories like Protozoa, Metazoa, and key examples including amoeba and sponges. Perfect for students studying animal classification.