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Questions and Answers
What is the main characteristic of the spongocoel in sponges?
Which type of sponge body plan is characterized by a simple, large cavity with a straightforward water flow pathway?
What distinguishes Class Calcispongiae within the phylum Porifera?
In terms of reproductive strategies, which statement accurately describes sponges?
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Which of the following correctly describes the feeding process in sponges?
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What is the scientific name for the species commonly known as modern humans?
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Which of the following reproductive strategies do sponges utilize?
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Which characteristic describes the body plan of sponges in Phylum Porifera?
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What type of habitat do encrusting sponges typically thrive in?
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How do sponges primarily extract oxygen from their environment?
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What is a distinctive feature of the cellular organization of sponges?
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Which statement is true regarding sponge larvae?
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How do sponges primarily excrete waste products?
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What is the main function of the pinacoderm in sponges?
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Which of the following structures provides elasticity and resilience to sponges?
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What are the two types of spicules mentioned, and how do they differ?
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Which cell type in sponges is responsible for digestion and nutrient transport?
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What role do ostia play in the sponge body plan?
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How do Lophocytes contribute to the sponge's structure?
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What is a characteristic feature of free-standing sponges?
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What distinguishes Archaeocytes from other sponges' cells?
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Study Notes
Porifera
- Sponges are the most basal animal group, meaning they are the simplest and most ancient
- Sponges are sessile filter feeders that are bound to the seabed, characterized by bearing pores on their body
- Sponge larvae are pelagic and planktonic
- Sponges are mostly marine (8600+ species) but can be freshwater (150+ species)
Poriferan Body Plan
- Sponges have a cellular grade of organization, meaning they lack true organs and tissues
- Sponges are asymmetrical or radial, meaning they lack a defined body plan
- Sponges lack true germ layers and a developmental pattern
- Sponges lack a true coelom
Poriferan Digestion, Respiration, and Excretion
- Sponges digest food intracellularly through choanocytes engulfing food particles, before being digested within amoebocytes
- Sponges respire via diffusion across cell membranes as cells absorb oxygen through water flowing into the body
- Sponges excrete via diffusion, with ammonia diffusing out of cells and carried away by the current
Poriferan Reproduction
- Asexual reproduction: gemmulation, budding, and fragmentation
- Sexual reproduction: external, with gametes being fertilized in the water, resulting in planktonic larvae
- Sponges are typically dioecious (separate sexes)
Types of Sponges
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Encrusting:
- Grow as thin, spreading layers that adhere closely to surfaces
- Found in high-energy environments with stronger water currents
- Often found in rocky intertidal zones and coral reefs
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Free-Standing:
- Grow in various three-dimensional shapes, including barrel, tube, vase, or branching forms
- Independent from substrates and often taller, allowing for enhanced filtration
Spongocoel
- The central cavity of the sponge where water collects
- Not a true coelom
- Asconoid: Simple, large cavity, with a straightforward water flow pathway
- Syconoid: Surrounded by a more complex canal system, where water passes through radial canals before reaching it
- Leuconoid: Reduced or absent due to a complex network of flagellated chambers
Suspension-Feeding
- Water enters from the canals of pore cells in pinacoderm
- Water enters the spongocoel
- Collars of choanocyte trap food particles
- Food vacuoles envelope trapped food (phagocytosis)
- Protein molecules taken in (pinocytosis)
- Water exits the sponge via the large osculum
Class Calcispongiae
- Also known as Calcarea
- Small (2m in diameter)
Class Cubozoa
- Voracious predators that are known for their potent venom, complex eyes, and more active swimming style
- Usually small, with a cube- or box-like shape with tentacles hanging from each corner
- Reproduction: A complex life cycle that includes a polyp stage and a dominant medusa stage
- Can be either dioecious or hermaphroditic depending on the species
Pinacoderm
- The outermost, protective layer of the sponge, consisting of pinacocytes
- Helps regulate water flow by controlling the size of the ostia
- Water enters the spongocoel through the many ostia, and exits through one single osculum
Mesohyl
- A gelatinous, protein-rich extracellular matrix that fills the space between the outer pinacoderm and the inner layers (ex. choanocyte layer)
- Acts as a connective tissue that houses various cells and skeletal components, providing structural support and helping with internal transport of waste and nutrients
- Spongin - collagen-based protein fibers that provide structural support and give the sponge elasticity and resilience
- Spicules - Structural elements secreted by sclerocytes that provide support and defense, acting as a kind of internal skeleton for the sponge
- Calcareous: Made up of calcium carbonate, making it more fragile and less durable in acidic or deep-sea environments
- Siliceous: Made up of silica and can act as optic fibers, which allows light to be transmitted
Cells
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Pinacocytes:
- Flat, thin protective cells that help maintain the sponge’s shape
- Minor movement and contraction of the body, regulating pores and controlling the flow of water
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Archaeocytes (Amoebocytes):
- Totipotent cells, capable of differentiating into other cell types
- Moves freely in the mesohyl, involved in digestion, nutrient transport, immune response, and repair/regeneration
- Collencytes: Stationary, star-shaped cells that secrete collagen, forming and supporting the mesohyl
- Lophocytes: Highly mobile cells that secrete collagen and deposit collagen fibers as they move, producing the sponge’s structural framework
- Spongocytes: Produce spongin, a fibrous protein that forms part of the skeleton, especially common in sponges that lack a rigid mineral skeleton
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Description
Explore the fascinating world of Porifera, the simplest animal group, commonly known as sponges. This quiz covers their body plan, feeding methods, and basic biological functions. Discover how these ancient organisms thrive in marine and freshwater environments.