Porifera/Sponges (Bio 11 Unit 2 Quest 2)

Phylum Porifera (Sponges)

• Characteristics:
• Simplest and most primitive animals
• Lack true tissues and organs
• Have specialized cells (collar cells, amoebocytes)
• Asymmetrical body plan
• No nervous system, brain, or muscle tissue
• Reproduction:
• Hermaphroditic: produce both male and female gametes
• Sexual reproduction through free-swimming larva that undergo metamorphosis
• Asexual reproduction through budding or branching
• Feeding:
• Water and food enter through pores into a central cavity (mesenchyme)
• Collar cells create water currents to filter food and expel waste through the osculum
• Ecological Role:
• Serve as a food source for marine animals
• Provide shelter for smaller invertebrates
• Some engage in symbiotic relationships with photosynthetic organisms (bacteria, protists)

Phylum Cnidaria

• Characteristics:
• Include hydra, jellyfish, sea anemones, and corals
• Exhibit radial or biradial symmetry
• Possess true tissues, formed from ectoderm and endoderm with mesoglea in between
• Have specialized tissues for nerve, muscle, and digestion
• Body Forms:
• Two main body forms: polyp (sessile) and medusa (motile)
• Specialized functions for feeding, defense, and reproduction
• Feeding:
• Use nematocysts (stinging cells) for prey capture and defense
• Food digested in gastrovascular cavity with a single opening for intake and waste expulsion
• Reproduction:
• Alternation of sexual and asexual generations
• Asexual reproduction by budding; sexual reproduction involves medusae releasing eggs or sperm
• Planula larva develops into a polyp
• Ecological Role:
• Critical for marine ecosystems, providing habitat and protecting coastal regions
• Influential in the diversity of marine life, supporting fish and other organisms
• Threatened by pollution and environmental changes which impact coral reefs

Key Terms:

• Hermaphroditic: Organism producing both male and female gametes
• Metamorphosis: Development process from larva to adult form
• Nematocysts: Stinging cells for capturing prey in cnidarians
• Mesoglea: Jelly-like substance between cell layers in cnidarians

Comparison of Sponges and Cnidarians:

• Sponges:
• Asymmetrical body plan, no true tissues, and no nervous system
• Asexual and sexual reproduction
• Cnidarians:
• Radial symmetry, true tissues, and simple nervous system
• Asexual and sexual reproduction with complex life cycles

Important Observations:

• Sponges and cnidarians are crucial indicators of ocean health and biodiversity
• Conservation efforts are vital in preserving coral reefs and sponge habitats to maintain ecosystem balance.