Porifera Flashcards

Animal Kingdom Overview

  • Diversity: Animals are characterized by a vast diversity in species, habitats, and biological functions.

  • Habitat: Found in a wide range of environments, from terrestrial to aquatic (marine and freshwater).

  • Morphology & Characteristics:

    • Heterotrophic: Animals cannot make their own food and must consume organic material.

    • Multicellular: Composed of multiple cells that function together.

    • No Cell Walls: Unlike plants, animal cells lack rigid cell walls.

    • Complex Development: Begins with a zygote, undergoes cleavage (either spiral for protostomes, radial for deuterostomes) leading to a blastula, which folds to form a gastrula with blastopore, developing into germ layers and body cavities.

    • Complex Tissues: Specialized groups of cells, allowing for distinct structures (e.g., organs).

    • Complex Movement: Presence of nerve and muscle tissues enables movement.

Animal Development Overview

  • Cleavage:

    • Early cell division process post-fertilization (Mitosis).

    • Two primary types:

      • Spiral (found in protostomes).

      • Radial (found in deuterostomes).

    • Development types:

      • Determinant: Early cell fate in protostomes, type of cell being made is decided early on in its lifecycle.

      • Indeterminate: Cells can develop into any type of cell in deiterostomes

  • Gastrulation: Formation of germ layers:

    • In protostomes, the blastopore develops into the mouth.

    • In deuterostomes, it becomes the anus.

Cell Organization: Tissues and Body Cavity

  • Germ Layers Formation:

    • Ectoderm: Develops into outer body covering and nervous system.

    • Mesoderm: Forms skeletal and muscle systems.

    • Endoderm: Creates digestive systems.

  • Body Cavity Types:

    • Coelom: Body cavity that houses internal organs, providing space and structure (isolated from exterior).

    • Diploblastic: (Cnidarians - Endoderm/Ectoderm).

    • Triploblastic: Have all three germ layers.

Phylum Porifera (Sponges)

  • Diversity:

    • Around 26,000 species, predominantly marine (with 150 freshwater species).

  • Phylogeny:

    • Part of sub-kingdom Parazoa, sharing a common ancestor with eumetazoans.

  • Characteristics:

    • Lack true tissues and symmetry.

    • Abundant in deep seas; sessile (immobile) adults anchored to the substrate.

    • Utilize chemicals for defense against predators and growth of other organisms.

Body Structure of Sponges

  • Body Layers:\

  • Mesohyl: Gelatinous protein matrix filled with amoebocytes which can transform into various cell types, aiding in structural support and nutrient transport.

  • Epithelial Cells: Protective outer layer controlling entry of water through pores (ostia).

  • Choanocytes (Collar Cells):

  • Inner layer responsible for feeding and water circulation.

  • Flagella generate water currents for feeding and nutrient uptake.

    • Amoebocytes are versatile cells found within the mesohyl of sponges (Phylum Porifera). Their primary functions include:

    • Nutrient Transport: They can move through the gelatinous matrix to transport nutrients throughout the sponge.

    • Cell Transformation: Amoebocytes can differentiate into various cell types to fulfill different roles in the sponge, aiding in regeneration and repair.

    • Support: They contribute to the structural integrity of the sponge by providing support and assisting in the formation of spicules.

    • Defense: Some amoebocytes may play a role in the sponge's defense mechanisms against pathogens.

Water Flow and Pore System

  • Ostia (Pores): Allow water to enter the sponge.

  • Porocytes: Cells regulating water flow by opening/closing ostia.

  • Osculum: Exit opening for filtered water.

Sponge Defense Mechanisms

  • Sclerocytes/ Spongocytes: Produce spicules for structural integrity and defense.

  • Myocytes: Muscle cells facilitating contraction and signaling within slightly mobile areas of sponges.

Reproduction in Sponges

  • Methods:

    1. Asexual: Fragmentation, where new sponges grow from broken pieces.

    2. Sexual:

      • Choanocytes transform into sperm released into water.

      • Sperm can enter ostia of another sponge, reaching an egg in the mesohyl.

      • Following fertilization, motile larvae develop, followed by settling on a substrate and transitioning to adult form.

  • Sponge larvae: Critical role in distribution and population continuation post-reproduction.