Animal Kingdom Phyla 1

Overview of Animal Kingdom

  • Animal Classification
    • The animal kingdom is divided into vertebrates and invertebrates.
    • Vertebrates: Animals with a backbone (less than 5% of the animal kingdom).
    • Invertebrates: Animals without a backbone (95% of animal kingdom).
    • Examples commonly named: birds, mammals, fish, frogs, lizards.

Invertebrates

  • Importance of Invertebrates
    • Invertebrates make up most of the phylums in the animal kingdom, focusing on roughly 11 major phyla this semester.
    • Invertebrate phyla examples: horseshoe crabs, snails, clams, worms.

Phylum Porifera (Sponges)

  • Characteristics of Porifera

    • Oldest phylum in the animal kingdom.
    • Sponges are defined by having many pores ("peripheral" means porous).
    • Lack defined symmetry (asymmetrical) and have a simple organizational structure.

  • Structure and Function

    • Made of individual cells, notably collar cells (choanocytes):
    • Collar cells filter feed by drawing water into the sponge.
    • Flagella on each collar cell draw water into the central cavity of the sponge, filtering nutrients and oxygen.
    • Process known as filter feeding, which operates similarly to endocytosis.

  • Reproduction

    • Sponges reproduce asexually through budding (genetically identical offspring).
    • Also reproduce sexually by releasing gametes into the water (broadcast spawning).
    • Sponges are hermaphrodites, containing both male and female reproductive structures.

  • Skeleton

    • Have a hydrostatic skeleton (water provides structural support).

  • Ecosystem Role

    • Sponges are filter feeders, maintaining water quality by filtering food particles and excreting waste back into the water.
    • Associated with microbial communities, affecting their weight and function in ecosystems.

Phylum Cnidaria (Jellyfish, Anemones, Corals)

  • Characteristics of Cnidaria

    • Includes jellyfish, corals, and sea anemones.
    • Have stinging cells called cnidocytes (used for capturing prey).

  • Body Forms

    • Two main forms:
    • Medusa (free-floating form, e.g., jellyfish).
    • Polyp (sessile form, e.g., sea anemones and corals).

  • Symmetry and Structure

    • Generally exhibit radial symmetry.
    • Have a simple digestive system with a mouth/anus that serves both functions.
    • Limited tissue layers (two epithelial layers with mesoglea).

  • Feeding Mechanism

    • Capture prey using tentacles with cnidocytes, which release toxins.
    • Digestion occurs in the gastrovascular cavity.

  • Corals

    • Corals live in colonies and can form hard calcium carbonate exoskeletons.
    • Play a crucial role in forming coral reefs, which are biodiversity hotspots.
    • Coral bleaching occurs when temperature rises or when symbiotic algae (zooxanthellae) leave the coral, resulting in loss of color and nutrients.

  • Environmental Sensitivity

    • Corals are sensitive to temperature changes and ocean pH due to excess carbon dioxide in the atmosphere leading to ocean acidification.
    • A healthy coral reef has a pH around 8.1 but can be harmed by acidity, affecting calcium carbonate structures.

Phylum Echinodermata (Sea Stars, Sea Cucumbers, Sea Urchins)

  • Characteristics of Echinoderms

    • Exhibit radial symmetry as adults but bilateral symmetry as larvae.
    • Possess spiny skin and a unique water vascular system used for movement and feeding.
    • Includes classic examples like sea stars and sand dollars.

  • Movement and Feeding

    • Tube feet (podia) operate via the water vascular system, allowing them to adhere to surfaces and move.
    • Predators of shelled animals; they can evert their stomachs to digest prey externally.

  • Ecological Role

    • Considered keystone species; crucial for maintaining the diversity of marine ecosystems by controlling prey populations.
    • Significant predators that regulate populations of shelled organisms.
    • Their removal from ecosystems can result in decreased biodiversity.

  • Reproduction

    • Can reproduce both sexually and asexually (e.g., by fragmentation).

Conclusion

  • Discussion on the importance of invertebrates in ecosystems and their various survival mechanisms.

  • Introduction to upcoming lab activities and classification worksheets for reviewing different phyla.

  • Additional References

    • Study aids like charts showing characteristics of different phyla for better comprehension.
    • Future laboratory sessions will involve examining specimens and further discussions.