Animal Phyla and Features

Animal Phyla

  • General Classification

  • Animals categorized into various phyla based on structural and functional features.

  • Key classifications include Bilaterally symmetrical, Ecdysozoans, Protostomes, Lophotrochozoans, and Deuterostomes.

  • Major Phyla

  • Porifera (sponges)

  • Cnidaria (jellyfish, corals, anemones)

  • Ctenophora (comb jellies)

  • Nematoda (roundworms)

  • Platyhelminthes (flatworms)

  • Annelida (segmented worms)

  • Mollusca (snails, clams, octopuses)

  • Arthropoda (insects, arachnids, crustaceans)

  • Echinodermata (sea stars, sea urchins)

  • Chordata (lancelets, vertebrates)

General Features of Animals

  • Characteristics

  • Heterotrophic (cannot make their own food)

  • Multicellular and lack cell walls

  • Diploid organisms with flexible cellular structures

  • Diverse forms and habitats

  • Primarily sexual reproduction

  • Development follows a common pattern

  • Possess unique tissues

  • Invertebrates account for 99% of all species, with most found in marine environments.

  • Significant land-dwelling phyla:

  • Arthropoda (spiders and insects)

  • Mollusca (snails)

  • Chordata (vertebrates)

The Animal Family Tree

  • Taxonomy
  • Animals traditionally classified based on anatomical features, relevant for creating phylogenies.
  • Recent shifts towards molecular systematics (gene sequences) have changed understanding and classification.

Key Transitions in Body Plan

  • Evolution showcased by six major transitions:
  1. Tissues: First significant evolutionary step; all but sponges have defined tissues.
  2. Bilateral Symmetry: Facilitates movement and body specialization.
  3. Body Cavity: Internal space for organ support and material distribution.
  4. Segmentation: Body subdivision allowing for organ system development.
  5. Molting: Shedding for growth in certain animal groups.
  6. Deuterostome Development: Distinguished by the embryonic development pattern where the mouth forms separate from the blastopore.

Specific Phylum Features

  • Phylum Porifera (Sponges)

  • Simplest animals; lack defined tissues, consist of specialized cells in a gel matrix; filter feeders.

  • Phylum Cnidaria

  • Radially symmetrical; exhibit extracellular digestion; possess cnidocytes (stinging cells) for predation.

  • Classes: Hydrozoa, Scyphozoa, Anthozoa, Cubomedusa.

  • Phylum Platyhelminthes (Flatworms)

  • Include parasitic and free-living species; acoelomate with bilateral symmetry; most lack a complete digestive system.

  • Phylum Nematoda (Roundworms)

  • Possess a pseudocoelom; many species are parasitic; unsegmented body covered by a flexible cuticle.

  • Phylum Mollusca

  • Coelomate; three regions: head-foot, visceral mass, mantle.

  • Groups: Gastropods, Bivalves, Cephalopods.

  • Phylum Annelida

  • Segmentation helps in movement, with repeated and specialized segments.

  • Earthworms illustrate important adaptations for soil health.

  • Phylum Arthropoda

  • Most diverse phylum; jointed appendages and chitin exoskeleton; includes insects, arachnids, and crustaceans.

  • Phylum Echinodermata

  • Marine animals with spiny skin; exhibit bilateral symmetry as larvae, radial symmetry as adults.

  • Phylum Chordata

  • Characterized by notochord, nerve cord, pharyngeal pouches, and post-anal tail; includes vertebrates and non-vertebrates like tunicates.

Conclusion:

  • Animalia exhibits diverse forms, complex evolutionary history with important transitions shaping body plans; essential understanding for biology and taxonomy.