Overview of Animal Biology and Phyla

Introduction to Animal Biology

• Initial perception of biology as animal-focused.
• Realization: Biology encompasses much more, with animals being a small part.
• Importance of understanding cells, genetics, evolution, ecology for animal study.

Definition of Animals

• Animals are multicellular, eukaryotic, and have specialized cells.
• Most have specialized tissues, are heterotrophs (consume rather than produce food).
• Differ from fungi (external digestion) as animals ingest food.
• Most are motile at some life stage.

Animal Characteristics Vocabulary

• Symmetry
  • Radial Symmetry: Multiple planes divide the body (useful for sessile animals).
  • Bilateral Symmetry: Body divides into similar right and left halves (aids forward movement).
• Cephalization: Concentration of nervous tissue in head, useful for sensory organ placement.
• Triploblastic: Animals with three germ layers - ectoderm, mesoderm, endoderm.
  • Protostomes: First embryonic opening becomes the mouth.
  • Deuterostomes: First embryonic opening becomes the anus.
  • Coelom: Fluid-filled body cavity derived from mesoderm.

Overview of 9 Major Animal Phyla

1. Phylum Porifera

• Examples: Sponges.
• Characteristics: Aquatic, mostly saltwater, sessile adults, porous body, intracellular digestion.
• Structures: No true tissues/organs, mostly no symmetry, no cephalization, no coelom.

2. Phylum Cnidaria

• Examples: Jellies, sea anemones, hydras.
• Characteristics: Aquatic, one gut opening, can have extracellular digestion, radial symmetry.
• Structures: Polyps and medusas, stinging organelles, no cephalization, no coelom.

3. Phylum Platyhelminthes

• Examples: Flatworms like planarians and tapeworms.
• Characteristics: Aquatic or terrestrial, usually one gut opening, parasitic species common.
• Structures: Bilateral symmetry, cephalization, no coelom, protostomes.

4. Phylum Nematoda

• Examples: Nematodes like hookworms and pinworms.
• Characteristics: Huge ecological impact, can be parasitic or beneficial to soil.
• Structures: Very small, bilateral symmetry, cephalization, pseudocoelom, protostomes, two gut openings.

5. Phylum Mollusca

• Examples: Snails, clams, octopuses.
• Characteristics: Aquatic or terrestrial, many have shells, radula, muscular foot.
• Structures: Bilateral symmetry, cephalization, coelom, protostomes.

6. Phylum Annelida

• Examples: Earthworms, leeches, tubeworms.
• Characteristics: Aquatic or terrestrial, segmented bodies, often with setae.
• Structures: Bilateral symmetry, cephalization, coelom, protostomes.

7. Phylum Arthropoda

• Examples: Insects, spiders, crustaceans.
• Characteristics: Aquatic or terrestrial, many can fly, jointed appendages, segmented bodies.
• Structures: Exoskeleton, metamorphosis advantages, bilateral symmetry, cephalization, coelom, protostomes.

8. Phylum Echinodermata

• Examples: Sea stars, sea urchins, sea cucumbers.
• Characteristics: Aquatic, saltwater, radial symmetry in adults, regeneration abilities.
• Structures: No cephalization, coelom, deuterostomes.

9. Phylum Chordata

• Examples: Fish, amphibians, reptiles, birds, mammals (includes humans).
• Characteristics: Includes vertebrates and some invertebrates (e.g., lancelet).
• Structures: Notochord, dorsal nerve cord, pharyngeal slits, postanal tail, thyroid gland.
• Segmented, bilateral symmetry, cephalization, coelom, deuterostomes.

Conclusion

• Most animal species are invertebrates.
• Discovery in animal biology is ongoing, encouraging continued exploration.