Lecture Notes on Animal Biology

Introduction to Biology

• Initial expectation of biology focused on animals.
• Surprising breadth of topics in biology beyond just animals.
• Personal journey from high school to grad school with limited animal-focused classes until a zoology course in grad school.
• Importance of understanding cellular biology for studying animals.

Definition of Animals

• Animals share common characteristics:
  • Multicellular and composed of eukaryotic cells.
  • Specialized cells performing specific functions.
  • Most animals have specialized tissues.
  • Heterotrophs: must consume food; do not produce their own.
  • Generally motile at some stage of life cycle.

Key Vocabulary in Animal Classification

• Symmetry:
  • Radial Symmetry: Can be divided into similar portions from multiple planes (e.g., pie slices).
  • Bilateral Symmetry: Divided into mirror-image halves (e.g., humans).
• Cephalization: Concentration of nervous system tissue in the head region.
• Triploblastic Animals: Three germ layers (ectoderm, endoderm, mesoderm).
• Protostomes vs. Deuterostomes:
  • Protostomes: Blastopore (first opening) develops into the mouth.
  • Deuterostomes: Blastopore develops into the anus.
• Coelom: Body cavity formed from mesoderm; provides cushioning and space for organs.

Overview of Major Animal Phyla

1. Phylum Porifera (Sponges)

   • Aquatic, mostly saltwater, sessile adults.
   • Porous body structure; intracellular digestion.
   • Lack of symmetry, cephalization, and coelom.

2. Phylum Cnidaria (Jellies, Sea Anemones, Hydras)

   • Aquatic, can be saltwater or freshwater.
   • One gut opening (mouth/anus), intracellular and extracellular digestion.
   • Radial symmetry, no cephalization, and no coelom.

3. Phylum Platyhelminthes (Flatworms)

   • Aquatic or terrestrial; many are parasitic.
   • One gut opening; bilateral symmetry and cephalization.
   • No coelom; protostomes.

4. Phylum Nematoda (Roundworms)

   • Includes hookworms and pinworms; major ecological impacts.
   • Microscopic size; bilateral symmetry and cephalization.
   • Pseudocoelom; two gut openings (mouth and anus); protostomes.

5. Phylum Mollusca (Mollusks)

   • Includes snails, clams, octopuses; both aquatic and terrestrial.
   • Many have shells; bilateral symmetry and cephalization.
   • True coelom; protostomes.

6. Phylum Annelida (Segmented Worms)

   • Includes earthworms and leeches; both aquatic and terrestrial.
   • Segmented body; bilateral symmetry and cephalization.
   • True coelom; protostomes.

7. Phylum Arthropoda (Insects, Spiders, Crustaceans)

   • Jointed appendages, segmented bodies; both aquatic and terrestrial.
   • Tough exoskeleton; bilateral symmetry and cephalization.
   • True coelom; protostomes.

8. Phylum Echinodermata (Sea Stars, Sea Urchins)

   • Aquatic, saltwater only.
   • Larvae have bilateral symmetry; adults have radial symmetry.
   • Lack cephalization, but have a coelom; deuterostomes.

9. Phylum Chordata (Vertebrates)

   • Includes fish, amphibians, reptiles, birds, mammals.
   • Defined by the presence of a notochord; bilateral symmetry and cephalization.
   • True coelom; deuterostomes.

Conclusion

• Overview provided of 9 major animal phyla.
• Acknowledgment that there are more phyla and characteristics to explore.
• Encouragement to remain curious in the study of animals.