Lecture Notes on Kingdom Animalia

Introduction to Animals

• Animals belong to the kingdom Animalia.
• Common references often focus on vertebrates, but this includes all animals like insects and water bears.
• We are part of the Metazoa group, characterized by cells with nuclei.

Phylogeny of Animals

• Metazoa includes diverse organisms from jellyfish to spiders.
• Classification in the class will focus on:
  • Invertebrates: animals without a spinal cord.
  • Vertebrates: animals with a spinal cord.

Characteristics of Animals

• All animals are:
  • Eukaryotic: have a nucleus.
  • Multicellular: composed of multiple cells.
  • Motile: capable of movement at some stage in life.
  • Heterotrophic: obtain food by consuming other organisms.
• Lack cell walls and generally go through a blastula stage during development.

Evolution of Animals

• Animals appeared approximately 530 million years ago during the Cambrian explosion.
• The Cambrian explosion saw a rapid increase in diversity, with organisms having segmentation.
• All modern animals can trace their ancestry back to this period.

Classification of Invertebrates

1. Tissue Organization:

   • Sponges: simple organisms with a bag of tissues.
   • True Tissues: more complex organisms.

2. Symmetry:

   • Radial Symmetry: organisms that can be cut in any direction (e.g., jellyfish).
   • Bilateral Symmetry: organisms with distinct left and right sides (e.g., humans).

3. Development:

   • Protostomes: mouth forms from the initial opening (e.g., mollusks).
   • Deuterostomes: anus forms from the initial opening (e.g., echinoderms). Humans are deuterostomes.

4. Further Grouping of Protostomes:

   • Acoelomates: no body cavity (e.g., flatworms).
   • Coelomates: possess a body cavity.
     • Pseudocoelomates: body cavity not fully surrounded by mesoderm.
     • True Coelomates: body cavity fully surrounded by mesoderm.

Major Invertebrate Groups

• Sponges: live in oceans, filter seawater.
• Cnidarians: include jellyfish and sea anemones.
• Flatworms: e.g., planarians.
• Mollusks: diverse group including clams, snails, squids.
• Annelids: segmented worms, e.g., leeches.
• Arthropods: largest group including insects and crustaceans.
• Nematodes: roundworms.
• Echinoderms: e.g., sea stars, sea urchins.

Classification of Vertebrates

• Vertebrates encompass:
  • Lancelets: simple chordates.
  • Lampreys: jawless fish.
  • Cartilaginous Fish: sharks and rays.
  • Bony Fish: diverse group including most fish.
  • Amphibians: e.g., frogs.
  • Reptiles: includes birds and dinosaurs.
  • Mammals: characterized by milk production.

Modern Classification

• Current methods involve DNA analysis to classify organisms and determine evolutionary relationships, moving away from traditional morphology-based classification.

Conclusion

• Overview of animal diversity is vast, with many more species than covered in lecture. This provides a foundational understanding of animal classification.