Lecture Notes: Kingdom Animalia

Introduction

• Topic: Kingdom Animalia
• Focus: Characteristics, body plans, classification

Characteristics of Animals

• Domain: Eukarya (all animals are eukaryotic)
  • Cells have a nucleus and membrane-bound organelles
• Multicellular: Composed of multiple cells
• Heterotrophic: Consume other organisms for energy
• Reproduction:
  • Mostly sexual reproduction, some asexual
  • Some species reproduce both ways
• Movement:
  • All animals can move at some point in their life cycle

Animal Cell Structure

• No cell wall, only a cell membrane
• Tissues:
  • Cells organized into tissues (except sponges)
  • Tissues form organs and organ systems in complex animals
• Specialization:
  • Cells have specialized structures for feeding, digestion, protection

Classification of Animals

• Invertebrates: No backbone (90-99% of animals)
  • Often have exoskeletons for support and protection
• Vertebrates: Have a backbone
  • Endoskeletons that grow with the animal
  • Include mammals and other vertebrates

Habitats

• Found in all environments where life is supported:
  • Marine, freshwater, terrestrial ecosystems

Reproduction

• Sexual Reproduction:
  • Internal fertilization: Sperm and egg join inside body
  • External fertilization: Sperm and egg join outside body in water
• Asexual Reproduction:
  • Hermaphrodites: Produce both sperm and egg (e.g., earthworms)
  • Budding and fragmentation (e.g., sponges, starfish)

Animal Development

• Zygote undergoes mitosis to form embryo
• Stages:
  • Blastula: Hollow ball of cells filled with fluid
  • Gastrula: Forms different tissue layers
• Tissue Layers:
  • Endoderm: Forms digestive organs
  • Mesoderm: Forms complex organ systems (not in all animals)
  • Ectoderm: Develops into nervous tissue and skin

Body Symmetry

• Asymmetry: No symmetry (e.g., sponges, corals)
• Radial Symmetry: Bodies can be divided along any plane (e.g., jellyfish, starfish)
• Bilateral Symmetry: Divisible into mirror-image halves (e.g., humans)
  • Associated with cephalization and advanced movement

Body Cavities and Development

• Acoelomates: No fluid-filled body cavity (e.g., flatworms)
• Pseudocoelomates: Partially lined body cavity (e.g., roundworms)
• Coelomates: Fully lined body cavity (most animals after mollusks)
• Development Types:
  • Protostome: Mouth develops first (e.g., snails)
  • Deuterostome: Anus develops first (e.g., mammals, birds)

Classification and Questions

• Visualize classification through cladograms
• Questions for Review:
  1. Which invertebrate group is an acoelomate?
  2. Characteristics of mollusks?
  3. Chordates' closest invertebrate relatives?
  4. Which invertebrate group lacks true tissues?
  5. Commonalities between annelids and arthropods?

Conclusion

• Importance of understanding animal classification and characteristics
• Encouraged to review and answer questions based on lecture chart