Biology: Classification and Characteristics of Animals

Classification of Animals

• Kingdom Animalia: multicellular, eukaryotic, heterotrophic organisms
• Divided into two main groups:
  • Invertebrates (without backbone): 95% of animal species
  • Vertebrates (with backbone): 5% of animal species

Characteristics of Animals

• Multicellularity: composed of multiple cells
• Eukaryotic cells: cells with true nucleus and membrane-bound organelles
• Heterotrophy: obtain energy by consuming other organisms or organic matter
• Ability to move: most animals have the capacity for movement
• Sensory capabilities: respond to stimuli from environment

Body Structure of Animals

• Symmetry:
  • Radial symmetry: body parts arranged around a central axis (e.g., starfish)
  • Bilateral symmetry: body parts arranged on either side of a central axis (e.g., humans)
• Body cavity:
  • Coelom: fluid-filled cavity between body wall and digestive system
  • Pseudocoelom: fluid-filled cavity between body wall and digestive system, but not lined by mesoderm
• Body systems:
  • Nervous system: receives and processes information
  • Circulatory system: transports oxygen and nutrients
  • Digestive system: breaks down and absorbs nutrients
  • Excretory system: removes waste products

Animal Behavior

• Types of behavior:
  • Instinctual behavior: innate, unlearned behaviors
  • Learned behavior: acquired through experience and environment
  • Social behavior: interactions with other animals
• Communication methods:
  • Visual signals: body language, coloration
  • Auditory signals: sounds, vocalizations
  • Chemical signals: pheromones, scent markings