18.08 Kingdom Animalia

Overview

• The Animalia kingdom comprises multicellular, eukaryotic organisms that are exclusively heterotrophic (rely on consuming organic material for energy).
• Unique to this kingdom is the presence of a nervous system, which facilitates communication and response to stimuli.
• Diverse Forms: Ranges from simple sponges to complex mammals.

Characteristic Features of Animals

1. Eukaryotic and Multicellular:

• Organized cells form specialized tissues and organs.

1. Heterotrophic Nutrition:

• Cannot photosynthesize; obtain energy by consuming other organisms.

1. Cell Structure:

• No Cell Walls:
  • Cells are flexible, allowing for diverse body shapes and movement.
• Small, Temporary Vacuoles:
  • Includes lysosomes and food vacuoles.
• No Chloroplasts:
  • Exceptions: Some, like coral polyps, house photosynthetic protoctists (symbiotic relationship).

1. Communication:

• Animals have a nervous system for coordination and communication.
• Also use chemical signaling (e.g., hormones).

1. Specialized Cells:

• Some cells have cilia for movement or sensory functions (e.g., in respiratory tracts of mammals).

Ecological Role

• Consumers:
  • Occupy various levels of food chains (herbivores, carnivores, omnivores, decomposers).
  • Contribute to ecosystem balance, impacting prey populations and nutrient cycling.

Examples

• Crown-of-thorns Starfish (Acanthaster planci):
  • Feeds on coral, causing significant damage to parts of the Great Barrier Reef during population explosions (Figure 18.13).

Key Term

• Animalia: A kingdom of multicellular, eukaryotic, heterotrophic organisms characterized by the presence of a nervous system and specialized tissues.

Comparison of Eukaryotic Kingdoms

Questions

• a. Which eukaryotic kingdoms contain:
  • i. Autotrophic organisms:
    • – Protoctista (e.g., algae).
    • – Plantae (all members).
• ii. Heterotrophic organisms:
  • – Protoctista (e.g., protozoa).
  • – Fungi (all members).
  • – Animalia (all members).