Structural Organisation in Animals

Fundamental Properties and Characteristics of Animals

• Kingdom Classification:

  • Animals belong to Kingdom Animalia, also referred to as Metazoans.
  • They are eukaryotic organisms, characterized by having a well-defined nucleus.

• Nutritional Modes:

  • Heterotrophic Nutrition: Animals are heterotrophs, meaning they are dependent on other organisms for food and nutrition.
  • Holozoic Mode of Nutrition: Involves taking in complete food first through ingestion, followed by internal digestion.

• Fundamental Physiological Capabilities:

  • Growth: Structural expansion and development.
  • Reproduction: Process by which organisms produce offspring or new individuals of their kind.
  • Movement and Locomotion:
  • Movement: Defined specifically as a change in posture.
  • Locomotion: Defined specifically as a change in physical position.

Cellular Differentiation and Division of Labour

• Unicellular Organisms:

  • All basic biological activities (such as digestion and reproduction) are performed by a single cell.
  • Example: Amoeba.

• Multicellular Organisms:

  • Characterized by a division of labour, where different cells specialize to perform distinct physiological functions.
  • Example: Hydra.

Hierarchy of Structural Organization

• Progressive Levels of Organization:

  • Cells $\rightarrow$ Tissues $\rightarrow$ Organs $\rightarrow$ Organ Systems.

• Primary Tissue Types:

  • Cells organize into tissues. Animal bodies are composed of four basic tissue types:
  • Epithelial tissue
  • Connective tissue
  • Muscular tissue
  • Neural tissue

• Organs:

  • Formed when different tissues are organized in a specific pattern (arrangement) and specific proportion ($\%$) to perform a common function.

• Organ Systems:

  • Formed when two or more organs interact both physically and chemically to perform integrated functions.
  • Example: Digestive system.