Organisation and Hierarchical Structure in Multicellular Organisms

SACE Key Ideas and Learning Objectives

• Explain the hierarchical structural organization of cells, tissues, organs, and systems.
• Use specific examples from both plants and animals to explain the organization of cells into tissues, tissues into organs, and organs into systems.
• Illustrate the relationship between the structure and function of cells, tissues, organs, and/or systems.
• Explain how organ systems in a multicellular organism are interdependent and function together to ensure the survival of the organism.
• Understand how lifestyle choices affect the functioning of organs and systems within an organism.

Hierarchical Structure of Multicellular Organisms

• The hierarchy consists of different levels of organization in which each level forms part of the next higher level.
• All multicellular organisms follow this hierarchical structure, which progresses as follows:
  • Cells: The basic unit of life. The same type of cells are organized into tissues.
  • Tissues: Groups of specialized cells with similar structure and function. Different tissues are organized into organs.
  • Organs: Groups of tissues that work together to carry out one or more specific functions.
  • Organ Systems: Groups of organs that work together to perform a specific function. These systems are interdependent.
  • Organism: The complete living entity made up of integrated organ systems.

Specialised Cells and Animal Tissues

• Multicellular organisms require specialized cells to survive. These cells group together into tissues, organs, and systems that work together to ensure survival and proper functioning.
• There are 4 main types of tissue in animals:

Epithelial Tissue

• Consists of sheets of epithelial cells that are tightly packed.
• Provides a protective barrier against pathogens, fluid loss, and injury.
• Covers the external body surface of an animal and lines organs and cavities inside the body.
• Plays active roles including:
  • Absorption and secretion of materials in the stomach and intestines.
  • Gas and nutrient exchange.
  • Removal of mucus, pathogens, and dust in the upper respiratory tract.

Connective Tissue

• Consists of cells and fibers that connect other tissues and organs together.
• Cell types include:
  • Red and white blood cells.
  • Fat cells.
  • Bone cells (provide structure and support to the body).
• Fibrous components include reticular fibers, elastic fibers, and collagen fibers.
• These fibers provide connectivity, strength, and flexibility.

Muscle Tissue

• Responsible for movement.
• There are 3 main types of muscle tissue:
  • Skeletal muscle tissue: Responsible for voluntary movement; attached to bones.
  • Smooth muscle tissue: Responsible for involuntary actions; found in organs.

Nervous Tissue

• Involved in sending, receiving, and processing information.
• Cell types include:
  • Neurons (nerve cells): Receive and transmit electrochemical signals (information) throughout the body of an organism.
  • Glial cells: Provide insulation, remove dead neurons, and provide materials required for respiration.
• Nervous tissue forms the central nervous system (brain and spinal cord) and the peripheral nervous system.

Animal Organs and Organ Systems

• Organs are groups of tissue that work together to carry out functions. Examples include:
  • Skin: Consists of epithelial, nervous, muscle, and connective tissue.
  • Stomach: Consists of epithelial, nervous, muscle, and connective tissue.
  • Brain: Consists of nervous and connective tissue.

Human Organ Systems

• There are 11 organ systems in the human body. Key systems include:

• Additional organ systems in the human body include:
  • Muscular System
  • Integumentary System
  • Lymphatic System
  • Endocrine System
  • Skeletal System
  • Male Reproductive System
  • Female Reproductive System
  • Urinary System

Plant Organization: Tissues and Organs

• Plant cells are grouped into tissues of similar size, shape, and function.

Plant Tissue Types

• Dermal tissue: Provides a protective cover over the body of the plant.
• Vascular tissue: Consists of cells involved in transporting materials between different organs.
• Ground tissue: Consists of different cell types that store food and energy, perform photosynthesis, and provide structural support.

Plant Organs

• Land plants have 3 basic organs:
  • Root: Physically anchors and supports a plant in the soil.
  • Stem: Holds a plant upright, allowing leaves to obtain sunlight and carbon dioxide from the air.
  • Leaves: Collect sunlight and make sugars.

Plant Organ Systems

• Land plants consist of two major organ systems:
  • Root System (primary and secondary): Anchors the plant in the ground and absorbs water and minerals from the soil.
  • Shoot System: Consists of the stem and leaves that produce, store, and transport sugars.

Interdependence and Lifestyle Factors

Interdependence of Organ Systems

• Organ systems do not operate in isolation. The function of one organ system is dependent on the proper function of other organ systems to ensure the health and survival of the organism.
• Example: The digestive system breaks down food into nutrients, which are then passed to the blood (circulatory system) to be transported around the body.

Lifestyle Choices and System Functionality

• Lifestyle choices play a major role in determining the effectiveness and health of organ systems. These choices can either enhance or harm well-being over time.