Structural Organization in Animals [JEE Notes]

1. Basics of Structural Organization:

• Tissues:

• Definition: A group of cells with a similar structure and function. -(4 Types of Tissues)

  • Epithelial Tissue (covering and lining)
  • Connective Tissue (support and protection)
  • Muscular Tissue (movement and contraction)
  • Nervous Tissue (coordination and regulation)

• Organs:

  • Definition: A structure made up of different tissues that perform specific functions. -(Examples of Organs)
    • Heart
    • Lungs
    • Stomach
    • Liver

• Organ Systems:

• Definition: A group of organs that work together to perform a specific function. -(Major Organs Systems in Animals)

  • Digestive System: Converts food into energy.
  • Respiratory System: Takes in oxygen and expels carbon dioxide.
  • Circulatory System: Pumps blood throughout the body.
  • Excretory System: Removes waste products.
  • Nervous System: Controls and coordinates the body’s activities.
  • Endocrine System: Regulates the body’s functions through hormones.
  • Musculoskeletal System: Provides support and movement.

2. Animal Tissues:

• Epithelium:

• Structure:

  • Cells closely packed together with little extracellular material.
  • Covers and lines the surfaces of organs and cavities.

• Types:

• Simple Epithelium: Single layer of cells.

• Stratified Epithelium: Multiple layers of cells.

• Glandular Epithelium: Secretes substances such as mucus or enzymes.

• Connective Tissue:

• Structure:

• Cells widely separated by an extracellular matrix.

• Types:

• Loose Connective Tissue: Loosely arranged cells in a gel-like matrix.

• Dense Connective Tissue: Tightly packed cells in a dense matrix.

• Adipose Tissue: Cells specialized to store fat.

• Cartilage: Flexible connective tissue with specialized cells called chondrocytes.

• Bone: Hard connective tissue with specialized cells called osteocytes.

• Muscle Tissue:

  • Structure:
  • Cells specialized for contraction.
  • Contains contractile proteins actin and myosin.
  • Types:
    • Skeletal Muscle: Voluntary movement of bones
    • Smooth Muscle: Involuntary movement of internal organs.
    • Cardiac Muscle: Pumping of the heart.

• Nervous Tissue:

• Structure:

  • Neurons: Specialized cells that conduct electrical signals.
  • Neuroglia: Support cells that provide nutrients and protection for neurons.

3. Organ Systems and Functions

• Digestive System:

  • Structure:
  • Mouth, esophagus, stomach, small intestine, large intestine, rectum, anus.
  • Accessory Organs: Liver and Pancreas
  • Functions:
  • Breaks down food into nutrients that can be absorbed by the body.
  • Eliminates undigested materials as waste.

• Respiratory System:

  • Structure:
    • Nose, pharynx, larynx, trachea, bronchi, bronchioles, and lungs.
  • Functions:
  • Takes in oxygen from the atmosphere.
  • Removes carbon dioxide from the bloodstream.

• Circulatory System:

  • Structure:
  • Heart, Blood Vessels (arteries, veins, capillaries), Blood components (Red Blood Cells, White Blood Cells, Platelets, Plasma)
  • Functions:
    • Pumps blood throughout the body.
    • Transports oxygen, nutrients, hormones, and waste products.

• Excretory System:

  • Structure:
  • Kidneys, Ureters, Urinary Bladder, Urethra
  • Functions:
  • Removes nitrogenous waste products from the bloodstream.
  • Regulates water and electrolyte balance.

• Nervous System:

• Structure:

  • Central Nervous System (Brain, Spinal Cord)
  • Peripheral Nervous System (Sensory neurons, Motor neurons, Autonomic Nervous System)

• Functions:

  • Controls and coordinates the body’s activities.
  • Receives, processes, and responds to stimuli.

• Endocrine System:

  • Structure:
  • Various Glands (Pituitary, Thyroid, Adrenal, Pancreas, etc.)
  • Functions:
  • Regulates the body’s functions through hormones.
  • Controls processes like growth, metabolism, reproduction.

• Musculoskeletal System:

  • Structure:
    • Bones, Joints, Muscles
  • Functions:
    • Provides support and protection for the body.
    • Facilitates movement and locomotion.

References:

• NCERT Biology Class 11: Chapter 1 -“The Living World”
• NCERT Biology Class 11: Chapter 2-“Biological Classification”
• NCERT Biology Class 12: Chapter 3-“Human Reproduction”.
• NCERT Biology Class 12: Chapter 5-“Principles of Inheritance and Variation”