This guide provides short notes, key points, and effective study tips for the "Living Tissues" lesson, helping you prepare efficiently for your O/L examination.

Part 1: Plant Tissues

Short Notes & Key Concepts

• What is a Tissue? A group of cells with a common origin, modified to perform a specific function.

• Main Types of Plant Tissues:

  1. Meristematic Tissues: Actively dividing cells responsible for plant growth.

     • Characteristics: Small cells, thin walls, large nucleus, no large central vacuole, no intercellular spaces.

     • Types & Functions:

       • Apical Meristem: Found at the tips of roots and shoots. Responsible for increasing the length/height of the plant.

       • Lateral Meristem (Cambium): Found along the sides of stems and roots. Responsible for increasing the diameter/girth of the plant.

       • Intercalary Meristem: Found at the base of nodes and leaves (common in grasses). Responsible for the growth of internodes.

  2. Permanent Tissues: Tissues that have lost the ability to divide and are specialized for specific functions.

     • Simple Permanent Tissues (Made of one cell type):

       • Parenchyma: The most common plant tissue. Living, thin-walled, spherical cells with large vacuoles and intercellular spaces. Functions: Photosynthesis, food/water storage, provides turgor support.

       • Collenchyma: Living cells with unevenly thickened corners (cellulose). Provides flexible mechanical support to young stems and leaves.

       • Sclerenchyma: Dead cells with thick, evenly lignified walls. No intercellular spaces. Provides rigid mechanical support and strength. Two types: fibres (long) and sclereids (short, e.g., in guava, pear).

     • Complex Permanent Tissues (Made of multiple cell types):

       • Xylem: Transports water and minerals from roots to the rest of the plant and provides mechanical support. Components include vessel elements, tracheids (both are dead and transport water), xylem fibres (support), and xylem parenchyma (storage).

       • Phloem: Transports manufactured food (mainly sucrose) from leaves to other parts of the plant (this process is called translocation). Components include sieve tube elements (living, transport food), companion cells (living, control sieve tubes), phloem fibres (support), and phloem parenchyma (storage).

Part 2: Animal Tissues

Short Notes & Key Concepts

• Four Main Types of Animal Tissues:

  1. Epithelial Tissue: Covers external and internal surfaces of the body.

     • Characteristics: Tightly packed cells resting on a basement membrane.

     • Functions: Protection (skin), absorption (intestine), secretion (glands), filtration (kidney).

  2. Connective Tissue: Connects and supports other tissues.

     • Characteristics: Composed of cells and fibres scattered within a large matrix.

     • Blood: A special fluid connective tissue. The matrix is the plasma. It contains Red Blood Cells (transport oxygen), White Blood Cells (immunity), and Platelets (clotting).

  3. Muscle Tissue: Specialized for contraction and relaxation, causing movement.

     • Skeletal Muscle: Attached to bones. Voluntary (consciously controlled), striated (striped), multinucleated cells. Becomes fatigued.

     • Smooth Muscle: Found in the walls of internal organs (e.g., stomach, bladder). Involuntary (unconsciously controlled), non-striated, uninucleated cells. Does not fatigue easily.

     • Cardiac Muscle: Found only in the heart wall. Involuntary, striated, uninucleated, and branched cells. Never becomes fatigued.

  4. Nervous Tissue: Specialized for transmitting nerve impulses.

     • The basic unit is the neuron (nerve cell).

     • Main Parts: Cell body, dendrites (receive signals), and axon (transmits signals away).

     • Main Function: Coordination and control of body activities by receiving stimuli and transmitting impulses to effectors (muscles and glands).

Exam Tips & Tricks

1. Master the Diagrams: Be able to draw and label simple diagrams for:

   • Parenchyma, Collenchyma, and Sclerenchyma cells.

   • Xylem and Phloem tissues.

   • The three types of muscle tissue (Skeletal, Smooth, Cardiac).

   • A typical neuron. O/L questions often ask you to identify or draw these.

2. Create Comparison Tables: This is the most effective way to study this chapter. Make tables to compare:

   • Meristematic vs. Permanent Tissues.

   • Parenchyma vs. Collenchyma vs. Sclerenchyma (Structure, Cell Type, Function).

   • Xylem vs. Phloem (Components, Function, Direction of Transport).

   • Skeletal vs. Smooth vs. Cardiac Muscle (Control, Striations, Nuclei, Location, Fatigue).

3. Structure -> Function Link: Always ask yourself "WHY?" Why are sclerenchyma cells dead with thick walls? (For maximum rigid support). Why do red blood cells lack a nucleus? (To maximize space for haemoglobin). Understanding this link helps you remember the facts.

4. Memorize Keywords: Pay attention to key terms like "lignified," "striated," "voluntary," "matrix," and "translocation." Know their definitions.

Important Points to Remember

• Growth: Plants grow in length from apical meristems and in girth from lateral meristems.

• Transport: Xylem = Water up. Phloem = Food flow everywhere.

• Support: Collenchyma = Flexible support (like a young plant stem). Sclerenchyma = Rigid support (like wood or a coconut shell).

• Muscle Control: The only muscle you control consciously is skeletal muscle.

Heart Muscle: Cardiac muscle is unique to the heart and never tires.