Lesson Notes By Weeks and Term v5 - Grade 11

Lesson Video

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Performance objectives

• Relate plant tissue structure to function.
• Relate animal tissue structure to function.
• Describe how tissue arrangement forms organs.
• Explain how tissue malfunctions can lead to diseases.
• Compare and contrast plant and animal tissues.

Lesson summary

Welcome to Week 7 of Life Sciences! This week, we're diving deeper into the fascinating world of plant and animal tissues. We will be revising previously learned concepts and building upon them with more complex ideas. Understanding tissues is crucial because they form the foundation of all organs and organ systems in both plants and animals, including ourselves. For example, understanding how xylem transports water in plants can help us address challenges related to water scarcity in South Africa. Similarly, knowing about muscle tissue helps us understand human health and disease.

Lesson notes

2.1 Plant Tissues: Structure and Function Plants are organized into tissue systems: dermal, ground, and vascular.

Dermal Tissue: Epidermis: The outer protective layer. In leaves and stems, it's covered by a cuticle, a waxy layer that prevents water loss. In roots, root hairs extend from epidermal cells to increase surface area for water absorption. In the Karoo, many succulents have thickened cuticles to survive the dry climate.

Periderm:* Replaces the epidermis in older stems and roots, forming the bark.

Ground Tissue: Parenchyma:* Most abundant, with thin walls. Functions in photosynthesis, storage, and secretion. Found in the mesophyll of leaves, cortex of stems and roots, and pulp of fruits.

Example: The fleshy part of a mango is primarily parenchyma.

Collenchyma:* Unevenly thickened walls, providing flexible support. Found in young stems and petioles (leaf stalks). Allows stems to bend in the wind without breaking.

Sclerenchyma: Thick, lignified walls for rigid support.

Two types: fibers (long and slender) and sclereids (short and irregular). Fibers are used in making rope and linen from plants such as hemp and flax, which have been cultivated in South Africa.

Vascular Tissue: Xylem: Transports water and minerals from roots to shoots. Contains tracheids (tapered cells) and vessel elements (wider cells joined end-to-end). Xylem's lignified walls provide structural support.

Example Calculation: If a tree transpires 50 litres of water per day and its xylem vessels have an average diameter of 0.05 mm, we can calculate the average velocity of water flow. First, convert litres to cubic meters: 50 L = 0.05 m³. Then, calculate the cross-sectional area of a single xylem vessel: A = πr² = π(0.000025 m)² ≈ 1.96 x 10⁻⁹ m². Assume there are 1000 vessels actively transporting water. The total area is then 1000 A ≈ 1.96 x 10⁻⁶ m². Now, calculate the volume flow rate: Q = 0.05 m³/day. Convert this to m³/second: Q ≈ 5.79 x 10⁻⁷ m³/s. Finally, calculate the average velocity: v = Q/A ≈ (5.79 x 10⁻⁷ m³/s) / (1.96 x 10⁻⁶ m²) ≈ 0.295 m/s. So, the average velocity of water flow is approximately 0.295 m/s.

Phloem: Transports sugars (produced during photosynthesis) from source to sink. Contains sieve-tube elements (living cells that conduct sugars) and companion cells (support sieve-tube elements). The sap in sugar cane, a major crop in South Africa, is transported by the phloem. 2.2 Animal Tissues: Structure and Function Animal tissues are broadly classified into epithelial, connective, muscle, and nervous tissues.

Epithelial Tissue: Covers body surfaces and lines internal organs and cavities. Functions in protection, secretion, absorption, and excretion. Classified by shape (squamous, cuboidal, columnar) and number of layers (simple, stratified).

Simple squamous epithelium:* Thin, allows diffusion (e.g., lining of air sacs in lungs).

Stratified squamous epithelium:* Protects against abrasion (e.g., epidermis of skin).

Columnar epithelium: Secretes and absorbs (e.g., lining of the small intestine). Often has microvilli to increase surface area.

Connective Tissue: Supports, connects, and separates different tissues and organs. Characterized by an extracellular matrix consisting of fibers (collagen, elastic, reticular) embedded in a ground substance.

Loose connective tissue:* Holds organs in place (e.g., under the skin).

Fibrous connective tissue:* Dense, strong (e.g., tendons, ligaments).

Adipose tissue:* Stores fat for energy and insulation.

Cartilage:* Flexible support (e.g., ears, nose, joints).

Bone:* Rigid support, protects organs.

Blood:* Transports oxygen, nutrients, and waste products.

Muscle Tissue: Responsible for movement.

Three types: Skeletal muscle:* Voluntary movement (e.g., biceps). Striated appearance.

Smooth muscle:* Involuntary movement (e.g., walls of the digestive tract). Non-striated appearance.

Cardiac muscle: Found only in the heart. Involuntary, striated, and has intercalated discs for coordinated contraction.

Nervous Tissue: Transmits electrical signals.

Neurons: Conduct nerve impulses. Composed of a cell body, dendrites (receive signals), and an axon (transmits signals).

Neuroglia (glial cells):* Support and nourish neurons. 2.3 Tissue Arrangement and Organ Function The arrangement of tissues determines the function of an organ.

Plant Organs: Leaves:* Epidermis protects, mesophyll (parenchyma) carries out photosynthesis, vascular bundles (xylem and phloem) transport water and sugars.

Stems:* Epidermis protects, cortex (parenchyma and collenchyma) provides support, vascular bundles (xylem and phloem) transport water and sugars.

Roots:* Epidermis absorbs water and minerals, cortex (parenchyma) stores food, vascular cylinder (xylem and phloem) transports water and sugars.

Animal Organs: Stomach:* Epithelium lines the lumen (inside space), connective tissue provides support, muscle tissue churns food, nervous tissue controls muscle contractions and secretions.