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Biology · 100 Level
This is the complete lecture note for BIO 108 General Biology Practical II, prepared for Biology students at 100 Level. You can read it online below, open it in the full viewer, or download the PDF for offline study. It pairs with the course's video lectures, so you can read and watch together.
BIO la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS
BIO la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Course code: BIO 108 Course title: General Biology Practical II Course credit load: 1 Unit Series 1: Anatomy of Flowering Plants • Part 1.1: Internal Anatomy of the Stem o Sub Part 1.1.1: Tissues of the primary vegetative body o Sub Part 1.1.2: Transverse section of a dicot stem o Sub Part 1.1.3: Transverse section of a monocot stem • Part 1.2: Internal Anatomy of the Root o Sub Part 1.2.1: Transverse section of a dicot root o Sub Part 1.2.2: Transverse section of a monocot root o Sub Part 1.2.3: Comparison of root and stem anatomy • Part 1.3: Internal Anatomy of the Leaf o Sub Part 1.3.1: Transverse section of a dorsiventral leaf o Sub Part 1.3.2: Transverse section of an isobilateral leaf o Sub Part 1.3.3: Stomata and epidermal structures Introduction Anatomy is the study of the internal structure of organisms. In flowering plants, the primary vegetative body comprises the stem, root, and leaf, each containing characteristic arrangements of mature tissues. Examining transverse sections (T.S.) under a microscope reveals these tissue
BIO la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS patterns and allows students to distinguish between dicot and monocot organisation and between stem, root, and leaf. This Series describes the five major plant tissues visible in sections (parenchyma, collenchyma, sclerenchyma, xylem, and phloem), explains how to interpret transverse sections of dicot and monocot stems, roots, and leaves, and introduces epidermal structures including stomata. This knowledge forms the practical foundation for all plant biology work in this course. Series Learning Outcomes Upon completing this Series, you should be able to: • SLO 1.1 describe the five major tissue types of the primary vegetative body and identify them in microscope sections (Linked to Part 1.1), • SLO 1.2 describe and draw a labelled transverse section of a dicot and a monocot stem (Linked to Part 1.1), • SLO 1.3 describe and draw labelled transverse sections of dicot and monocot roots and compare them with stem sections (Linked to Part 1.2), • SLO 1.4 describe and draw a labelled transverse section of a dorsiventral and an isobilateral leaf (Linked to Part 1.3), and • SLO 1.5 describe the structure and function of stomata and other epidermal features (Linked to Part 1.3). 1.1 Internal Anatomy of the Stem 1.1.1 Tissues of the primary vegetative body The primary vegetative body of a flowering plant contains five major tissue types. Parenchyma: thin-walled, living cells with large vacuoles; the most common tissue; functions in storage, photosynthesis, and packing; forms the cortex, pith, and mesophyll. Collenchyma: living cells
BIO la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS with unevenly thickened cellulose walls at corners; provides flexible support in young stems and petioles. Sclerenchyma: dead cells with thick lignified secondary walls; provides rigid mechanical support; two types: fibres (elongated; provide tensile strength) and sclereids (shorter, irregular; e.g. stone cells in pear fruit). Xylem: dead hollow vessels and tracheids with lignified walls; transports water and minerals upward; also provides support. Phloem: living sieve tube elements and companion cells; transports organic solutes (mainly sucrose) from leaves to other organs. Fill in the blank: ________ is the most common plant tissue; its thin-walled living cells with large vacuoles function in storage, photosynthesis, and packing in the cortex, pith, and mesophyll. Figure 1.1: Photographs and diagrams of the five major plant tissue types 1.1.2 Transverse section of a dicot stem A T.S. of a young dicot stem (e.g. Helianthus/sunflower or Ranunculus/buttercup) shows the following zones from outside to inside: epidermis (one cell thick; may have trichomes/hairs;
BIO la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS waxy cuticle); cortex (parenchyma; may include collenchyma just below the epidermis; sometimes contains chloroplasts); endodermis (not always distinct in stem); pericycle; vascular bundles (arranged in a ring); and pith (central parenchyma). Each vascular bundle in a dicot stem is collateral: xylem faces the centre (adaxial), phloem faces the outside (abaxial), with a cambium strip between them. A bundle cap of sclerenchyma fibres often sits above the phloem. The vascular bundles are discrete and arranged in a ring. This ring arrangement is the single most diagnostic feature distinguishing a dicot stem from a monocot stem in transverse section. Fill in the blank: In a dicot stem T.S., vascular bundles are arranged in a ________ with xylem facing the centre and phloem facing the outside; a strip of cambium lies between them (collateral open bundle).
BIO la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Figure 1.2: Diagram and microscope photograph of a dicot stem T.S. 1.1.3 Transverse section of a monocot stem A T.S. of a monocot stem (e.g. maize/Zea mays or sugarcane) differs from a dicot stem in several key ways. The vascular bundles are scattered throughout the ground tissue (not arranged in a ring); there is no separate cortex or pith (the ground tissue is uniform throughout); there is no cambium between xylem and phloem (closed collateral bundle); and the bundles are typically surrounded by a thick bundle sheath of sclerenchyma. Individual monocot vascular bundles, when viewed at higher power, show: phloem (sieve tubes and companion cells) on the outer side; xylem on the inner side with a characteristic Y-shape or V-shape formed by two large metaxylem vessels flanking a protoxylem lacuna (an air space
BIO la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS where the first xylem vessels have been torn apart by stem elongation). The absence of cambium means monocot stems cannot undergo secondary growth. Fill in the blank: In a monocot stem T.S., vascular bundles are ________ throughout the ground tissue; each bundle is a closed collateral bundle (no cambium); the absence of cambium means monocot stems cannot undergo secondary growth.
BIO la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Figure 1.3: Diagram and microscope photograph of a monocot stem T.S. Pilot questions 1.1 1. State the five major tissue types of the primary vegetative body and give one function of each.
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