Lesson 01 - Living Tissues (Part 01) | Grade 11 Science in English
DP Education - Scienceγ»76 minutes read
Grade 11 students are studying biology focusing on living tissues forming organs and systems in organisms. An activity introduces students to plant tissues, identifying cell types and structures, aiding in understanding tissue organization, including meristematic and permanent tissues.
Insights
- Cells combine to form tissues, which are adapted for specific functions like photosynthesis or transport in plants.
- Plant tissues are classified into meristematic and permanent tissues, with meristematic tissues responsible for active cell division and growth.
- Permanent tissues, like sclerenchyma, provide mechanical strength and support to the plant body, with distinct cell types and functions in plant structures.
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Recent questions
What is the focus of biology lessons for Grade 11 students?
Tissues
How are plant tissues observed in a biology activity?
Using a microscope
What are the main types of tissues in plants?
Meristematic and permanent
What are the functions of parenchyma tissue in plants?
Photosynthesis, storage, support
What is the primary function of sclerenchyma tissue in plants?
Provide support
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Summary
00:00
Exploring Biology: Observing Plant Tissues Under Microscope
- Grade 11 students are delving into biology lessons on living tissues, building on prior knowledge of living organisms' structures and characteristics.
- Organisms are composed of cells, which combine to form tissues, then organs, systems, and ultimately the body of multicellular organisms.
- The focus of the chapter is on tissues, the second level of organization, with discussions on plant and animal tissues.
- An activity is introduced to observe plant tissues using a beetle leaf, potato tube, and balsam plant stem.
- The process involves preparing temporary slides by obtaining thin peels or layers from each plant part.
- For the beetle leaf, thin peels of the lower epidermis are observed to identify stomata, guard cells, and other epidermal cells.
- The potato tube's thin layers reveal spherical cells of similar size, while the balsam plant stem's cross-section displays varying cell sizes and shapes.
- Each plant part requires a clean glass slide, a drop of water, transferring the specimen, and covering it with a coverslip to avoid air bubbles.
- Observations are made under a microscope, starting with low power and transitioning to higher power for clearer views of cell structures.
- The activity aims to help students recognize the different types of cells that form tissues in various plant parts, enhancing their understanding of tissue organization.
25:46
Plant Tissues: Cells, Types, and Functions
- Different plant parts have varying types of cells, with the beetle leaf having green cells, the potato tuber spherical cells, and the balsam plant stem showing various cell types.
- Similar cells grouped together form tissues, with the lower epidermis of the beetle leaf showing stomata, guard cells, and epidermal cells.
- The potato tuber exhibits different cell types compared to the beetle leaf, with distinct cells visible in a thin section.
- The cross-section of the balsam stem displays a dark layer at the periphery, different cell types in the middle, and a vascular bundle for transport.
- Tissues are groups of cells with a common origin, adapted for specific functions like photosynthesis, storage, or transport.
- Plant and animal tissues differ, with plant tissues classified based on their functions and origins.
- An activity involving observing the external view of plant roots, like the prop root of rampay, highlights differences in tissues based on color and structure.
- The growing part of a root differs from the mature part due to varying tissue types, with the tip being soft and light while the mature section is rough and dark.
- Observing the longitudinal section of a root, like the prop root of rampay, under a microscope reveals differences in cell size, color, and arrangement, indicating distinct tissue types.
- The longitudinal section shows meristematic tissue with small, dark cells at the root cap and larger, elongated cells with nuclei in the mature part, demonstrating different tissue characteristics.
54:59
Plant Tissues: Meristematic vs Permanent
- In plants, two main types of tissues are present: meristematic tissue and permanent tissue.
- Meristematic tissue is responsible for active cell division, leading to plant growth.
- Permanent tissue, on the other hand, consists of modified cells that do not divide.
- Meristematic tissues continuously divide through mitosis, producing identical cells for growth.
- Meristematic tissues are crucial for plant growth, found in shoot apex and root apex.
- Meristematic tissues lack differentiation, contain distinct nuclei, and have a high number of mitochondria.
- Intercellular space may be absent in meristematic tissues, and they lack a central vacuole and chloroplasts.
- Meristematic tissues are classified into apical, intercalary, and lateral meristems based on their location in the plant.
- Apical meristems are found in shoot apex, root apex, and axillary buds, aiding in plant height increase.
- Intercalary meristems are present in grass family plants, increasing internode length, while lateral meristems contribute to plant diameter growth in dicot plants.
01:25:53
Specialized Permanent Tissues in Plants
- Permanent tissues are specialized tissues that have lost the ability to divide and perform specific functions.
- Permanent tissues are classified into two groups: simple permanent tissues and complex permanent tissues.
- Simple permanent tissues consist of only one type of cell, while complex permanent tissues have more than one type of cell.
- Three types of simple permanent tissues are parenchyma, collenchyma, and sclerenchyma.
- Parenchyma cells are spherical in shape with thin cell walls and a large central vacuole.
- Parenchyma tissues are abundant in plants and are found in various parts such as the cortex and pith of stems, roots, fleshy fruits, and leaves.
- Functions of parenchyma tissue include photosynthesis, food storage, water storage, and providing support to herbaceous plants.
- Collenchyma tissue provides mechanical strength and support to the plant body with polygonal-shaped cells and thickened cell walls at the corners.
- Collenchyma tissues are found in herbaceous stems and in the veins of dicot leaves, providing support and aiding in photosynthesis.
- Sclerenchyma tissue, like collenchyma, provides mechanical strength and support to the plant body, with two types of cells: fibers and sclereids.
01:54:08
"Sclerenchyma Tissue: Structure, Function, and Examples"
- Sclerenchyma tissue consists of elongated cells, with longitudinal sections showing elongated long cells and cross sections displaying polygonal shapes.
- The cell wall of sclerenchyma tissue is composed of cellulose, with lignin deposits causing cell death, resulting in dead cells lacking cytoplasm, central vacuole, and organelles.
- The center part of the cell becomes the lumen due to the absence of cytoplasm and organelles, with cell walls evenly thickened and cells tightly packed.
- Connections between adjacent cells, known as pits, provide connections in both longitudinal and cross sections of sclerenchyma tissue.
- Sclerenchyma fibers are longer, while sclereids are shorter cells, with different names like sclerenchyma fiber or sclerity depending on the tissue they are present in.
- Sclerenchyma tissue features include lignin deposits causing cell death, resulting in a lumen, evenly thickened cell walls, and tightly packed cells.
- Sclerenchyma tissue is observed through a permanent slide in the lab, showcasing polygonal cells with thick cell walls and a visible lumen.
- Sclerenchyma tissue fibers are found in xylem and phloem, as well as in examples like coconut husk, agave fibers, and cotton wool.
- Sclereids are located in the endocarp of coconut, camphor, and mango fruits, as well as in the pericarp of guava and pear fruits, and the seed coat of coffee and dates.
- The primary function of sclerenchyma tissue is to provide support to the plant body due to the presence of lignin in the cell walls of dead cells.
02:20:06
Plant Tissues: Xylem and Phloem Overview
- Xylem tissue is a complex permanent tissue responsible for transporting water and minerals absorbed by plant roots.
- The cells in xylem tissue are lignified, dead cells with high mechanical strength to withstand water pressure and provide support to the plant body.
- Phloem tissue is another complex permanent tissue made up of multiple cell types, including sieve tube elements, companion cells, phloem parenchyma, and phloem fibers.
- Sieve tube elements in phloem tissue transport food, mainly sucrose, throughout the plant as phloem sap.
- Companion cells control the activities of sieve tube elements, while phloem parenchyma stores food and phloem fibers provide support.
- Phloem tissue has three living cell types (sieve tube elements, companion cells, phloem parenchyma) and one dead cell type (phloem fibers), unlike xylem tissue which has three dead cell types and one living cell.
