2.7.7Inquiry Process
Drawing Root and Stem Structure- Skills — IB Biology HL Revision Notes & Topical Questions
5 min read 4 parts Lesson 79 of 160
Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
Part 1 of 4Dicot Stem
Plan diagrams show tissue layers and not individual cells.
Epidermis
- Epidermis The outer protective layer of the stem, often covered by a cuticle that reduces water loss.
Cortex
- Cortex A layer of cells between the epidermis and the vascular tissue that gives support and stores food.
Vascular bundles
- Vascular bundles Bundles arranged in a ring, each with xylem on the inner side and phloem on the outer side.
Cambium
- Cambium A thin layer of dividing cells between xylem and phloem in each bundle that produces new vascular tissue.
Pith
- Pith Parenchyma cells at the centre of the stem that store food.
Part 2 of 4Dicot Root
Epidermis with root hairs
- Epidermis with root hairs The outer layer bears extensions that increase the area for absorbing water and minerals.
Cortex
- Cortex Wide layer of storage cells with air spaces that water passes through on its way inwards.
Endodermis
- Endodermis A ring of cells around the vascular tissue that regulates which substances enter the xylem.
Central vascular tissue
- Central vascular tissue Xylem forms a solid star or X shape, with phloem lying between its arms.
| Feature | Stem | Root |
|---|---|---|
| Xylem position | Inner part of each bundle | Central star shape |
| Bundles | Ring near edge | Central core |
| Pith | Present | Usually absent |
Part 3 of 4Drawing Method
1
Examine the section at low power and decide the outline and the proportion of each tissue.
2
Draw the outline with a sharp pencil using continuous lines and no shading.
3
Draw the boundaries between tissues without drawing individual cells.
4
Add label lines with a ruler, from the structure to the side of the page.
5
Add a title and, if possible, the magnification or a scale bar to show size.
Part 4 of 4Exam Checklist & Tips
2.7.7 – Key Points for the Exam
- Vascular bundle A strand of xylem and phloem running through the plant.
- Cambium A tissue of dividing cells that produces new xylem and phloem.
- Endodermis The inner layer of the root cortex surrounding the vascular tissue.
- Cortex The tissue between the epidermis and the vascular tissue.
Common Mistakes
- Drawing individual cells in a plan diagram.
- Placing the phloem inside the xylem in a stem bundle; phloem is on the outside.
- Giving the root a pith; dicot roots have a solid central xylem instead.
- Forgetting to label the cambium between xylem and phloem.
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