Topic: Translocation
Lesson 1: Introduction to Translocation
| Section | Details |
|---|---|
| Objective | – Describe translocation as the movement of sucrose and amino acids in the phloem from sources to sinks. – Understand the role of sources and sinks in translocation. |
| Activities | Starter (5 mins): Show an animation or diagram of phloem transport in plants and ask students to identify what might be moving through the phloem. Main (25 mins): 1. Define translocation as the movement of sucrose and amino acids through the phloem. 2. Explain the roles of sources and sinks: – Sources: Parts of the plant that produce or release sucrose and amino acids (e.g., leaves during photosynthesis). – Sinks: Parts of the plant that use or store sucrose and amino acids (e.g., roots, growing fruits, or storage organs). 3. Use diagrams to illustrate the direction of transport in the phloem. Plenary (10 mins): Students label a diagram of a plant, identifying potential sources and sinks and the direction of translocation. |
| Resources | Diagrams of phloem transport, animations of translocation, worksheets for labeling sources and sinks. |
| Time | 40 minutes |
| Homework | Write a paragraph explaining why translocation is essential for plant growth and survival. |
| Assessment | Students accurately label diagrams and describe the roles of sources and sinks during discussions. |
| Past Paper Practice | IGCSE Biology 0610/22/M/J/20 Q5(a). |
Lesson 2: Understanding Sources and Sinks
| Section | Details |
|---|---|
| Objective | – Describe sources as the parts of plants that release sucrose or amino acids and sinks as the parts of plants that use or store sucrose or amino acids. – Understand that sources and sinks can interchange roles. |
| Activities | Starter (5 mins): Ask students to brainstorm examples of plant parts that produce or store food. Main (25 mins): 1. Discuss examples of sources and sinks: – Leaves act as sources during photosynthesis. – Roots and fruits act as sinks by storing sucrose. 2. Explain that plant parts may act as both sources and sinks at different times: – Roots act as sources when stored sucrose is transported to growing parts. – Young leaves act as sinks when they require sucrose for growth. 3. Use diagrams to show these dynamic roles. Plenary (10 mins): Students create a table listing plant parts and their roles as sources or sinks during different stages of the plant’s lifecycle. |
| Resources | Diagrams of plant parts, example tables for source-sink roles, worksheets for creating tables. |
| Time | 40 minutes |
| Homework | Write a short explanation of how roots can be both a source and a sink depending on the plant’s stage of growth. |
| Assessment | Students complete the source-sink table correctly and explain the interchange of roles during discussions. |
| Past Paper Practice | IGCSE Biology 0610/31/O/N/19 Q3(b). |
Lesson 3: Mechanism of Translocation in the Phloem
| Section | Details |
|---|---|
| Objective | – Explain the mechanism of translocation in the phloem and why some plant parts act as both sources and sinks. |
| Activities | Starter (5 mins): Show a diagram of phloem sieve tubes and ask students to predict how sucrose and amino acids move through them. Main (25 mins): 1. Describe the structure of phloem sieve tubes and their role in transport. 2. Explain the pressure-flow hypothesis: – Sucrose is actively loaded into the phloem at sources, creating high pressure. – Water enters the phloem by osmosis, helping move sucrose to sinks. – Sucrose is actively unloaded at sinks, reducing pressure. 3. Discuss the role of energy from respiration in driving translocation. Plenary (10 mins): Students write a short explanation of the pressure-flow mechanism, using diagrams to support their description. |
| Resources | Diagrams of phloem sieve tubes, animations of the pressure-flow hypothesis, worksheets for summarizing the mechanism. |
| Time | 40 minutes |
| Homework | Research how translocation is affected when phloem tubes are damaged and write a short report. |
| Assessment | Students describe the mechanism of translocation accurately and link it to the roles of sources and sinks. |
| Past Paper Practice | IGCSE Biology 0610/22/M/J/20 Q6(a). |
Key Notes for Teachers:
- Use diagrams and animations to explain the dynamic relationship between sources and sinks.
- Emphasize the active nature of translocation and its dependence on energy from respiration.
- Encourage students to relate translocation to real-life plant processes, such as fruit development and storage.
Key Notes for Students:
- Translocation is the movement of sucrose and amino acids in the phloem from sources to sinks.
- Plant parts like leaves, roots, and fruits can act as sources or sinks depending on the plant’s stage of growth.
- The pressure-flow hypothesis explains how sucrose is actively transported through the phloem.
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