Lesson Notes By Weeks and Term v4 - SHS 1

Lesson Video

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Performance objectives

• Describe the main organs of the excretory system.
• Explain the processes of waste removal.
• Identify the types of waste produced by the body.
• Understand the importance of waste removal for health.

Lesson summary

This lesson explores excretion, one of the fundamental processes for life. Just as we must sweep our rooms and take out the rubbish to keep our homes clean and healthy, our bodies must constantly remove harmful waste products generated from its daily activities (metabolism). If these wastes build up, they become toxic and can lead to serious illness or death. Understanding how our body's "sanitation system" works is crucial for appreciating our health and making choices that keep our bodies functioning well, especially in our Ghanaian climate where hydration and hygiene are so important.

Lesson notes

This section breaks down the essential information needed to understand the processes of waste removal. A. What is Excretion? Metabolism: This refers to all the chemical reactions that occur within the cells of our body to maintain life. Examples include respiration (to produce energy), protein synthesis (to build body parts), and breaking down old cells. Metabolic Waste: These are the unwanted or harmful by-products of metabolism. They are not just leftover food, but rather substances produced by the cells themselves. Key examples in humans are: Carbon Dioxide (CO₂): A waste product of aerobic respiration. Urea: Produced in the liver from the breakdown of excess amino acids (proteins). It is highly toxic in large amounts. Excess Salts: Mineral salts that the body does not need. Excess Water: Water that is surplus to the body's requirements. Definition of Excretion: Excretion is the process by which metabolic waste products and other toxic substances are removed from the body of an organism. Its main purpose is to prevent the accumulation of these harmful substances and to maintain a constant internal environment (a concept called homeostasis). B. Excretion vs. Egestion (A Common Point of Confusion)

It is very important not to confuse excretion with egestion.

| Feature | Excretion | Egestion (Defecation) | | :--- | :--- | :--- | | What is removed? | Metabolic waste products (e.g., urea, CO₂). | Undigested and unabsorbed food materials (faeces). | | Origin of waste? | Produced by the body's cells during metabolism. | Material that was eaten but never entered the body's cells. | | Main Organ(s)? | Kidneys, Lungs, Skin. | Anus (end of the large intestine). | | Is it excretion? | Yes, it is true excretion. | No, it is not considered excretion in the biological sense. |

Example: When you eat *waakye*, the carbohydrates and proteins are digested and absorbed into your blood. Your cells use them for energy and growth. The carbon dioxide produced during energy release is an excretory product. The urea produced from breaking down excess protein is an excretory product. However, the fibrous part of the beans (*shito* ingredients, vegetables) that cannot be digested passes through the intestines and is removed as faeces. This is egestion. C. The Excretory Organs and Their Processes

Evaluation guide

• Describe the processes for the removal of waste from the human body.
• Project -based Learning:
•  In mixed -ability groups , do a mini -investigation on the processes of removal of waste
• by the human excretory system using technological devices.