I/GCSE Biology Chapter Analysis - Chapter 2: Structure and Function of Living Organisms - Excretion (Part 1)
This time, let's explore the IGCSE Biology Chapter 2 sub-topic on excretion.
Excretion is the process by which organisms remove the waste products of metabolism from their bodies. In living organisms, the main waste products are carbon dioxide and oxygen.
Origin of Carbon Dioxide and Oxygen:
Carbon dioxide is produced as a by-product of cellular respiration, the process by which cells convert the energy in glucose into a form that can be used by the organism. During this process, the carbon in glucose is converted into carbon dioxide, which is then released from the body.
Oxygen, on the other hand, is a product of photosynthesis, the process by which plants and some other organisms use the energy from sunlight to convert carbon dioxide and water into glucose and oxygen. The oxygen produced as a by-product of this process is then released from the plant through the stomata (tiny pores) on the leaves.
Excretory Products:
The main excretory products in humans are:
- Carbon dioxide: Expelled from the lungs during exhalation.
- Water: Expelled from the skin as sweat and from the lungs as water vapor.
- Urea: Produced in the liver as a result of the breakdown of excess amino acids and filtered out by the kidneys.
- Uric acid: Produced as a result of the breakdown of nucleic acids and filtered out by the kidneys.
The Urinary System:
The urinary system is responsible for the excretion of waste products and the regulation of water balance in the body. It consists of the following components:
- Kidneys: The kidneys filter the blood, removing waste products and excess water, which are then converted into urine.
- Ureters: The tubes that carry the urine from the kidneys to the bladder.
- Bladder: The organ that stores the urine until it is ready to be expelled from the body.
- Urethra: The tube that carries the urine from the bladder out of the body.
The Structure of a Nephron:
The basic functional unit of the kidney is the nephron, which consists of the following parts:
- Bowman's capsule and glomerulus: The glomerulus is a network of blood vessels surrounded by the Bowman's capsule. This is where the initial filtration of the blood takes place.
- Convoluted tubules: The filtered fluid then passes through the convoluted tubules, where the composition of the fluid is further modified through the reabsorption of useful substances and the secretion of waste products.
- Loop of Henle: The loop of Henle is a U-shaped structure that plays a crucial role in the concentration of urine.
- Collecting duct: The collecting duct is the final part of the nephron, where the concentrated urine is collected and transported to the bladder.
Through the coordinated functions of the kidneys, the urinary system is responsible for the excretion of waste products and the maintenance of the body's water balance, pH, and other important physiological processes.
Work hard for your I/GCSE Biology examination!
End of analysis. Great!
