Excretion in Plants and the Mammalian Kidney
Excretion and Homeostasis · Excretion and the Kidney
Syllabus tag: KCSE | Biology | Form 2 | Topic 5 Excretion and Homeostasis
Lesson objectives
By the end of this topic, you should be able to:
- Define excretion and name the excretory products of plants and animals.
- Describe the structure of the kidney and the nephron.
- Explain ultrafiltration, selective reabsorption and osmoregulation.
- Explain kidney failure and its treatment.
Summary
Excretion is the removal of metabolic waste — waste produced by the body's own chemical reactions. Plants have no special organs and use diffusion, storage and leaf fall. Mammals use the kidney, whose functional unit is the nephron. Urine is formed in two stages: ultrafiltration forces small molecules out under pressure, then selective reabsorption takes back what the body needs.