Edexcel IGCSE Biology 复习笔记 1.1.3 Living Organisms: Excretion

Edexcel IGCSE Biology 复习笔记 1.1.3 Living Organisms: Excretion

Excretion

 

 

  • Chemical reactions that take place inside living cells are described as metabolic reactions
  • Metabolic reactions produce waste products, some of which may be toxic
  • These toxic products must be eliminated from the body
  • Excretion is the removal of toxic materials and substances from organisms

 

Excretion in animals

  • Waste products excreted by animals include:
    • Carbon dioxide from respiration
    • Water from respiration and other chemical reactions
    • Urea which contains nitrogen resulting from the breakdown of proteins

     

 

 

 

Excretion-in-animals

 

Excretion in humans, the waste products and organs involved

 

 

 

Excretion in plants

  • Waste products excreted by plants include:
    • Oxygen from photosynthesis
    • Carbon dioxide from respiration
    • Water from respiration and other chemical reactions

     

 

 

 

Excretion-in-plants

 

Excretion in plants, the waste products and the difference between day and night

 

 

Exam Tip

Excretion is often confused with egestion. Remember that the waste products removed through excretion have originated from chemical reactions in the cells. However, the waste products produced in egestion are in the form of faeces and originate from the remains of the substances not absorbed during digestion.

转载自savemyexam

更多IGCSE课程
翰林国际教育资讯二维码