4.2. ATMOSPHERE AND LIVING THINGS

The atmosphere is essential for living things. It provides:

• A protective filter against solar radiation.
  • X-rays and gamma rays are absorbed in the ionosphere.
  • Ultraviolet rays (UV) are absorbed in the stratosphere by the ozone layer.
• Regulation of global temperature due to the greenhouse effect.
  

  YouTube: ESA “Paxi Greenhouse effect”.

  Some of the visible light that arrives at the surface of our planet is absorbed by the ground and warms it. The warm ground emits infrared radiation, which heats the atmosphere. This phenomenon is the greenhouse effect and it keeps the Earth warm.
• The oxygen (O₂) we need to breathe.
• The carbon dioxide (CO₂) used in photosynthesis.
• The nitrogen (N₂) used by some bacteria as a nutrient.