9.1 The composition and evolution of the Earth's atmosphere

• How did the Earth's initial atmosphere form?

  Volcanic activity
• Why were photosynthetic organisms important for the Earth's atmosphere?

  Produced oxygen
• What are the primary functions of the Earth's atmosphere?

  Protects and regulates
• Match the gas with its approximate percentage in the Earth's atmosphere:

  Nitrogen ↔️ 78%

  Oxygen ↔️ 21%

  Argon ↔️ 0.9%

  Carbon dioxide ↔️ 0.04%
• The Earth's atmosphere is held in place by gravity
• Volcanic activity released carbon dioxide, water vapor, and ammonia into the Earth's initial atmosphere
• What is the major gas in Earth's atmosphere and its percentage?

  Nitrogen (N₂), 78%
• How was the Earth's initial atmosphere primarily formed?

  Volcanic activity
• Which process released oxygen into Earth's atmosphere, allowing aerobic life to evolve?

  Photosynthesis
• What type of organism first released oxygen into the Earth's atmosphere through photosynthesis?

  Cyanobacteria
• During the transition period, oxygen increased while carbon dioxide decreased.
• Carbon dioxide (CO₂) makes up 0.04% of Earth's atmosphere.
• The lack of oxygen in Earth's initial atmosphere hindered the development of aerobic life forms.


  True
• The lack of oxygen in Earth's initial atmosphere hindered the development of aerobic life forms.

  True
• The absence of oxygen in Earth's initial atmosphere limited the development of aerobic life forms.


  True
• Photosynthetic organisms release oxygen into the atmosphere, enabling aerobic life to evolve.


  True
• Nitrogen accounts for 78% of Earth's current atmosphere.

  True
• What is the Earth's atmosphere defined as?

  Layer of gases
• Volcanic activity released gases such as carbon dioxide, water vapor, and ammonia into the Earth's initial atmosphere.


  True
• Arrange the following gases in order of their abundance in the Earth's current atmosphere:

  1️⃣ Nitrogen

  2️⃣ Oxygen

  3️⃣ Argon

  4️⃣ Carbon dioxide
• The most abundant gas in the Earth's atmosphere is nitrogen
• The gases in the Earth's atmosphere play crucial roles in supporting life, such as absorbing ultraviolet radiation and regulating temperature.


  True
• Why is oxygen essential in the Earth's atmosphere?

  Supports aerobic life
• What was the limiting factor for aerobic life in the Earth's initial atmosphere?

  Absence of oxygen
• Oxygen (O₂) constitutes 21% of Earth's atmosphere.
• Carbon dioxide (CO₂) was highly abundant in the Earth's initial atmosphere.
• Photosynthesis converts carbon dioxide and water into glucose and releases oxygen.
• The reduction of carbon dioxide and ammonia in the atmosphere was pivotal in supporting diverse life forms.


  True
• What are three key functions of the Earth's atmosphere?

  Absorbing UV radiation, warming surface, reducing temperature extremes
• What process formed the Earth's initial atmosphere?

  Volcanic activity
• What process primarily formed Earth's initial atmosphere?

  Volcanic activity
• What role did volcanic activity play in forming Earth's initial atmosphere?

  Released volcanic gases
• Steps in the development of an oxygen-rich atmosphere on Earth:

  1️⃣ Photosynthesis by cyanobacteria

  2️⃣ Gradual increase in atmospheric oxygen

  3️⃣ Development of aerobic life
• In the early atmosphere, carbon dioxide and ammonia levels were high, while oxygen was completely absent
• The current level of carbon dioxide in Earth's atmosphere is approximately 0.04%
• The major gases in the Earth's atmosphere are nitrogen, oxygen, argon, and carbon dioxide
• The development of an oxygen-rich atmosphere was primarily due to photosynthetic organisms
• Current trends in atmospheric composition are a major environmental concern due to increasing carbon dioxide levels.


  True
• How does the Earth's atmosphere reduce temperature extremes?

  Heat retention
• What are the key roles of the Earth's atmosphere in protecting life?

  UV protection, greenhouse effect