Science

• Air sacs in the lungs are holes called alveoli
• Alveoli have a lot of blood vessels known as capillaries wrapped around them
• The structure of an air sac includes:

  • A wall made of one layer of thin cells
  • Blood capillaries on the outside of the alveoli
  • Capillaries pressed tightly against the alveolus
  • Capillary wall made up of a single layer of very thin cells
• Gas exchange in the air sac involves:

  • Oxygen from the air going into the blood
  • Carbon dioxide from the blood going into the air
  • This process is known as gaseous exchange
• During gas exchange in the air sac:

  • Blood from the heart (inside the capillary) has less oxygen and a lot of carbon dioxide
  • Blood to the heart (air sac) has more oxygen and less carbon dioxide
  • Oxygen particles move from the air sac through thin-walled cells into the blood through diffusion
  • Oxygen dissolves in the blood and combines with haemoglobin inside red blood cells
• Quick question: Draw the structure of an air sac and label:

  • Blood capillary
  • Air sac
  • Blood from the heart
  • Blood to the heart
  • The direction of oxygen diffusion
  • The direction of carbon dioxide
  • The direction of inspired air
  • The direction of expired air
• Earth's climate has cycled between glacial and interglacial periods for the last 450,000 years
• Interglacial periods are characterized by permanent ice close to the north and south poles
• Glacial periods involve ice spreading much further south from the north pole
• Yuka lived in a very cold glacial period until about 10,000 years ago
• Yuka, a frozen body discovered in 1977 in eastern Siberia, lived and died about 39,000 years ago during an even colder period
• Ice ages are periods where Earth experiences cold periods with glacial and interglacial periods
• During ice ages, there is no permanent ice formation due to the warm Earth climate
• Ancient glaciers carried boulders away as they moved slowly downhill
• Evidence of Earth being colder in the past includes boulders, fossils of animals and plants, pollen evidence, and the formation of peat bogs in specific conditions
• Pressure in liquids increases with depth
• The wall of a dam is wider at the bottom to make it stronger where pressure from the water is greatest
• In liquids, pressure increases with depth because the weight of the liquid caused by gravity pushes on the particles, increasing the force on the particles
• Pressure in liquids is equal in all directions as particles move randomly in all directions
• Pressure in gases is the same inside and outside a balloon before it is blown
• Particles in gases move randomly and collide with the container walls
• More particles in a gas lead to more collisions, increasing the force and creating high pressure
• Pressure in gases also increases with depth, similar to liquids
• Earth's atmosphere is made up of gases, with atmospheric pressure highest at sea level
• At sea level, atmospheric pressure is 100000N/m square, equivalent to two large elephants pushing on every square meter
• Increasing the temperature of a gas increases its pressure
• Atmosphere is a layer of gas above the Earth's surface
• Earth formed 4600 million years ago
• The Earth was hot and molten for millions of years before cooling and forming a solid crust
• Early atmosphere was formed by volcanic activities producing gases and water vapor
• Water vapor produced by volcanoes fell as rain, forming the first lakes and oceans
• Fossil fuels are formed when organisms die and rot, releasing carbon back into the environment
• Some organisms turn into fossil fuels like oil and coal, locking up carbon until burned
• Bioplastics are biodegradable materials from renewable sources like vegetable oil and food waste
• Renewable sources include wind, tidal, and solar energy
• Pressure in liquids increases with depth
• The wall of a dam is wider at the bottom to make it stronger where pressure from the water is greatest
• In liquids, pressure increases with depth because the weight of the liquid caused by gravity pushes on the particles, increasing the force on the particles
• Pressure in liquids is equal in all directions as particles move randomly
• Pressure in gases is the same inside and outside a balloon before it is blown up