Earth as a planet

• The earth is the third planet from the sun and the fifth-largest planet in the solar system
• Earth is the only planet which supports life
• 70 per cent of the earth's total area is covered by water
• The family of the sun is called the Solar System
• Members of the solar system

  • Planets
  • Satellites
  • Asteroids
  • Comets
  • Meteorites
• The planets in order of their distance from the sun are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune
• Shape of the Earth

  • Bulges slightly at the centre
  • Flattened at the poles
• In the olden days, the earth was considered to be a flat disc with steep edges
• Aryabhatta, the 5th century Indian astronomer and mathematician, believed in the round shape of the earth
• Pythagoras, the 6th century Greek philosopher, said the earth was spherical in shape
• Today, we have convincing evidence to prove that the earth is spherical in shape
• Proof that the Earth is Spherical in shape

  • Sighting of a ship
  • Bedford Level Experiment
  • Pole Star
  • Satellite Pictures
  • Lunar Eclipse
  • Circular Horizon
  • Sunrise and Sunset
  • Circumnavigation
• The earth is said to be an Oblate Spheroid, which means it bulges at the equator and is flattened at the poles
• The earth belongs to the Solar system and all planets in this system are spherical in shape
• Features that make Earth habitable


  • Distance from the Sun
  • Temperature
  • Atmosphere
  • Water
• The earth is at an optimum distance from the sun, which makes life possible
• The earth has an average temperature of 17°C which is suitable for life to exist
• The earth's atmosphere is a mixture of gases like nitrogen, oxygen, carbon dioxide, helium and argon
• Ozone in the earth's atmosphere absorbs the harmful ultraviolet rays of the sun
• The earth's atmosphere prevents loss of heat from the earth's surface and helps to keep the earth warm
• 70 per cent of the earth's surface is covered by water
• Water cycle

  1. Evaporation from oceans

  2. Transpiration from plants

  3. Condensation

  4. Precipitation
• The self-regulating and self-sustaining structural and functional unit of the biosphere is called the Ecosystem
• The ecosystem depends upon the sun for its energy
• The atmosphere receives heat from the sun by solar radiation and loses heat by earth's radiation. In this way a balance is maintained
• Gases in the earth's atmosphere

  • Nitrogen
  • Oxygen
  • Carbon dioxide
  • Helium
  • Argon
• Ozone present in the earth's atmosphere absorbs the harmful ultraviolet rays of the sun
• The atmosphere also prevents loss of heat from the earth's surface and helps to keep the earth warm
• Earth is a watery planet with 70 per cent of the earth's surface being covered by water
• Ecosystem

  The self-regulating and self-sustaining structural and functional unit of the biosphere
• Examples of ecosystems


  • Pond
  • Lake
  • Desert
  • Grassland
  • Meadow
  • Forests
• There is an exchange of materials and energy within the ecosystem as well as between adjoining ecosystems. They are all interconnected and hence, interrelated
• Biosphere

  The part of the earth's terrestrial system-including air, land and water-in which life develops and where life processes in turn get transformed
• Water can absorb enormous amount of heat without causing much change in its temperature
• But for the tremendous amount of water on the earth, far greater day and night temperature variations would exist
• Lithosphere

  The solid crust of the earth
• Due to the weathering of the rocks, the surface of the earth has been formed, which provides soil layer essential for supporting plant life
• Soil also provides various nutrients necessary for the growth of plants, which in turn support all forms of animal life directly or indirectly
• Biosphere


  The narrow realm of contact and interaction between the atmosphere, lithosphere and hydrosphere
• Biosphere provides all the necessities for all the species living on earth, i.e., light, heat, water, food and habitats