Planet Earth is unique – it supports life!
Our solar system consists of the sun (which is a star) with nine planets that orbit around it.
- Earth is the only planet known to have water, oxygen and living organisms.
- The sun is the primary energy source for life on earth and provides light and heat.
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About 72% of the earth is covered with water, but most of it is salty.
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1% of the water is fresh water.
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2% of the water is ice, frozen at the poles.
What makes the sea salty?
Salts come from two sources:
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Salts are washed out of rocks and travel via rivers into the ocean.
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Salts come from the ocean floor where water seeps through cracks into the hot crust of the earth and chemical reactions remove and add salts to the water.
Sea water consists of 96% water and 3% common salt; 80 different elements can be found in the remaining 1%, including gold. The sea contains approximately 35gm of salt for each litre of water or 35 parts per thousand (ppt). Salinity is higher at the equator due to evaporation and at the poles due to the removal of water as ice.
Living in salty water.
Seawater is a comfortable place in which to live. Life itself probably began in the sea. Water supports plants and animals so they don''t need strong bones or woody trunks. Their bodies have similar salt concentrations to the seawater so they do not gain or lose water. Animals on land lose water to the air and must drink, while animals in fresh water absorb too much water. Marine birds and turtles have special salt glands and get rid of excess salt in tear-like drops.
