Lesson 2
The earth
- Earth is one of eight planets orbit the sun under the effect of gravity.
- Earth completes one orbit around the sun in 365.25 days.
- Earth is the third planet from the sun on distance of 150 million km.
- Earth is a spherical body almost circular with flatness at two poles.
- The equatorial diameter increase by 22km from the polar diameter.
Volume of earth: Earth is the fifth planet in size, its diameter average is about 6368 km.
Mass of earth : Earth is planet in the inner planets with mass of
5.9 x 1024 kg.
Characteristics of earth planet and continuity of life
1- Earth atmosphere : consists of mixture of gases with different ratio; oxygen 21%,nitrogen (78%) ,(carbon dioxide 0.03%) water vapour (variable –other gases (very small ratio)
1- Importance of atmosphere:
1- Oxygen gas essential for living organisms for respiration and burning process (combustion of fuel) nitrogen reduce the effect of oxygen gas on combustion and used by living to form protein carbon dioxide used by green plants in photosynthesis.
2- Atmosphere and its great expansion in space cause complete burning of millions of small meteors that fall on earth and decrease the speed of large ones and burn part of it.
3- Weather phenomena and climate like wind movement and formation of clouds and rain.
4- Atmosphere help to preserve suitable temperature on earth.
5- Atmosphere contain ozone layer which protect living organisms from harmful sunrays (ultraviolet rays).
2- Aquatic envelope of earth :Distribution of water on earth surface. Water represents about 71%of the earth surface.
salty water 97% (seas and oceans )
fresh water 3%(rivers ,lakes ,frozen ice at poles ) and under ground water.
2- Importance of water for living organisms:
1- Used by plants in photosynthesis
2- Important for completing vital process as digestion ,and exists in blood structure ,regulates body temperature.
3- Helps to maintain suitable temperature on land
4- Aquatic envelope represent the life environment for large number of living organisms more than 50% fall known living organisms.
3- Suitable temperature of earth help continuity of life
4- Gravity
1- Causes stability of living organisms and things on earth surface.
2- Keeps earth atmosphere.
3- Stability of aquatic envelope
5- suitable air pressure: atmosphere pressure is 76 cm/hg
Inner structure of earth
Earth is formed from many layers. Heavy materials (iron and nickel ) exist down and lower density substance float on the surface.
Earth consists of three layers:
1- earth crust
2- mantle
3- earth core ( inner –outer)
Layers of earth
Crust
Mantle
Core
External layer comparatively light its thickness ranges between 8 to 40 km
Rocky layer exist after crust its thickness about 2885 km
Inner core
Outer core
Molten metals of thickness 2270 km
Solid layer of iron and nickel its diameter is 1216 km
The earth
- Earth is one of eight planets orbit the sun under the effect of gravity.
- Earth completes one orbit around the sun in 365.25 days.
- Earth is the third planet from the sun on distance of 150 million km.
- Earth is a spherical body almost circular with flatness at two poles.
- The equatorial diameter increase by 22km from the polar diameter.
Volume of earth: Earth is the fifth planet in size, its diameter average is about 6368 km.
Mass of earth : Earth is planet in the inner planets with mass of
5.9 x 1024 kg.
Characteristics of earth planet and continuity of life
1- Earth atmosphere : consists of mixture of gases with different ratio; oxygen 21%,nitrogen (78%) ,(carbon dioxide 0.03%) water vapour (variable –other gases (very small ratio)
1- Importance of atmosphere:
1- Oxygen gas essential for living organisms for respiration and burning process (combustion of fuel) nitrogen reduce the effect of oxygen gas on combustion and used by living to form protein carbon dioxide used by green plants in photosynthesis.
2- Atmosphere and its great expansion in space cause complete burning of millions of small meteors that fall on earth and decrease the speed of large ones and burn part of it.
3- Weather phenomena and climate like wind movement and formation of clouds and rain.
4- Atmosphere help to preserve suitable temperature on earth.
5- Atmosphere contain ozone layer which protect living organisms from harmful sunrays (ultraviolet rays).
2- Aquatic envelope of earth :Distribution of water on earth surface. Water represents about 71%of the earth surface.
salty water 97% (seas and oceans )
fresh water 3%(rivers ,lakes ,frozen ice at poles ) and under ground water.
2- Importance of water for living organisms:
1- Used by plants in photosynthesis
2- Important for completing vital process as digestion ,and exists in blood structure ,regulates body temperature.
3- Helps to maintain suitable temperature on land
4- Aquatic envelope represent the life environment for large number of living organisms more than 50% fall known living organisms.
3- Suitable temperature of earth help continuity of life
4- Gravity
1- Causes stability of living organisms and things on earth surface.
2- Keeps earth atmosphere.
3- Stability of aquatic envelope
5- suitable air pressure: atmosphere pressure is 76 cm/hg
Inner structure of earth
Earth is formed from many layers. Heavy materials (iron and nickel ) exist down and lower density substance float on the surface.
Earth consists of three layers:
1- earth crust
2- mantle
3- earth core ( inner –outer)
Layers of earth
Crust
Mantle
Core
External layer comparatively light its thickness ranges between 8 to 40 km
Rocky layer exist after crust its thickness about 2885 km
Inner core
Outer core
Molten metals of thickness 2270 km
Solid layer of iron and nickel its diameter is 1216 km
