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Theory:

Oxygen in water:
When water is heated for some time (before it starts boiling), we can see that small bubbles form on the inner surface of the vessel. These bubbles are seen as the air dissolved in water escapes. Water turns into vapour and begins to boil when heating continues.
 
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Boiling water
 
Water bodies like ponds, lakes, rivers and seas have some amount of dissolved oxygen in it. Aquatic plants and animals inhale dissolved oxygen present in water.
Example:
Frogs respire through their moist skin.

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Frog
 
Aquatic animals like fish respire through their gills.
 
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Fish
Oxygen in soil:
When water is poured over a lump of soil, small air bubbles come out of the soil, indicating the presence of the air.
 
Several plants and organisms living in the soil use oxygen to breathe. Various organisms like earthworms, rabbits, meerkats, and kangaroo mice form burrows and holes deep inside the soil.
 
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Rabbit and earthworm
 
These holes make the air to move in and out of the soil. During rainy seasons, when water fills up these spaces in the soil, animals and worms come out for respiration.