What is the substance that is inhaled and
what is it required for? and How is the substance that is exhaled
produced and why does it have to be
removed?

The substance that is inhaled is oxygen. It is used to provide energy to your body/muscles. Carbon dioxide is the substance that is exhaled and it is produced in the cells in our bodies in order to break down the food that we eat and subsequently produce energy for sustaining life. CO2 is considered waste and must be removed from the body because it is the result of used oxygen/energy.

Explanation:

Our diaphragm allows us to inhale and exhale oxygen/carbon dioxide. Oxygen is used as ATP energy when it powers our muscles/body. Oxygen is used to convert food into energy for our bodies and once it is all used up, it becomes carbon dioxide. From there, the waste that is a result of oxygen is exhaled through our lungs.

relative dating involves things like higher layers are most recent than rocks lower in the sequence. this can be extended to the known sequence of fossils. rocks containing rabbit fossils are later than those containing dinosaur fossils.  

absolute dating methods mainly use radioactive elements that have known rates of decay and produce recognizable products. for example potassium 40 decays to produce argon. once a rock has solidified the argon is trapped. by measuring the argon and potassium0 you can get an accurate number for the age.  

some other methods are good for archaeological ages. dendrochronology involves recognizing the sequence of tree rings. the orientation of magnetized particles in baked clay can be used to date a fire.

hope this .. .