Out of water the gills become dry and stick to each other. Thus gas exchange cannot occur.

During drowsiness, our breathing rate slows down. The lungs do not get enough oxygen from the air resulting in yawning. Yawning brings extra oxygen into the lungs and helps us to keep awake.

During heavy exercise, more energy is required which cannot be fulfilled by respiration. Thus, to fulfil this demand, anaerobic respiration takes place in muscles which involves partial breakdown of glucose. The partial breakdown of glucose produces lactic acid which accumulates and cause muscle cramps.
Glucose\(\overset { absence }{ \underset { of\ { O }_{ 2 } }{ \xrightarrow{} } } \)Lactic acid+Energy

During heavy exercise, more energy is required. But the supply of oxygen that provide energy is limited. The anaerobic respiration in muscle cells takes place to fulfil the demand of energy. The partial breakdown of glucose produce lactic acid.
The accumulation of lactic acid causes muscle cramps.
Glucose\(\xrightarrow[of\ CO_2]{absence}\)Lactic acid + Energy.

All the organisms need energy for their various functions. Energy is released from the breakdown of food (glucose) with the help of oxygen. The breathing ensures the continuous supply of oxygen to different body cells.  

We exhale a mixture of gases together with carbon dioxide.

Breathing rate is the lowest during sleep and highest while jumping.

Yes. When we feel drowsy our breathing rate becomes slow

Yes, because after physical activity we require energy.

Anaerobic respiration

The CO₂ released by us is used by plants during the process of respiration and they release O₂ as a result of this process which is used by rest of the organisms.

 Insects possess special organ called spiracles for respiration.

When we exhale into lime water its colour changes, into slightly milky white because exhaled air contains CO₂,

Earthworm is an animal where exchange of gases during breathing or respiration takes place through its thin and moist skin

The end product formed during anaerobic respiration in yeast are
(i) Ethyl alcohol
(ii) Carbon dioxide
(iii) Energy