Physical activity causes an increase in your heart rate. Your body have to change the way it behaves so you don’t get ill or sick or pass out during physical exertion
I believe it's lactic acid and energy.
<h2>Answer:</h2>
The two reasons are given below:
- Natural selection.
- Lack of food
<h3>Explanation:</h3>
Natural selection is the phenomenon of the evolution in which the organisms able to fit in the changing environment survive while other organism died. Hence the survival if the fittest and then these organisms. Further reproduce to give birth organisms more fit to the changing environment.
The long neck giraffe survive but short neck died. So the population of long neck increased while short neck go extinct.
Other reason is the change of food resource. The food resource change from grass to long trees.
