Restriction of blood flow, something is blocking the blood flow, heart has slowed down and is being pushed to hard.
The concept of the struggle for existence<span> concerns the competition or battle for resources needed to live. It can refer to human society, or to organisms in nature. The concept is ancient, and the term </span>struggle for existence<span> was in use by the end of the 18th century. From the 17th century onwards the concept was associated with a population exceeding resources.
Hope this helped!
STSN</span>
