Pericardial sac also known as pericardium is a cone-shaped sac
made of fibrous tissue surrounding the heart and the blood vessels. It has two
parts: the inner coat which is double-layered supporting the heart; and the
outer coat which is solid and heavily built attached to the diaphragm and the
rear part of the breastbone.
Adaptation is evolutionary process that fits organisms to their environment, increasing their evolutionary fitness. It is in a first place, a process rather then a part of a body or a physical form.
Adaptation is one of two main processes that explain the observed diversity of species. Other process is speciation.
All adaptations help organisms survive in their environments.
The adaptive traits may be physiological, behavioural or structural.
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