The muscles that contract (during cold or fright), the slanted hair follicle is pulled upright, dimpling the skin surface with goosebumps are called arrector pili muscle.
The arrector pili muscle are tiny muscle that attaches to the base of the hair follicle at one end and to the dermal tissue on the other end. When the body feels cold or fright the body generate heat and the arrector pili muscle contract all at once, that causes goosebumps on the skin.
The arrector pili muscle acts as the thermoregulator. Straight stand hair increases air trapping, so that the heat loss from the body decreases. The arrector pili muscle are mediated by the sympathetic nervous system.
To learn more about sympathetic nervous system here
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Can you be more specific to the question
The main reason is because they are heavy, and because they don't have to chase their food. They're not predators and their shells give them protection like running away gives protection to other herbivores.
Answer:
A. physical characteristics of a trait
Peristalsis helps in storing food, breaking down food down and mixing it with juices secreted by stomach lining. Peristalsis in stomach helps in partial digestion of food called chyme.
