What is rigor mortis and what causes it?

Answer and Explanation:

A couple of hours after the death of an individual or creature, the joints of the body solidify and become secured. This solidifying is called rigor mortis.  

Contingent upon body temperature and different conditions, rigor mortis endures roughly 72 hours.

The partial contraction of the skeletal muscles leads to the occurrence of this phenomena.

temporary rigidity of muscles after death; partial contraction of skeletal muscles

Explanation: Rigor mortis is defined as the temporary stiffness of a body's muscles and joints following death. It only lasts for a couple of hours (approximately 72 hours) depending on body temperature and other factors. Rigor mortis is caused by the skeletal muscles partially contracting resulting in stiffness. This causes the muscles to be unable to relax, leading to the body's joints becoming fixed in place.

organisms that lack symmetry are called asymmetrical and belong to phylum porifera/sponges.

organisms with specialized stinging cells belong to phylum cnidaria. stinging cells are called cnidoblast cells.

cnidarians show two morphological forms : polyp (sessile) and medusa (mobile)

filter feeding is observed in porifera members.  

alternation of generation is observed in coelenterata or cnidaria. there is alternation of asexual polyp form and sexual medusoid form. it is also referred as metagenesis.