Which are the special proteins in muscles that contract and relax to cause movement?

 

In animals, parthenogenesis means development of an embryo from an unfertilized egg cell. In plants parthenogenesis is a component process of apomixis.Apogamy is a type of reproduction, occurring in some ferns, in which the sporophytedevelops from the gametophyte without fusion of gametes.Adventitious embryony also called sporophytic budding, is a type of apomixis in which an embryo develops directly from nucellus or integument tissue.So, all three are correct.

Plasmodesmata are interrupted by narrow pores carrying fine strands of cytoplasm, which interlink the contents of the cells.

Calcitonin is 32-amino acid linear polypeptide hormone that is produced in humans primarily by the parafollicular cells of the thyroid, and in many other animals in the ultimopharyngeal body. It acts to reduce blood calcium, opposing the effects of parathyroid hormone.