question_answer 37)

  Morula is a developmental stage (a) between the zygote and blastocyst                  (b) between the blastocyst and gastrula (c) after the implantation                                             (d) between implantation and parturition

Answer:

                  (a)The haploid nucleus of the sperms and that ofthe ovum fuse together to form adiploid zygote. As the zygote moves through the isthmus of the oviduct towards the uterus, the mitotic division (cleavage) starts and forms 2, 4, 8, 16 daughter cells called  blastomeres. The embryo with 8-16 blastomeres is called a morula. Themorula continues to divide and transforms into blastocyst as it moves further to get embedded in the endometrium of the uterus. This is called implantation.