Question

10.Development of axes: animal-vegetal, anteroposterior, dorso-ventral; their fixing during specific stages of development 11. Alternative pathway of development 12. Differentiate between techniques: heterochronic transplantation, clonal analysis, heterotopic transplantation, isolation 13. Bottle cells and blastopore 14.Differentiate : coelom, archenteron, blastocoel, blastopore, primitive groove 15. Definitions: migration, invagination, intercalation, ingression, epiboly, involution, convergent extension, delamination 16. Patterns of gastrulation in different groups of animals 17. Definition of Neurulation 18. Compare neurulation in Birds and in Amphibians

Answer 1

ANSWER:8

Development of animal-vegetal axis:An embryo is basically divided into two parts:

i)animal pole

ii)vegetal pole

Animal pole is basically the part that will divide into three germ layers in later stage of life.On the other side vegetal pole is the one differentiating into extraembryonic membrane that will protect and nourish the embryo.Animal pole is highly pigmented and the vegetal pole is less pigmented.

The development of animal-vegetal axis occurs prior to fertilization.sperm enters the ova during the process of fertilization .The point of sperm entry is the Dorso ventral axis;and cells opposite to the point are sperm entry are the ones forming dorsal portion of the body.

anteroposterior :ends from head end to the opposite end of body or tail.