Answer:
Gastrulation takes place after cleavage and the formation of the blastula and the primitive streak. It is followed by organogenesis, when individual organs develop within the newly-formed germ layers. Each layer gives rise to specific tissues and organs in the developing embryo.Cells in each germ layer differentiate into tissues and embryonic organs. The ectoderm gives rise to the nervous system and the epidermis, among other tissues. The mesoderm gives rise to the muscle cells and connective tissue in the body. The endoderm gives rise to the gut and many internal organs.
You can easily remember it because the scientific name of leech is Hirudinaria. So it secretes anticoagulant named hirudin. Which help it to feed blood longer
A dependent variable is a value that depends on another, so what relies on the other! :)
