1. the first and shortest stage of prenatal development is where the the zygote begins to grow in complexity during the first two weeks of conception. 2. the stage lasts from 2 - 8 weeks following fertilization, when major organs and basic anatomy begin to develop. 3. the stage lasts from 8 weeks until birth and involved the differentiation of major organs.

The first and Shortest stage of prenatal development is Germinal stage, where the zygote begins to grow in complexity during first two weeks of conception.

The embryonic stage lasts from 2-8 weeks following fertilisation,when major organ and basic anatomy begin to develop.

The fetal stage lasts from 8 weeks until birth and involved the differentiation of major organs.

Explanation:

Periods of pregnacy and major events are as follows:

answer:   option a) glucagon was secreted by his pancreas before he ate the cookies because blood glucose was low. insulin was secreted after he ate the cookies because his blood glucose was high.

explanation: