Months
Gastrulation
100

This animal is pregnant for 10 months

What are cattle. 

100

Forms glands of the respiratory and digestive systems

What is the endoderm

200

This animal is pregnant for 11 months

What are horses?

200

Forms muscle, bone, circulatory system, urinary and reproductive systems

What is the Mesoderm

300

These animals are pregnant for 4 months

What is a pig

300

Forms epidermis of skin, nervous system and integumentary system

What is ectoderm
400

These animals are pregnant for five months

What are sheep and goats

400

Begins with the fusion of two gametes

What is fertilization

500

These animals are "pregnant" for three weeks

What are chickens?

500

Is the process in which a zygote is transformed into an adult organism

What is embryonic development