Answer: 3. They were born of one fertilized ovum.
Explanation: A zygote is formed
when an egg is fertilized by a sperm. The zygote then undergoes a mitotic division into two and each half will further develop into a separate embryo. The two embryos formed will develop into identical twins.
During stressful situations the sympathetic nervous system is activated <span />
Answer:
In animals that give live birth, the fetal circulation is the circulatory system of a fetus. The term usually encompasses the entire fetoplacental circulation, which includes the umbilical cord and the blood vessels within the placenta that carry fetal blood.
It's an important part of the bird's ability to maintain its body temperature.
Air is a poor conductor of heat, so the air trapped among the feathers
prevents the loss of heat in cold atmosphere, and prevents overheating
in hot atmosphere. Much like our wearing several layers of clothing.
