In humans, the yolk sac is the
site of origin for blood cells and primordial germ cells. The human yolk sac is
a membrane located outside the embryo and it is connected by a tube through the
umbilical opening to the embryo's midgut. The yolk sac serves as an early site
for the formation of blood and in time, is incorporated into the primitive gut
of the embryo.
Answer:
A. Gravity
Explanation:
The strong gravity, or "Pull" of the Earth is what keeps the moon in orbit.
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A parasite could determine the size of the population. Whether it grows or shrinks. It could also change genetics
Answer:
Earth can be divided into three main layers: the core, the mantle and the crust. Each of these layers can be further divided into two parts: the inner and outer core, the upper and lower mantle and the continental and oceanic crust. Both the inner and outer core are made up of mostly iron and a little bit of nickel.
Explanation:
