Explanation

Demography is the statistical study of human populations.

Demography examines the size, structure, and movements of populations over space and time. 

Explanation

A solar eclipse can only take place during the phase of the new moon

when the moon passes directly between the sun and Earth and its shadows fall upon Earth's surface.

Explanation

Thus, the First law of thermodynamics furnishes the relationship between:

• heat
• work
• the internal energy of the system

Explanation

• Membranes present around the embryo are Chorion
• ***
• Chorion is also called Serosa
• in reptiles, birds, and mammals, the outermost membrane around the embryo.
• It develops from an outer fold on the surface of the yolk sac.
• **
• The fetal membranes or extraembryonic membranes, are membranes associated with the developing fetus.
• The two chorioamniotic membranes are the amnion and the chorion
  

Explanation

Entomology is the study of insects and their relationship to humans, the environment, and other organisms.

while

Zoology is the study of all animals.

Biology is a natural science concerned with the study of life and living organisms.

Etymology investigates and documents the lives.