Fill in the Blanks Animal reproduction gaps4Online version Fill in the gaps with the appropriate word. by Gabriel Pérez Comendador 1 born zygote embryo sperm embryo survive sperm ovum ovum Internal fertilization occurs when a and an meet and unite . The union of a and an creates a new cell called a . Then it starts to divide and grow into an . The develops until it is ready to externally , then it is .