Give two differences between a male and a female gamete.

In human females,where does the implantation and development of the embryo occur?

What is the effect of $DNA$ copying,which is not perfectly accurate,on the reproduction process? How does the amount of $DNA$ remain constant though each new generation is a combination of $DNA$ copies of two individuals?

Describe sexually transmitted diseases (STDs) and mention the ways to prevent them.

$(a)$ Draw a sectional view of the human female reproductive system and label the parts where:
$(i)$ eggs develop.
$(ii)$ fertilization takes place.
$(iii)$ the fertilized egg gets implanted.
$(b)$ Describe,in brief,the changes the uterus undergoes:
$(i)$ to receive the zygote.
$(ii)$ if the zygote is not formed.

$A$ part of the male reproductive system is shown below. Study the diagram and answer the questions that follow.
$(a)$ Two parts have been incorrectly labelled. Identify them.
$(b)$ Give the function of urethra.
$(c)$ Which hormone is released by testis?