Reproduction

1
Section 13.2

• Reproduction

2
Sex Cells

• Male- sperm
• Female- egg
• Zygote- when sperm and egg unite to form one cell
• Single cell rapidly divides to form trillions of
  cells

3
Males

• Primary reproductive organ- testes
• Testes- where sperm is produced
• Sperm have a head and tail and move very fast
• Sperm contain half of DNA
• Sperm production begins at puberty
• Testes located in scrotum- sac located outside of
  the body- keeps sperm at ideal temperature

4
Testosterone

• Secreted by the testes
• Causes many changes in males
• Changes in secondary sexual characteristics
• Deepening of voice, growth of body hair, and
  development of reproductive organs

5
Females

• Primary reproductive organ- ovary
• Ovary contains eggs which are released monthly
  starting in puberty
• Egg contains half of DNA
• Changes in secondary sexual characteristics
• Body hair growth, breast development, development
  of reproductive organs, and onset of menstrual
  cycle.

6
Menstrual cycle

• Lasts approximately 28 days
• First 3-7 days marked by bleeding- shedding of
  lining of uterus (menstrual period)
• Release of one egg at a time
• Egg travels down fallopian tubes- passageway from
  ovary to uterus
• Process called ovulation

7
Fertilization

• Occurs when sperm unites with egg- forms zygote
• Zygote now contains complete DNA
• Fertilization occurs in fallopian tube
• Zygote travels to uterus where it will implant
  itself
• Menstrual cycle will not begin

8
Twins

• Sometimes woman releases two eggs at once.
• If both are fertilized you will have fraternal
  twins- not identical
• Sometimes one egg is fertilized by single sperm
  but later divides to form 2 separate cells- this
  forms identical twins