pt. 2 (animal reproduction)

• External Fertilization


  Occurs outside the female body. May be triggered by water temperature or length of daylight in aquatic creatures.
• Spawning


  Females and males release eggs and sperm at each other
• Internal Fertilization


  Occurs inside the female body. Most often found in land-based animals or in some aquatic animals.
• Reproductive Modes

  • Oviparity
  • Ovoviviparity
  • Viviparity
• Oviparity


  Fertilized eggs are laid outside the female's body and develop there. Nourishment is received from the yolk that is part of the egg.
• Ovoviviparity


  Fertilized eggs are retained in the female but the embryo obtains nourishment from the egg's yolk. When hatched, yolk and young are both developed. The young are alive when hatched.
• Viviparity


  The young develops within the female, receiving nourishment from the placenta. The offspring develops in the female and is born alive.
• Spermatogenesis


  The process by which sperm cell production occurs.
• Oogenesis


  The process of formation of female gametes.
• Male Hormones

  • Testosterone
  • FSH (Follicle-stimulating hormone)
  • Luteinizing Hormone (LH)
  • Gonadotropin Releasing Hormone (GnRH)
• Testosterone


  Rises at puberty. Influences the development of secondary male characteristics, maintains reproductive tract, promotes sperm production, influences sex drive & behavior.
• FSH (Follicle-stimulating hormone)


  Promotes/initiates sperm production. Secreted by pituitary gland.
• Luteinizing Hormone (LH)


  Assists spermatogenesis and initiates production of testosterone. Secreted by pituitary gland.
• Gonadotropin Releasing Hormone (GnRH)


  Secreted by hypothalamus gland. Causes pituitary to release FSH and LH. Testosterone production is regulated by NEGATIVE FEEDBACK.
• Menstrual Cycle Stages

  • Follicle Stage
  • Ovulation
  • Luteal Phase/Corpus Luteum
  • Menstruation
• Follicle Stage (Day 1 - Day 13)


  FSH and estrogen levels increase in the body at Day 1 - Day 10. At Day 7, as the egg matures, estrogen is secreted by the ovaries. Follicles produce low levels of estradiol that then inhibits GNRH secretion and causes endometrial arteries to constrict, resulting in menstruation.
• Ovulation (Day 14)


  Negative Feedback - the high levels of estrogen in the blood decreases the secretion of FSH which prohibits the growth of mature ovarian follicles. The pituitary gland then secretes luteinizing hormone causing ovulation. Ovulation occurs due to the maturation of follicles within the ovaries (with the help of Follicle Stimulating Hormones). Growing follicles produce estradiol which stimulate GnRH secretion and cause the endometrium to thicken.
• Luteal Phase/Corpus Luteum (Day 15 - 27)


  After ovulation, corpus luteum is formed. Progesterone - creates thick uterine lining and prohibits the development of follicles in the ovaries. Secretes estradiol and progesterone that blocks GnRH production and causes the endometrium to further develop.
• Menstruation (Day 28)


  Walls of the uterus shed, resulting in menstruation.
• Human Fertilization


  1 sperm fuses with 1 egg creating a zygote
• Cleavage


  Process in the Oviduct where the zygote divides by mitosis increasing the amount of cells.