Reproduction

Question 1

Asexual reproduction

Answer 1

○ Progeny are practically genetically identical to the parent
○ Examples: Budding, fragmentation (piece of body becomes offspring), parthenogenesis (egg w/o fertilization)

Question 2

Sexual Reproduction

Answer 2

○ Reproduction of progeny from two parents that contribute nearly equal amounts of genetic material
○ 2 haploids –> diploid
○ Is beneficial because it generates variation

Question 3

Generalized Life Cycle

Answer 3

• Life cycle begins with two haploid cells, which forms a zygote that then multiplies into a blastula, which then folds into itself forming the gastrula

Question 4

Hermaphroditism

Answer 4

• Capacity to produce egg and sperm at the same time
• Serial hermaphrodites change sex in response to environmental cues, either protogynous (female –> male) or protandrous (male –> female)

Question 5

Vivipary

Answer 5

○ Most mammals
○ Young develop within the female body
- Internal fertilization

Question 5

Sex Determination

Answer 5

• Determining sex is done through chromosomes in mammals
  
  • Birds and butterflies are the opposite, males are ZZ females ZW
  • Honeybees and some ants have females and fertilized and males as unfertilized
• Temperature of eggs in many reptiles determines sex, possibly due to hormone levels in egg

Question 6

Ovipary

Answer 6

○ Ova laid and all development occurs externally
○ Fertilization can be external or internal
○ Birds, some fish and reptiles

Question 6

Ovo-Vivipary

Answer 6

○ Ova is laid within the mothers body
○ Develops and hatches internally until birth
○ Some reptiles and fish

Question 6

LH

Answer 6

Made in the anterior pituitary, Leydig cells, stimulates androgen synthesis and release. Converts progesterone to testosterone

Question 6

Androgens

Answer 6

Made in the testes, responsible for secondary sex characteristics and sperm

Question 7

FSH

Answer 7

Made in anterior pituitary, Sertoli cells, produces sperm

Question 8

Birth

Answer 8

• Induced by contraction of smooth muscles of uterus
  
  • Contractions begin in response to a series of hormonal changes
    ○ Progesterone levels decrease
    ○ Prostaglandins and oxytocin are released by fetus
    Placenta is expelled after birth

Question 8

Prostaglandins

Answer 8

Found in the uterus of mate, induce changes within the uterus that affect sperm motility

Question 8

GnRH

Answer 8

Made in the hypothalamus, stimulates LH and FSH

Question 8

Fertilization

Answer 8

• Sexual reproduction requires haploid gametes to come in close contact
  
  • Gametes require and aqueous environment, which is difficult for terrestrial animals and leads to high levels of gamete failure
  • After fertilization the zygote multiplies and becomes a blastocyst, which implants itself into the uterus, releases trophoblast becoming the placenta
    ○ Placenta is the interface between the mother and fetus and is composed of cells derived from both
    ○ Placenta has vital endocrine function
    Placenta produces estrogen and progesterone

Question 9

Prolactin’s Role in Lactation

Answer 9

• Prolactin is released from anterior pituitary that controls milk production
  ○ It increases mammary gland mass and ensures biosynthetic machinery in place
  ○ Is released due to increased estrogen levels during pregnancy
  High levels of progesterone and estrogen suppress milk production during pregnancy

Question 9

Menstrual Cycle

Answer 9

• Estrous Cycle
  ○ Sexual receptivity coincides with specific phase of cycle
  ○ Amount of uterine tissue lost in minimal to moderate
  ○ Present in most mammals except primates
  
  • Menstrual Cycle
    ○ Sexual receptivity occurs at many phases of the cycle
    ○ Amount of uterine tissue lost is substantial
    ○ Present mainly in primates
    ○ Has 3 phases: follicular, ovulation, and luteal
    § Follicular: Follicles get larger and larger until it reaches the edge of the ovary, causing ovulation, when the ova is released into the duct for fertilization
    § Luteal: Causes raise in hormone production and gets egg ready for a safe fertilization and eventually dies w/o fertilization, causing menstruation
    § FSH begins the menstrual cycle