lesson 18 transcript + study guide Flashcards
adaptive features of sexual reproduction
genetic diversity
increases evolutionary adaptability
can better respond to changing enviroments
asexual reproduction
faster
genetically identical offspring
used by hydra and parthenogenesis
oviparous
Eggs are laid outside the body;
embryo develops externally (e.g. birds, reptiles).
ovoviviparous
Fertilized eggs develop inside the female, but nourishment comes from the egg yolk, not the mother (e.g. some sharks, reptiles).
viviparous
Offspring develop inside the mother, receive nourishment via the placenta (e.g. most mammals)
parthenogenesis
Asexual reproduction from unfertilized eggs (e.g. honeybees, Komodo dragons).
synchronous hermaphrodites
Organisms with both ovaries and testes at the same time (e.g. earthworms).
sequential hermaphrodites?
Organisms that change sex during life.
Protandry = male → female
Protogyny = female → male (e.g. bluehead wrasse)
Marsupials
give birth to underdeveloped young; continue developing in a pouch
Placentals
young develop fully in the uterus and are nourished by the placenta
Estrous
Fertile period is when in “heat”; no menstruation
Menstrual
Endometrial lining shed monthly; can mate any time (e.g. humans, apes)
FSH in spermatogenesis
stimulates Sertoli cells to support sperm production
LH in spermatogenesis
stimulates Leydig cells to produce testosterone
LH in oogenesis
stimulates follicle growth
FSH in oogenesis
triggers ovulation and development of the corpus luteum
HCG: Human Chorionic Gonadotropin
Produced by the embryo after implantation
Maintains corpus luteum → keeps progesterone high
Prevents menstruation and supports early pregnancy
Detected in pregnancy tests
GnRh
hypothalamus
stimulates anterior pituitary to release LH and FSH
FSH
anterior pituitary
stimulates follicle growth , estrogen production, initiates oogenesis
LH
anterior pituitary
triggers ovulation
stimulates corpus luteum
promotes progesterone
estrogen
follicles
stimulates proliferation (thickening of uterine lining)
develops and maintains secondary sexual characteristics
works with LH/FSH on the cycles follicular phase
progesterone
source: corpus luteum
maintains endometrium
inhibits FSH via negative feedback
