chapter 46. animal reproduction - quia · animal reproduction chapter 46. 2 apbi olgy 2004-2005...
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2004-2005AP Biology
Animal Reproduction
Chapter 46.
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Sexual & asexual reproduction Asexual
production of offspring with genes from oneindividual
Sexual formation of gametes & fertilization genetic recombination & variation
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Parthenogenesis Development of an unfertilized egg
honey bees drones = males produced through
parthenogenesis → haploid workers & queens = females produced from
fertilized eggs → diploid
queen worker drone
Honey bee eggs hatch regardless of whether the are fertilized. Thefemale bees--queens & workers--develop from fertilized eggs thatcontain 32 chromosomes. These 32 chromosomes consist of twosets of 16, one set from each parent. Hence female bees are said tobe diploid in origin. The males (drones) develop from unfertilized eggwhich contain only one set of 16 chromosomes from their mother.Drones are thus haploid in origin This reproduction by thedevelopment of unfertilized eggs is called parthenogenesisDrones develop by parthenogenesis from unfertilized eggs that thequeen produces by withholding sperm from the eggs laid in largedrone cells. Drones lack stings and the structures needed for pollencollection; in the autumn they are ejected by the colony to starve,unless the colony is queenless. New drones are produced in thespring for mating.Both queens and workers are produced from fertilized eggs. Queenlarvae are reared in special peanut-shaped cells and fed more of thepharyngeal gland secretions of the nurse bees (bee milk or royaljelly) than the worker larvae are. The precise mechanism for thiscaste differentiation is still uncertain. Although workers are similar inappearance and behavior to other female bees, they lack thestructures for mating. When no queen is present to inhibit thedevelopment of their ovaries, however, workers eventually begin to layeggs that develop into drones.
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Differentworlds…
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Hermaphrodites
flat worm
earth worms mating
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Fertilization External
usually aquatic animals Internal
usually terrestrial animals
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Development External
in water (eggs) on land (amniotic eggs) oviparous: lay eggs ovoviparous: live births from eggs
sharks & some snakes
Internal placenta viviparous:
live placental birth
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Adaptive advantages? What is the adaptive value of each
type of sexual reproduction number of eggs? level of parental of care habitat?
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Human reproduction Male reproductive system
over 100 million per day!
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Male reproductive system
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Testosterone regulated by
FSH & LH frompituitary
Hormonecontrol oftestes
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Spermatogenesis
Meiosisproducesgametes inseminiferoustubules
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spermatocytes
seminiferoustubule
sperm
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Female reproductive system
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Female reproductive system
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Sex hormones: female Estrogen
ovaries stimulates uterine lining growth 2° female sex characteristics regulated by FSH & LH from pituitary
Progesterone ovaries stimulates uterine lining growth regulated by FSH & LH from pituitary
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Hormoneregulationof femalecycleWhat happens in:pituitary glandovaryuterus
Menopause46-54ovaries lose
response toFSH & LH
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Oogenesis
state of eggwhen fertilized
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Ovarian cycle
Stages ofdevelopmentin ovary
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Fertilization
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Early development
blastocyst
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Placenta Materials exchange across membranes
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Fetal developmentamniotic sac
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BirthHormoneinduction
positive feedback
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Birth