Animal Reproduction

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Animal Reproduction
Asexual-All genes from one parent, mitotic cell
division many offspring-little variation
Fission Budding Gemmules Fragmentation
Regeneration Parthenogenesis-between-Daphnia,
males of social insects, some fishes,
amphibians, lizards Sexual-Fusion of haploid
gametes to form a zygote gametes produced
by meiosis ovum-large sessile
spermatozoon-small motile sexual recombination -
fewer offspring - greater variation
Hermaphroditism-most mate, all indv. Are
potential mates sequential
hermaphroditism External fertilization
Internal fertilization
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Parthenogenesis with Male stimulation but
not fertilization
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External fertilization
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Male parental care
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Hermaphroditism
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Testes-seminiferous tubules Leydig
cells-produce testosterone scrotum- epididymis-
6m. long tubules takes 20 days for sperm to pass
through vas deferens-during ejaculation carry
sperm up into the abdomen, over the urinary
bladder and connect to the urethra inside the
prostate gland semen-secretions of the seminal
vesicles (alkaline mucus, fructose,
prostaglandins) prostate gland (citrate and
anticoagulant) Bulbourethral glands (alkaline
fluid that precedes the sperm) and 300 million
sperm
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the penis is composed of three cylinders of
spongy erectile tissue that fills with blood
pinching off the veins leaving it and the blood
pressure causes an erection prepuce or foreskin
may be removed by circumcision
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ovaries contain many follicles (400,000 all
formed before a woman is born only 1,000 or so
are released-ovulation) that each contain one egg
cell (secondary oocyte) corpus luteum- follicular
tissue after ovulation continues to secrete
estrogen and progesterone oviducts/Fallopian
tubes have funnelshaped openings the drape the
ovaries and cilia pull the egg into it
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uterus- endometrium- cervix- vagina-
hymen-membrane that partially covers the opening
to the vagina labia minora and labia
majora-folds of skin tissue around the opening to
the vagina clitoris-erectile tissue similar to
the penis
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Ovary crossection with Several developing
follicles
Oocyte in a follicle
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Ovulation
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GnRH-regulates FSH and LH release from the
pituitary FSH-acts on the seminiferous tubules
to increase spermatogenesis LH-stimulates Leydig
cells to make androgens which stimulate sperm
production
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• Estrous cycles occur in all non-primate mammals.
  Estrus-period just before ovulation and is the
  only time when most the females of most species
  will copulate. Due to pheromones and physical
  changes males know when ovulation occurs.
  Endometrium is reabsorbed if fertilization does
  not occur
• Menstrual cycle-occurs in humans and other
  primates no indications of when ovulation
  occurs. Menstruation occurs when the endometrium
  is shed from the uterus through the cervix and
  vagina.

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Hypothalamus monitors levels of estrogen and
progesterone in blood. It secretes releasing
factors (GnRHs) that cause the pituitary to
release LH and FSH. FSH causes a follicle to
develop and release estrogen which causes the
lining of uterus to thicken. Ovulation triggered
by a spurt of LH released by the
pituitary. Follicle then becomes the corpus
luteum and secretes progesterone
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fertilization can only occur for 24 hours after
ovulation blastocyst implants 7 days after
conception and releases human chorionic
gonadotropin (HCG)
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5 weeks,1cm long 14 weeks, 6cm long 20
weeks, 30cm
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