Chapter 46 Animal Reproduction

Chapter 46 Animal ReproductionAsexual-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, lizardsSexual-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

Fission or Budding

Parthenogenesis with two females

Parthenogenesis with Male stimulation but notfertilization

External fertilization

Male parental care

Hermaphroditism

Testes-seminiferous tubules – Leydig cells-produce testosteronescrotum- 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

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 erectionprepuce or foreskin may be removed by circumcision

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 funnel–shaped openings the drape the ovaries and cilia pull the egg into it

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

Ovary crossection withSeveral developing follicles Oocyte in a follicle

Ovulation

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

• 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.

Hypothalamus monitors levels of estrogen and progesterone in blood. It secretes releasing factors (GnRH’s) 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

fertilization can only occur for 24 hours after ovulationblastocyst implants 7 days after conception and releases human chorionic gonadotropin (HCG)

5 weeks,1cm long 14 weeks, 6cm long 20 weeks, 30cm