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ANIMAL REPRODUCTION CHAPTER 46
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Figure Frogs mating
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Figure 46.0x1 Utethesia ornatrix mating
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Figure 46.0x2 Red beetles mating
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Figure 46.1 Two from one: asexual reproduction of a sea anemone (Anthopleura elegantissima)
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Figure 46.x1 Aphid giving live birth
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ASEXUAL REPRODUCTION Fission Budding Fragmentation Regeneration
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REPRODUCTIVE CYCLES Earthworms
Parthenogenesis – egg develops without being fertilized Wasps, bees, ants, daphnia (creates haploid adults) Whiptail lizards: all females Komodo dragon (if not males) Hermaphrodites – individual has both male and female reproductive systems Earthworms
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Figure 46.2 Sexual behavior in parthenogenetic lizards
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Sequential hermaphroditism – when an individual reverses its sex
Male first – protandrous (oysters) Female first – protogynous (wrasses- reef fishes)
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Figure 46.3 Sex reversal in a sequential hermaphrodite
A male Caribbean bluehead wrasse and two smaller females are feeding on a sea urchin. All bluehead wrasses are born female, but the oldest, largest individuals change sex and complete their lives as males.
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MECHANISMS OF REPRODUCTION
Internal fertilization – sperm deposited in or near female reproductive tract and fertilization occurs in female tract Mammals, birds, reptiles Usually produce fewer offspring often with parental care of young External fertilization – eggs shed by female and fertilized by male in the environment Fish, amphibians, aquatic invertebrates Usually produce many offspring with little or no parental care of young
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Figure 46.x2 Sea urchin sperm fertilizing an egg
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Figure 46. 5 Parental care in an invertebrate (a giant water bug)
Figure Parental care in an invertebrate (a giant water bug). The female glues her fertilized eggs to the male’s back.
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Figure 46.4 The release of eggs and external fertilization
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Human REPRODUCTIVE SYSTEMS Flatworms Hermaphrodite Honeybees
Spermatheca (a sac in females where sperm can be stored for a year or more) Human
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Figure 46.6 Reproductive anatomy of a parasitic flatworm
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Figure 46.7 Insect reproductive anatomy
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Male Reproductive Parts
Epididymis – 6m long tubules where sperm become motile and ability to fertilize Vas deferens – during ejaculation sperm enter these ducts that runs from epididymis to ejaculatory duct (behind bladder), which empties into urethra Seminal vesicles – contributes more than half of semen (sugar, mucus, enzymes, basic) Prostate gland – largest semen-secreting gland (enzymes, citrate, acidic) Bulbourethral glands – secrete mucus to neutralize acidity just before ejaculation (can contain sperm)
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Figure 46.8 Reproductive anatomy of the human male
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Figure 46.8 Reproductive anatomy of the human male
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Female Reproductive Parts
Follicle – consists of one egg surrounded by follicle cells, which nourish and protest egg and produce estrogen Ovulation – egg expelled from follicle Corpus leteum – left-over follicle tissue, which secretes additional estrogen and progesterone Oviduct (fallopian tube) – tube with cilia on ovary end that leads to uterus (where fertilization usually occurs) Endometrium – inner lining of uterus Cervix – neck of uterus Bartholin’s gland – secrete mucus to lubricate for sex
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Figure 46.9 Reproductive anatomy of the human female
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Figure 46.9 Reproductive anatomy of the human female
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Figure Ovulation
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HUMAN SEXUAL RESPONSE Vasocongestion – increased blood flow causes filling of tissue with blood Erection Myotonia – increased muscle tension Nipple erection; tension in arms/legs Orgasm – rhythmic, involuntary contractions of reproductive structures
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Spermatogenesis Takes ~70 days for sperm to mature Oogenesis FSH during puberty stimulates first meiotic division Second meiotic division stimulated by fertilization One cell becomes ovum while smaller polar cells disintegrate
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Figure 46.11 Spermatogenesis
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Figure 46.12 Structure of a human sperm cell
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Figure 46.13a Oogenesis
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Figure 46.13b Oogenesis
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SEX HORMONES GnRH – controls release of LH and FSH
LH – stimulates androgen (testosterone) production in males and corpus leteum development in females FSH – increases spermatogenesis in males and follicle growth in females Testosterone – stimulates spermatogenesis and sex characteristics
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SEX HORMONES Estrogen – increases both LH and FSH production (especially LH) Progesterone - promotes thickening of endometrium in preparation of pregnany (along with estrogen) Human chorionic gonadotropin (HCG) – maintains progesterone and estrogen levels so lining is not shed if egg is fertilized
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Figure 46.14 Hormonal control of the testes
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Figure 46.15 The reproductive cycle of the human female
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FEMALE SEX PATTERNS Menstrual cycle – endometrium (uterine lining) shed (period) Estrous cycle – endometrium reabsorbed by uterus and no extensive bleeding occurs (heat) More pronounced behavioral changes Climate and seasons affect estrous cycles
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Menopause – ovaries lose responsiveness to LH and FSH and decrease in estrogen production
Possible that losing ability to have children allowed female to provide better care of her children thereby increasing their survival
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Figure 46.16 Formation of the zygote and early postfertilization events
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Figure 46.17 Placental circulation
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Figure 46.18 Human fetal development
20 weeks (by 24 weeks will be ~30cm 5 weeks, 1 cm 14 weeks, 6 cm
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Figure 46.19 Hormonal induction of labor
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Figure 46.20 The three stages of labor
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Figure 46.21 Some contraceptive methods
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