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ANIMAL REPRODUCTION
CHAPTER 46
Figure 46.0 Frogs mating
Figure 46.0x1 Utethesia ornatrix mating
Figure 46.0x2 Red beetles mating
Figure 46.1 Two from one: asexual reproduction of a sea anemone (Anthopleura elegantissima)
Figure 46.x1 Aphid giving live birth
ASEXUAL REPRODUCTION
Fission BuddingFragmentationRegeneration
REPRODUCTIVE CYCLESParthenogenesis – egg develops without being fertilized
Wasps, bees, ants, daphnia (creates haploid adults)Whiptail lizards: all femalesKomodo dragon (if not males)
Hermaphrodites – individual has both male and female reproductive systems
Earthworms
Figure 46.2 Sexual behavior in parthenogenetic lizards
(a)
Sequential hermaphroditism – when an individual reverses its sex
Male first – protandrous (oysters)Female first – protogynous (wrasses- reef fishes)
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.
MECHANISMS OF REPRODUCTION
Internal fertilization – sperm deposited in or near female reproductive tract and fertilization occurs in female tract
Mammals, birds, reptilesUsually 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 invertebratesUsually produce many offspring with little or no parental care of young
Figure 46.x2 Sea urchin sperm fertilizing an egg
Figure 46.5 Parental care in an invertebrate (a giant water bug). The female glues her fertilized eggs to the
male’s back.
Figure 46.4 The release of eggs and external fertilization
REPRODUCTIVE SYSTEMS
FlatwormsHermaphrodite
HoneybeesSpermatheca (a sac in females where sperm can be stored for a year or more)
Human
Figure 46.6 Reproductive anatomy of a parasitic flatworm
Figure 46.7 Insect reproductive anatomy
Male Reproductive PartsEpididymis – 6m long tubules where sperm become motile and ability to fertilizeVas deferens – during ejaculation sperm enter these ducts that runs from epididymis to ejaculatory duct (behind bladder), which empties into urethraSeminal 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)
Figure 46.8 Reproductive anatomy of the human male
Figure 46.8 Reproductive anatomy of the human male
Female Reproductive PartsFollicle – consists of one egg surrounded by follicle cells, which nourish and protest egg and produce estrogenOvulation – egg expelled from follicleCorpus leteum – left-over follicle tissue, which secretes additional estrogen and progesteroneOviduct (fallopian tube) – tube with cilia on ovary end that leads to uterus (where fertilization usually occurs)Endometrium – inner lining of uterusCervix – neck of uterusBartholin’s gland – secrete mucus to lubricate for sex
Figure 46.9 Reproductive anatomy of the human female
Figure 46.9 Reproductive anatomy of the human female
Figure 46.10 Ovulation
HUMAN SEXUAL RESPONSE
Vasocongestion – increased blood flow causes filling of tissue with blood
ErectionMyotonia – increased muscle tension
Nipple erection; tension in arms/legs
Orgasm – rhythmic, involuntary contractions of reproductive structures
Spermatogenesis Takes ~70 days for sperm to mature
Oogenesis FSH during puberty stimulates first meiotic divisionSecond meiotic division stimulated by fertilizationOne cell becomes ovum while smaller polar cells disintegrate
Figure 46.11 Spermatogenesis
Figure 46.12 Structure of a human sperm cell
Figure 46.13a Oogenesis
Figure 46.13b Oogenesis
SEX HORMONES
GnRH – controls release of LH and FSHLH – stimulates androgen (testosterone) production in males and corpus leteum development in femalesFSH – increases spermatogenesis in males and follicle growth in femalesTestosterone – stimulates spermatogenesis and sex characteristics
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
Figure 46.14 Hormonal control of the testes
Figure 46.15 The reproductive cycle of the human female
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 changesClimate and seasons affect estrous cycles
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
Figure 46.16 Formation of the zygote and early postfertilization events
Figure 46.17 Placental circulation
Figure 46.18 Human fetal development
5 weeks, 1 cm 14 weeks, 6 cm 20 weeks (by 24 weeks will be ~30cm
Figure 46.19 Hormonal induction of labor
Figure 46.20 The three stages of labor
Figure 46.21 Some contraceptive methods