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