Asexual reproduction involves the formation of individuals whose genes all come from one parent. There is no fusion of sperm and egg.

Sexual reproduction is the formation of offspring by the fusion of haploid gametes. Ovum: female gamete - usually large and nonmotile. Spermatozooan: male gamete - usually small and

motile. Sexual reproduction increases genetic variation among

offspring.

Both asexual and sexual reproduction occur in the animal kingdom

Sexual Reproduction

Asexual Reproduction

SexualityHermaphroditism versus Gonochorism

Acropora sp., a hermaphoditic coralAcropora sp., a hermaphoditic coral

Fungia scutaria, a gonochoric coralFungia scutaria, a gonochoric coral

eggseggs

sperm packetsperm packet

egg cloudegg cloud

Hermaphroditism: both sexes in the same individuals

Gonochorism: sexes are separate

Brooding vs Broadcast SpawningBrooding vs Broadcast Spawning

broadcast spawnerbroadcast spawnerPocillopora damicornis, a brooderPocillopora damicornis, a brooder

planula in polypplanula in polyp

released gametesreleased gametesD. GulkoD. Gulko

Brooding: eggs develop to planula stage in gastrovascular cavity of parent polyp

Broadcast Spawning: eggs and sperm are shed into the water column where fertilization and development occurs

Sequential hermaphroditism: an individual reverses its sex during its lifetime. Protogynous: female to male

• Protandrous: male to female

Parthenogenesis

Egg development without fertilization• Aphid• Daphnia• Honeybee• Whiptail lizard• Komodo Dragon• Hammerhead Shark

Internal fertilization requires cooperative behavior that leads to copulation.

Internal and external fertilization both depend on mechanisms ensuring that

mature sperm encounter fertile eggs of the same species

External fertilization requires a moist habitat that will protect a developing egg from desiccation and heat stress.– Specific mating behaviors assure that sperm and

egg will be in the same place at the same time.

Surinam Toad

Pheromones: chemical signals released by one organism that influence the behavior of other individuals of the same species. Many act as male attractants.

femalemale

Internal fertilization usually results in the production of fewer zygotes than does internal fertilization. However, the survival rate is lower for external

fertilization than it is for internal fertilization.

Species with internal fertilization usually produce fewer zygotes but

provide more parental protection than species with external fertilization

The externally fertilized eggs of fishes and amphibians are surrounded by a gelatinous coat.

The internally fertilized amniote eggs of birds, reptiles, and monotremes are protected by calcium and protein shells. In mammals the embryo is retained within the

females reproductive tract.

Platypus egg New born platypuses and Mom

– Parental care ofoffspring may occurregardless of whetherfertilization is externalor internal.

The least complex reproductive systems lack gonads. Polychaete worms lack gonads.

Eggs and sperm develop from undifferentiated cells lining the coelom.

• Some reproductive systems, such as that seen in parasitic flatworms, can be very complex.

Complex reproductive systems have evolved in many animal phyla

Reproductive anatomy of a parasitic flatworm

Most insects have separate sexes with complex reproductive systems. In many species the female reproductive

system includes a spermatheca, a sac in which sperm may be stored for a year or more.

The basic plan of all vertebrate reproductive systems are very similar. However, there are variations.

In many non-mammalian vertebrates the digestive, excretory, and reproductive systems share a common opening to the outside, the cloaca.

Mammals have separate opening for the digestive and reproductive systems. Female mammals also have separate openings

for the excretory and reproductive systems.

Reproductive Anatomy of the Human Male. The scrotum and the penis are the external

components of the reproductive system. The internal reproductive organs consist of

gonads, accessory sex glands, and ducts.

Human reproduction involves intricate anatomy and complex behavior

Male Reproductive System

Male Reproductive System

External structure of the penis: The shaft of the penis is covered by relatively

thick skin.

The sensitive glans penis is covered by thinner skin.

The glans is covered by the prepuce which may be removed by circumcision.

There is no verifiable health benefit to circumcision.

The penis is composed of three layers of spongy erectile tissue. During sexual arousal the erectile tissue fills

with blood from arteries. The resultant increased pressure seals off the

veins that drain the penis.

The engorgement of the penis with blood causes an erection.

An erection is essential to the insertion of the penis into the vagina.

The penis of some mammals possesses a baculum, a bone that helps stiffen the penis.

Impotence can result from the consumption of alcohol and other drugs, and emotional, nervous system, or circulatory problems. Treatment includes drugs and penile implant

devices.

Viagra® acts by promoting the action of nitric oxide.

Testes

Testes are the male gonads. Consists of many highly coiled seminiferous

tubules surrounded by layers of connective tissue.

Sperm form in seminiferous tubules. Leydig cells (interstitial cells), scattered

between seminiferous tubules produce androgens (ex. testosterone).

Testes are located in the scrotum, outside the body cavity. This keeps testicular temperature cooler

than the body cavity. The testes develop in the body cavity and

descend into the scrotum just before birth.

From the seminiferous tubules sperm pass to the coiled tubules of the epididymis. It takes about 20 days for sperm to pass

through the tubules of the epididymis. In the epididymis sperm become motile

and gain the ability to fertilize.

Semen Seminal fluid is thick, yellowish, and

alkaline. It contains mucus, fructose, a coagulating

enzyme, ascorbic acid, and prostaglandins.

Accessory glands: seminal vesicle prostate gland bulbourethral gland

Seminal vesicle:• A pair of glands that secrete a liquid component

of semen into the vas deferens. • Secretion is alkaline, which neutralizes the

acidic condition of the female genital tract.• Seminal fluid contains fructose.

Seminal Vesicle

Prostate gland:• Location- surrounds and opens into the urethra where it

leaves the bladder. • Secretion- slightly alkaline fluid that activates the sperm

and prevents them from sticking together Prostate problems are common in males over 40. Prostate cancer is one of the most common cancers

in men.

Prostate

Bulbourethral gland (Cowper’s gland): • Location- paired glands that lie beneath the prostate• Secretion- a thick, clear alkaline mucous that drains into

the membranous urethra. • Function- It acts to wash residual urine out of the urethra

when ejaculating semen-- raises pH; neutralizes acidity of urine.

Bulbourethral gland

Ejaculation propels sperm from the epididymis to the vas deferens. The vas deferens run from the scrotum and

behind the urinary bladder.

Here each vas deferens joins with a duct from the seminal vesicle to form an ejaculatory duct.

The ejaculatory ducts open into the urethra. The urethra drains both the excretory and

reproductive systems.

Ejaculation

A male usually ejaculates about 2 – 5 mL of semen; each milliliter containing about 50 – 130 million sperm.

– Bulbourethral fluid also carries some sperm released before ejaculation.• This is one of the reasons why the

withdrawal method of birth control has a high failure rate.

Ejaculate

Spermatogenesis

Mature Spermatozoa

tail

mitochondria

nucleus

acrosomehead

Seminiferous Tubules

spermatogonium

1º spermatocyte

2º spermatocyte

spermatidsSertoli cell

spermatozoa

Seminiferous Tubules

Seminiferous Tubules

Sperm Maturation & Development

(maturation: 62-72 days)

Hormones Involved in Spermatogenesis

• Gonadotropin Releasing Hormone (GnRH)• Follicle Stimulating Hormone (FSH)• Interstitial Cell Stimulating Hormone (ICSH),

also called LH• Testosterone• Inhibin

HypothalamusHypothalamusHypothalamusHypothalamus

Anterior Anterior PituitaryPituitaryAnterior Anterior PituitaryPituitary

GnRHGnRH

FSHFSHICSH/LHICSH/LH

Hormonal Control of

Spermatogenesis

Interstitial CellsInterstitial CellsInterstitial CellsInterstitial Cells

ICSH/LHICSH/LH

TestosteroneTestosterone

Hormonal Control of Spermatogenesis

Sertoli CellsSertoli CellsSertoli CellsSertoli Cells

TestosteroneTestosterone

SpermatogenesisSpermatogenesis

FSHFSH

InhibinInhibin

Hormonal Control of Spermatogenesis

Feedback Inhibition

InhibinInhibinActs on anterior pituitaryActs on anterior pituitaryInhibits FSH productionInhibits FSH production

TestosteroneTestosteroneActs on hypothalamusActs on hypothalamusInhibits GnRH productionInhibits GnRH production

Hormonal Control of Spermatogenesis

Some Other Effects of Some Other Effects of TestosteroneTestosterone

• muscle and bone growthmuscle and bone growth• facial and pubic hair growthfacial and pubic hair growth• thickening of vocal cordsthickening of vocal cords• growth of pharyngeal cartilagegrowth of pharyngeal cartilage• hair follicle effectshair follicle effects• stimulates sebaceous glandsstimulates sebaceous glands

Reproductive Anatomy of the Human Reproductive Anatomy of the Human FemaleFemale

External reproductive structures: labia clitoris vaginal opening

Internal reproductive structures: ovaries fallopian tube (uterine tube) cervix uterus vagina fimbrae

Biology 100Biology 100Human BiologyHuman Biology

cervix

vagina

fimbriaeuterine tubeovary

uterus

bladder

urethraclitorisl. minoral. majoravaginal orifice

Female Reproductive System

Biology 100Biology 100Human BiologyHuman Biology

uterine tube

ovaryovary

egg

uterus

cervix

vagina

endometriummyometrium

perimetrium

Oogenesis in the Ovary

Oogenesis

• Ovary- contains 400,000 oocytes; release about 500 in a lifetime

• Ovary- under influence of FSH. The follicles mature every 28 days

• Primary follicle produces estrogens• And primary oocyte completes its 1st division

produces 2ndary oocyte and polar body

Oogenesis

• Aprox 1/2 way through the 28 day cycle the follicle reaches the mature Vesticular or Graffian follicle stage.

• Estrogen levels rise and release LH and FSH and triggers ovulation.

• The 2ndary oocyte travels down the uterine tube to the uterus.

• If fertilized by sperm, it will produce a zygote

Oogenesis

OvumOvum

Hormones Involved in the Hormones Involved in the Female Reproductive CycleFemale Reproductive Cycle

• Gonadotropin Releasing Hormone Gonadotropin Releasing Hormone (GnRH)(GnRH)

• Follicle Stimulating Hormone (FSH)Follicle Stimulating Hormone (FSH)• Luteinizing Hormone (LH)Luteinizing Hormone (LH)• EstrogenEstrogen• ProgesteroneProgesterone

HypothalamusHypothalamusHypothalamusHypothalamus

Anterior PituitaryAnterior PituitaryAnterior PituitaryAnterior Pituitary

GnRHGnRH

FSHFSHLHLH

Female Hormonal Female Hormonal CycleCycle

Follicle CellsFollicle CellsFollicle CellsFollicle Cells

LHLH

EstrogenEstrogen

FSHFSH

Female Hormonal Female Hormonal CycleCycle

The Uterine The Uterine CycleCycle

Ovarian CycleOvarian Cycle

Hormone Fluctuation

Some Other Effects of Some Other Effects of EstrogenEstrogen

• breast development• external genitalia growth• stimulates bone growth• increases HDL and lowers

LDL

Menopause: cessation of ovarian and menstrual cycles. Usually occurs between ages 46 and 54. Due to ovaries decreased responsiveness

to gonadotropins.

Menopause affects: changes in sexual desire triggers mood swings causes debilitating hot flashes may lead to bone and heart problems short-term memory loss insomnia

Mammary glands. Are present in both males and females. Are not a component of the reproductive

system. Contain epithelial tissue that secrete milk.

Milk drains into a series of ducts opening at the nipple.