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Chapter 46: Animal Reproduction1. What are the 2 ways that animals reproduce?

- Asexual – mitosis – same genes as parent- Fission – separation of a parent into 2 or individuals of the same size- Budding – individuals split as an outgrowth from an existing one

- Some cnidarians- Fragmentation – breaking of the body into several pieces followed by

regeneration- Sponges, cnidarians, tunicates

- Sexual – fusion of haploid gametes- Motile sperm swims to non-motile egg- Increases genetic variability

2. What are the 2 types of sexual reproduction?- External – eggs shed by female & fertilized by male in wet environment

- Courtship behaviors involved- Pheromones used

- Internal - sperm deposited in or near female reproductive tract & fertilized within female- Fewer zygotes but more parental care- Embryo develops in reproductive tract

Figure 46.5 External fertilization

Eggs

Chapter 46: Animal Reproduction1. What are the 2 ways that animals reproduce?2. What are the 2 types of sexual reproduction?

- External – eggs shed by female & fertilized by male in wet environment- Courtship behaviors involved- Pheromones used

- Internal - sperm deposited in or near female reproductive tract & fertilized within female- Fewer zygotes but more parental care- Embryo develops in reproductive tract

3. What is parthenogenesis?- Process in which an egg develops without fertilization- Produces haploid adults that produce eggs without meiosis- Daphnia (water flea), bees (male drones), wasps, ants

Figure 46.3 Sexual behavior in parthenogenetic lizards

Time

Ova

rysi

zeH

orm

ones

Beh

avio

r

Ovulation Ovulation

ProgesteroneEstrogen

Female-like

Male-like

Female-like

Male-like

(a) Both lizards in this photograph are C. uniparensfemales. The one on top is playing the role of a male. Every two or three weeks during the breeding season, individuals switch sex roles.

(b) The sexual behavior of C. uniparens is correlated with the cycle of ovulation mediated by sex hormones. As blood levels of estrogen rise, the ovaries grow, and the lizard behaves like a female. After ovulation, the estrogen level drops abruptly, and the progesterone level rises; these hormone levels correlate with male behavior.

Chapter 46: Animal Reproduction1. What are the 2 ways that animals reproduce?2. What are the 2 types of sexual reproduction?3. What is parthenogenesis?4. What does the male reproductive tract look like?

Seminal vesicle

(Rectum)

Vas deferens

Ejaculatory duct

Prostate gland

Bulbourethral gland

(Urinarybladder)

(Pubic bone)

Erectiletissue of

penis

Urethra

Glans penis

Prepuce

Vas deferens Epididymis

Testis

Scrotum

Figure 46.10 Reproductive anatomy of the human male

External – scrotum & penisInternal – gonads produce sperm & hormones

- testes – packed with highly coiled seminiferous tubules- accessory glands that help sperm movement

- seminal vesicles - bulbourethral glands- prostate gland

Erectile tissueof penis

Prostate gland

(Urinarybladder)

Bulbourethral gland

Vas deferensEpididymisTestis

Seminalvesicle(behind bladder)

Urethra

Scrotum

Glans penis

5. Where do the sperm travel during ejaculation?Propelled from epididymis vas deferens ejaculatory duct

6. How many sperm are released during ejaculation? 2 – 5 mL of semen per ejaculationx 50 – 130 million sperm per mL 100 – 650 million sperm per ejaculation

7. What happens after ejaculation?- Prostaglandins in semen thin mucus as the opening of the uterus &

stimulate uterine contractions which help semen move up uterus- Semen (slightly alkaline) neutralizes vagina (slightly acidic)

- Protects sperm & increases motility- Initially sperm are coagulated & become liquified so sperm can swim

8. How does viagra work?- Promotes the action of nitric oxide (NO) which enhances relaxation of

smooth muscle in blood vessels of penis so blood can enter erectile tissue

9. What does the female reproductive anatomy look like?

Figure 46.9 Reproductive anatomy of the human female

Glans

(Rectum)

Cervix

Vagina

Bartholin’s gland

Vaginal opening

Ovary

Oviduct

Labia majora

Labia minora

(Urinary bladder)

(Pubic bone)

Uterus

Urethra

Shaft

Prepuce Clitoris

External – clitoris & 2 sets of labia which surround the clitoris & vaginal openingInternal – pair of gonads (ovaries) with ducts & chambers for gametes & fetus

Vagina

Uterus

Cervix

OvariesOviduct

Uterine wallEndometrium

Follicles

Corpus luteum

Ovaries – contain many follicles- Follicle – all formed before birth

- egg cell surrounded by follicle cells which nourish & protect the egg- produce estrogens

- Endometrium – inner lining of uterus- After ovulation, “egg” falls down the oviduct into uterus

7. What happens after ejaculation?- Prostaglandins in semen thin mucus as the opening of the uterus &

stimulate uterine contractions which help semen move up uterus- Semen (slightly alkaline) neutralizes vagina (slightly acidic)

- Protects sperm & increases motility- Initially sperm are coagulated & become liquified so sperm can swim

8. How does viagra work?- Promotes the action of nitric oxide (NO) which enhances relaxation of

smooth muscle in blood vessels of penis so blood can enter erectile tissue9. What does the female reproductive anatomy look like?10. How are “eggs” made?

- Oogenesis

Figure 46.11 Human OogenesisOvary

Primary germ cell in embryo

Differentiation

OogoniumOogoniumin ovary

Mitoticdivision

Primary oocyte,arrested in prophaseof meiosis I(present at birth)

Completion of meiosis Iand onset of meiosis II

Primaryoocytewithinfollicle

Secondary oocyte,arrested at meta-phase of meiosis II

Firstpolarbody

Ovulation

Entry ofsperm triggerscompletion ofmeiosis II

Ovum

Growingfollicle

Mature follicle

Rupturedfollicle

Ovulatedsecondary oocyte

Corpus luteum

Degeneratingcorpus luteum

2n

2n

nn

nn

Secondpolarbody

Follicles grow in response to FSH completing meiosis I & stopping at metaphase II

Smaller polar body is discardedSecondary oocyte is ovulated…NOT AN EGGMeiosis is completed IF 2° oocyte is fertilizedAfter ovulation, remaining tissue reorganizes to

form the corpus luteum

7. What happens after ejaculation?- Prostaglandins in semen thin mucus as the opening of the uterus & stimulate

uterine contractions which help semen move up uterus- Semen (slightly alkaline) neutralizes vagina (slightly acidic)

- Protects sperm & increases motility- Initially sperm are coagulated & become liquified so sperm can swim

8. How does viagra work?- Promotes the action of nitric oxide (NO) which enhances relaxation of smooth

muscle in blood vessels of penis so blood can enter erectile tissue9. What does the female reproductive anatomy look like?10. How are “eggs” made?

- Oogenesis 11. How are sperm made?

- Spermatogenesis

EpididymisSeminiferous tubule

Testis

Cross sectionof seminiferoustubule

Sertoli cellnucleus

Lumen ofSeminiferous tubule

Spermatogonium

Primary spermatocyte(in prophase of meiosis I)

Secondary spermatocyte

Earlyspermatids

Spermatids(at two stages ofdifferentiation)

Differentiation(Sertoli cells providenutrients)

Meiosis II

Meiosis I completed

Mitotic division,producing large numbersof spermatogonia

Sperm cells

Acrosome

NucleusMitochondria

Neck

TailPlasma membrane

Head Midpiece

2n

2n

n n

nnnn

n n n n

Differentiation andOnset of meiosis I

Figure 46.12 Human Spermatogenesis

- Seminiferous tubules – produce sperm- Leydig cells – secrete testosterone &

other androgens- Sertoli cells – provide nutrition for

spermatids so they can mature- Takes 65 – 75 days to make sperm- 20 days to travel epididymis where

they mature & are stored

7. What happens after ejaculation?- Prostaglandins in semen thin mucus as the opening of the uterus & stimulate uterine contractions which help semen

move up uterus- Semen (slightly alkaline) neutralizes vagina (slightly acidic)

- Protects sperm & increases motility- Initially sperm are coagulated & become liquified so sperm can swim

8. How does viagra work?- Promotes the action of nitric oxide (NO) which enhances relaxation of smooth muscle in blood vessels of penis so blood

can enter erectile tissue9. What does the female reproductive anatomy look like?10. How are “eggs” made?

- Oogenesis 11. How are sperm made?

- Spermatogenesis12. What are the differences between spermatogenesis & oogenesis?

- Unequal cytokinesis in oogenesis produces 1 haploid ovum (& 2 polar bodies) & not 4 haploid sperm- Spermatogenesis mitosis occurs throughout life but ovary has all its follicles at birth- Oogenesis has long resting periods but spermatogenesis is uninterrupted & continuous

13. How do hormones control the menstrual cycle?

Figure 46.13 The reproductive cycle of the human femaleControl by hypothalamus Inhibited by combination of

estrogen and progesterone

Stimulated by high levelsof estrogen

Inhibited by low levels ofestrogen

Hypothalamus

Anterior pituitary

GnRH

FSH LH

Pituitary gonadotropinsin blood

LH

FSHFSH and LH stimulatefollicle to grow

LH surge triggersovulation

Ovarian cycle

Growing follicle Maturefollicle

Corpusluteum

Degenerating corpus luteum

Estrogen secretedby growing follicle inincreasing amounts

Progesterone andestrogen secretedby corpus luteum

Follicular phase Luteal phaseOvulation

Ovarian hormonesin blood

Peak causes LH surge

Estrogen Progesterone

Estrogen levelvery low

Progesterone and estro-gen promote thickeningof endometrium

Uterine (menstrual) cycle

Endometrium

Menstrual flow phase Proliferative phase Secretory phase

0 5 10 14 15 20 25 28

Day

s

1

(a)

(b)

(c)

(d)

(e)

3

6

7 8

4

5

2

9

10

GnRH – Gonadotropin Releasing Hormone- hypothalamus- stimulates release of FSH & LH

by anterior pituitaryFSH - Follicle Stimulating Hormone

- follicle grows & expresses LH receptorsLH - Lutenizing Hormone

- triggers ovulation (1 day after LH peak)- stimulates formation of corpus luteum

Estrogen – produced by growing follicle- stimulates GnRH release which triggers

more LH & FSH- estrogen peak causes LH peak

Progesterone – from corpus luteum- maintains thick endometrium in

preparation for embryo implantIf pregnancy does not occur the endometrium is shed….menstruation.Menopause – cessation of ovulation & menstru-

ation because ovaries lose responsive-ness to LH & FSH & estrogen decreases

7. What happens after ejaculation?8. How does viagra work?9. What does the female reproductive anatomy look like?10. How are “eggs” made?11. How are sperm made?12. What are the differences between spermatogenesis & oogenesis?13. How do hormones control the menstrual cycle?14. How do hormones control the male reproductive system?

- GnRH, FSH, & LH

Figure 46.14 Hormonal control of the testes

Stimuli from otherareas in the brain

Hypothalamus

GnRH from thehypothalamus reg-ulates FSH and LH

release from theanterior pituitary.

FSH acts on theSertoli cells of the

seminiferoustubules, promotingspermatogenesis.

LH stimulates the Leydig cells to maketestosterone, whichin turn stimulatessperm production.

Anteriorpituitary

Negativefeedback

Leydig cellsmake

testosteronePrimary andsecondary sexcharacteristics

Sertoli cells

Spermatogenesis Testis

7. What happens after ejaculation?8. How does viagra work?9. What does the female reproductive anatomy look like?10. How are “eggs” made?11. How are sperm made?12. What are the differences between spermatogenesis & oogenesis?13. How do hormones control the menstrual cycle?14. How do hormones control the male reproductive system?

- GnRH, FSH, & LH15. What is detected in pregnancy tests?

- HCG – human chorionic gonadotropin- Mimics LH which keeps corpus luteum secreting estrogen & progesterone- Endometrium stays thick

16. What happens after fertilization?

Fig 46.15 Formation of the zygote and early post-fertilization events

Ovary

Uterus

Endometrium

From ovulation to implantationEndometrium Inner cell mass

Cavity

BlastocystTrophoblast

Ovulation releases asecondary oocyte, whichenters the oviduct.

1

The blastocyst implants in the endometriumabout 7 days after conception.

5

Cleavage continues. By the time the embryoreaches the uterus, it is a ball of cells.It floats in the uterus forseveral days, nourished byendometrial secretions. It becomes a blastocyst.

4

Fertilization occurs. A sperm enters the oocyte; meiosis of

the oocyte finishes; and the nuclei of the ovum and sperm

fuse, producing a zygote.

2

Cleavage (cell division)begins in the oviduct

as the embryo is movedtoward the uterus

by peristalsis and themovements of cilia.

3

(a)

Implantation of blastocyst(b)

Inner cell mass – develops into embryo & extra-embryonic membranesTrophoblast – outer layer of blastocyst that grows out & mingles with endometrium &

helps form the placentaPlacenta – disk shaped organ containing embryonic & maternal blood vessels

Figure 46.16 Placental circulation

Placenta

Umbilical cord

Chorionic villuscontaining fetalcapillaries

Maternal bloodpools

Uterus Fetal arterioleFetal venuleUmbilical cord

Maternal portionof placenta

Fetal portion ofplacenta (chorion)

Umbilical arteriesUmbilical vein

Maternalarteries

Maternalveins

As placenta forms, HCG levels decline & placenta secretes its own progesteroneFetal nutrients gained from maternal blood pools….no mixing of blood.

7. What happens after ejaculation?8. How does viagra work?9. What does the female reproductive anatomy look like?10. How are “eggs” made?11. How are sperm made?12. What are the differences between spermatogenesis & oogenesis?13. How do hormones control the menstrual cycle?14. How do hormones control the male reproductive system?

- GnRH, FSH, & LH15. What is detected in pregnancy tests?

- HCG – human chorionic gonadotropin- Mimics LH which keeps corpus luteum secreting estrogen & progesterone- Endometrium stays thick

16. What happens after fertilization?17. How do hormones regulate parturition, aka child birth?

Figure 46.18 A model for the induction of labor

Estrogen Oxytocin

fromovaries

from fetusand mother'sposterior pituitary

Induces oxytocinreceptors on uterus

Stimulates uterusto contract

Stimulatesplacenta to make

Prostaglandins

Stimulate morecontractions

of uterus

Pos

itive

fee

dbac

k

Figure 46.19 The three stages of labor

PlacentaUmbilicalcordUterusCervix

Dilation of the cervix

Expulsion: delivery of the infant

UterusPlacenta(detaching)

Umbilicalcord

Delivery of the placenta

1

2

3

7. What happens after ejaculation?8. How does viagra work?9. What does the female reproductive anatomy look like?10. How are “eggs” made?11. How are sperm made?12. What are the differences between spermatogenesis & oogenesis?13. How do hormones control the menstrual cycle?14. How do hormones control the male reproductive system?

- GnRH, FSH, & LH15. What is detected in pregnancy tests?

- HCG – human chorionic gonadotropin- Mimics LH which keeps corpus luteum secreting estrogen & progesterone- Endometrium stays thick

16. What happens after fertilization?17. How do hormones regulate parturition, aka child birth?18. How does contraception work?

Figure 46.20 Mechanisms of some contraceptive methodsMale Female

Method Event Event Method

Production ofviable sperm

Production ofviable oocytes

VasectomyCombinationbirth control pill (or injection,patch, orvaginal ring)Sperm transport

down maleduct system

Ovulation

Abstinence

Condom

Coitusinterruptus(very highfailure rate)

Spermdepositedin vagina

Capture of theoocyte by the

oviduct

Abstinence

Tubal ligation

Spermicides;diaphragm;cervical cap;progestin alone(minipill, implant,or injection)

Sperm movementthrough female

reproductivetract

Transportof oocyte in

oviduct

Meeting of sperm and oocytein oviduct

Morning-after pill (MAP)Union of sperm and egg

Implantation of blastocyst in properly prepared

endometrium

Birth

Progestin alone

Birth control pills – estrogen & progesterone combo- prevents ovulation by decreasing the release

of GnRH which inhibits FSH & LH

Morning after pill – higher doses of estrogen & progesterone- prevents fertilization or implantation