1. Chapter 46
Animal Reproduction

2. Sexual & asexual reproduction
offspring all have same genes (clones)
______________
Sexual
gametes (sperm & egg)  fertilization
mixing of genes  ___________

3. ___________________ Development of an unfertilized egg honey bees
drones = males produced through parthenogenesis  haploid
workers & queens = females produced from fertilized eggs  diploid
Honey bee eggs hatch regardless of whether the are fertilized. The female bees--queens & workers--develop from fertilized eggs that contain 32 chromosomes. These 32 chromosomes consist of two sets of 16, one set from each parent. Hence female bees are said to be diploid in origin. The males (drones) develop from unfertilized egg which contain only one set of 16 chromosomes from their mother. Drones are thus haploid in origin This reproduction by the development of unfertilized eggs is called parthenogenesis
Drones develop by parthenogenesis from unfertilized eggs that the queen produces by withholding sperm from the eggs laid in large drone cells. Drones lack stings and the structures needed for pollen collection; in the autumn they are ejected by the colony to starve, unless the colony is queenless. New drones are produced in the spring for mating.
Both queens and workers are produced from fertilized eggs. Queen larvae are reared in special peanut-shaped cells and fed more of the pharyngeal gland secretions of the nurse bees (bee milk or royal jelly) than the worker larvae are. The precise mechanism for this caste differentiation is still uncertain. Although workers are similar in appearance and behavior to other female bees, they lack the structures for mating. When no queen is present to inhibit the development of their ovaries, however, workers eventually begin to lay eggs that develop into drones.
queen
worker
drone

4. Different strokes… parthenogenesis in aphids sex-change in fish
sex-change in fish

5. ________________ earthworms mating flat worm
Having functional reproductive system of both sexes
earthworms mating
flat worm

6. Fertilization Joining of egg & sperm _____________
usually aquatic animals
usually land animals

7. Development External Internal development in eggs
fish & amphibians in water
soft eggs= exchange across membrane
birds & reptiles on land
hard-shell amniotic eggs
structures for exchange of food, O2 & waste
sharks & some snakes
live births from eggs
Internal
placenta
exchange food & waste
live birth

8. Adaptive advantages?
What is the adaptive value of each type of sexual reproduction
number of eggs?
level of parental of care
habitat?

9. Human Reproduction: Reproductive hormones
___________________
from testes
Functions
Prenatal development of male genitalia
sperm production
2° sexual characteristics
Maintenance of sex drive
_______________
from ovaries
functions
egg production
prepare uterus for fertilized egg
LH & FSH
testes or ovaries

10. Sex hormone control in males
Hypothalamus
GnRH
Pituitary
FSH & LH
Testes
testosterone
Body cells

11. Male reproductive system
Sperm production
over ____________ produced per day!
~2.5 million released per drop!

12. Male reproductive system
Testes
produces sperm & hormones
_____________
sac that holds testicles outside of body
Epididymis
where sperm mature
______________
tubes for sperm to travel from testes to penis
Prostate, seminal vesicles, Cowper’s (bulbourethal) glands
nutrient rich fluid to feed & protect sperm
buffer to counteract acids in vagina

13. Male reproductive system
seminiferous tubule
Male reproductive system
sperm
spermatocytes
Testes & epididymis
sperm production & maturation
Glands
seminal vesicles, prostate, bulbourethal
produce seminal fluid = nutrient-rich

14. Leydig cells are responsible for the production of testosterone.
Spermatogenesis
Spermatogenesis occurs within each testis in small tubules called _________________
_________________
This light micrograph shows a cross section of seminiferous tubules, blood vessels and the interstitial _______________.
Leydig cells are responsible for the production of testosterone.

15. Spermatogenesis
Mitosis and meiosis may be taking place at any time in the spermatogonia. Mitosis replenishes numbers of cells, meiosis produces actual sperm (spermatozoa)
____________ help nourish sperm cells during meiosis

16. Spermatogenesis 2005-2006 MEIOSIS I MEIOSIS II Epididymis Testis
Germ cell
(diploid)
Coiled
seminiferous
tubules 1°
spermatocyte
(diploid)
MEIOSIS I 2°
spermatocytes
(haploid)
MEIOSIS II
Vas deferens
Spermatids
(haploid)
Spermatozoa
Cross-section of
seminiferous tubule

17. Hormonal control of sperm production
LH (_______________ hormone) stimulates Leydig cells to produce testosterone
FSH (___________ - stimulating hormone) and testosterone stimulate meiosis in spermatogonia to produce spermatozoa

18. Role of epididymis, seminal vesicles, and prostate in semen production
Sperm cells were produced in seminiferous tubules, carried thru the lumen, and sent to the epididymis. They are _______ briefly in the epididymis.
On sexual arousal, millions of sperm cells are moved from the epididymis into the ________________.
_________________ add large volume of fluid which has a high conc. of fructose for energy for the sperm cells to swim (approx. 70% of the fluid in
semen is added by the seminal
vesicles.)
The _________ adds more fluid: alkaline
which helps the sperm survive the acidic
environment in a female’s vagina.

19. Female reproductive system

20. Female reproductive system
Ovaries
produces eggs & hormones
Uterus
nurtures fetus; lining builds up each month
______________________
tubes for eggs to travel from ovaries to uterus
_____________
opening to uterus, dilates 10cm (4 inches) for birthing baby
Vagina
birth canal for birthing baby

21. Female reproductive system

22. Menstrual cycle
Starting at puberty, human females begin a hormonal cycle called the menstrual cycle. Each cycle lasts (on average) 28 days.
The purpose is to time the release of an egg (ovum) for possible fertilization and later implantation into the inner lining of the uterus (____________________)
The implantation must occur when the endometrium is rich with blood vessels.
The breakdown of the blood vessels leads to menstrual bleeding (________________); a sign that no pregnancy has occurred

23. Hormones Hypothalamus Pituitary Endometrium of uterus progesterone
regulatory center for the menstrual cycle.
The hypothalamus produces a hormone called GnRH (gonadotrophin-releasing hormone).
The target tissue of GnRH is the anterior pituitary gland, which results in the pituitary producing and secreting 2 hormones into the bloodstream:
FSH and LH.
The target tissues for these 2 hormones are the ovaries
Hypothalamus
Pituitary
FSH & LH
estrogen
progesterone
Endometrium of uterus

24. Effects of FSH and LH on the ovaries
To increase the production and secretion of __________ by the follicle cells of the ovary
Estrogen enters the bloodstream
Its target tissue is the endometrium of the uterus
Result is growth of lining (increase in blood vessels)
Stimulates egg development in ovaries

25. Egg maturation in ovary
A spike in levels of FSH and LH leads to ovulation (release of oocyte from the follicle)
The outer ring of follicle cells begin to divide and fill in the ‘wound’ area left by ovulation which forms a ____________. The corpus luteum produces progesterone for days after ovulation.
Progesterone (hormone) ___________ the thickened endometrium
If no pregnancy, the corpus luteum eventually breaks down = less estrogen and
progesterone

26. LH
Menstrual cycle
FSH
… as estrogen and progesterone levels fall, the highly vascular endometrium can no longer be maintained. The capillaries begin to rupture and menstruation begins.
The drop in progesterone and estrogen also signals the _____________ to begin secreting GnRH and another menstrual cycle begins.
ovulation = egg release
egg development
corpus luteum
estrogen
progesterone
lining of uterus
days 7 14 21 28

27. Oogenesis
In ovaries, cells called ________ go thru mitosis repeatedly to build up numbers of cells. Then those oogonia grow into larger cells (primary oocytes) and start meiosis, but the process stops at Prophase I, until puberty.
Then ____ periodically stimulates a follicle to grow and induces its primary oocyte to complete meiosis I and start meiosis II
ovulation
Meiosis 2 completed
triggered by fertilization

28. Comparison of spermatogenesis and oogenesis
Millions of sperm produced every day
4 gametes for every cell that begins meiosis
Very small
Occurs in testis
Released during ejaculation
Haploid nuclei
Continues throughout all of life, starting at puberty
One egg is ovulated per menstrual cycle
One gamete is produced for each cell that begins meiosis (plus polar bodies)
Eggs are ‘large’
Occurs in ovaries
Released during ovulation
Haploid nuclei
Ovulation starts at puberty, occurs with each menstrual cycle, then stops at menopause

29. Fertilization

30. Fertilization
Enzymes from acrosome are released at the _____________. Sperm head enters egg, plasma membranes fuse together. This initiates the ___________________.

31. Fertilization and the cortical reaction
As soon as the sperm reaches the nucleus, the ________________ fuse with the cell membrane and release their enzymes to the outside, making it impermeable to any other sperm cells.

32. Early human embryonic development: Cleavage
Fertilization triggers the zygote to start repeated mitotic divisions as it moves down the Fallopian tube toward the uterus
By the time the embryo reaches the uterus, it is approx. 100 cells and is ready to implant into the endometrium of the uterus. At this point, it’s a hollow ball of cells called a ________________.

33. A few days later, the embryo imbeds itself in the uterine lining
A few days later, the embryo imbeds itself in the uterine lining. At this point, a woman's body begins to secrete a pregnancy hormone known as _______. This hormone maintains production of progesterone from the ovary, a crucial factor in maintaining a pregnancy.

34. HCG specifics HCG = Human ____________ Gonadotrophin.
It enters the bloodstream of the mother
its target tissue is the ______________. HCG acts to maintain the secretory functions of this gland beyond the length of time typical of a normal menstrual cycle. The corpus luteum continues to make both estrogen and progesterone and the endometrium is maintained.
Later on in pregnancy, the ________ will take over estrogen and progesterone production.

35. Organogenesis Umbilical blood vessels Mammalian embryo Chorion
Bird embryo
Amnion
Yolk
sac
Allantois
Fetal blood vessels
Placenta
Maternal blood vessels

36. Placenta
Materials exchange across membranes

37. Role of the Placenta
When fully formed, 2 fetal blood vessels within the umbilical cord carry fetal blood to the placenta. The blood is ________________ and carries waste products (_____, urea, hormones). This fetal blood exchanges materials (not blood) with the maternal bloodstream.
Another fetal blood vessel returns the ‘clean’ blood to the fetus (has oxygen and __________, hormones)
At no time do the 2 bloods actually mix
When the corpus luteum stops producing estrogen and progesterone, the placenta starts producing and secreting them.

38. Role of the amniotic fluid
_____________ extends all the way around the fetus
The fluid within it is called amniotic fluid
Several functions:
Provides cushioning effect if something happens to mom’s abdomen
Provides safe environment where fetus has free movement and can exercise its developing muscles and skeleton
Provides ______________ stability

39. Human fetal development
4 weeks
7 weeks

40. Human fetal development
10 weeks

41. Human fetal development
12 weeks
20 weeks

42. Human fetal development
24 weeks (6 months; 2nd trimester)
fetus is covered with fine, downy hair called lanugo. Its skin is protected by a waxy material called vernix

43. Human fetal development
30 weeks (7.5 months)
umbilical cord

44. Getting crowded in there!!
32 weeks (8 months)
The fetus sleeps 90-95% of the day & sometimes experiences REM sleep, an indication of dreaming

45. Hormone induction
Birth
positive feedback

46. Birth (36 weeks) 2005-2006 Intestine Placenta Umbilical cord Wall of
uterus
Bladder
Cervix
Vagina

47. The end of the journey!