1. Chapter 46: Animal Reproduction
Sections 46.1 and 46.2
Erin Foeri
Period 2A

2. Concept 46.1- Both asexual and sexual reproduction occur in the animal kingdom
Sexual reproduction- fusion of egg and sperm (haploid) to form zygote (diploid)
Asexual reproduction- offspring created without fusion of gametes

3. Mechanisms of Asexual Reproduction (Invertebrates)
Fission
Budding
Fragmentation and Regeneration
Parthenogenesis
Fission- one parent organism divides into two offspring of equal size
Budding- new organism derived from overgrowth of original
Fragmentation and Regeneration- parts of organism cut off, these parts regenerate into new organisms
Parthenogenesis- egg develops without being fertilized; can be haploid or diploid

4. Advantages of Sexual vs. Asexual
Sexual- unique combinations, varied genotypes (rid population of harmful genotypes quickly, adaption sped up)
Asexual- successful genotypes efficiently and rapidly

5. Sexual Reproductive Cycles
Ovulation- release of mature eggs at midpoint of each cycle
Enhance chances of offspring survival
Controlled by change of season/environmental cues and hormones
Purpose of reproductive cycles- animals conserve energy sources and only reproduce when environmental conditions are in favor
Environmental cues such as day length, seasonal temperature, rainfall, and lunar cycles influence sex cycles

6. Variations in Patterns of Sexual Reproduction
Solution when difficult to find mates:
Hermaphroditism- organism has both male and female reproductive systems
Some can self-fertilize, two hermaphrodites can mate
Hermaphrodites can mate with each other, and capable of self-fertilization

7. Parthenogenesis- Sex Reversals
Complex form of parthenogenesis; both of these lizards are female- one female’s estradiol hormone level is high before ovulation; after ovulation, estradiol drops and progesterone (male hormone) increases- behaves like a male
Benefit- when actual sexual behaviors are simulated (when lizard is mounted), more eggs are likely to be released than parthenogenetic lizards that ovulate in isolation
**Found in some fish, amphibians, and reptiles

8. Concept Fertilization depends on mechanisms that bring together sperm and eggs of the same species
External fertilization- eggs fertilized in environment
Internal fertilization- sperm deposited in or near female reproductive tract
Pheremones- chemical signals released by mating animals
External fertilization- female releases egg into environment, male fertilizes it
Internal fertilization- adaption that increases efficiency of sperm reaching egg, even in dry environments
Pheremones- can change the physiology and behavior of mating animal; always used no matter which method of fertilization

9. Ensuring the Survival of Offspring
Internal vs. External
More gametes= lower survival rate
Spawning- release of gametes in mass numbers
Less protection- gelatinous coat, no internal membrane
Greater protection of embryo
Certain adaptions that protect from water loss/other damage
Egg-laying animals- shells are calcium and protein rich

10. Gamete Production and Delivery
Simple systems
No gonads (gamete-producing organs)
Gametes develop from undifferentiated cells
Elaborate systems
Tubes and glands to carry, nourish, and protect gametes

11. Insect Reproductive Anatomy

12. parthenogenesis in aphids
Animal homosexuality
Gender change in fish

13. Video: Hydra Releasing Sperm
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14. Initiated external fertilization.
Figure 46.6 External fertilization.

15. External fertilization Internal fertilization Pros Cons
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16. Parental care: Surinam toad mom mouth-brooding cichlids
Figure 46.7 Parental care in an invertebrate.

17. At what are we looking?
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18. A cloaca of a red-tailed hawk
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19. Gender-specific reproductive anatomy
Accessory gland
Ovary
Testis
Oviduct
Spermatheca
Vas deferens
Ejaculatory duct
Seminal vesicle
Uterus
Accessory gland
Penis and claspers
Vulva
Figure 46.8 Insect reproductive anatomy.
(a) Male fruit fly
(b) Female fruit fly

20. Animation: Female Reproductive Anatomy Right-click slide / select “Play”
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21. Major vestibular (Bartholin’s) gland Labia minora Labia majora
Figure 46.10
Oviduct
Ovary
Uterus
(Urinary bladder)
(Pubic bone)
(Rectum)
Urethra
Cervix
Body
Vagina
Glans
Clitoris
Prepuce
Major vestibular (Bartholin’s) gland
Labia minora
Labia majora
Vaginal opening
Oviduct
Ovaries
Figure Reproductive anatomy of the human female.
Follicles
Corpus luteum
Uterus
Uterine wall
Endometrium
Cervix
Vagina

22. Mammary Glands
The mammary glands are not part of the reproductive system but are important to mammalian reproduction
Within the glands, small sacs of epithelial tissue secrete milk
animation
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23. Male Reproductive Anatomy
The male’s external reproductive organs are the scrotum and penis
Internal organs are the gonads, which produce sperm and hormones, and accessory glands
Most mammals have a baculum (penile bone)
Raccoon’s baculum 
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24. Animation: Male Reproductive Anatomy Right-click slide / select “Play”
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25. Seminal vesicle (behind bladder)
Figure 46.11
Seminal vesicle (behind bladder)
(Urinary bladder)
Prostate gland
Bulbourethral gland
Urethra
Erectile tissue of penis
Scrotum
Vas deferens
Epididymis
Testis
(Urinary bladder)
Seminal vesicle
(Urinary duct)
Figure Reproductive anatomy of the human male.
(Rectum)
(Pubic bone)
Vas deferens
Erectile tissue
Ejaculatory duct
Prostate gland
Urethra
Penis
Bulbourethral gland
Vas deferens
Glans
Epididymis
Testis
Prepuce
Scrotum

26. Accessory Glands
Semen is composed of sperm plus secretions from three sets of accessory glands
The two seminal vesicles contribute about 60% of the total volume of semen
The prostate gland secretes its products directly into the urethra through several small ducts
The bulbourethral glands secrete a clear mucus before ejaculation that neutralizes acidic urine remaining in the urethra
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27. Gametogenesis
Spermatogenesis, the development of sperm, is continuous and prolific (millions of sperm are produced per day; each sperm takes about 7 weeks to develop
Oogenesis, the development of a mature egg, is a prolonged process
Immature eggs form in the female embryo but do not complete their development until years or decades later
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28. Spermatogenesis differs from oogenesis in three ways
All four products of meiosis develop into sperm while only one of the four becomes an egg
Spermatogenesis occurs throughout adolescence and adulthood
Sperm are produced continuously without the prolonged interruptions in oogenesis
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30. Cross section of seminiferous tubule Secondary spermatocyte
Figure 46.12aa
Epididymis
Seminiferous tubule
Sertoli cell nucleus
Spermato- gonium
Primary spermatocyte
Testis
Cross section of seminiferous tubule
Secondary spermatocyte
Spermatids (two stages)
Figure Exploring: Human Gametogenesis
Sperm cell
Lumen of seminiferous tubule

31. Primordial germ cell in embryo Mitotic divisions
Figure 46.12ab
Primordial germ cell in embryo
Mitotic divisions
Spermatogonial stem cell 2n
Mitotic divisions
Spermatogonium 2n
Mitotic divisions
Primary spermatocyte 2n
Meiosis I
Secondary spermatocyte n n
Meiosis II
Figure Exploring: Human Gametogenesis
Early spermatid n n n n
Differentiation (Sertoli cells provide nutrients)
Sperm cell n n n n

32. Neck Tail Midpiece Head Plasma membrane Acrosome Nucleus Mitochondria
Figure 46.12ac
Neck
Tail
Midpiece
Head
Plasma membrane
Acrosome
Nucleus
Figure Exploring: Human Gametogenesis
Mitochondria

33. Figure 46.12 Exploring: Human Gametogenesis
Figure 46.12b
Primary oocyte within follicle
Ovary
Growing follicle
Primordial germ cell
In embryo
Mitotic divisions 2n
Oogonium
Mitotic divisions
Primary oocyte (present at birth), arrested in prophase of meiosis I
Mature follicle 2n
Ruptured follicle
Completion of meiosis I and onset of meiosis II
First polar body n n
Secondary oocyte, arrested at metaphase of meiosis II
Ovulated secondary oocyte
Figure Exploring: Human Gametogenesis
Ovulation, sperm entry
Completion of meiosis II
Second polar body
Corpus luteum n
Fertilized egg n
Degenerating corpus luteum

34. 46.4: The interplay of tropic and sex hormones regulates mammalian reproduction
Gonadotropin-releasing hormone (GnRH) secreted by hypothalamus
-Follicle stimulating hormone (FSH)
-Luteinizing hormone (LH)
Steroid Hormones:
Males: Androgens → Testosterone
Sex characteristics, deeper voice, facial hair
Females: Estrogens → Estradiol and progesterone
Breast and pubic hair development, influences sexual behavior
Regulate gametogenesis by...
-Targeting tissues in gonads
-Regulating sex hormone production

35. Hormonal Control of Female Reproductive Cycles
Secretion of hormones in females is cyclic
Menstrual / Uterine cycle
-Changes in the uterus
-Shedding of blood and endometrium through cervix and vagina
Ovarian cycle
-Changes in the ovaries
Ovulation
-Endometrium thickens w/ blood vessels
-Preparation for implantation

36. The reproductive cycle of a human female

37. The Ovarian Cycle Hormone release signals follicle growth
Estradiol increases in follicular phase
Second oocyte released at ovulation
Follicular tissue → corpus luteum
The corpus luteum disintegrates due to low gonadotropin levels
Ovarian steroid hormones decrease & negative-feedback ends

38. Uterine (Menstrual) Cycle
Ovarian hormones stimulate uterus to prepare for embryo
Proliferative phase coordinated to follicular phase (endometrial thickening)
Secretory phase coordinates with luteal phase
Menstrual flow phase (shedding of endometrium) coordinates with growth of ovarian follicles
Endometriosis: swelling of uterine lining cells that have migrated to an ectopic location

39. Menopause After 500 cycles ovulation and menstruation ceases
Decline in estradiol production
Unusual phenomenon

40. Menstrual vs. Estrous Cycles
Endometrium thickens before ovulation in all female mammals
Uterus reabsorbs it if an embryo is not implanted
Estrus period around ovulation is the female mating time (heat)
Length and frequency varies among animals
1/yr
5 days

41. Hormonal Control of the Male Reproductive System
Sertoli cells nourish developing sperm
Leydig cells secrete testosterone
-Promote spermatogenesis
Testosterone regulates FSH, LH, and GnRH levels
Inhibin reduces FSH secretion

42. Human Sexual Response Testosterone, prolactin, and oxytocin
Physiological responses in both sexes: vasocongestion and myotonia
Four Phases: 1. Excitement 2. Plateau 3. Orgasm 4. Resolution
Inner vagina expands & depression for sperm forms
Breathing and heart rate increases
Contractions of reproductive structures
Semen released & ejaculated
Organs return to normal state
Muscles relax
Males enter refractory period
Prepares for coitus →
erection, enlargement, lubrication and myotonia

43. 46.5 In placental mammals, an embryo develops fully within the mother’s uterus
Egg develops into an embryo in reproduction

44. Conception, Embryonic Development, and Birth
Conception in the oviduct is when sperm fuses with an egg
Zygote forms and begins dividing
Division by mitosis, with cleavage, gives rise to blastocyst
Embryo implants into endometrium and releases human chorionic gonadotropin (hCG) to prevent menstruation
Ectopic pregnancy occurs when a fertilized egg develops in fallopian tube

46. First Trimester
Human gestation divided into three trimesters, each with three months
Most radical change for mother and embryo in first tri.
Endometrium grows over the blastocyst during implantation
Embryo obtains nutrients from endometrium in first 2-4 weeks

47. Trophoblast grows outward and forms placenta with the endometrium
The umbilical cord carries blood to the placenta and returns via umbilical vein
Identical twins develop if the embryo splits during the first month
Fraternal twins develop if two eggs are fertilized
Body organs are developed in the
first trimester (organogenesis)
By 8 weeks, embryo is called a
fetus

48. -Growth of placenta and uterus
Changes in the mother:
-Mucus plug
-Growth of placenta and uterus
-Cessation of ovulation and menstrual cycle
-Breast enlargement
-Nausea is common
Changes in embryo:

49. Second & Third Trimester
-Uterus grows and pregnancy is apparent
-Fetus is very active
-hCG declines; corpus luteum deteriorates; and the placenta takes over the production of progesterone to maintain the pregnancy
-Fetus fills the space between embryonic membranes
-Labor is induced by hormones produced by the fetus
-Regulators and hormones induce and regulate further contractions

50. Three stages of labor:
1. Thinning and dilation of the cervix
2. Expulsion of the baby
3. Delivery of the placenta
Mammals lactate and newborns suckle their mother’s milk

51. Maternal Immune Tolerance of the Embryo and Fetus
Embryo is foreign to mother due to paternal genes on its surface
Regulation of immune process altered by pregnancy
Acceptance of offspring may be due to the suppression of the immune response in the uterus

52. Contraception and Abortion
Contraception can be categorized in three ways:
Preventing release of eggs and sperm
Keeping eggs and sperm apart
Preventing implantation of an embryo

53. Fertilization can be prevented by abstinence or barriers
Rhythm method is temporary abstinence when conception is most likely
Hormone based contraceptives mimic negative feedback in the ovarian cycle and inhibits ovulation and follicle development
Abortion is the termination of a pregnancy
Spontaneous abortion (miscarriage)
occurs in ⅓ of pregnancies

54. Modern Reproductive Technologies
Amniotic fluids or fetal cells can be obtained for genetic analysis
Amniocentesis and chorionic villus
Ultrasounds can show fetal condition
Genetic testing of the fetus brings rise to many ethical arguments

55. Infertility Treatment:
Assisted reproductive technologies
In vitro fertilization (IVF)
Mixed in culture dishes, then returned to embryo
Intracytoplasmic sperm injection (ICSI)
Sperm injected with needle into oocyte