1. Chapter 46 Animal Reproduction
By: Audrey Del Re and Becca Krauss

2. Two Types of Reproduction
Sexual
- Majority of eukaryotic species reproduce sexually
- fusion of haploid gametes forms diploid cell, zygote
Asexual
- involves two-step process: fragmentation & regeneration

3. Asexual Reproduction Types: Advantages: Two step process:
Budding: separation of parent organism into two individuals of equal size
Fission: new individuals arise from outgrowths of existing ones
Parthenogenesis: an egg develops without being fertilized
Advantages:
In stable, favorable environments because it keeps passing on successful genotypes
Two step process:
Fragmentation: the breaking of the body into several pieces
Regeneration: the regrowth of the lost body part

4. Sexual Reproduction Advantages: Reproductive cycle:
Production of various phenotypes, may enhance reproductive success in changing environment.
Shuffling of genes during sexual reproduction might get rid of unwanted genes quickly.
Reproductive cycle:
Controlled by hormones regulated by the environment
Females go through ovulation
Occurs at the midpoint of each cycle
Some organisms switch between sexual and asexual due to the environment
Reproductive Patterns:
Hermaphroditism
Sex reversal

5. Fertilization The union of sperm and egg
External Fertilization: eggs released into environment, where the male fertilizes them
Needs moist habitat
Spawning: process where entire species releases their gametes into the water at about the same time.
Chemical or environmental triggers to release gametes
Non-synchronous fertilization in a population
One female’s eggs to one male
Courtship behavior
Leads to mate selection and higher probability of success.
Produces a lot of gamete, few survive.

6. Fertilization
Internal Fertilization: sperm are released in or near the female reproductive tract, where fertilization then occurs
Pheromones: chemicals released by organisms that act as a mate attractant
During mating, sperm are ejaculated into the female reproductive system
Produce fewer zygotes
Gonads: the organs that produce gametes in most animals

7. Female Reproductive Organs
External Structure:
Clitoris and vaginal opening surrounded by two sets of labia
Internal Organs Function:
Produces eggs and reproductive hormones
Houses the embryo and fetus
Internal Organs Structure: (gonads)
Pair of ovaries on each side of the uterus
Outer layer has follicles made up of oocytes (partially developed eggs)
Oogenesis: formation and development of ovum
Before ovulation follicles produce estradiol (primary female sex hormone)
If no fertilization occurs the corpus luteum degenerates and is released
Menstrual cycle then starts over

8. Female Reproductive Organs Continued
Oviduct: (fallopian tubes) connects the uterus and the ovaries
Contractions of the oviduct and cilia help the egg travel down to the uterus
Uterus: (womb) thick muscular organ that expands during pregnancy
Endometrium: inner lining; richly supplied with blood vessels
Cervix: neck of the uterus; opens into the vagina.
Vagina: muscular, but elastic chamber; the sire for insertion of the penis and deposition of sperm; birth canal
Vulva: collective term for the external female genitals
Labia majora: encloses and protects the rest of the vulva
Mammary glands: produces milk in the breasts
Usually only in females

9. Male Reproductive Organs
External Structure:
Scrotum and penis
Internal Organs Function:
Produces sperm and reproductive hormones
Ducts that carry sperm and secretions
Testes: male gonads
Seminiferous tubules: where sperm forms
Leydig cells: produces testosterone
Scrotum: maintains testis temperature
Testicle: testes within a scrotum
Ejaculation: the sperm is released from the epididymis through the vas deferens
Urethra: outlet for excretions
Accessory glands: produce secretions that combine with sperm to make semen
Seminal vesicles, prostate gland, bulbourethral glands
Penis: contains urethra and three cylinders of erectile tissues

10. Human Sexual Response Physical reactions predominant in both sexes:
Vascongestion: the filling of a tissue with blood
Myotonia: increased muscle tension
Four phases of sexual response cycle:
Excitement: prepares the vagina and penis for coitus
Plateau: excitement symptoms continue; breathing and heart rate increase
Orgasm
Male has two stages: Emission and Expulsion
Female: the uterus and outer vagina contract
Females can have multiple; males need to recover after each
Resolution: reverses the responses of the earlier stages

11. Gametogenesis The production of gametes
Spermatogenesis: formation and development of sperm
Continuous; in the testes
Oogenesis: development of mature eggs
Development does not complete for years
Differences:
Sperm: all four products of meiosis develop into mature gametes Eggs: meiosis is unequal
Sperm: mitotic division throughout most of life Eggs: mitotic divisions are complete before birth
Sperm: produces mature sperm in continuous sequence Eggs: have long interruptions

12. Hormones Regulate Reproduction
Hypothalamus secretes gonadotropin-releasing hormone (GnRH)
Triggers anterior pituitary to secrete Follicle Stimulating Hormones (FSH) and Luteinizing Hormone (LH)
Regulates gametogenesis (regulates sex hormone production)
Principal Sex Hormones
Male: androgens (testosterone)
Female: estrogens (estradiol, progesterone)
Induce formation of secondary sex characteristics

13. Hormonal Control
Male: testosterone regulates blood levels of GnRH, FSH, and LH through inhibitory effects on hypothalamus and anterior pituitary
Inhibin: reduces FSH secretion by pituitary gland
Together, these negative feedback circuits maintain androgen production at ideal levels
Female: two cycles
Menstrual/Uterine Cycle: changes in uterus; shedding of endometrium from uterus (if no pregnancy)
Estrdiol is involved
Ovarian cycle: cyclic events that occur in the ovaries

15. Conception, Embryonic Development, and Birth
Conception aka fertilization: sperm fuses with egg
Cleavage: 24 hours after conception, process of dividing zygote
After 2-3 days, embryo arrives at uterus as 16-celled ball
Blastocyst: 1 week after fertilization, embryonic stage
Embryo implants into endometrium
Human chorionic gonadotropin (hCG): secreted by implanted embryo, maintains secretions of progesterone and estrogens
Pregnancy/Gestation: condition of carrying 1+ embryos
266 days/38 wks

16. Pregnancy Trimesters First Trimester: Second Trimester:
three months each
First Trimester:
2-4 weeks embryo obtains nutrients directly from the endometrium
Placenta: formed by outer layer of blastocyst (trophoblast) and the endometrium
Organogenesis: the development of the body organs
4th week heart begins beating
8th week FETUS and heartbeat detectable
Second Trimester:
30cm in length and is very active
Third Trimester:
50cm in length; 3-4kg
LABOR: process by which childbirth occurs; induced by estradiol
Dilation
Delivery of baby
Delivery of placenta

17. Contraceptives, Abortion, and Repro. Tech.
Deliberate prevention of pregnancy
Temporary Abstinence/Rhythm Method/Natural Family Planning
Withdrawal
Barrier Methods: Condom, Birth Control, Diaphragm
Sterilization: tubal ligation, vasectomy
Abortion: forced miscarriage
Detecting Disorders: ultrasound imaging, amniocentesis, chorionic villus sampling, blood sample from mother
Treating Infertility: assisted reproductive technologies, in vitro fertilization, intracytoplasmic sperm injection

18. THE END!!!!!!!