Ch. 46 Animal Reproduction
1 Essential Questions:
How do animals achieve reproductive success?
What diverse mechanisms do animals use to reproduce?
2 Two types of reproduction: 1. Asexual no fusion of egg and sperm are involved to make offspring sea anemones budding
3 fission Separation of parent organism into two individuals of equal size budding new individuals forming and then splitting off from other ones gemmules in sponges, several types of cells come together in sponge and a protective coat surrounds them fragmentation body breaks into pieces and creates new adults, associated with regeneration ex. sponges, cnidarians, tunicates, Linckia sea stars
4 some organisms can do either sexual or asexual depending on conditions ex. Daphniafemale can produce two eggs depending on environment one can be fertilized, one develops by parthenogenesis egg can develop without being fertilized (adult would be haploid no meiosis to make gamete) asexual under favorable conditions, sexual under unfavorable
In bees, males (drones) are produced this way male females are produced from fertilized egg queen sterile female worker
5 parthenogenic lizards no males in species, all female but can behave as males during breeding season eggs undergo doubling in chromosomes from meiosis without fertilization both are females, one on top is behaving as a male
every two/three weeks switch sex roles related to ovulation
6 male and female behaviors are related to ovulation and hormone levels
Ovulation the release of mature eggs
7 2. Sexual reproductionwhere gametes (ovum or spermatozoon) fuse to form a zygote (fertilized egg) sperm = motile ovum = nonmotile function increase genetic variability
Utethesia ornatrix red beetles
8 Why do animals have reproductive cycles? a. conserve resources and reproduce when have lots of energy b. reproduce when conditions are favorable for offspring survival
controlled by hormones and environmental factors (temperature, rainfall, length of daylight, lunar cycles)
Hermaphroditismindividual with both male and female reproductive organs can fertilize themselves or a mate ex. earthworms
9 sequential hermaphroditism (sex reversal) individual reverses its sex during its lifetime protogynous = female first protandrous = male first
Wrasses live in harems, if male dies, largest female becomes male, produces sperm instead of eggs
Oysters are protoandrous females are larger and lay more eggs
10 What are the mechanisms of sexual reproduction? Fertilization union of egg and sperm external fertilizationeggs and sperm come together in the external environment
Produce huge numbers of zygotes, but small number survive must have moist habitats depends on timing
11 can have courtship behaviors, trigger release of eggs ex. fish, amphibians once one organism has released eggs, may trigger other organisms to also release their eggs
*need moist environment why?
pheromoneschemical signals that influence behavior of others mate attractants minute amount is very powerful ex. gypsy moth
12 internal fertilization sperm deposited in female reproductive tract where fertilization occurs requires specific reproductive structures (copulatory organs and receptacles) places for storage and transport of eggs usually reproduce fewer offspring, have a better tendency to survive greater parental care resistant eggshells can retain embryo in body for development pouch, uterus
13 Parental care giant water bug protects offspring by gluing them to the back of the male he keeps them moist
14 Reproductive systems can be complex or simple parasitic flatworm hermaphrodites
complex
simple polycheate worms: separate sexes but no gonads eggs and sperm develop from undifferentiated cells lining the coelom
15 Honeybee reproductive structures
spermatheca sac that can store sperm for up to a year cloacacommon opening for digestive, excretory and reproductive systems in nonmammalian vertebrates
16 Human Male reproductive system
17 external organs = a. scrotum holds testes at lower body temp. b. peniscopulatory organ internal organs = a. testes contain seminiferous tubules (sperm form here) Leydig cells produce testosterone and androgens b. epididymuswhere sperm passes from seminiferous tubules, where sperm mature (20 days)become motile c. vas deferens tube from epididymus during ejaculation where sperm travel
18 d. ejaculatory duct tube from vas deferens to urethra e. urethra tube to external body, carries both semen and urine (not at same time) f. glands that add substances along the way 1. seminal vesiclesprovide thick, yellow, basic fluid for sperm (60% of semen volume) 2. prostate gland largest semen secreting gland;thin, milky contains anticoagulant enzymes and citrate (sperm nutrient) problem in men over 40 gets enlarged and cuts off flow of urine, can be cancerous test with digital rectal exam
19 3. bulbourethral gland pair of glands below prostate secretes clear fluid that neutralizes any acid in urethra before semen comes through does contain some sperm (bad for withdrawal method of birth control)
ejaculated semen = 25ml of semen (1 tablespoon) 1ml =50130 million sperm prostaglandins in semen thin mucus of cervix and help contract uterus semen initially coagulates (uterine contractions help it move) and then anticoagulant breaks it apart so sperm can swim
20 penismade of erectile tissue, fills with blood during erection some animals (walruses, raccoons, rodents) have a baculumbone inside the penis
impotenceinability to maintain an erection causes: alcohol, drugs, emotional problems treatments: penile implants, Viagra(relaxes smooth muscles of blood vessels so blood can enter) glans penis tip of penis prepuce foreskin, removed during circumcision
21 anterior view
22 Female Reproductive System
23 external organs a. clitoris made of erectile tissue b. labia folds of skin surrounding clitoris and vagina labia minoraslender skin folds labia majorathick, fatty skin folds, around labia minora internal organs a. ovaries in abdominal cavity, attached to uterus by mesenteries contains follicles (egg cell surrounded by layers of follicle cells, protect and nourish egg) woman born with 400,000 follicles, only a few hundred released during life produces estrogens female sex hormones
24 ovulationprocess of egg being expelled from ovary remaining follicle tissue becomes corpus luteum in ovary corpus luteum secretes estrogens and progesterone (maintains uterine lining during pregnancy) if egg not fertilized, corpus luteum disintegrates b. oviduct fallopian tube, has fimbrae that pull egg into oviduct, where fertilization occurs c. uterus womb, muscular, where embryo matures endometrium lining of uterus d. cervixend of uterus that opens into the vagina e. vagina birth canal, thin walled tube, receives penis during intercourse f. hymenmembrane that partially covers the vagina
25 Internal organs
26 ovary follicle
27 Ovulation
28 g. mammary glandspresent in males and females usually only function in women low level of estrogen in men prevent breasts form developing
29 How are sperm and eggs made? Spermatogenesis = process of making sperm occurs in seminiferous tubules
30 seminiferous tubules sperm
31 sperm structure
32 oogenesisprocess of making eggs (ova) FSH follicle stimulating hormone stimulates a follicle to grow, makes primary oocyte to complete meiosis I and start meiosis II penetration of egg by sperm cell triggers completion of meiosis II
33 oogenesis in ovary
34 How are hormones involved? In male androgens (testosterone most important) responsible for primary (development of ducts, external anatomy, sperm production) and secondary sex characteristics (deepening of voice, facial/axillary/pubic hair, thickening of muscles)
sex drive, aggressiveness
controlled by hypothalamus and anterior pituitary
35 Hormonal control of testes
LH stimulates FSH acts on Leydig cells to seminiferous make tubules to androgens, increase stimulate sperm spermatogenesis production
36 In females two cycles in female mammals a. menstrual cycle in humans and primates humans about 28 days b. estrous cycle other mammals (called heat) these mammals only copulate around time of ovulation both have ovulation after endometrium thickens if no egg fertilized in menstruation uterine lining sheds (menstruation) in estrous endometrium is reabsorbed by uterus
37 How does the menstrual cycle work? day 1 = first day of menstruation (menstrual flow phase) usually lasts a few days ~ day 5 endometrium begins to regenerate and thicken (12 weeks) (proliferative phase) day 14 ovulation day 1428 endometrium continues to thicken, and develops glycogen producing glands (secretory phase) if no egg implants, cycle starts over
38 What about the ovarian cycle? parallels the menstrual cycle follicular stage several follicles start to mature egg enlarges in follicle and coat of follicle thickens (only one continues to grow) ends with ovulation follicle and ovary wall rupturereleases secondary oocyte corpus luteum secretes female hormones during luteal phase cycle starts again with new follicles forming
39 What roles do hormones play in these cycles? Five hormones: a. GnRH gonadotropinreleasing hormone released by hypothalamus regulates FSH and LH release from pituitary triggered by follicular phase of ovarian cycle b. FSH follicle stimulating hormone stimulates follicle growth secreted by anterior pituitary gonadotropin c. LH luteinizing hormone after ovulation stimulates transformation of follicular tissue to corpus luteum secreted by anterior pituitary gonadotropin
40 d. Estrogens secreted by growing follicles, and later by corpus luteum signal uterus to start thickening endometrium increasing estrogen inhibits FSH and LH production (neg. feedback) high level stimulates production of FSH and LH responsible for secondary sex characteristics (pubic/axillary hair, fat in breasts and hips, increased water retention, breast development, sexual behavior) e. progesterone secreted by ovaries, and later corpus luteum in positive feedback increase in LH conc. caused by increasing estrogen induces final maturing of follicle ovulation occurs 1 day after LH surge
41 menopause usually start between 4654 considered menopause if have not had menstrual cycle for 1 year ovaries lose response to gonadotropins declined production of estrogen symptoms: "hot flashes", decrease lubrication of vagina, some may grow some facial hair treatment estrogen replacement therapy herbal remedies
42 43 What happens in pregnancy? pregnancy = gestation human = 266 days, rodents = 21 days, elephants = 600 days Three trimesters a. first trimester zygote begins cleavage, after 34 days is ball of cells blastocyst sphere of cells with flattened cavity, implants into endometrium (grows over blasotsyst) placenta is formed for nutrients, gas exchange and disposal of metabolic wastes
44 organogenesis heart (4th week), other organs develop is fetus at end of first trimester human chorionic gonadotropin secreted by embryo to maintain secretion of estrogen and progesterone, if did not take over for LH from mother could get spontaneous abortion detected by pregnancy tests progesterone helps form mucus plug over cervix mother's breasts enlarge
45 formation of blastocyst
46 b. second trimester fetus grows quickly to 30 cm. mother feels movement, by middle can see movement on stomach area placenta secretes progesterone, HCG decreases abdominal area grows, pregnancy obvious c. third trimester rapid growth to 33.5 kg (~ 7 pounds) 50 cm length fetal activity may decrease due to lack of space mother's abdominal organs are compressed and moved estrogens very high at end of trimester, trigger oxytocin receptor formation on uterus oxytocin produced by fetus and mother's anterior pituitary gland stimulate uterine contractions (positive feedback)
47 Placental development
48 Human fetal Development
49 Birth (partuition) uterine contractions (labor) first stage cervix thins and opens second stage expulsion of baby final stage delivery of placenta
50 Stages of delivery First stage
Second stage
Third stage
51 Lactation unique to mammals
decreased progesterone shut off negative feedback of anterior pituitary allow prolactin production (stimulates milk production after 23 days)
becomes postive feedback mechanism
colostrum is initial fluid coming out of breast before milk comes in (contains maternal antibodies that help infant until own immune system kicks in)
52 How come the baby is not rejected as foreign when it contains the father's genes?
trophoblasthelps with implantation and becomes part of fetal placenta believed to prevent immune response by inhibiting mother's Tlymphocytes by making "suppressor" Tcells, so can't attack foreign tissue if male surface antigens are similar to mother's, no suppressor cells get made and embryo is attacked may be cause of miscarriages other hypothesis trophoblast secretes enzyme that breaks tryptophan down which is necessary for T cell survival (necessary to maintain pregnancy)
53 How do we prevent pregnancy? 1. abstinence 100 % effective 2. rhythm method no intercourse when conception is possible (egg lives 2448 hrs, sperm 72 hrs) 8090% effective 3. condom 90% effective 4. IUD intrauterine device prevent implantation of blastocyst
http://www.fwhc.org/birthcontrol/iudinfo.htm
54 5. diaphragm 90% effective
55 6. cervical cap
http://www.fwhc.org/birth control/capinfo.htm
56 7. birth control pills 99% effective, combinations of synthetic progestin and estrogens, stop release of GnRH, prevents ovulation
8. Norplant implanted under skin, alters cervix mucus so sperm can't get in
9. DepoProvera injection similar to Norplant
10. sterilization vasectomy or tubal ligation
57 contraceptive methods
58 Technology advances for genetic diseases
1. amniocentesis
2. chorionic villus sampling
3. ultrasound
4. blood samples
Technology advances for fertilization invitro fertilization
59 Ultrasound
60 4D ultrasound
http://www.prolifeamerica.com/4DUltrasoundpictures/index.cfm?photo=17#photos
61 62