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

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Presentation on theme: "Sections 46.1 and 46.2 Erin Foeri Period 2A Chapter 46: Animal Reproduction."— Presentation transcript:

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

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

4 Advantages of Sexual vs. Asexual

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

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

7 Parthenogenesis- Sex Reversals

8 Concept 46.2- 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

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 Gender change in fish Animal homosexuality

13 © 2011 Pearson Education, Inc. Video: Hydra Releasing Sperm

14 Initiated external fertilization.

15 © 2011 Pearson Education, Inc. External fertilizationInternal fertilization ProsConsProsCons

16 Parental care: Surinam toad mom mouth- brooding cichlids Surinam toad mom mouth- brooding cichlids

17 At what are we looking? © 2011 Pearson Education, Inc.

18 A cloaca of a red- tailed hawk © 2011 Pearson Education, Inc.

19 Gender-specific reproductive anatomy (a) Male fruit fly (b) Female fruit fly Accessory gland Ejaculatory duct Penis and claspers Testis Vas deferens Seminal vesicle Ovary Accessory gland Oviduct Spermatheca Uterus Vulva

20 © 2011 Pearson Education, Inc. Animation: Female Reproductive Anatomy Right-click slide / select Play

21 Figure 46.10 (Rectum) Cervix Vagina Major vestibular (Bartholins) gland Vaginal opening Oviduct Ovary Uterus (Urinary bladder) (Pubic bone) Urethra Body Glans Prepuce Clitoris Labia minora Labia majora Ovaries Oviduct Follicles Corpus luteum Uterine wall Endometrium Vagina Uterus Cervix

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 –animationanimation © 2011 Pearson Education, Inc.

23 Male Reproductive Anatomy The males 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) –Raccoons baculum © 2011 Pearson Education, Inc.

24 Animation: Male Reproductive Anatomy Right-click slide / select Play

25 Seminal vesicle (behind bladder) Urethra Scrotum (Urinary bladder) Prostate gland Bulbourethral gland Erectile tissue of penis Vas deferens Epididymis Testis Seminal vesicle (Rectum) Vas deferens Ejaculatory duct Prostate gland Bulbourethral gland Vas deferens Epididymis Testis Scrotum (Urinary bladder) (Urinary duct) (Pubic bone) Erectile tissue Urethra Glans Prepuce Penis Figure 46.11

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 © 2011 Pearson Education, Inc.

27 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 © 2011 Pearson Education, Inc. Gametogenesis

28 Spermatogenesis differs from oogenesis in three ways 1.All four products of meiosis develop into sperm while only one of the four becomes an egg 2.Spermatogenesis occurs throughout adolescence and adulthood 3.Sperm are produced continuously without the prolonged interruptions in oogenesis © 2011 Pearson Education, Inc.


30 Epididymis Seminiferous tubule Testis Cross section of seminiferous tubule Spermato- gonium Primary spermatocyte Spermatids (two stages) Secondary spermatocyte Sperm cell Sertoli cell nucleus Lumen of seminiferous tubule Figure 46.12aa

31 Primordial germ cell in embryo Mitotic divisions Spermatogonial stem cell Spermatogonium Mitotic divisions Primary spermatocyte Meiosis I Meiosis II Secondary spermatocyte Early spermatid Sperm cell Differentiation (Sertoli cells provide nutrients) 2n2n 2n2n 2n2n n n n n n n n n n n Figure 46.12ab

32 Figure 46.12ac Plasma membrane Tail Neck Midpiece Head Mitochondria Nucleus Acrosome

33 2n2n 2n2n n n n n Ovary Primordial germ cell Mitotic divisions Oogonium In embryo Primary oocyte (present at birth), arrested in prophase of meiosis I Completion of meiosis I and onset of meiosis II Secondary oocyte, arrested at metaphase of meiosis II First polar body Ovulation, sperm entry Completion of meiosis II Second polar body Primary oocyte within follicle Growing follicle Mature follicle Ruptured follicle Ovulated secondary oocyte Corpus luteum Degenerating corpus luteum Fertilized egg Figure 46.12b

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 Prepares for coitus erection, enlargement, lubrication and myotonia 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

43 46.5 In placental mammals, an embryo develops fully within the mothers 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 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 mothers 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 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

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