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CHAPTER 26 Reproduction and Development Figures 26.1 – 26.2.

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Presentation on theme: "CHAPTER 26 Reproduction and Development Figures 26.1 – 26.2."— Presentation transcript:

1 CHAPTER 26 Reproduction and Development Figures 26.1 – 26.2

2 During ejaculation, a man releases up to 500 million sperm, only one of which may fertilize an egg

3 You have trillions of cells in your body, and they all arose from one original cell

4 An American woman is 4 times more likely to deliver triplets today than 25 years ago Even though a woman is born with up to half a million developing gametes, she will only use about 500 during her lifetime

5 On November 19, 1997, news reports heralded the arrival of the Iowa septuplets BIOLOGY AND SOCIETY: RISE OF THE SUPERTWINS Figure 26.1

6 Other sets of multiple births soon followed What accounted for the sudden rash of multiple births?

7 All of these multiple births were by women who had taken fertility drugs because they couldnt become pregnant naturally Couples turn to fertility drugs to overcome their natural reproductive limitations

8 Reproduction is the creation of new individuals from existing ones UNIFYING CONCEPTS OF ANIMAL REPRODUCTION

9 In asexual reproduction Asexual Reproduction –One parent produces genetically identical offspring

10 Binary fission –Is the simplest type of asexual reproduction –Involves a single parent cell splitting through mitosis into two genetically identical offspring cells

11 Some multicellular organisms reproduce by a similar means called fission, in which one organism splits into two or more individuals Figure 26.2a

12 Fragmentation is the breaking of a parent body into several pieces Regeneration, which follows fragmentation, is the regrowth of a whole animal from the pieces

13 Budding –Is the splitting off of new individuals from existing ones Figure 26.2b

14 Asexual reproduction has a number of advantages –It allows a species to perpetuate itself if its individual members are sessile or isolated from one another –It allows organisms to multiply quickly

15 One potential disadvantage of asexual reproduction is that it produces genetically uniform populations

16 Sexual reproduction Sexual Reproduction –Involves the fusion of gametes (sperm and egg) from two parents –Increases the genetic variability among offspring

17 Some animals can reproduce both sexually and asexually Figure 26.3a

18 Some species are hermaphrodites with both male and female reproductive systems Figure 26.3b

19 The mechanics of fertilization play an important part in sexual reproduction

20 Many organisms use external fertilization, in which parents discharge their gametes into the water, where fertilization occurs Figure 26.3c

21 Other organisms use internal fertilization, which occurs within the females body Internal fertilization requires copulation, or sexual intercourse

22 Both sexes of humans have HUMAN REPRODUCTION –A pair of gonads, the organs that produce gametes –Ducts to store and deliver the gametes –Structures to facilitate copulation

23 The ovaries Female Reproductive Anatomy –Are the site of gamete production in human females Figure 26.4 Ovaries Uterus Cervix (neck of uterus) Oviduct Follicles Corpus luteum Wall of uterus Endometrium (lining of uterus) Vagina

24 The ovaries contain follicles –Each follicle consists of a single developing egg cell surrounded by layers of cells that nourish and protect it –The follicles also produce estrogen, the female sex hormone

25 Ovulation –Is the process by which an egg cell is ejected from the follicle Figure 26.5

26 The egg enters the oviduct, which is a tube in which cilia sweep the egg toward the uterus

27 The uterus is the actual site of pregnancy The cervix, the narrow neck at the bottom of the uterus, opens into the vagina, or birth canal During copulation, the vagina serves as a repository for sperm

28 Female reproductive anatomy Figure 26.6 Rectum (digestive system) Cervix Vagina Vaginal opening Oviduct Ovary Uterus Bladder (excretory system) Pubic bone Urethra (excretory system) Shaft Glans Clitoris Labia minora Labia majora Prepuce

29 The penis Male Reproductive Anatomy –Contains erectile tissue

30 The testes –Are the male gonads, enclosed in a sac called the scrotum –Produce sperm

31 Several glands –Contribute to the formation of the fluid that carries, nourishes, and protects sperm Semen –Consists of this fluid and sperm

32 Seminal vesicle Rectum (digestive system Vas deferens Prostate gland Vas deferens Epididymis Testis Bladder (excretory system) Pubic bone Erectile tissue of penis Urethra Glans of penis Prepuce Male reproductive anatomy, side view Figure 26.7a Scrotum

33 Male reproductive anatomy, front view Figure 26.7b Bladder (excretory system) Prostate gland Erectile tissue of penis Vas deferens Epididymis Testis Seminal vesicle (behind bladder) Urethra Scrotum Glans of penis

34 Gametogenesis –Is the production of gametes Human gametes –Are haploid cells that develop by meiosis

35 Diploid cell in embryo Differentiation and onset of meiosis I Primary oocyte, arrested in prophase of meiosis I; present at birth Completion of meiosis I and onset of meiosis II First polar body Secondary oocyte, arrested at metaphase of meiosis II; released from ovary Entry of sperm triggers completion of meiosis II Second polar body Ovum (haploid) Corpus luteum Ovulation Sperm Ruptured follicle Ovary Mature follicle Growing follicle Oogenesis Oogenesis is the development of eggs within the ovaries Figure 26.8

36 Spermatogenesis –Is the formation of sperm cells

37 Figure 26.9 Diploid cell Differentiation and onset of meiosis I Primary spermatocyte Meiosis I completed Secondary spermatocyte Meiosis II Developing spermatids Differentiation Sperm cells (haploid) Testis Scrotum Penis Epididymis Testis Seminiferous tubule Cross section of seminiferous tubule Center of seminiferous tubule

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