1. Reproduction and Development Figures 26.1 – 26.2
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. BIOLOGY AND SOCIETY: RISE OF THE SUPERTWINS
On November 19, 1997, news reports heralded the arrival of the Iowa septuplets
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 couldn’t become pregnant naturally
Couples turn to fertility drugs to overcome their natural reproductive limitations

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

9. Asexual Reproduction In 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 female’s body
Internal fertilization requires copulation, or sexual intercourse

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

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

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

29. Male Reproductive Anatomy
The penis
Contains erectile tissue

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

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

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

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

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

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

36. Spermatogenesis
Spermatogenesis
Is the formation of sperm cells

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