Animal Reproduc5on. Chapter 46. Asexual and Sexual Reproduc5on. Asexual and Sexual Reproduc5on. Sexual reproduc-on

Size: px

Start display at page:

Download "Animal Reproduc5on. Chapter 46. Asexual and Sexual Reproduc5on. Asexual and Sexual Reproduc5on. Sexual reproduc-on"

Amelia Poole
5 years ago
Views:

Chapter 46 Animal Reproduc5on BIOL 223 Sexual reproduc-on Asexual and Sexual Reproduc5on crea5on of an offspring by fusion of a male gamete (sperm) and female gamete (egg) to

or more individuals of about the same size Budding new individuals arise from outgrowths of exis5ng ones Fragmenta-on breaking of the body into pieces some or all of which

1 Chapter 46 Animal Reproduc5on BIOL 223 Sexual reproduc-on Asexual and Sexual Reproduc5on crea5on of an offspring by fusion of a male gamete (sperm) and female gamete (egg) to form a zygote Asexual reproduc-on crea5on of offspring without the fusion of egg and sperm Many invertebrates reproduce asexually binary fission separa5on of a parent into two or more individuals of about the same size Budding new individuals arise from outgrowths of exis5ng ones Fragmenta-on breaking of the body into pieces some or all of which develop into adults must be accompanied by regenera-on regrowth of lost body parts Parthenogenesis Asexual and Sexual Reproduc5on development of a new individual from an unfer5lized egg 1

Asexual and Sexual Reproduc5on Sexual reproduc5on results in gene5c recombina5on which provides poten5al advantages: More varia5on in offspring providing an increase in the reproduc5ve success of

2 Asexual and Sexual Reproduc5on Sexual reproduc5on results in gene5c recombina5on which provides poten5al advantages: More varia5on in offspring providing an increase in the reproduc5ve success of parents in changing environments increase in the rate of adapta5on shuffling of genes and the elimina5on of harmful genes from a popula5on Reproduc5ve Cycles and PaNerns Ovula-on release of mature eggs at the midpoint of a female cycle Most animals exhibit reproduc5ve cycles related to changing seasons controlled by hormones and environmental cues Animals may reproduce asexually or sexually or they may alternate these methods Reproduc5ve Cycles and PaNerns Sexual reproduc5on is a special problem for organisms that seldom encounter a mate hermaphrodi-sm, each individual has male and female reproduc5ve systems Some hermaphrodites can self- fer5lize Individuals of some species undergo sex reversals male to female reversal (certain oysters, clownfish) female to male reversal (Labroides dimidiatus) 2

fer-liza-on Fer5liza5on union of egg and sperm external fer-liza-on eggs shed by the female are fer5lized by sperm in the external environment internal fer-liza-on sperm are

of Offspring OUen more offspring produced than the environment can handle When coupled with low survival rate Species with external fer5liza5on produce more gametes than species

amniote eggs with protec5ve layers Some other animals retain the embryo which develops inside the female Gamete Produc5on and Delivery Sexual reproduc5on requires Produc5on of

3 fer-liza-on Fer5liza5on union of egg and sperm external fer-liza-on eggs shed by the female are fer5lized by sperm in the external environment internal fer-liza-on sperm are deposited in or near the female reproduc5ve tract fer5liza5on occurs within the tract requires behavioral interac5ons and compa5ble copulatory organs Eggs Ensuring the Survival of Offspring OUen more offspring produced than the environment can handle When coupled with low survival rate Species with external fer5liza5on produce more gametes than species with internal fer5liza5on Species with internal fer5liza5on provide greater protec5on of the embryos and more parental care embryos of some terrestrial animals develop in amniote eggs with protec5ve layers Some other animals retain the embryo which develops inside the female Gamete Produc5on and Delivery Sexual reproduc5on requires Produc5on of gametes gonads organs that produce gametes Some simple systems do not have gonads but gametes form from undifferen5ated 5ssue Most are complex systems That develop, nurture and store gametes 3

Gamete Produc5on and Delivery Most insects have separate sexes with complex reproduc5ve systems spermatheca Female organ in which sperm is stored during/auer copula5on Vas deferens Seminal vesicle

4 Gamete Produc5on and Delivery Most insects have separate sexes with complex reproduc5ve systems spermatheca Female organ in which sperm is stored during/auer copula5on Vas deferens Seminal vesicle (a) Male honeybee (drone) Accessory gland Ejaculatory Testis duct Penis Accessory gland (b) Female honeybee (queen) Ovary Oviduct Spermatheca Vagina Gamete Produc5on and Delivery Cloaca common opening between the external environment and the diges5ve, excretory, and reproduc5ve systems common in non- mammalian vertebrates mammals usually have a separate opening to the diges5ve tract Human Female Reproduc5ve Anatomy Human female anatomy external reproduc5ve structures include the clitoris and two sets of labia internal organs pair of gonads and a system of ducts and chambers that carry gametes and house the embryo and fetus 4

Fig. 46-10 Oviduct (Rectum) Cervix Ovary Uterus (Urinary bladder) (Pubic bone) Urethra Vagina Vaginal opening Shaft Glans Clitoris Prepuce Labia minora Labia majora Ovaries Oviduct Follicles Uterus

5 Fig Oviduct (Rectum) Cervix Ovary Uterus (Urinary bladder) (Pubic bone) Urethra Vagina Vaginal opening Shaft Glans Clitoris Prepuce Labia minora Labia majora Ovaries Oviduct Follicles Uterus Uterine wall Endometrium Corpus luteum Cervix Vagina Ovaries Ovaries contain many follicles consist of a par5ally developed egg cell (oocyte) surrounded by support cells Oogenesis Monthly development of an oocyte into an ovum (egg) Ovula5on expels an oocyte from the follicle Remaining follicular 5ssue becomes corpus luteum secretes hormones that help to maintain pregnancy If the egg is not fer5lized the corpus luteum degenerates into corpus albicans Ovaries 5

The ovum travels from the ovary to the uterus via an oviduct, or fallopian tube Cilia in the oviduct convey the egg to the

embryo Narrow opening of uterus into the vagina Vagina and Vulva vagina thin- walled chamber repository for sperm during

Anatomy Human male external reproduc5ve organs scrotum, and penis Internal organs gonads that produce sperm and hormones

Erectile tissue of penis Vas deferens Epididymis Testis (Urinary bladder) Seminal vesicle (Urinary duct) (Rectum) Vas

6 The ovum travels from the ovary to the uterus via an oviduct, or fallopian tube Cilia in the oviduct convey the egg to the uterus Endometrium Inner lining of uterus has many blood vessels cervix Oviducts and Uterus for nourishment of the poten5al embryo Narrow opening of uterus into the vagina Vagina and Vulva vagina thin- walled chamber repository for sperm during copula5on serves as the birth canal vulva consists of the labia majora, labia minora, hymen, and clitoris Male Reproduc5ve Anatomy Human male external reproduc5ve organs scrotum, and penis Internal organs gonads that produce sperm and hormones accessory glands Seminal vesicle (behind bladder) Urethra Scrotum (Urinary bladder) Prostate gland Bulbourethral gland Erectile tissue of penis Vas deferens Epididymis Testis (Urinary bladder) Seminal vesicle (Urinary duct) (Rectum) Vas deferens Ejaculatory duct Prostate gland Bulbourethral gland Vas deferens Epididymis Testis Scrotum (Pubic bone) Erectile tissue Urethra Penis Glans Prepuc e 6

testes Male gonads consist of highly coiled tubes Leydig cells seminiferous tubules Testes loca5on of sperm forma5on surrounded by connec5ve 5ssue

Ducts Epididymis Mass of coiled tubes adjacent to tes5s Receives newly formed sperm From seminiferous tubules ejacula-on sperm are propelled through

accessory glands two seminal vesicles 60% of total volume of semen Nourishment for travelling sperm, basic ph prostate gland Secretes alkaline fluid

7 testes Male gonads consist of highly coiled tubes Leydig cells seminiferous tubules Testes loca5on of sperm forma5on surrounded by connec5ve 5ssue produce testosterone Produc5on of normal sperm cannot occur at the body temperatures of most mammals Scrotum holds testes outside body at lower temp Ducts Epididymis Mass of coiled tubes adjacent to tes5s Receives newly formed sperm From seminiferous tubules ejacula-on sperm are propelled through the muscular vas deferens and the ejaculatory duct then exit the penis through the urethra Semen composed of sperm plus secre5ons from three sets of accessory glands two seminal vesicles 60% of total volume of semen Nourishment for travelling sperm, basic ph prostate gland Secretes alkaline fluid directly into the urethra two bulbourethral glands secrete a clear mucus before ejacula5on neutralizes acidic urine remaining in the urethra Accessory Glands 7

Penis human penis composed of three cylinders of spongy erec5le 5ssue During sexual arousal erec5le 5ssue fills with blood from arteries (engorgement) causing an erec5on Gamete Forma5on Gametogenesis

8 Penis human penis composed of three cylinders of spongy erec5le 5ssue During sexual arousal erec5le 5ssue fills with blood from arteries (engorgement) causing an erec5on Gamete Forma5on Gametogenesis produc5on of gametes by meiosis differs in females and males Spermatogenesis produc5on of mature sperm sperm are small and mo5le produced throughout the life of a sexually mature male Fig a Epididymis Seminiferous tubule Testis Cross section of seminiferous tubule Sertoli cell nucleus Spermatogonial stem cell Primordial germ cell in embryo 2n Spermatogonium 2n Primary spermatocyte 2n Meiosis I Lumen of seminiferous tubule Secondary spermatocyte n n Meiosis II Plasma membrane Tail Neck Midpiece Head Spermatids (at two stages of differentiation) Early spermatid n n n n Differentiation (Sertoli cells provide nutrients) Mitochondria Nucleus Sperm n n n n Acrosome 8

Gamete Forma5on Ovary Oogenesis development of mature oocytes Primary oocyte within follicle (eggs) Primordial germ cell In embryo Growing follicle can

prophase of meiosis I Completion of meiosis I and onset of meiosis II n Secondary oocyte, arrested at metaphase of meiosis II Ovulation, sperm entry

9 Gamete Forma5on Ovary Oogenesis development of mature oocytes Primary oocyte within follicle (eggs) Primordial germ cell In embryo Growing follicle can take many years 2n Oogonium Eggs contain stored nutrients and are much larger First polar n body Primary oocyte 2n (present at birth), arrested in prophase of meiosis I Completion of meiosis I and onset of meiosis II n Secondary oocyte, arrested at metaphase of meiosis II Ovulation, sperm entry Mature follicle Ruptured follicle Ovulated secondary oocyte Second polar n body Completion of meiosis II Corpus luteum n Fertilized egg Degenerating corpus luteum 9

Chapter 46 ~ Animal Reproduction

Chapter 46 ~ Animal Reproduction Overview Asexual (one parent) fission (parent separation) budding (corals) fragmentation & regeneration (inverts) parthenogenesis Sexual (fusion of haploid gametes) gametes