BIOL 118 1st Edition Lecture 31Outline of Last Lecture I. Introduction to Chemical Signals in AnimalII. Cell-to-Cell Signaling: An OverviewIII. 3 Hormone Signaling PathwaysIV. Chemical Characteristics of HormonesV. How is the Production of Hormones Regulated?VI. The Hypothalamus-Pituitary AxisOutline of Current Lecture I. Introduction to Animal ReproductionII. Asexual & Sexual ReproductionIII. Mechanisms of Sexual Reproduction: GametogenesisIV. Fertilization & Egg DevelopmentV. Role of Sex Hormones in Sexual ReproductionVI. Pregnancy & Birth In MammalsCurrent LectureIntroduction to Animal Reproduction- Reproductive systems of animals are highly variableo Some species switch between asexual and sexual reproductiono In sexual reproduction, fertilization may be external or internalo Egg development may take place inside or outside the mother’s body- In humans, the male reproductive system includes structures specialized producing & storing sperm, synthesizing semen- Human female reproductive system includes specialized structures for producing eggs, receiving sperm, & caring for the developing embryoo Hormones from the pituitary gland & female reproductive organs regulate the menstrual cycle via positive or negative feedbacko Pregnancy is maintained by hormonal signals from the embryo & the mother’s reproductive organsAsexual & Sexual Reproduction- Asexual reproduction: based on mitosis & results in offspring that are genetically identical to one another & to their parent; equivalent to cloningThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.o Budding: offspring forms in or on the parent; when fully developed, the offspringbreaks awayo Fission: an individual splits into 2 organismso Parthenogenesis: female produces and offspring without fertilization from a maleo Eggs can be produced by mitosis or meiosis- Sexual reproduction: based on meiosis & fusion of haploid gametes usually from different parents; results in offspring that are genetically differentMechanisms of Sexual Reproduction: Gametogenesis- Gametogenesis: Mitotic cell divisions, meiotic cell division, & developmental events thatresult in the production of male & female gameteso Spermatogenesis: formation of sperm Spermatogonia: diploid cells that divide by mitosis to generate cells that undergo meiosis Occurs continuously through male’s adult life Spermatogonia divide by mitosis to produce primary spermatocytes, which undergo meiosis I & produce 2 secondary spermatocytes At end of meiosis II, result is 4 haploid cells called spermatids, which mature into spermo Oogenesis: formation of eggs Oogonia: diploid cells that divide by mitosis to form primary oocytes Only one of the 4 haploid product (ovum) matures into an egg Polar bodies: other cells that do not mature into eggs Production of primary oocytes stops early in development, or before birtho Vast majority occurs in a sex organ (gonad) Male: testes females: ovaries- Four components of mammalian sperm:o Head contains the nucleus & enzyme acrosome for penetrating the eggo Neck contains 1 centriole, which will combine with the centriole contributed by the eggo Midpiece contains mitochondria, which supplies the ATP that sperm uses to swimto the eggo Tail with flagellum for swimming- Contents of an egg cell:o Yolk: nutrient source loaded with protein & fatso Vitelline envelope: outside the cell membrane In sea animals, may be surrounded by jelly-like layer to protect the egg (zonapellucida)Fertilization & Egg Development- Fertilization: joining of sperm & egg to form diploid zygoteo Many animal species release gametes into the environment & external fertilization occurs Most of these lice in aquatic environments & tend to produce large numbers of gametes Gametogenesis responds to environmental cues that indicate a favorable season for breeding Pheromones: chemical messengers that might be involved in coordination of the release of the gameteso In other animals, males deposit sperm into the reproductive tracts of females & internal fertilization occurs Copulation: males deposit sperm directly into the female reproductive tract with the aid of a copulatory organ (penis) Males may also package their sperm into a spermatophore, which is then placed into the female’s reproductive tract by the male or female - Sperm competition: competition between sperm from different males to fertilize the eggs of the same femaleo Second-male advantage: when two males mate with a single female, the last oneto copulate fathers 85% of the offspring produced (not universal, but widespread)o In fruit flies, second male’s sperm physically dislodged & replaced first male’s gametes from female’s sperm storage area Fluid that accompanies sperm is able to displace stored sperm from competing males- Once fertilization occurs, embryo is either laid as an egg outside the mother’s body or retained insideo Oviparous: egg is laid outside the mother’s body & the embryo develops in the external environment-care of young varies Care of young is variableo Viviparous: egg remains within the mother’s body Embryo develops & receives nutrition directly from the mothero Ovoviviparious: offspring develops inside the mother’s body, but are nourished by nutrient-rich yolk in the egg- Anatomy of human male reproductive organso Spermatogenesis & sperm storage- sperm are produced in the testes & stored in the nearby epididymiso Production of additional fluids- accessory are formed in the seminal vesicles, prostate gland&bulbourethral gland These accessory fluids are added to sperm before ejaculation or expulsion from the bodyo Semen: combination of sperm & accessory fluids expelled during ejaculationo Vas deferens: tubes that transport sperm from the epididymis to the ejaculatory ducto Urethra: longer tube that passes through the penis & services both the reproductive & urinary systems in males - Female reproductive systemso Ovary: where meiosis occurs &egg cells (ova) are producedo Mature egg cell is a membrane-bound structure consisting of a haploid nucleus, afull complement of other organelles, & a large supply of nutrients in the form of yolko Humans are viviparous vertebrates; female retains the embryo & provides the nourishmento External anatomy of human female reproductive system Labia minora/majora: folds
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