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animal reproduction sexual reproduction asexual reproduction biology

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This document covers animal reproduction, focusing on sexual and asexual reproduction mechanisms. It explains concepts like budding, fission, and fragmentation, as well as the role of reproductive cycles in animals.

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‭ ODULE‬ ‭11.2:‬ ‭THE‬ ‭UROGENITAL‬ ‭SYSTEM‬ ‭-‬ M ‭SEXUAL REPRODUCTION: AN EVOLUTIONARY‬ ‭ANIMAL REPRODUCTION & DEVELOPMENT‬ ‭ENIGMA‬ ‭Reproduction in the An...

‭ ODULE‬ ‭11.2:‬ ‭THE‬ ‭UROGENITAL‬ ‭SYSTEM‬ ‭-‬ M ‭SEXUAL REPRODUCTION: AN EVOLUTIONARY‬ ‭ANIMAL REPRODUCTION & DEVELOPMENT‬ ‭ENIGMA‬ ‭Reproduction in the Animal Kingdom‬ ‭ exual‬ ‭Females:‬ ‭Have‬ ‭half‬ ‭as‬ ‭many‬ ‭daughters‬ ‭as‬ S ‭asexual‬ ‭females.‬ ‭It‬ ‭is‬ ‭also‬ ‭the‬ ‭“twofold‬ ‭cost”‬ ‭of‬ ‭ exual‬ ‭Reproduction:‬ ‭The‬ ‭creation‬ ‭of‬ ‭an‬ ‭offspring‬ S ‭sexual‬ ‭reproduction‬ ‭(a‬ ‭male‬ ‭is‬ ‭needed,‬ ‭but‬ ‭in‬ ‭by‬ ‭fusion‬ ‭of‬ ‭a‬ ‭male‬ ‭gamete‬ ‭(sperm)‬ ‭and‬ ‭female‬ ‭asexual‬ ‭reproduction‬ ‭only‬ ‭females‬ ‭are‬ ‭required).‬ ‭gamete (egg) to form a zygote.‬ ‭Despite‬ ‭this,‬ ‭almost‬ ‭all‬ ‭eukaryotic‬ ‭species‬ ‭reproduce sexually.‬ ‭ sexual‬ ‭Reproduction:‬ ‭The‬ ‭creation‬‭of‬‭an‬‭offspring‬ A ‭without the fusion of egg and sperm.‬ ‭MECHANISMS OF ASEXUAL REPRODUCTION‬ ‭ udding:‬ ‭A‬ ‭simple‬ ‭form‬ ‭of‬ ‭asexual‬ ‭reproduction‬ B ‭found only among invertebrates.‬ ‭ y‬‭producing‬‭offspring‬‭of‬‭varied‬‭phenotypes,‬‭sexual‬ B ‭reproduction‬ ‭may‬ ‭enhance‬ ‭reproductive‬ ‭success‬ ‭of‬ ‭parents‬ ‭when‬ ‭environmental‬ ‭factors‬ ‭change‬ ‭relatively rapidly‬‭.‬ ‭ sexual‬ ‭reproduction‬ ‭is‬ ‭expected‬ ‭to‬ ‭be‬ ‭most‬ A ‭advantageous in‬‭stable, favorable environments‬‭.‬ F‭ ission:‬ ‭It‬ ‭is‬ ‭found‬ ‭in‬ ‭many‬ ‭invertebrates.‬ ‭It‬ ‭is‬ ‭the‬ ‭Reproductive Cycles‬ ‭separation‬ ‭of‬‭a‬‭parent‬‭into‬‭two‬‭or‬‭more‬‭individuals‬ ‭of about the same size.‬ I‭t‬ ‭is‬ ‭controlled‬ ‭by‬ ‭hormones‬ ‭and‬ ‭environmental‬ ‭cues‬‭.‬ ‭Most‬ ‭animals‬ ‭exhibit‬ ‭reproductive‬ ‭cycles‬ ‭related‬ ‭to‬ ‭changing‬ ‭seasons‬‭(climate‬‭change‬‭can‬ ‭decrease reproductive success).‬ S‭ ome‬ ‭organisms‬ ‭can‬ ‭reproduce‬ ‭sexually‬ ‭or‬ ‭asexually,‬ ‭depending‬ ‭on‬ ‭the‬ ‭conditions‬ ‭(Ex:‬ ‭Jellyfish).‬ F‭ ragmentation:‬ ‭It‬ ‭is‬ ‭the‬ ‭breaking‬ ‭of‬ ‭the‬ ‭body‬ ‭into‬ ‭pieces,‬ ‭some‬ ‭or‬ ‭all‬ ‭of‬ ‭which‬‭develop‬‭into‬‭adults.‬‭It‬ ‭must‬ ‭be‬ ‭accompanied‬ ‭by‬ ‭regeneration,‬ ‭the‬ ‭regrowth of lost body parts.‬ ‭ arthenogenesis:‬ ‭It‬ ‭is‬ ‭the‬ ‭development‬ ‭of‬ ‭a‬ ‭new‬ P ‭individual‬ ‭from‬ ‭an‬ ‭unfertilized‬ ‭egg.‬ ‭It‬ ‭is‬ ‭mainly‬ ‭observed‬ ‭in‬ ‭invertebrates,‬ ‭but‬ ‭is‬ ‭observed‬ ‭rarely‬‭in‬ ‭some vertebrates.‬ ‭21‬ ‭VARIATION IN PATTERNS OF SEXUAL REPRODUCTION‬ ‭ ll‬ ‭fertilization‬ ‭requires‬ ‭critical‬ ‭timing,‬ ‭often‬ A F‭ or‬ ‭many‬ ‭animals,‬ ‭finding‬ ‭a‬ ‭partner‬ ‭for‬ ‭sexual‬ ‭mediated‬ ‭by‬ ‭environmental‬ ‭cues,‬ ‭pheromones,‬ ‭reproduction may be challenging.‬ ‭and/or courtship behavior.‬ ‭ ermaphroditism:‬ ‭Each‬ ‭individual‬ ‭has‬ ‭male‬ ‭and‬ H ‭GAMETE PRODUCTION & DELIVERY‬ ‭female‬ ‭reproductive‬ ‭systems.‬ ‭Two‬ ‭hermaphrodites‬ ‭can mate. Some can self-fertilize.‬ ‭ onads:‬‭These‬‭are‬‭organs‬‭that‬‭reproduce‬‭gametes.‬ G ‭‬ ‭Ex: Clown fish, slugs, A. uniparens females‬ ‭Some‬ ‭simple‬ ‭systems‬ ‭do‬ ‭not‬ ‭have‬ ‭gonads,‬ ‭but‬ ‭gametes‬‭from‬‭undifferentiated‬‭tissue‬‭(cells‬‭lining‬‭the‬ ‭coelom).‬ ‭ ost‬ ‭insects‬ ‭have‬ ‭separate‬ ‭sexes‬ ‭with‬ ‭complex‬ M ‭reproductive systems.‬ ‭ any‬‭female‬‭insects‬‭have‬‭a‬‭spermatheca‬‭,‬‭in‬‭which‬ M ‭sperm is stored during copulation‬‭.‬ ‭ ex‬‭Reversals:‬‭Some‬‭species‬‭exhibit‬‭male‬‭to‬‭female‬ S ‭reversal‬ ‭(like‬ ‭certain‬ ‭oysters),‬ ‭while‬ ‭others‬ ‭exhibit‬ T‭ he‬ ‭gametes‬ ‭it‬ ‭produces‬ ‭is‬ ‭the‬ ‭sperm‬ ‭while‬ ‭the‬ ‭female to male reversal (like coral reef fish).‬ ‭gonad is the testes in this example.‬ F‭ ERTILIZATION‬ ‭It‬ ‭is‬ ‭the‬ ‭union‬ ‭of‬ ‭egg‬ ‭and‬ ‭sperm‬ ‭and‬ ‭plays‬ ‭an‬ ‭important part in sexual reproduction.‬ ‭ xternal‬ ‭Fertilization:‬ ‭Eggs‬ ‭shed‬ ‭by‬ ‭the‬ ‭female‬ ‭are‬ E ‭fertilized by sperm in an external environment.‬ ‭ ‬‭moist‬‭habitat‬‭is‬‭required‬‭to‬‭allow‬‭sperm‬‭to‬‭swim‬‭to‬ A ‭the‬ ‭egg‬ ‭and‬ ‭to‬ ‭prevent‬ ‭the‬ ‭gametes‬ ‭from‬ ‭drying‬ ‭out.‬ T‭ he‬‭gonad‬‭this‬‭time‬‭is‬‭the‬‭ovary‬‭while‬‭the‬‭gametes‬ ‭ pawning:‬ ‭Individuals‬ ‭cluster‬ ‭in‬ ‭the‬ ‭same‬ ‭area‬ S ‭it produces is the egg.‬ ‭to‬ ‭release‬ ‭their‬ ‭gametes‬ ‭into‬ ‭the‬ ‭water‬ ‭at‬ ‭the‬ ‭same time.‬ ‭ loaca:‬ ‭It‬ ‭is‬ ‭a‬ ‭common‬ ‭opening‬ ‭between‬ ‭the‬ C ‭external‬ ‭environment‬ ‭and‬ ‭the‬ ‭digestive,‬ ‭excretory,‬ I‭nternal‬‭Fertilization:‬‭Sperm‬‭are‬‭deposited‬‭in‬‭or‬‭near‬ ‭and reproductive systems.‬ ‭the‬ ‭female‬ ‭reproductive‬ ‭tract,‬ ‭and‬ ‭fertilization‬ ‭occurs‬ ‭within‬ ‭the‬ ‭tract.‬ ‭It‬ ‭requires‬ ‭behavioral‬ I‭t‬ ‭is‬ ‭common‬ ‭in‬ ‭non-mammalian‬ ‭vertebrates‬‭.‬ ‭interactions‬ ‭between‬ ‭and‬ ‭compatible‬ ‭copulatory‬ ‭Mammals‬ ‭usually‬ ‭have‬ ‭a‬ ‭separate‬ ‭opening‬ ‭to‬ ‭the‬ ‭organs‬‭.‬ ‭digestive tract.‬ ‭22‬ ‭HUMAN MALE REPRODUCTIVE ANATOMY‬ T‭ he‬ ‭external‬ ‭reproductive‬ ‭organs‬ ‭include‬ ‭the‬ ‭ ucts:‬ ‭From‬ ‭the‬ ‭seminiferous‬ ‭tubules,‬ ‭sperm‬ ‭pass‬ D ‭scrotum and penis.‬ ‭into the coiled duct‬‭of the‬‭epididymis‬‭.‬ ‭The internal organs include:‬ ‭ uring‬ ‭ejaculation‬‭,‬ ‭sperm‬ ‭are‬ ‭propelled‬ ‭through‬ D ‭‬ ‭Gonads‬‭: produce sperm and hormones‬ ‭the‬‭vas‬‭deferens‬‭and‬‭the‬‭ejaculatory‬‭duct‬‭,‬‭then‬‭exit‬ ‭‬ ‭Accessory‬‭glands‬‭:‬‭secrete‬‭products‬‭needed‬ ‭the penis‬‭through the‬‭urethra‬‭.‬ ‭for sperm movement‬ ‭‬ ‭Ducts‬‭: carry sperm and glandular secretions‬ ‭Accessory Glands:‬ ‭ emen:‬ ‭Composed‬ ‭of‬ ‭sperm‬ ‭+‬ ‭secretions‬ ‭from‬ S ‭three sets of accessory glands.‬ ‭ eminal‬ ‭Vesicles:‬ ‭Contribute‬ ‭about‬ ‭60%‬ ‭of‬ ‭the‬ S ‭total volume of semen (1).‬ ‭ rostate‬ ‭Gland:‬ ‭Secretes‬ ‭its‬ ‭products‬ ‭directly‬ P ‭into the urethra (2).‬ ‭ ale‬ ‭Gonads‬ ‭/‬ ‭Testes:‬ ‭It‬ ‭consists‬ ‭of‬ ‭highly‬ ‭coiled‬ M ‭ ulbourethral‬ ‭Glands:‬ ‭Secrete‬ ‭a‬ ‭clear‬ ‭mucus‬ B ‭tubes. The sperm form in‬‭seminiferous tubules‬‭.‬ ‭that‬ ‭neutralizes‬ ‭acidic‬ ‭urine‬ ‭remaining‬ ‭in‬ ‭the‬ ‭urethra (3).‬ T‭ he‬ ‭Leydig‬ ‭cells‬ ‭surrounding‬ ‭the‬ ‭tubules‬ ‭produce‬ ‭hormones‬‭.‬ ‭The‬ ‭testes‬ ‭are‬ ‭held‬ ‭outside‬ ‭the‬ ‭ enis:‬ ‭It‬ ‭is‬ ‭composed‬ ‭of‬ ‭three‬ ‭cylinders‬ ‭of‬ ‭spongy‬ P ‭abdominal‬ ‭cavity‬ ‭in‬ ‭the‬ ‭scrotum‬ ‭where‬ ‭erectile tissue.‬ ‭temperature is lower.‬ ‭ lans:‬ ‭Also‬ ‭called‬‭the‬‭head‬‭of‬‭the‬‭penis,‬‭has‬‭a‬ G ‭thinner skin covering than the shaft‬ ‭ repuce:‬ ‭It‬ ‭is‬ ‭a‬ ‭fold‬ ‭of‬ ‭skin‬ ‭that‬ ‭surrounds‬ ‭the‬ P ‭glans.‬ ‭HUMAN FEMALE REPRODUCTIVE ANATOMY‬ ‭External Reproductive Structures‬ ‭ agina:‬ ‭It‬ ‭is‬‭a‬‭muscular‬‭but‬‭elastic‬‭chamber‬‭that‬‭is‬ V ‭the‬ ‭repository‬ ‭for‬ ‭sperm‬ ‭during‬ ‭copulation‬ ‭and‬ ‭serves as the birth canal‬‭.‬ ‭23‬ I‭t‬ ‭opens‬ ‭to‬ ‭the‬ ‭outside‬‭at‬‭the‬‭vulva‬‭,‬‭which‬‭consists‬ ‭of‬ ‭the‬ ‭following:‬ ‭(1)‬ ‭labia‬‭majora‬‭,‬‭(2)‬‭labia‬‭minora‬‭,‬ ‭(3) hymen, and (4) clitoris.‬ ‭ litoris:‬‭It‬‭has‬‭a‬‭head‬‭called‬‭a‬‭glans‬‭covered‬‭by‬‭the‬ C ‭prepuce, a small hood of the skin.‬ ‭Internal Reproductive Structures‬ ‭ ogenesis:‬ ‭The‬ ‭development‬ ‭of‬ ‭a‬ ‭mature‬ ‭egg;‬ ‭a‬ O ‭prolonged‬ ‭process‬‭.‬ ‭Immature‬ ‭eggs‬ ‭form‬ ‭in‬ ‭the‬ ‭female‬‭embryo‬‭but‬‭do‬‭not‬‭complete‬‭development‬ ‭until years later.‬ F‭ emale‬‭Gonads‬‭/‬‭Ovaries:‬‭This‬‭lies‬‭in‬‭the‬‭abdominal‬ ‭cavity.‬ ‭ ach‬‭ovary‬‭contains‬‭many‬‭follicles‬‭,‬‭which‬‭consist‬‭of‬ E ‭oocytes‬‭surrounded by support cells.‬ ‭ viduct‬ ‭/‬ ‭Fallopian‬ ‭Tube:‬ ‭It‬ ‭is‬ ‭where‬ ‭the‬ ‭egg‬ ‭cell‬ O ‭travels from the ovary to the uterus.‬ ‭ ndometrium‬ ‭/‬ ‭Uterus‬ ‭Lining:‬ ‭It‬ ‭has‬ ‭many‬ ‭blood‬ E ‭vessels.‬ ‭ ervix:‬ ‭This‬ ‭is‬ ‭where‬ ‭the‬ ‭uterus‬ ‭narrows‬‭.‬ ‭It‬ ‭then‬ C ‭opens into the vagina‬‭.‬ S‭ econdary‬ ‭oocyte‬ ‭will‬ ‭start‬ ‭after‬ ‭the‬ ‭female‬ ‭undergoes puberty.‬ ‭ AMETOGENESIS‬ G ‭It is the production of gametes.‬ S‭ permatogenesis‬ ‭differs‬ ‭from‬ ‭Oogenesis‬ ‭in‬ ‭Three‬ ‭Ways‬ ‭ permatogenesis:‬ ‭It‬ ‭is‬ ‭the‬ ‭formation‬ ‭of‬ ‭sperm;‬ S ‭continuous‬ ‭and‬ ‭prolific‬‭.‬ ‭Hundreds‬ ‭of‬ ‭millions‬ ‭of‬ ‭ 1:‬ ‭All‬ ‭four‬ ‭products‬ ‭of‬ ‭meiosis‬‭develop‬‭into‬‭sperm‬ # ‭sperm‬ ‭are‬ ‭produced‬ ‭per‬ ‭day;‬ ‭each‬ ‭sperm‬ ‭takes‬ ‭while only‬‭one of the four‬‭becomes an‬‭egg‬‭.‬ ‭about 7 weeks‬‭to develop.‬ ‭ 2:‬ # ‭Spermatogenesis‬ ‭occurs‬ ‭throughout‬ ‭adolescence and adulthood.‬ ‭ 3:‬ ‭Sperm‬ ‭are‬ ‭produced‬ ‭continuously‬ ‭without‬ # ‭prolonged interruptions in oogenesis.‬ ‭24‬ ‭HUMAN REPRODUCTION & HORMONES‬ F‭ ollicular‬‭Phase:‬‭It‬‭is‬‭characterized‬‭by‬‭follicle‬‭growth‬ ‭Human reproduction is coordinated by hormones.‬ ‭and‬ ‭an‬ ‭increase‬ ‭in‬ ‭estradiol‬‭.‬ ‭It‬ ‭ends‬ ‭at‬ ‭ovulation‬ ‭and the‬‭secondary oocyte is released‬‭.‬ ‭ onadotropin-releasing‬ ‭hormone‬ ‭(GnRH):‬ ‭It‬ ‭is‬ G ‭secreted‬‭by‬‭the‬‭hypothalamus‬‭.‬‭It‬‭directs‬‭the‬‭release‬ L‭ uteal‬‭Phase:‬‭It‬‭is‬‭where‬‭follicular‬‭tissue‬‭is‬‭left‬‭behind‬ ‭of‬ ‭FSH‬ ‭(follicle-stimulating‬ ‭hormone)‬ ‭and‬ ‭LH‬ ‭to‬‭transform into a corpus luteum‬‭.‬ ‭(luteinizing hormone) from the anterior pituitary.‬ ‭ orpus‬ ‭Luteum:‬ ‭It‬ ‭secretes‬ ‭progesterone‬ ‭and‬ C F‭ SH‬ ‭and‬ ‭LH:‬ ‭They‬ ‭regulate‬ ‭the‬ ‭processes‬ ‭in‬ ‭the‬ ‭estradiol‬‭,‬‭which‬‭exert‬‭negative‬‭feedback‬‭on‬‭the‬ ‭gonads and the‬‭production of sex hormones‬‭.‬ ‭hypothalamus and pituitary.‬ ‭Testosterone:‬‭It is the‬‭main androgen‬‭.‬ ‭ strogen:‬ ‭It‬ ‭consists‬ ‭mainly‬ ‭of‬ ‭estradiol‬ ‭and‬ E ‭progesterone‬‭.‬ S‭ ex‬ ‭hormones‬ ‭serve‬ ‭many‬ ‭functions‬ ‭in‬ ‭addition‬ ‭to‬ ‭gamete‬ ‭production,‬‭including‬‭sexual‬‭behavior‬‭and‬ L‭ H‬ ‭surge‬ ‭triggers‬ ‭ovulation.‬ ‭The‬ ‭corpus‬ ‭luteum‬ ‭is‬ ‭the‬ ‭development‬ ‭of‬ ‭primary‬ ‭and‬ ‭secondary‬ ‭sex‬ ‭then‬‭formed‬‭and‬‭sends‬‭signals‬‭to‬‭the‬‭hypothalamus‬ ‭characteristics.‬ ‭and‬ ‭pituitary‬ ‭to‬ ‭decrease‬‭the‬‭secretion‬‭of‬‭FSH‬‭and‬ ‭LH which prevents another egg to be released.‬ ‭ ormonal‬ ‭Control‬ ‭of‬ ‭the‬ ‭Female‬ ‭Reproductive‬ H ‭Cycles‬ ‭THE UTERINE (MENSTRUAL) CYCLE‬ T‭ he‬ ‭secretion‬ ‭of‬ ‭hormones‬ ‭and‬ ‭the‬ ‭reproductive‬ ‭ roliferative‬ ‭Phase:‬ ‭It‬ ‭is‬ ‭the‬ ‭thickening‬ ‭of‬ ‭the‬ P ‭events they regulate are‬‭cyclic‬‭.‬ ‭endometrium‬ ‭and‬ ‭it‬ ‭coincides‬ ‭with‬ ‭the‬ ‭follicular‬ ‭phase‬‭.‬ ‭ rior‬ ‭to‬ ‭ovulation,‬ ‭the‬ ‭endometrium‬ ‭thickens‬ ‭with‬ P ‭blood‬ ‭vessels‬ ‭in‬ ‭preparation‬ ‭for‬ ‭embryo‬ ‭ ecretory‬ ‭Phase:‬ ‭It‬ ‭is‬ ‭the‬ ‭secretion‬‭of‬‭nutrients‬‭and‬ S ‭implantation.‬ ‭coincides with the luteal phase‬‭.‬ I‭f‬ ‭an‬ ‭embryo‬ ‭does‬ ‭not‬ ‭implant‬ ‭the‬ ‭endometrium,‬ ‭ enstrual‬ ‭Flow‬ ‭Phase:‬ ‭The‬ ‭shedding‬ o M ‭ f‬ ‭the‬ ‭the‬ ‭endometrium‬ ‭is‬ ‭shed‬ ‭in‬ ‭a‬ ‭process‬ ‭called‬ ‭endometrium‬ ‭coincides‬ ‭with‬ ‭the‬ ‭growth‬ ‭of‬ ‭new‬ ‭menstruation‬‭.‬ ‭ovarian follicles‬‭.‬ ‭ ormones‬ ‭closely‬ ‭link‬ ‭the‬ ‭two‬ ‭cycles‬ ‭of‬ ‭female‬ H ‭reproduction.‬ ‭‬ ‭Uterine‬‭Cycle‬‭(Menstrual‬‭Cycle):‬‭Changes‬‭in‬ ‭the uterus‬ ‭‬ ‭Ovarian Cycle‬‭: Changes in the ovaries.‬ T‭ HE OVARIAN CYCLE‬ ‭It‬‭is‬‭the‬‭sequential‬‭release‬‭of‬‭GnRH‬‭then‬‭FSH‬‭and‬‭LH‬ ‭which stimulates follicle growth.‬ ‭ rogesterone‬ ‭and‬ ‭estradiol‬ ‭promote‬ ‭thickening‬ ‭of‬ P ‭endometrium.‬ ‭25‬

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