Reproduction and Development Chapter 26

Asexual Reproduction

Cost of Sexual Reproduction Specialized cells and structures must be formed Special courtship and parental behaviors can be costly Nurturing developing offspring, either in egg or body, requires resources (usually from mother)

Stages of Development Eggs and sperm form Gamete formation frog egg Sperm and an egg fuse to form zygote Fertilization frog sperm Mitotic cell divisions produce daughter cells Cleavage Cell divisions, migrations, and rearrangements produce primary tissues Gastrulation midsectional views Specialized organs and tissues form in prescribed spatial patterns at prescribed times Organ Formation top view side view Growth, tissue Specilazation Organs grow and assume specialized functions Fig. 27-4, p.464

Primary Tissues Ectoderm Endoderm Mesoderm Outer most primary tissue, Nervous Tissue, outter portions of body covering Endoderm Source of gut inner linning and organs derived from it Mesoderm Forms between outter and inner primary tissues, gives rise to muscles, most of the skeleton,circulatory, repro., excre.,connective tissue of gut and integumentary

Development of the Leopard Frog transformation to adult nearly completed adult, three years old sexual reproduction (meiosis through fertilization) organ formation tadpole cleavage zygote

Development of the Leopard Frog Fig. 27-5b-j, p.465

Morphogenesis Programmed growth of tissues and organs Cells migrate along prescribed routes Sheets of cells expand and fold Cell deaths shape body parts

Male Reproductive System bladder seminal vesicle vas deferens prostate gland bulbourethral gland urethra epididymis scrotum testis penis

A Sperm’s Journey Testes Epididymis Vas deferens Ejaculatory ducts Produces immature sperm Epididymis Matures and stores sperm Vas deferens Ejaculatory ducts Urethra

Male Components and Accessory Glands PROSTATE GLAND EJECULATORY DUCT SEMINAL VESICLE urinary bladder URETHRA urethra anus anterior posterior BULBOURETHRAL GLAND VAS DEFERENS PENIS erectile tissue EPIDIDYMIS TESTIS Fig. 27-7, p.467

Sperm Formation Spermatogonium (2n) divides by mitosis to form primary spermatocyte (2n) Primary spermatocyte divides by meiosis to form 4 haploid spermatids (n)

secondary spermatocyte immature sperm (haploid) Sperm Production MITOSIS MEIOSIS I MEIOSIS II lumen Sertoli cell spermato-gonium (diploid) secondary spermatocyte late spermatid immature sperm (haploid) early spermatids primary spermatocyte Fig. 27-9b, p.468

A Mature Sperm Spermatids mature to become sperm Head Midpiece Tail Glandular products + sperm = semen

Hormonal Control Testosterone Follicle-stimulating hormone (FSH) Produced by Leydig cells in testes Controlled by luteinizing hormone (LH) Follicle-stimulating hormone (FSH) Starts sperm production LH and FSH produced by pituitary, controlled by hypothalamus

Female Reproductive Organs ovary ovary oviduct uterus uterus oviduct vagina clitoris vagina

The Uterus Myometrium Endometrium Cervix Thick layer of smooth muscle in walls Endometrium Uterine lining Cervix Connects uterus and vagina

Menstrual Cycle The fertile period for a human female occurs on a cyclic basis Menstrual cycle lasts about 28 days on average

Menstrual Cycle Follicular phase Ovulation Luteal phase Menstruation Uterine lining regenerates Oocyte matures Ovulation Oocyte released from ovary Luteal phase Hormones thicken endometrium

The Ovarian Cycle Girl is born with primary oocytes already in ovaries Oocytes are suspended in meiosis 1 Meiosis resumes, one oocyte at a time, with the first menstrual cycle

Female Hormonal Control Hypothalamus GnRH Rising estrogen stimulates surge in LH Anterior pituitary Progesterone, estrogens LH FSH Ovary follicle growth, oocyte maturation Estrogen Corpus luteum forms

Fertilization Sperm penetrates egg cytoplasm Secondary oocyte undergoes meiosis II, forms mature egg Egg nucleus and sperm nucleus fuse to form diploid zygote

Fertilization oviduct ovary Ovulation uterus follicle cell opening of cervix egg nucleus vagina zona pellucida Fig. 27-14, p.472

Contraception Effectiveness