Animal Reproduction & Development 2007-2008

Sexual & asexual reproduction offspring all have same genes (clones) Little to no variation Fragmentation and budding Sexual gametes (sperm & egg)  fertilization mixing of genes  variation Budding- small part that breaks off, hydra and yeast fragmentation breaking of parent into smaller pieces regeneration must occur then. Annelids, sea stars some fungus and plants does not mean that they do not reproduce sexually too, this is just a means for “emergency” 4/14/2017

Parthenogenesis Egg development without a male contribution Wasps, honeybees, aphids, komodo dragons, some fish, frogs and lizards Usually produces males 4/14/2017

Mechanisms of sexual reproduction Fertilization(union of sperm and egg) external internal Timing Compatible copulatory organs All species produce more offspring than the environment can handle Survival??? Pheromones chemical signals that influence the behavior of others (mate attractants) 4/14/2017

Reproductive hormones LH & FSH Testosterone from testes functions sperm production 2° sexual characteristics Estrogen from ovaries egg production prepare uterus for fertilized egg testes or ovaries 4/14/2017

Sex hormone control in males Hypothalamus GnRH Pituitary FSH & LH Gonadotropin releasing hormone Testes testosterone Body cells 4/14/2017

Male reproductive system Testicle (seminiferous tubules) Male reproductive system sperm spermatocytes Testes & epididymis sperm production & maturation Sperm production over 100 million produced per day! ~2.5 million released per drop! Glands seminal vesicles, prostate, bulbourethal produce seminal fluid = nutrient-rich (sugars)

Spermatogenesis Produce semen by age 7 Produce sperm by puberty (11-14 Epididymis Testis Germ cell (diploid) Coiled seminiferous tubules 1° spermatocyte (diploid) MEIOSIS I 2° spermatocytes (haploid) MEIOSIS II Vas deferens Spermatids (haploid) Spermatozoa Cross-section of seminiferous tubule 4/14/2017

Female reproductive system 4/14/2017

Female reproductive system Ovaries produces eggs & hormones Uterus nurtures fetus; lining builds up each month Fallopian tubes tubes for eggs to travel from ovaries to uterus Cervix opening to uterus, dilates 10cm (4 inches) for birthing baby Vagina birth canal for birthing baby Ovaries in a protective capsule with many follicles 4/14/2017

Menstrual cycle Hypothalamus Pituitary Ovaries Body cells GnRH LH FSH Hypothalamus egg development ovulation = egg release GnRH corpus luteum Pituitary FSH & LH estrogen About 450 cycles occur in a womans lifetime and then menopause progesterone Ovaries lining of uterus estrogen Body cells 4/14/2017 days 7 14 21 28

Female hormones cells that used to take care of developing egg FSH & LH release from pituitary stimulates egg development (follicle) & hormone release peak release = release of egg (ovulation) Estrogen released from ovary cells around developing egg stimulates growth of lining of uterus lowered levels = menstruation Progesterone released from “corpus luteum” in ovaries cells that used to take care of developing egg stimulates blood supply to lining of uterus 4/14/2017

Egg maturation in ovary Corpus luteum produces progesterone to maintain uterine lining 4/14/2017

Oogenesis Unequal meiotic divisions unequal distribution of cytoplasm release Oogenesis Unequal meiotic divisions unequal distribution of cytoplasm 1 egg 2 polar bodies Cell stored in ovaries Meiosis 1 completed during egg maturation Cell matures in follicle on ovary ovulation Meiosis 2 completed triggered by fertilization

Fertilization fertilization Cleavage Morula Blastocyst Implantation gastrulation neurulation Organogenesis Fetus

Fertilization Joining of sperm & egg sperm head (nucleus) enters egg Acrosome (enzyme filled vesicle)

Cleavage Repeated mitotic divisions of zygote 1st step to becoming multicellular unequal divisions establishes body plan different cells receive different portions of egg cytoplasm & therefore different regulatory signals

Cleavage zygote  morula  blastula establishes future development gastrulation morula blastula

Gastrulation Establish 3 cell layers ectoderm mesoderm endoderm gastrulation in primitive chordates Gastrulation Establish 3 cell layers ectoderm outer body tissues skin, nails, teeth nerves, eyes, lining of mouth mesoderm middle tissues blood & lymph, bone & notochord, muscle excretory & reproductive systems endoderm inner lining digestive system lining of respiratory, excretory & reproductive systems ectoderm mesoderm endoderm

Neurulation Formation of notochord & neural tube develop into nervous system develops into CNS (brain & spinal cord) Neural tube Notochord develops into vertebral column

Organogenesis Organ development and differentiation from germ layers

Placenta Materials exchange across membranes

Human fetal development 4 weeks 7 weeks

Human fetal development 10 weeks

Human fetal development 12 weeks 20 weeks

Human fetal development The fetus just spends much of the 2nd & 3rd trimesters just growing …and doing various flip-turns & kicks inside amniotic fluid Week 20

Human fetal development 24 weeks (6 months; 2nd trimester) fetus is covered with fine, downy hair called lanugo. Its skin is protected by a waxy material called vernix

Human fetal development 30 weeks (7.5 months) umbilical cord

Getting crowded in there!! 32 weeks (8 months) The fetus sleeps 90-95% of the day & sometimes experiences REM sleep, an indication of dreaming

Fetal slide notes

Apoptosis Programmed cell death Sculpts body parts Genetically programmed elimination of tissues & cells that were used for only short periods in embryo or adult human embryos develop with webs between toes & fingers, but they are not born that way! 2004-2005

positive feedback Birth

Birth (36 weeks) Intestine Placenta Umbilical cord Wall of uterus Bladder Cervix Vagina