Human Life Cycle Notes Fertilization: joining of sperm and egg forming zygote. Zygote (one-cell stage): fertilized egg Pre-birth Development: Zygote → Embryo → Fetus → (birth) → newborn baby Embryo: from “two cell stage” to 8 weeks; cell division occurs. Fetus: 9 weeks to birth ~ 9 month

Ovulation, Fertilization, Zygote Cell Division Watch video fertilized egg, life begins fallopian tube uterus, womb

Zygote fetus newborn baby 9 months Birth

Amniotic Sac: fluid filled sac that cushions/protects embryo/fetus Placenta: regulating organ between baby & mother; nutrients/oxygen in & waste out Umbilical cord: connects embryo to placenta (belly button) (see transparancy) Birth: ~ 9 month in humans; three stages: labor, delivery, afterbirth Labor: strong muscular contractions of uterus, cervix (opening) enlarges Delivery: from uterus to outside world Afterbirth: contractions push placenta and other membranes/fluid out through the vagina.

Amniotic Sac

Human Life Cycle Notes Multiple Birth Identical twins: from a single fertilized egg that splits results in two genetically identical individuals (copies; natural clone). Fraternal twins: two different eggs released & fertilized by two different sperm; two different individuals sharing the same womb

Adolescence (13-19): gradual change from child to adult Infancy (1-2 yrs): dramatic change in shape & size; nervous / muscular system development; learning new physical skills. Childhood (2-12 yrs): more active, independent, further physical & mental changes Adolescence (13-19): gradual change from child to adult Puberty (9-15yrs): At 12-14 yrs, ability to reproduce; produce baby Young Adult: 20 to 50yrs Senior Adult: 60+ yrs; wisdom, knowledge about life Aging: (30+ yrs) skin begins to wrinkle, decrease muscle strength, changing hair color, eye problems (40-65 yrs) menopause (ovulation, menstruation stops), decrease sperm Slow Aging: diet, exercise

Human Life Cycle Notes Infancy Childhood Adolescence Young Adult Senior Adult