Stages of Development

Pollination Pollination – The process of the pollen and seeds uniting in flowering plants. – Seed + Pollen = Zygote Once roots begin to establish and leaves emerge from the ground = Seedling

Fertilization Fertilization – the process when the sperm and egg unite in animals. Fertilization – 200 million sperm are in a race to reach the egg, located in the oviduct. Only 1 can fertilize the egg!

Fertilization Cleavage Blastocyst Implantation

Stages of Development The development of an offspring takes place in two phases after fertilization: 1.Prior to birth a.Zygote b.Embryo c.Fetus 2.After birth a.Infancy b.Childhood c.Adolescence d.Adulthood

Stage 1 - Zygote – From 0-3 days of development. – Shortest stage of development – A series of rapid cell divisions takes place, cleavage. 1 cell becomes 2, 2 becomes 4, 4 becomes 8….. – The number of cells increases but the size of the cell remains the same. – At the end of the cell division process the Hollow ball of cells = blastocyst, blastula. Implants itself in the uterine wall

Cleavage

Stage 2 - Embryo From 3 days to 8 weeks of development. – Implanted in the uterine wall. – Several membranes begin to form around the embryo. A.Amniotic Sac - fluid filled sac that cushions and protects the developing baby. – Acts like a water balloon around the baby. Amniotic Sac Embryo

Placenta & Umbilical Cord B. Placenta – a transfer station between the mother and embryo of nutrients, oxygen and wastes. – Uses diffusion to transfer materials back and forth. C. Umbilical cord – cord that connects the placenta to the embryo. – Contains blood vessels. Carbon dioxide from baby to mother. Oxygen from mother to baby. Umbilical Cord Placenta

Fetus 3. Fetus - 8 weeks until birth – Longest stage of development. – Development of eyes, ears, cheeks, arms and legs. – After 3 months the gender can be determined. – Around 4 months the mother can feel the first signs of movement. – 6-9 months are months of rapid growth.

A Developing Fetus Diagram Placenta Amniotic Sac Umbilical Cord Uterus Cervix Vagina Fetus

Fetal Development 9 weeks16 weeks20 weeks

Fetal Development 28 weeks32 weeks36-38 weeks

Stages of Development 9 - f 6 - e 3 - z 11 - newborn 2 - z 7 - f 8 - f 5 - e 4 - z 10 - f 1 - fertilization

Birth Full-term pregnancy, gestation = 40 weeks or 9 months. Muscular contractions of the uterus push the baby down through the cervix and into the vagina, birth canal = labor – Labor is complete when both the baby and placenta have been pushed from the mother’s body.

Stages of Birth Cesarean Section - movie

Multiple Births Usually only one baby develops at a time but sometimes more than one baby can occur in a single pregnancy: – Fraternal twins: 2 eggs fertilized by 2 sperm – 2 boys, 2 girls or boy and girl – Separate placentas – separate amniotic sacs

Multiple Births – Identical twins: 1 egg fertilized by 1 sperm – Zygote splits into two during cell division » -100% identical 2 boys or 2 girls One placenta two amniotic sacs

Gestation (Pregnancy) Lengths Mammal SpeciesGestation Length (days) Opossum12 Rabbit31 Dog61 Human280 Horse330 Whale360 Indian Elephant624

Stages of Development – After Birth 1.Infancy: birth – 2 years – Time of rapid growth Heads are much bigger than bodies. – Head growth will slow as the body, arms and legs catch up. – Mental and muscular skills begin and develop Communication, roll over, crawl, walk, suck thumb, grab items…

Stages of Development – After Birth 2. Childhood: 2 – 13 years – Growth is not as rapid but still steady – Physical and mental abilities continue to develop Memory strengthened Muscular skills develop Baby teeth are lost and replaced with permanent Language skills develop

Stages of Development – After Birth 3. Adolescence: 13 – teenage years Begins at the onset of puberty - Secondary sex characteristics start to appear and develop. – Males: » Voices deepen » Shoulders widen » Testosterone produced in the testes » Sperm produced in the testes » Facial and body hair develops – Females: » Ovaries release estrogen » Menstrual cycle begins » Hips widen » Breasts develop

Stages of Development – After Birth 4. Adulthood: around 20 years on – Growth stops at the end of adolescence – Aging begins to take place around 30 years Metabolism slows down Physical strength declines Bones become more brittle, osteoporosis Skins becomes less elastic and wrinkles Hair loses pigment – turns gray Women stop producing estrogen and therefore egg production – Menopause – A female can no longer have children