Download Notes - Stages of Development

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.
– 200 million sperm are in a race to reach the egg,
located in the oviduct.
• Only 1 can fertilize the egg!
Cleavage
Blastocyst
Fertilization
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.
b.
c.
d.
Infancy
Childhood
Adolescence
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.
Embryo
A. Amniotic Sac - fluid filled sac
that cushions and protects the
developing baby.
– Acts like a water balloon around
the baby.
Amniotic Sac
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.
Oxygen from mother
to baby.
Carbon dioxide from
baby to mother.
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
Fetus
Umbilical Cord
Uterus
Cervix
Vagina
Fetal Development
9 weeks
16 weeks
20 weeks
Fetal Development
28 weeks
32 weeks
36-38 weeks
Stages of Development
3-z
11 - newborn
6-e
9-f
5-e
1 - fertilization
2-z
8-f
4-z
7-f
10 - f
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.
Cesarean Section - movie
Stages of Birth
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 Species
Opossum
Gestation Length
(days)
12
Rabbit
31
Dog
61
Human
280
Horse
330
Whale
360
Indian Elephant
624
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