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Chapter 8Growth andDevelopment
Lesson 3Heredity and theLife Cycle
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Teacher’s notes are available in the notes section of this presentation.
chromosomes
genes
fetus
prenatal care
Tiny strands of matter that carry the codes forinherited traits
The basic units of heredity
What the developing unborn baby is known as from the eighth week until birth
Special care to ensure that an expecting mother and the baby remain healthy
In this lesson, you will learn to
explain how inherited traits are passed along.
identify changes to the developing baby.
recognize stages in the life-cycle.
Analyzing a Graphic
Using this diagram as a
guide, describe the stages
of development before birth.
After 3 months
After 6 months
After 9 months
The Developing Baby
Heredity
Heredity is the process by which parents pass certain traits to their children.
Hair color and body build are examples of inherited traits.
Heredity
Traits are passed along by chromosomes.
chromosomes Tiny strands of matter that carry the
codes for inherited traits
Chromosomes are made up of genes.
genes The basic units of heredity
Chromosomes and Fertilization
Among each sperm’s 23 chromosomes, one alone determines the gender of the fertilized egg cell.
An egg caries only an X chromosome. Sperm carry either an X or Y chromosome.
If a sperm carries an X chromosome, a female will result. If a sperm carries a Y chromosome, a male will result.
Development Before Birth
The newly fertilized
egg travels downthe fallopian tube
to the uterus.
The egg attaches itself to the wall of the uterus.
The egg begins to be divided
millions of times.
The tissues, organs, and body
systems are eventually formed.
The Developing Baby
Time Size Features Development
fertilization microscopic arms, legs, fingers, toes, eyes, ears
heart is beating; nervous system is forming; cannot survive outside uterus
6 months after fertilization
about 14 inches long; weighs about 2 pounds
hair, eyebrows, fingernails, toenails
can move and kick; sucks thumb; can hear sounds; might survive outside uterus
9 months after fertilization
18–20 inches long; weighs 7–9 pounds
smooth skin, fully developed organs
eyes open and close; fingers can grasp; body organs and systems can now work on their own; ready for birth
The Developing Baby
In the uterus, the fetus receives oxygen and nutrients through a tube called the umbilical cord.
fetus What the developing unborn baby is known as from the eighth week until birth
The Developing Baby
Throughout pregnancy, an expectant mother needs prenatal care.
prenatal care Special care to ensure that the expectant mother and the baby remain healthy
Prenatal care includes eating healthy foods, getting enough rest, and seeing the doctor regularly.
The Life Cycle
The life cycle is divided into six major stages.
Infancy Childhood AdolescenceEarly
AdulthoodMiddle
AdulthoodLate
Adulthood
Age 1 Ages1–11
Ages12–18
Ages19–30
Ages30–60
Ages60+
What I Learned
Recall How many chromosomes are there in most cellsof the human body? What is the one exception?
Lesson 3 Review
What I Learned
Identify Name two developments that may take placeduring early adulthood.
Lesson 3 Review
Thinking Critically
Explain What determines whether a baby will be male or female?
Lesson 3 Review
Thinking Critically
Apply Yvonne hopes to become a lawyer when shereaches adulthood. What skills can she develop now during her teens to help her achieve her career goals?
Lesson 3 Review
Chapter 8Growth andDevelopment
Lesson 3Heredity and theLife Cycle
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