Chapter 12
Growing and
Changing
Lesson 5
Heredity and
Human Development
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 chromosomes
Threadlike structures that carry genes
 genes
The basic units of heredity
 cell
The basic unit of life
 tissue
A group of similar cells that do a particular job
 organ
A body part made up of different tissues joined to perform
a particular function
 body
A group of organs that work together to carry out
system related tasks
 embryo
The developing organism from two weeks until the
end of the eighth week of development
 fetus
The developing organism from the end of the eighth
week until birth
In this lesson, you will learn to
 explain how humans inherit certain characteristics.
 identify the basic unit of life.
 describe how a fetus develops.
 identify ways an expectant mother can care for her developing
fetus.
Analyzing a Graphic
Levels of
Body Structure
Using the diagram shown here,
create a concept map about the
different levels of body structure.
As you read the lesson, fill in the
concept map.
Cells
Heredity
When a sperm and egg unite, the newly fertilized
egg has a complete set of chromosomes.
chromosomes Threadlike structures that carry genes
Genes carry the codes for inherited traits.
genes The basic units of heredity
Heredity
Fertilization and Human Development
How does a single cell become a person made of
many cells?
cell The basic unit of life
Soon after fertilization, the fertilized egg begins to
divide and multiply.
Fertilization and Human Development
Groups of cells make up tissues and tissues then
make up organs.
tissue A group of similar cells that do a particular job
organ A body part made up of different tissues joined to
perform a particular function
Fertilization and Human Development
Eventually, an entire body system is formed.
body system A group of organs that work together to carry
out related tasks
Development of the Fetus
A fertilized egg is
called a zygote.
The zygote
divides to form 2
cells about 24
hours after
fertilization.
After one week,
the zygote
attaches to the
lining of the
uterus.
After another
week, the zygote
is called an
embryo.
embryo The developing organism from two weeks until the
eighth week of development
Fertilization and Human Development
After the eighth week, the human embryo is called a
fetus.
fetus The developing organism form the end of the eighth
week until birth.
Birth takes place about nine months after
fertilization.
Care During Pregnancy
Eat healthful
foods
Don’t take
unnecessary
drugs
Have regular
checkups
Positive
Health
Behaviors for
Expectant
Mothers
Don’t drink
alcohol
Beware of
infections
Don’t use
tobacco
Lesson 5 Review
What I Learned
Vocabulary Define chromosomes.
Lesson 5 Review
What I Learned
Identify List four levels of body organization from most
complex to most basic.
Lesson 5 Review
What I Learned
Describe Describe the development of a human from
the point of fertilization.
Lesson 5 Review
What I Learned
List What are four ways that a pregnant female can
care for her developing baby?
Lesson 5 Review
Thinking Critically
Apply A test of Ling’s fetus shows that its cells each
have one more chromosome than normal human cells.
How many chromosomes does each of her fetus
cells have?
Lesson 5 Review
Thinking Critically
Analyze Using the information given in Figure 12.9,
calculate the weight that the developing fetus gains at
each three month stage. During which stage does it
gain the most weight?
End of
Chapter 12
Growing and
Changing
Lesson 5
Heredity and
Human Development
Click for:
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>> Chapter 12 Assessment