Lesson 2 | Human Growth and Development



Name Date Class

LESSON 2

Human Growth and Development

A. Stages of Development

1. People go through stages of development after birth—infancy, childhood,

adolescence, and .

2. The time before birth is divided into stages beginning

with .

B. Fertilization

1. When the nucleus of the sperm joins with the nucleus of the egg,

is complete.

2. A fertilized egg is called a(n) .

3. As it moves toward the uterus, the zygote undergoes

and cell division, developing into a ball of cells.

4. twins develop when the inner cell mass of a zygote

divides in two.

5. When two eggs are released and fertilized—each by a different sperm—the result is

twins.

C. Development Before Birth

1. is the period of development from fertilized egg to

birth.

2. After the zygote attaches to the uterus, the outer cells of the zygote and cells from

the uterus form an organ called the .

3. The placenta exchanges materials between the and the

mother.

4. The outer zygote cells form a ropelike structure called the

that attaches the developing offspring to the placenta.

5. From the time a zygote attaches to the uterus until the end of the eighth week of

pregnancy, it is called a(n) .

6. Between nine weeks and birth, the embryo is a(n) .

7. A fetus receives all from its mother.

8. Other factors in a pregnant woman’s , such as smoke or

chemicals, can also affect a fetus’s growth and development.

Reproduction and Development 27

Name Date Class

Lesson Outline continued

D. Birth

1. A fetus leaves the mother’s body and enters the world through a process

called .

2. begins when hormones released by the endocrine

system cause muscles in the uterus to contract.

3. During labor, a small structure between the uterus and the vagina, called the

, opens to allow the fetus to emerge.

4. After the fetus is delivered, the breaks away from the

uterus and exits the woman’s body.

5. Sometimes doctors deliver a fetus by a surgical process called a(n)

, or C-section.

E. Infancy

1. The first two years of a newborn’s life are called .

2. During infancy, the brain continues to develop, teeth form, and

grow and get harder.

F. Childhood

1. The period between infancy and sexual maturity is .

2. During childhood, the continues to grow and develop,

and the child grows taller.

G. Adolescence

1. Following childhood is a period of growth called .

2. Males and females grow taller as muscles and continue

to grow.

3. The reproductive system matures in a process called .

H. Adulthood and Aging

1. At the end of adolescence, a person enters , which

continues through old age.

2. is the process of changes in the body over time.

28 Reproduction and Development

Name Date Class

LESSON 2

Human Growth and Development

Directions: On each line, write the term from the word bank that correctly completes each sentence. Each term

is used only once.

|adolescence |adulthood |aging |birth |childhood |

|embryo |fertilization |fetus |infancy |zygote formation |

30 Reproduction and Development

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Lesson Outline

Content Practice A

1. : when the nucleus of the sperm joins with the nucleus of the egg

2. : when a fertilized egg undergoes mitosis and cell division

3. : the time from fertilization to eight weeks when the zygote

attaches to the uterus

4. : the time from nine weeks to birth when all organ systems begin

to function

5. : when the baby leaves the mother’s body

6. : when the baby learns to sit up, stand, walk, and talk

7. : the time between infancy and sexual maturity when the brain

continues to grow and muscle strength increases

8. : when the reproductive system matures and boys and girls

develop pubic and underarm hair

9 : when adolescence ends and growing taller stops

10. : when hair turns gray and vision and hearing decline

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