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2.1: Growth, Development, and Puberty

Difficulty Level: At Grade Created by: CK-12
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How does your body change during puberty and how does it feel?

Did you look in the mirror this morning? Did your face look any different than it did yesterday? Unless you got a haircut or changed your hairstyle, chances are you look pretty much the same today as you did yesterday. But if you look at one of your photographs taken when you were much younger, you may be amazed at how much you have changed. Yet you will have no problem recognizing yourself. In this section you will begin learning about the changes your body goes through as it grows and matures.

“Took stock of my appearance today. I have only grown a couple of inches in the last year; so I must reconcile myself to the fact that I will be one of those people who never get a good view at the cinema. My skin is completely disfigured, my ears stick out and my hair has got three partings and won't look fashionable whichever way I comb it.”

-The Secret Diary of Adrian Mole, Age 1334

Sue Townsend

Our bodies change throughout our lives, but we maintain a certain likeness. Change makes it possible for us to grow from an infant to an adult-to grow taller and leaner, to change shape, and to even change in appearance. Constancy makes it possible for us to stay the same person throughout these changes.

Your body goes through two kinds of changes. The first type of change is growth, which means an increase in size. The second is development. Development involves not only getting bigger, but also improving what a particular organ or part of the body does.

During puberty, girls' breasts grow larger and boys' testes begin to produce sperm. Why would these changes be called “development” rather than “growth”?

Puberty Brainstorm How have you changed from childhood? Create a chart, sorting as many changes as you can think of under the headings Physical and Psychological. Look at Figure 1.1 for some examples.

The term growth usually refers to physical growth, such as getting taller. But the term development refers to physiological (physical) changes as well as psychological changes-changes in how we think, feel, and behave as we become more mature. Maturation is another word commonly used to describe the development of physical, emotional, and behavioral characteristics through the growth process.

As you become an adult, your physical development and psychological development occur together. We cannot understand one without the other. However, to more easily distinguish these two processes, we use the terms puberty and adolescence. Puberty is the time when physical growth and development that lead to sexual maturity occur. Adolescence is the time between being a child and becoming an adult, when psychological development and social development occur.

Weight gain
New responsibilities
Mood swings

Figure 1.1 Defining physical and psychological development.

In this unit on your changing body, you will learn more about the following:

  • How do males and females grow and develop during puberty?
  • What factors influence growth?
  • What are hormones and what do they do?
  • How does puberty make you feel?
  • What are some healthy ways you can take control of your body?

Activity 1-1: You Must Have Been a Beautiful Baby


Enormous changes occur as we grow and develop, but some characteristics remain identifiable throughout our lives. In this activity you try to identify your classmates from their baby pictures.


  • One picture of you between the ages of 2 and 5 Activity Report


Step 1 Bring in a picture of yourself between the ages of 2 and 5 and give it to your teacher. Put your name on the back.

Step 2 Your teacher will give your picture a number and post it along with the rest of the class pictures.

Step 3 Study the pictures and try to guess which picture belongs to which classmate. As you study the pictures, try to think about which physical characteristics will be most helpful in identifying people.

Step 4 Write your guesses on the Activity Report provided by placing the name next to the correct number.

Step 5 Summarize your conclusions about what characteristics helped you in your identification.

“As I go through changes I am confused because I feel new emotions and have new ideas and priorities. I no longer feel that my parents understand me nor that they are always fair or correct as they used to be. I'm no longer sure as to whether I am a child or adult.”



All animals go through a series of developmental stages. Since these stages are predictable and repeated in each generation, they make up a life cycle. The immature and mature forms of some species look dramatically different. For example, the caterpillar (the immature stage of a butterfly) looks nothing like the mature butterfly. Moreover, the basic difference between the immature and mature among animals is not just a matter of appearance, but one of function. The sexually mature animal can reproduce (produce offspring similar to itself); the sexually immature cannot.

Figure 1.2 Adolescence is one part of the human life cycle.

Humans go through predictable stages of growth, but the changes are not as dramatic as those of the butterfly. Puberty marks a stage of rapid growth and sexual development, signaling the end of childhood and the beginning of adulthood. All the body's systems undergo changes at this time, including the maturation of the reproductive system that allows us to reproduce, or have children.

Unlike in other animals, the ability to reproduce among humans is not enough to turn you into a full-fledged adult. In our society, adolescence is a lengthy process of psychological development and social learning that lasts about 10 years, roughly spanning from age 10 to age 20.

Prove it! Convince your class that the following statements are either reasonable or totally outrageous:

  1. I am a billion seconds old.
  2. I am a trillion minutes old.

By the end of puberty you and your friends end up in the same place biologically, but you may notice a lot of variation during puberty itself. To allow for these differences, we speak of age in two different ways. One is chronological age, which means how old you are or how many years you have lived. The other way we speak of age is developmental age. Developmental age refers to how developed you are in a biological sense at a given time.

Girls and boys of the same chronological age can look very different because they are at different developmental ages. You probably have compared yourself with others your age. Sometimes you may think another person is the model for what is normal. Perhaps he has a deeper voice and is taller, or she has wider hips. Chances are the person with whom you have been comparing yourself also feels uncertain about his or her appearance at times. He or she may even have looked at you to define what is “normal.”

Figure 1.3 Stages of growth from birth to age 16.

Describing Puberty Write down three words that describe puberty and adolescence and pass them in. The teacher will put them up on a board so your class can discuss them. Now create a poem, picture, or a paragraph using the words and concepts discussed.

Puberty occurs over time at fairly predictable ages. It is common to think of it as part of the process of children getting older. But growing older and entering puberty are not always the same thing. This is because puberty starts at somewhat different ages and moves at different rates for different people. “Normal” development refers to three interrelating concepts:

  1. Being like everyone else
  2. Developing changes within the average age ranges
  3. Whether or not everything works correctly, medically

Normal development, to you, probably refers to being like everyone else. While developing early or late is very normal, you may feel different. So, think of normal in a slightly different way. Normal development is a function of averages. To identify averages, the ages at which adolescents reach certain stages of puberty are collected, added together, and then divided by the number of persons studied. For example, a girl may develop breasts on average by age 13, but the normal range includes ages 8 to 17. “Normal” also refers to whether or not body parts work the way they should. Developing breasts at age 8 or 17 is less important than whether the breasts begin to function as they should (produce milk for a baby when the time comes).

Activity 1-2: Examining Differences


In our society, we consider it proper that our sexual organs and female breasts be covered when we are in public. Even when we go swimming, we wear bathing suits. As a result, most of us are not completely comfortable looking at human bodies, or pictures of human bodies, and we're not used to talking about what we see. Sometimes, however, it is important to be able to do this in a serious manner so that we can learn. It is particularly important in this unit, since it deals with growth and changes of the human body.

In this activity you look at pictures of people at various stages of physical development. You examine the pictures, look for differences, and make some conclusions about the types of changes that occur in puberty. You need to be respectful of others throughout this exercise and remain focused on the serious nature of the activity.


  • Activity Report


Step 1 Your teacher will divide you into groups.

Step 2 You will be given the Activity Report, and your teacher will go over the questions with you.

Step 3 Your group will be given time to study the pictures, make observations, and record your answers to the questions.

Step 4 Your teacher will then ask each group to report back to the entire class and compare observations.

“I stood there looking at this other person in the mirror who looked just like me, and all of a sudden I wasn't thinking at all. This other person in the mirror was someone and I was someone and I wasn't sure who because I didn't know either of us and we weren't the same person and I wasn't there at all, because I wasn't thinking, because my mind was quite blank.”


Going through Puberty

Puberty is not just a matter of the body changing, but also how you feel about these changes.

  • Do you sometimes feel you are on an emotional roller coaster, up one minute and down the next?
  • Are there times when you feel uncomfortable with the ways your body is changing?
  • Have people treated you differently because of your changing appearance?
  • Are there times when you feel “out of it” and think no one else could understand how you feel?
  • Have you quietly looked at others to see how your growth, development, or appearance compares with theirs?

If you answer “yes” to any of these questions, you are not alone. These very common feelings can be upsetting at times. There is joy as well as some concern in seeing oneself change. Since very little can be done about these changes, it is important to give yourself time to adjust. Here are a few stories from other teenagers going through puberty.

Janet's Story

“I started maturing when I was very young. And I never wanted to. When I was about nine I already started having breasts and I hated it. I was still a tomboy and I used to do anything to hide my chest, like wear baggy shirts and overalls all the time. Now that I'm older, I realize that I just didn't feel ready to grow up then. My body was leading the way and my feelings about changing were about a mile behind.” (Changing Bodies, Changing Selves, pg. 21)

Steve's Story

“Well, for me it was weird because I didn't even start growing until last year. Everybody thought there was something wrong with me because I still looked like a ten-year-old until I was 15 or 16. That has been a really bad experience for me because everybody around me was changing and I was standing still. I was changing in my head but not my body. My parents were even going to take me to the doctor to see if I was deformed or something like that, but they didn't, and finally last year I started to grow. My voice is changing and everything, so I guess I am normal after all, but I think it is going to be a while before I stop feeling like I'm different from everybody else.” (Changing Bodies, Changing Selves, pg. 11)

What does happen to your body during puberty? Figure 1.4 summarizes the changes you will read about in this unit.

What Do You Think?

Why do you think the legal age for marriage is 18 years old (in most states), although sexual maturity is often reached several years earlier? What are the advantages and disadvantages of early marriages?

What Happens to Your Body During Puberty?

What is normal? Normal can be different for each person. This chart shows the changes that take place in every adolescent's body during puberty. When and in what order these changes take place can't be pinpointed, but they will happen. If you are concerned or have questions, talk with a health professional.

Boys Girls
Reproductive Organs

Testes begin to enlarge and produce sperm.

Penis enlarges.

Wet dreams begin.

Ovaries begin to produce mature eggs.

Uterus enlarges.

Vagina enlarges.

Menstruation begins.

Secondary Sexual Characteristics

Facial hair appears.

Axillary hair appears.

Pubic hair appears.

Voice deepens.

Breasts develop.

Axillary hair appears.

Pubic hair appears.

Other Changes

Skeleton grows.

Muscles develop and become stronger.

Fat is deposited under skin.

Circulary system and respiratory system become more efficient.

Thinking skills mature.

Skeleton grows.

Muscles develop and become stronger.

Fat is deposited under skin.

Circulatory system and respiratory system become more efficient.

Thinking skills mature.

Figure 1.4 A summary of the physical changes boys and girls experience during puberty.

Give some examples of life cycles of other animals. How are they the same as or different from the human life cycle?

What Do You Think?

American society does not have formal “rites of passage” (events that mark new stages of development), but some “development markers” may serve similar functions. What are some “rites of passage” or “development markers” you can think of for adolescents in this country?

What kind of baby were you (fussy, sweet, active, sleepy, etc.)? What kind of behavior did you exhibit as a child? What physical characteristics distinguish you? What personality characteristics distinguish you? Think about these elements of yourself as they apply to you today: What is the you-in-you that remains constant throughout the changes in your life?

Each of us is different in some way. What does being different feel like? In what ways are you unique? What are some positive aspects, and what are some negative aspects?

Review Questions

  1. What is the difference between growth and development?
  2. What is the difference between puberty and adolescence?
  3. What is the difference between developmental and chronological age?
  4. What is normal development?
  5. What are some common feelings about experiencing puberty?

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