In this lesson, students come to understand that all living things have a life cycle that includes being born, developing into an adult, reproducing, and eventually dying. The goal of this introductory lesson is to engage students in the study of the developmental stages of animals. By watching the births of a variety of animals, they discover that different species begin life in different ways. Next, students study photographs of humans at different developmental stages, then measure their own height and compare it to their height at birth. These exercises help them understand that living things grow and change -- albeit at different rates -- during their life cycle. Finally, students examine images that highlight the development of different kinds of animal young and learn that many animals develop much faster than humans. This helps students begin to understand that the developmental stages of life vary from one species to another -- a concept that is further developed inLife Cycles of Frogs, Dragonflies, and Butterflies and Plant Life Cycles.
- Understand that all animals (including humans) have a life cycle that includes being born, developing into an adult, reproducing, and eventually dying
- Observe the changes that occur during the growth and development of humans
- Understand that the developmental stages of life vary from one species to another
Grade Levels: K-2, 3-5
- Two 45-minute blocks
- Large sheet of paper on which to draw a bar graph
- Tape measure
- Post-it Notes
- Optional: Baby or toddler photos of students in the class
If you choose to have students bring in their baby pictures, keep in mind the issues this might raise for foster or adopted children. You may want to have students bring in pictures of themselves at a slightly older age. We have included three baby pictures for you to use in this lesson.
Before the Lesson
- Attach the tape measure vertically to a wall or door for use measuring students' height. Mark the range of normal newborn heights (19-21 inches).
- Draw a bar graph on a large sheet of paper. Label the x axis "Number of Students." Label the y axis "Height in Inches." Post the bar graph on a bulletin board or chalkboard.
1. Tell students that all living things produce offspring (reproduce), but life begins in different ways for different animals. Show them the Hatchlings and Newborns video and encourage them to pay close attention to how the birth process varies from species to species. If possible, have them to watch the clip more than once. Then discuss the following questions:
- What was similar about the births of the chick and the turtle? (Possible answers: They hatch from eggs; Their mom's were not present)
- What was similar about the births of the goat and seal? (Live births, mom was present)
- For which animals was the mother present at birth?
- The birth of human babies is similar to that of which group of animals?
- In what ways did the newborns resemble their parents?
2. To help students understand that living things grow and change during their life cycle, have them work with a partner to study the pictures of the three human infants and the ten-year-old girl in the Baby Faces stills collection. Ask them to make observations and discuss the following with their partner:
- What similarities do you notice in the shape of the infants' heads and in their facial features?
- What differences do you notice?
3. Ask students to try to figure out which of the three babies grew into the ten-year-old girl. Students should collect evidence to support their choice. Have them look for similarities in head, jaw, and eye shape, as well as other physical characteristics. Discuss some of their evidence and ask:
- How did the shape of the girl's head, eyes, nose, and mouth change as she grew older?
- What other kinds of physical changes occur as newborns grow?
- How does body size change?
4. Tell students that most newborn human babies are between 19 and 21 inches long. To find out how much students have grown since birth, use the tape measure on the wall to measure their height. Then have students record their height on the bar graph. (Show them how.) Be sure to point out to students that at any given age there is a range of heights that is considered normal.
5. Discuss the following:
- Why do you think babies aren't born bigger than they are?
- If we assume that you were all 20 inches long at birth, how much have you grown since then?
- What kinds of things can affect how tall you'll be when you're fully grown? (Examples: heredity, nutrition)
- At what age do girls and boys typically reach their adult height? (early teens for girls, late teens for boys)
- Point out that all living things, not just humans, grow and change as they go through life. Ask students for examples of growth and change in other animals.
6. Explain that humans go through specific stages of growth and development: newborn infant, toddler, child, adolescent (teenager), young adult, middle-aged adult, and elderly adult. Write the names of the stages in a row on the board. As you mention the different stages, show students the Growing Up, Growing Old stills and ask them to point out the physical changes that occur at each stage. Explain that these stages of development make up the human life cycle.
7. Write the following age ranges under the names of the stages of development: infant: 0-1; toddler: 1-3; child: 4-10, adolescent (teenager): 11-18, young adult: 19-39; middle-aged adult: 40-65; elderly adult: 66 and older. Take a class poll. How many newborns do students have in their families? toddlers? children? teenagers? and so on.
8. Divide the class into small groups and have them discuss the following questions:
- In what stage(s) do we accomplish each of these developmental milestones: learning to talk, learning to walk, learning to ride a bike, learning to read, going to high school, going to college, getting married, having children, and retiring from work (add others of your choosing)?
- How old do most people in the United States live to be?
Now give each group a Post-it Note. Have them write the developmental milestone they discussed on the note, and stick it under the stage of life where they think it belongs. Encourage them to guess if they're not sure. Discuss and correct students' conclusions.
9. To help students understand that animals develop at different rates and that most have a much shorter life cycle than humans do, show students the Animal Babies stills. Ask them:
- In which seasons were the babies born? How can you tell?
- Why is it important for them to be born at this time?
- At just a few months old, what were the baby ducks already capable of doing? What about the baby foxes?
- At what age do humans learn to swim? feed themselves? get their own food? go off to live on their own?
- How are the life cycles of animal babies different from the human life cycle? How are they similar?
10. For homework, have students draw a picture of their family and include each person's name and stage of development (newborn, toddler, child, teenager, adult).
Benchmarks for Science Literacy
5 (Grades: K-2 ): The Living Environment
5A (Grades: K-2 ): Diversity of Life
5A/P1 (Grades: K-2 ): Some animals and plants are alike in the way they look and in the things they do, and others are very different from one another.
- 5A/P1 (Grades: K-2 ): Some animals and plants are alike in the way they look and in the things they do, and others are very different from one another.
5B (Grades: K-2 ): Heredity
- 5A (Grades: K-2 ): Diversity of Life
6 (Grades: K-2 ): The Human Organism
6A (Grades: K-2 ): Human Identity
6A/P1 (Grades: K-2 ): People have different external features, such as the size, shape, and color of hair, skin, and eyes, but they are more like one another than like other animals.
- 6A/P1 (Grades: K-2 ): People have different external features, such as the size, shape, and color of hair, skin, and eyes, but they are more like one another than like other animals.
6B (Grades: K-2 ): Human Development
- 6A (Grades: K-2 ): Human Identity