Life Cycle - Human Biology (2A)
Post Lab 

  • Analyzing how babies grow.
  • Comparing the head of a baby with that of an adult.
  • baby
  • brain
  • growth
  • worksheet

Students measure a baby’s head.



Body proportions change remarkably from birth to maturity.  At birth, a baby's head is one-fourth the size of the body, the forehead is wider than the chin, the lower jaw is small and receding.  Growth lengthens the limbs and trunk so that at about two years of age the general body configuration is longer and thinner and the head is about one fifth the size of the body.  At six years of age, the body has stretched out further so that the head occupies about one-sixth of its length.  The tendency for linear growth continues until puberty when the body tends to broaden relative to height.  At about age 15 the head is one-seventh the size of the body which is maintained through life.

  1. Give your students the "baby" worksheet.  Ask the students if they think babies have the same body parts as adults (Yes).  Ask the students if there are any differences between a baby's body and an adult's body? (Yes, the head is proportionally larger in a baby's.)
  2. Although this is a cartoon of a baby, it shows that one obvious difference, the size of the head appears out of proportion with the rest of the body.  Ask your students if they believe this cartoon is accurate.  Ask them to remember what a baby looks like and have them visually  compare the body size with the head size. 
  3. For a homework assignment see if the students can find out at what time a child's body is in proportion with its head.  Have the students ask their parents or observe their younger sisters, brothers, or friends. Record this information on the lab sheet.  This usually occurs about 5-8 years. 
  4. After you tabulate what students have observed, see if they can figure out why.  The brain size of a baby during the time in which it is developing inside the mother tells the mother's body when it's time for the new baby to emerge.  The rest of the body has not kept pace with the rapidly growing head.

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