Stages of Human Development

Name______Period______Date______ADDITIONAL INVESTIGATION Stages of Human Development

Pregnancy is divided into three main periods called trimesters, each lasting about 13 weeks. During the first eight to nine weeks of pregnancy, the developing baby is referred to as an embryo. Afterwards, the developing baby is referred to as a fetus. The first trimester can be divided into even smaller increments called stages. There are 23 stages during the first trimester of pregnancy, lasting from 1 day to 5 days. These stages, studied and defined by embryologist Franklin Paine Mall, provide a framework for the rapid changes an embryo undergoes as it grows. In this lab, you will use information from a Web site that shows the detailed changes that occur to a developing embryo and fetus to then categorize the significant developments at each stage.

PROBLEM What changes occur in a human embryo and fetus during pregnancy?

MATERIALS  Virtual human embryo Web site  classroom computer or access to computer lab  biology textbook  pencil

PROCESS SKILLS  Evaluating Data  Inferring

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PROCEDURE 1. Log on to the Web site provided by your teacher. 2. Your group will be assigned a trimester to study in more detail. As you read about the changes that occur to an embryo or fetus during this trimester, answer the questions below and complete Table 1 for your assigned trimester. a. Make a timeline that shows the major steps of development during the trimester you have been assigned. Indicate on which day(s) the event would occur on the timeline as well. ______b. What major changes to the head occurred during your trimester? ______c. How did the developing embryo or fetus change in size during your assigned trimester? ______d. Describe the development of major organs such as the heart, liver, kidneys, or lungs during your assigned trimester. ______e. Summarize the development of the embryo or fetus at the end of your assigned trimester. ______3. Share your findings with the rest of the class by filling in the appropriate table on the overhead projector or chalkboard.

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OBSERVATIONS

TABLE 1. DEVELOPMENTAL CHANGES DURING PREGNANCY

DEVELOPMENT CHANGES DURING THE ______TRIMESTER

Week Head Thorax Abdomen Limbs Other

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ANALYZE AND CONCLUDE 1. Identify List and describe the three layers of tissue in the embryo and what each layer of tissue will eventually form in the body. ______2. Explain What is the importance of cell differentiation? ______3. Explain What is an ectopic pregnancy? ______4. Infer Why is it important for a mother to eat well and stay healthy during pregnancy? ______5. Explain How can changing hormone levels affect a mother's health during and after pregnancy? ______