AP BIOLOGY Student Exploration: Embryo Development Gizmo

AP BIOLOGY Student Exploration: Embryo Development Gizmo Student Exploration: Embryo Development Vocabulary: Blastula, Carnegie stages, differentiation, ectoderm, embryo, embryology, embryonic stem cells, endoderm, fetus, gastrula, inner cell mass, mesoderm, morula, neurula, primitive streak, trilaminar disk, zygote Prior Knowledge Questions (Do these BEFORE using the Gizmo.) 1. The images below show embryos of different species at different stages of development. Label the images below with 1-4 from least developed to most developed. A 4 B 2 C 3 D 1 2. Which image above do you think is a human? Explain. 3 because it has not only a tail, but a head forming and little nubs where limbs could form. Gizmo Warm-up Embryology is the study of the development of embryos from a single cell to a multicellular fetus. In the Embryo Development Gizmo, you will compare the development of different animals and learn the details of mammalian development. To begin, be sure the COMPARE tab is selected. 1. What do the images have in common? They are all single cells. Click on the check box to turn on Scale bars and labels. You are observing the zygotes, or fertilized single cells, of five animals. 2. At this point, are you able to tell which animal is which? No. Explain. Some of the cells, like the human and mouse, look similar, but you cannot tell it a mouse cell. This study source was downloaded by from CourseH on :29:18 GMT -06:00 2019 Activity A: Comparative embryology Get the Gizmo ready:  Make sure the COMPARE tab is selected and the Developmental stage slider is on stage 1.  Turn off Scale bars and labels. Introduction: Comparative embryology compares embryos of different species to gain insight into how they are related. To provide a framework for this comparison, embryologists divide this process into 23 Carnegie stages. You will look at seven of these stages in this activity. Question: Can we use comparative embryology to determine the relatedness of species? 1. Challenge: Drag the labels to the embryos you think they belong to. Fill in the first row of the table below with your guesses. Then, move the Developmental stage slider one position to the right, to Carnegie stage 4. Rearrange your labels if necessary and fill in the next row of the table. Continue until you get to stage 23. Don’t turn on the Reveal answers check box until the end. (Note: Your guesses may change as you go through the stages. Don’t worry, they won’t be graded - this is just for fun!) Stage A B C D E 1 fish chicken human mouse frog 4 fish chicken human mouse frog 8 frog chicken human mouse fish 13 frog chicken mouse human fish 16 frog chicken mouse human fish 20 frog chicken mouse human fish 23 frog chicken mouse human fish 2. Reveal: Click Reveal answers. A. Did you guess correctly in the end? Yes B. At which stage were you able to tell which was which? 13 Explain: At Stage 13, the body shape begins to form and become clear. 3. Observe: Drag the Developmental stage slider back to stage 8. Turn on Scale bars and labels. What structure does all of the embryos have in common? The neutral groove becomes visible. The neural groove will fold into a neural tube and will become the central nervous system. (Activity A continued on next page) This study source was downloaded by from CourseH on :29:18 GMT -06:00 2019 Activity A (continued from previous page) 4. Observe: Switch to stage 13. What do all of the embryos have in common at this stage? The tail bud begins to form as well as the somites and brachial arches. In mammals, brachial arches develop into structures in the head and neck. In fish and frogs they become part of the jaw and structures that support the gills (and are eventually lost in frogs). Somites are blocks of tissue that divide an embryo into segments that will become part of the vertebrae. The tail bud is tissue that helps form the posterior of the animal. 5. Compare: Go to stage 16. A. What structure does all five embryos have in common? The heart forms. B. What structures are missing from the frog and fish? The limb buds. Frogs are born as limbless tadpoles and their arms and legs develop later. 6. Compare: Go to stage 20. What structure does mice and humans have in common that are missing from the other organisms? The umbilical cord. 7. Discuss: Looking at the similarities and differences between the organisms throughout development, which organisms are more closely and more distantly related to one another? Explain. Human and mouse are more closely related. Fish and frog also are more closely related. 8. Think and discuss: How do the similarities and differences between embryos provide evidence that evolution has occurred? The difference in how some embryos developed limb buds at stage 16 and the umbilical cord at stage 20 shows evolution because prior to humans were fish who do not share the development of either limb buds or an umbilical cord. Activity B: Investigating early development Get the Gizmo ready:  Switch to the DIFFERENTIATION tab.  Make sure Investigation is selected. Introduction: In the investigation mode, you will make your own observations about mammalian embryo development. This study source was downloaded by from CourseH on :29:18 GMT -06:00 2019 Question: How does an embryo develop from a single cell to a multicellular organism? 1. Observe: You are observing a single fertilized cell, right after a sperm and egg cell combined. Click Start to observe the cell undergoing morulation. Describe what you see. You see one cell split up into two cells, then multiply until it forms a multicellular ball shape. 2. Observe: Click Continue to watch the embryo undergo blastulation. A. Describe what you see. The cells go towards the membrane and towards one side mainly. B. Which developmental stage, from the COMPARE tab, does the embryo most resemble? 4. 3. Observe: Click Continue to watch the embryo undergo gastrulation. Describe what you see. A pocket of space in between the cells open up and then the cells begin moving to fill in the space left prior around the already existing cells on the membrane. 4. Observe: Click Continue to watch the embryo undergo neurulation. Describe what you see. It becomes an odd shape with an almost pearl in the middle and it clearly develops 4 limbs. If you click Continue again, you will see that this embryo will eventually grow into a gorilla.