Teacher Wrap-up Background Information Darwin noted the striking similarity among embryos of complex animals such as humans, chickens, frogs, reptiles, and fish. He wrote that the uniformity is evidence for evolution. He pointed out that human embryos pass through a number of embryonic stages inherited from their ancestors because they have inherited the developmental mechanisms from a common ancestor. These mechanisms are modified in a way that is unique to an organism's way of life. The similarities in comparative embryology are also evident in the early stages of development. For example, fish, bird, rabbit, and human embryos are similar in appearance in the early stages. They all have gill slits, a twochambered heart, and a tail with muscles to move it. Later on, as the embryos grow and develop, they become less and less similar. (http://www.cliffsnotes.com/study_guide/evidence-for-evolution.topicarticleid-8741,articleid-8636.html) Benchmark: SC.912.L.15.1 Explain how the scientific theory of evolution is supported by the fossil record, comparative anatomy, comparative embryology, biogeography, molecular biology, and observed evolutionary change. Materials: 1 sheet of Cardstock 4 Envelopes Scissors Instructions: 1. Print out the embryo sheet on cardstock. 2. Cut out the embryos in row one and place in an envelope labeled #3. 3. Cut out the embryos in row two and place them in an envelope labeled # 2. 4. Cut out the embryos that remain and place them in an envelope labeled #1. 5. Write down the answers and place them in an envelope marked answer key. 6. Place the student instructions and envelopes on the table. 7. Students will need to have paper to write down their answers to the questions.
Answers to Questions: Pre-questions A. What are some ways scientists have found evidence of preexisting organisms? Fossils, DNA, Analogous and Homologous structures B. How have scientists able to linked them to organisms that are present on earth today? By comparing the organism s structures with the fossil structure. Comparing DNA with fossil DNA Q1. How are these embryos similar? They have long tails, large heads, eyes, notochord and pharyngeal gill slits. Q2. How do they differ in structure? Some have larger heads and bigger eyes. The bodies are thinner on the A and B embryos. Q3. How are these embryos similar to the other embryos? A and B have developed long narrow tails. Embryos C through F have noticeable limbs. C and D have large eyes. Q4. Describe how each lettered embryo has changed? Embryo A: It has developed a long narrow tail, gills, limb buds and a mouth Embryo B: It has developed a long narrow tail, gills, a mouth, feathery things on its head, limb buds. Embryo C: It has developed large eyes, limb buds, head has a beak like mouth Embryo D: It has developed large eyes, limb buds, and rounded midsection Embryo E: It has developed a round head, limb buds, long tail, chest area is larger. Embryo F: It has developed a large midsection, and shorter tail. Q5. Make a hypothesis about what organism will develop from embryo A and embryo E. Accept reasonable predictions, student answers will vary. If embryo A continues to develop a long narrow tail, it will look like a fish. If embryo B continues to develop it will resemble a dog. Q7. Were your predictions correct about the animals? Student answer should be in response to their statements in question 5. Student answers will vary. Q8. Explain how these embryos can be used as evidence of a common ancestor between each of these six organisms? The embryos look a lot similar at a certain stage of development which could be a link to a common ancestor. Q9. As a scientist, if you reviewed Darwin s work today, would you accept this as evidence? Explain why or why not.
Student Wrap-up Background information There are several ways that scientist research to find out how organisms have evolved. Some have studied the embryological development in vertebrates. Vertebrates begin life in the same way and look similar but as they develop differences emerge. Benchmark: SC.912.L.15.1 Explain how the scientific theory of evolution is supported by the fossil record, comparative anatomy, comparative embryology, biogeography, molecular biology, and observed evolutionary change. Pre-questions A. What are some ways scientists have found evidence of preexisting organisms? Procedure B. How have scientists able to linked them to organisms that are present on earth today? 1. Take out the embryo pictures from envelope #1 and arrange in alphabetical order. Q1. How are these embryos similar? Q2. How do they differ in structure? 2. Take out the embryo pictures from envelope#2. These are the same organisms. They are older and more developed. 3. Arrange these pictures in alphabetical order under the first set. Q3. How are these embryos similar to the other embryos? Q4. Describe how each lettered embryo has changed? Q5. Make a hypothesis about what organism will develop from embryo A and embryo E. 4. Take the pictures out of envelope # 3. Match the embryos with the organisms in the envelope. Q7. Were your predictions correct about the animals? Q8. Explain how these embryos can be used as evidence of a common ancestor between each of these six organisms? Q9. As a scientist, if you reviewed Darwin s work today, would you accept this as evidence? Explain why or why not.
Source: http://www.starlarvae.org (Adapted from Gilbert 1997.)
Source: http://www.starlarvae.org (Adapted from Gilbert 1997.)