Gizmo Answer Key: Embryo Development

Name: Lilah Owens Date: 08-01-2022 Student Exploration: Embryo Development Directions: Follow the instructions to go through the simulation. Respond to the questions andprompts in the orange boxes. 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 B C D mouse frog human fish 2. Which image above do you think is a human? Explain. The human is C. Gizmo Warm-upEmbryology 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 detailsof mammalian development. To begin, be sure the COMPARE tab isselected. 1. What do the images have in common? They are all single cells. Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved

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. Activity A: Comparativeembryology 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 tostage 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 fish chicken human mouse frog 13 fish chicken human mouse frog 16 fish chicken human mouse frog 20 fish chicken human mouse frog 23 fish chicken human mouse frog 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. Stage 13 is when the body shape starts to take shape and become obvious. Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved

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. 4. Observe: Switch to stage 13. What do all of the embryos have in common at this stage? Along with the somites and brachial arches, the tail bud also starts to take shape. In mammals, brachial arches develop into structures in the head and neck. In fish and frogs they becomepart of the jaw and structures that support the gills (and are eventually lost in frogs). Somites are blocks oftissue that divide an embryo into segments that will become part of the vertebrae. The tail bud is tissue thathelps 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? The mouse and the human are more similar. Frogs and fish have a closer relationship. 8. Think and discuss: How do the similarities and differences between embryos provide evidence that evolution has occurred? Because fish existed before humans, which do not share the development of either limb budsor an umbilical cord, the variation in how certain embryos grew the limb buds at stage 16 andthe umbilical cord at stage 20 demonstrates evolution. Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved

Activity B: Investigatingearlydevelopment 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. 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. One cell is seen dividing into two and then multiplying until it takes the form of a multicellularball. 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. The cells move to fill in the empty area around the pre-existing cells on the membrane assoon as a pocket of space between them opens up. 4. Observe: Click Continue to watch the embryo undergo neurulation. Describe what you see. It definitely grows four limbs and takes on a strange shape with a nearly pearl-like center. If you click Continue again, you will see that this embryo will eventually grow into a gorilla. 5. Experiment: During development, cells undergo differentiation to become specialized cells such as muscle cells or nerve cells. You can investigate how this happens by dying certain cells and seeing whatthey become. Click Start over , then Start to return to the end of morulation. Drag the syringe on the left to the embryo on the right and release to label cells with a colored dye. The cells on the outside can be labeled one color andthe cells on the inside can be labeled another. Click Continue until “Gastrula” is highlighted on the flow chart. Which cells become the gastrula ? Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved

The blue cells that were on the inner part. The cells that disappear here will become part of the placenta, a fluid-filled organ that provides nutrients tothe fetus, while the other cells will become part of the adult organism. 6. Observe: Click Start over . Then click Start and Continue twice to reach the blastula stage. The cells inside the blastula have migrated to one side, creating a hollow center. Use the needle to label the cells onboth the inside and the outside of the mass, against the hollow center. Click Continue three times to advance to the end. Which cells become the body of the organism? The larger cell mass contains the red ones. The blue cells that were up against the hollow center will become the primitive yolk sac, a fluid filledstructure that provides nutrients to the embryo before the placenta forms. 7. Observe: Click Start over . Then click Start and Continue to reach the gastrula stage. Notice there are three layers of cells inside the embryo. Use the needle to label those cells, then advance to the end. A. What does the top layer of cells (blue) become in the adult? (Note – the cell types will be color-coded in the adult.) Given the image of an adult, it assumes the role of the brain's outermost layer and aportion of the brain. B. What does the middle layer (red) become? The limbs, ribcage, and spinal cord took on the color red. Moreover, it was integratedinto the skull. C. What does the bottom layer (yellow) become? The three cell layers developed into various components of the mature organism. Whatdoes that signify for the previously identical cells? They adapt and take on newresponsibilities to be useful for particular components of the new organism they willmake up. They undergo differentiation to join a fresh layer of cells: ectoderm,endoderm, or the mesoderm Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved

Activity C: Details ofdevelopment Get the Gizmo ready: ● On the DIFFERENTIATION tab, select the Summary mode. Introduction: Now that you’ve made some observations, you will go back and learn more about what is going on. In the summary mode, the steps in development will be explained. Question: How do cells differentiate during early development? 1. Observe: Click Start to watch morulation. Read the descriptions as you go. A. What is a morula ? A ball of 16 cells B. Click Continue again. Describe compaction. When the morula's cells are firmly linked together. 2. Observe: Click Continue to watch blastulation. ✏ Label the diagram at left. A. What happens to the embryoblasts? The inner cell mass (ICM), an open cavity, andthe blastocoel are formed by the embryoblastsgrouping together at one end. B. What is the blastocoel? The exposed space left behind by theconstruction of the ICM. C. Click Continue . What cells form in the inner cell mass ? Epiblasts and Hypoblasts Embryonic stem cells , cells that have the ability to differentiate into all the cells in the organism, may be collected from the inner cell mass at this developmental stage. D. Click Continue. What forms inside the epiblasts, and what will this structure do for the fetus? The fluid that will be produced by the amniotic cavity to protect the fetus. Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved

E. Click Continue . What do the hypoblasts become and what will that structure do for the embryo? The hypoblasts create a membrane that lines the blastocoel. Note: The trophoblasts will no longer be shown here, but they continue to provide support for the embryo and become part of the placenta later in development. 3. Observe: Click Continue to watch gastrulation. A. Describe what happens to the epiblast cells. The blastocoel is lined with a membrane made by thehypoblasts, forming an early yolk sac. The embryowill be fed by this sac before the placenta andumbilical cord develop. B. Click Continue . What is the primitive streak ? The depression along the top of the epiblast layer. C. Click Continue , then ✏ label the diagram above. What happens to the epiblasts now? Ectoderm cells develop from the epiblasts' outer layer. 4. Observe: Click Continue to watch neurulation. A. Describe what happens to the trilaminar disk . A Notachord is created by the rearrangement of mesodermal cells. B. Click Continue . Click the left, right, up and down arrows to observe different parts of the embryo. What do you notice about its shape? It resembles the shape of a dog bone. C. Switch to the COMPARE tab. Which developmental stage most resembles the neurula on the DIFFERENTIATION tab? Stage 8 D. Switch back to the DIFFERENTIATION tab and click Continue . What will the neural tube eventually form? The central nervous system 5. Observe: Click Continue . Click on different parts of the gorilla diagram to learn what the endoderm , mesoderm and ectoderm cells become. Fill out the table below. Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved

Ectoderm Mesoderm Endoderm Structure -Skin, nails, hair -Brain, nerves, spinal cord -Glands, including sweat glands and gland of nose and mouth -Muscle and tissue fat-Bones, cartilage, and connective tissue -Blood, heart, and lymph vessels -Lining of digestive tract -Liver, gall bladder, pancreas -lining of respiratory tract Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved