EMBRYOLOGY

Bell Ringer In your textbook, read pp. 696-697 Bell Ringer In your textbook, read pp. 696-697. Define the following words: * Zygote * Embryo * Blastula * Gastrula * Endoderm * Ectoderm * Mesoderm

Fertilization: the union of egg and sperm -Occurs in Fallopian Tubes (usually) - 200 million sperm to one egg (ovum)! -When 1 sperm penetrates the ovum, that prevents any other sperm from penetrating the egg - After fertilization, the egg and sperm and nuclei fuse, and a new diploid human ZYGOTE results (2n) - the first cell of the new animal...

Cleavage: The first days and weeks after conception Day 1: first cleavage - 1 cell becomes 2 Day 2: second cleavage - 4-cell stage Day 3: 6-12 cell stage - can test at this stage for genetic diseases if done by IVF Day 4: 16-32 cell stage - solid ball of cells - morula

Day 5: Solid morula develops into hollow, fluid-filled blastula The embryo will develop from the inner cell mass, or embryonic disc Day 6 -7: Blastocyst attaches to the endometrium and burrows in: implantation.

Days 7-10: Gastrulation: major cellular reorganization into 3 tissue (germ) layers Gastrula: Early embryo with 3 tissue layers. All cells have the same DNA; however, different cells now begin to "turn on" (or "express") different genes to become different organs. -Ectoderm: skin, nervous system -Endoderm: lining of gut and internal organs -Mesoderm: muscles, bones, heart  

Skin and nervous system Muscles, heart and circulatory system, skeleton Digestive organs (mouth, esophagus, stomach, intestines)

Use the diagram to answer the question Use the diagram to answer the question. This diagram shows a cross section of a developing mouse embryo. A single cell is removed at this stage and provided with nutrients. Can this single cell still form a new embryo? A.Yes, because every cell in any mouse embryo can develop into a new mouse. B.Yes, because the mouse embryo has not started to develop specialized organs. C.No, because every cell in any mouse embryo is unique and specialized. D.No, because the cells in the mouse embryo have started to differentiate into specialized tissues.

Use the diagram to answer the question Use the diagram to answer the question. This diagram shows a cross section of a developing mouse embryo. A single cell is removed at this stage and provided with nutrients. Can this single cell still form a new embryo? D.No, because the cells in the mouse embryo have started to differentiate into specialized tissues.

Embryonic stem cells are stem cells from a four- or five-day-old embryo that is called a blastocyst. Embryonic stem cells are considered to be pluripotent because they can differentiate into numerous cell types, such as blood, brain, or muscle cells. How are adult body cells different from embryonic stem cells? A. Adult body cells are unable to replicate B. Adult body cells have lost some chromosomes. C. Adult body cells have specialized into particular types of cells. D. Adult body cells can change into only one or two other cell types.

C. Adult body cells have specialized into particular types of cells. Embryonic stem cells are stem cells from a four- or five-day-old embryo that is called a blastocyst. Embryonic stem cells are considered to be pluripotent because they can differentiate into numerous cell types, such as blood, brain, or muscle cells. How are adult body cells different from embryonic stem cells? C. Adult body cells have specialized into particular types of cells.

Differentiation in embryos causes unspecialized cells to become specialized. In the late 1800s, Hans Driesch separated the cells of sea urchin embryos in the 2-cell stage. He found that the separated cells could develop into two smaller, but otherwise normal, larvae. Which conclusion about sea urchin development is supported by his results? A. Differentiation is controlled by the nucleus in each cell of the 2-cell stage. B. Differentiation in the embryo must occur sometime after the 2-cell stage. C. Differentiation in the larval stage is slower than in the 2-cell stage. D. Differentiation is a function of a hormone released by each cell.

Differentiation in embryos causes unspecialized cells to become specialized. In the late 1800s, Hans Driesch separated the cells of sea urchin embryos in the 2-cell stage. He found that the separated cells could develop into two smaller, but otherwise normal, larvae. Which conclusion about sea urchin development is supported by his results? B. Differentiation in the embryo must occur sometime after the 2-cell stage.

of a rat embryo. A researcher will compare the proteins Use the picture to answer the question. The picture shows the 8-cell stage in the development of a rat embryo. A researcher will compare the proteins found in the cells of the embryo. Which results are most likely from this comparison? A. The proteins are very similar to each other from one cell to the next. B. The proteins in each of the cells are distinct from those in each of the other cells. C. The cells can be divided into two equal groups, with similar proteins only among the cells in each group. D. The cells can be divided into two unequal groups, with similar proteins only among the cells in each group.

Use the picture to answer the question Use the picture to answer the question. The picture shows the 8-cell stage in the development of a rat embryo. A researcher will compare the proteins found in the cells of the embryo. Which results are most likely from this comparison? A. The proteins are very similar to each other from one cell to the next.