AP Biology 7.12 Origin of Life on Earth- Exam Style questions - FRQ

Ans:

(a) Describe the process of embryological development in a typical vertebrate embryo, beginning with a fertilized egg and ending with the development of three tissue layers.
(4 points maximum)

(b) Identify the developmental origin of TWO of the following tissues in vertebrates:

•  central nervous system
•  digestive system
•  muscle
  (2 points maximum)

(c) Identify and explain THREE differences between the embryological development of protostomes and the embryological development of deuterostomes.
(3 points maximum)

(d) Explain TWO unique properties of human embryonic stem cells that distinguish them from other human cell types. Describe a current medical application of human stem cell research.
(3 points maximum)

(a) A fertilized egg, or zygote, results from the fusion of a male and female gamete. The zygote is diploid. After fertilization, the zygote undergoes a series of mitotic divisions in a stage called cleavage. After cleavage, the group of cells becomes a hollow ball known as a blastula. During gastrulation, the group of cells fold in on each other to make the gastrula. At this stage, the gastrula forms the three tissue layers: ectoderm, mesoderm, and endoderm

(b) The central nervous system (CWS) is derived from the ectoderm, along w/skin and eyes. The digestive system mainly develops from the endoderm, while muscles, bones, and almost everything else derive from the mesoderm. 

(c) In protostomes, cleavage occurs in a spiral – like formation. Early in development, the cells of a protostome are already determined, meaning they can only give rise to cells that are distinct to be a certain part of the body. In protostomes, the mesoderm splits and terms two distinct  masses in early development. Deuterostomes differ in that cleavage occurs and forms an equally distributed mass of cells, unlike a spiral. The cells of a deuterostome in development are not determined early an meaning that any cell can give rise to a complete organism. And instead of the mesoderm splitting, in protostome development, the mesoderm does not split in deuterostome development.

(d) Human embryonic stem cells are undermined, so they can became any type of cell the body needs. This also means that  early on in embryonic development a cell that is removed. From the embryonic group can result in a complete organism, like mentioned above w/deuterostomes. A current medical application of human stem cell research is using bone marrow cells to help leukemia patients. Bone marrow cells can give rise to any type of erythrocyte, leukocyte, or lymphocyte. This is very helpful for people w/ Leukemia who have cancerous bone marrow. Stem cells from healthy bone marrow are being placed in the bone marrow of leukemia patients to see if this helps with their condition.