human embryo is much slower in terms of mitotic division when compared to the division capability of sea urchins. (Insert link) 4 . Discuss the major stages of sea urchin development with reference to your series of detailed drawings and observational notes. How did the embryonic cells compare in size with the original gamete cells? State reasons such a difference might exist. Compare these early stages of sea urchin development with a human embryo. The gametes initially observed under the microscope were not similar in size, nor were they perfectly circular but slightly irregular in shape. The motile sperms are usually about 1-3 µm (10-30 reticle units under 100x
EXERCISE 1 Page 2 of 4 magnification), compared to the size of the egg which is about 100-150 µm. After fertilization, the fertilization membrane increases the egg’s diameter and the number of cells increases in number. AS they cells multiply in number, each cell gets smaller in size. Repeated cellular division will occur to form a ball of cells known as the morul and then a blastula forms. The germ layers are formed during gastrulation. The pluteus larval stage is is formed when a gut and differentiated tissue are slightly visible. For the pluteus larvae, the group was not able to actually examine this stage, but past studies show that feeding begins during the larval stage and the larva grows larger than the zygote. The earlier embryonic stages are similar to that of human embryos; both humans and sea urchins are deuterostomes and both humans and sea urchins also form a morula, a blastula and finally a gastrula. After the pluteus larval stage, the larva matures into an adult sea urchin. 5. What species of sea urchin did you use and what is its native habitat? Describe any differences that might occur in terms of cell division and embryonic development if the sea urchin were allowed to develop at colder and warmer temperatures. Which condition most closely mimics the habitat of sea urchin species used in lab?
- Summer '19
- Bacteria, cells, Embryo, Sea urchin