1. It takes a couple of minutes after fertilization for the membrane to form and about an hour after fertilization for the first cleavage to occur.
2. After fertilization, a fertilization membrane is formed around the egg and the zygote begins to undergo cleavage. Each cell divides into two during each cleavage and the entire size of the zygote remains the same. In our experiment, we were only able to see the cells divisions, in which the sea urchin zygote was cleaved. However, in the permanent mount slides, we were able to see the blastula, gastrula and pluteus stages. A blastula is formed after a certain number of cleavages; it is just a ball of cells with a hollow center. The cells then begin to move into …show more content…
The null hypothesis is not rejected here. A paired t-test is done on the class data since data before and after the addition of the stimulant is analyzed. The test showed that the p-value for the comparison of the two data sets is 0.225, indicating that there is not enough evidence to show that there’s a statistical difference between the resting heart rate and the heart rate with coffee. The means of the resting heart rates and the heart rates with coffee are 84.36 beats/min and 79.88 beats/min respectively. They had a standard deviation of 19.24 beats/min for the resting heart rate and 20.13 beats/min for the heart rate with coffee …show more content…
Many more primitive organ structures can be seen in this, like the beginnings of ears.
6. After the cleavage stage, or the stage when the blastoderm is present, the cross section of an embryo would just appear to be a group of cells with a hollow center. At the beginning of gastrulation, the formation of the primitive streak would show a primitive groove in the cross section as well as a less hollow center as the mesoderm is formed. At the end of gastrulation, the presence of the notochord and somites, which are the end products of the formation of the mesoderm, would indicate developmental stage. After that, the presence of the neural tube after neurulation would indicate embryo stage.
7. The cleavage stage differs between sea urchins and chicks in that in chicks, the entire zygote is not cleaved. For chicks, only a small part of the zygote, the uppermost part specifically, is cleaved. In blastulation, the sea urchin embryo is made up of cells that are not very different from one another. In the chick embryo, there are two types of cells that are present during the blastulation stage. In gastrulation, the entire blastula is used in the formation of the gastrula with the three germ layers. In the chick, only one type of cell seen in the blastula stage is utilized in the formation of the germ