The semicircles are probably the longitude and the latitude, if that what you are talking about.
The answer is: mitochondria.
Mitochondria produces adenosine triphosphate (ATP), a molecule that the cells use as a source of energy. Through a process called cellular respiration, the mitochondria oxidases glucose to obtain the ATP. There are three main steps to this process: glycolysis, the Krebs cycle, and ATP Synthesis.
Answer:
The second sperm entry is blocked by the fertilized oocyte.
Explanation:
An ovum prevents polyspermy by two mechanism:
1. When the first sperm fuses with the oocyte then rapid depolarization of egg's plasma membrane takes place which prevents other sperms to fuse with the egg.
2. The fusion of sperm cause an increase in the amount of calcium ion in the cytosol of egg. This higher calcium level activates the development of egg which results in the change in the structure of the egg's outer layer. The outer layer(zona pellucida) becomes hard and prevent the entry of other sperms.
So the chromosomes from the 2nd sperm cell will not normally function in the resulting embryo because the fertilized oocyte block the entry of other sperms.
Recycling is the best act that us humans can do in order to provide a better environment. With the numerous amounts of garbage that we dispose, we forget to check that some can still be recycled into a different type of product. Recycling can effectively helps us prevent global warming as well.