Answer: Chromosomes become visible, crossing-over occurs, the nucleolus disappears, the meiotic spindle forms, and the nuclear envelope disappears. ... At the start of prophase I, the chromosomes have already duplicated. During prophase I, they coil and become shorter and thicker and visible under the light microscope.
Since fire is a chemical reaction, and oxygen is needed for that reaction, having a fire in a cave is a sure sign of the presence of oxygen.
Yes, that is true, is there something you wanted answered on this question?
Question is incomplete. Complete question is as follows:
All cells have
A. a covering called a plasma membrane that surrounds the cell and controls what information and materials enter and leave it.
B. An internal fluid that gives shape to the cell and supports the other things within it
.
C. A central zone or nucleus that contains the cell's genes.
D. All of the above
Answer:
D. All of the above
Explanation:
- All cells have a protective covering called plasma membrane. It allows the entry and exit of selective materials. Some cells can have an additional layer outside it which is called cell wall. For example, plant cells.
- All cells have an internal fluid where the components of the cell float. It is called cytoplasm or protoplasm. It maintains the shape of the cell and also provides a structure to it.
- All cells also have a zone where the genetic material is present. The genetic material is ultimately responsible for keeping the cell alive and forming various proteins. In prokaryotic cell it is present just in a zone in cytoplasm. In eukaryotes it is present inside an organelle called nucleus.
- Hence, all the above things are present in each cell.
