AP Bio Ch 9 Cellular Reproduction Quiz

In eukaryotic organisms like humans, reproduction of the cell and reproduction of the organism require two different kinds of division. Cell reproduction, known as cell division or mitosis, is the process by which a single cell divides into two identical daughter cells. This is essential for growth, repair, and maintenance of the organism's tissues. On the other hand, reproduction of the organism involves the fusion of two specialized cells, a sperm and an egg, through a process called sexual reproduction. This results in the formation of a new individual with a unique combination of genetic traits. Therefore, it is true that the two types of division are distinct and necessary for different aspects of an organism's life cycle.

Sexual reproduction involves the fusion of two gametes (sperm and egg) to form a zygote, which then develops into a new individual. This process requires a special type of cell division called meiosis, where the number of chromosomes is halved. On the other hand, asexual reproduction involves the production of offspring without the involvement of gametes. This can occur through various methods such as budding, fission, or fragmentation. Asexual reproduction typically involves mitosis, where cells divide and produce genetically identical offspring. Therefore, sexual and asexual reproduction do indeed require two different types of cell divisions.

The statement is false because the haploid (n) number of chromosomes is found only in the reproductive cells (sperm and egg) of humans and most other animals. In all other cells of the body, known as somatic cells, the chromosomes exist in pairs, resulting in the diploid (2n) number.

The statement is true because cell division in eukaryotes indeed involves two separate processes called mitosis and cytokinesis. Mitosis is the process of dividing the nucleus of the cell into two identical daughter nuclei, while cytokinesis is the division of the cytoplasm and the formation of two separate daughter cells. Both processes are essential for the growth and development of organisms, as well as for the repair and replacement of damaged or old cells.

This statement is false. The ability of a cell to divide is not solely determined by outside influences. Internal factors such as the cell's own genetic regulation and internal signaling mechanisms also play a crucial role in controlling cell division. These internal factors can include the presence of certain proteins, the activation of specific genes, and the cell's overall health and condition. Therefore, both external and internal factors influence whether a cell can divide or not.

DNA replication occurs during the S phase of the cell cycle, which happens before the cell enters the mitosis phase. Therefore, the statement that DNA replication occurs just before mitosis is false.

Brain and nerve cells, also known as neurons, have a limited ability to regenerate after injury. Unlike other cells in the body, neurons have exited the cell cycle, which means they are no longer able to divide and produce new cells. This lack of regenerative ability is one of the reasons why brain and nerve injuries can have long-lasting effects and often result in permanent damage. Therefore, the statement that brain and nerve cells are generally not able to regenerate after injury is true.

Short rays of microtubules called asters do not form around the centriole at the poles of dividing plant and animal cells. Asters are actually formed around the centrosome, which is located near the nucleus of the cell. The centrosome contains a pair of centrioles, and the asters radiate outwards from the centrosome to help organize the spindle fibers during cell division. Therefore, the statement is false.

Cytokinesis begins after the completion of anaphase. Anaphase is a stage in both mitosis and meiosis where sister chromatids or homologous chromosomes are pulled apart and move towards opposite poles of the cell. Once the separation of chromosomes is complete in anaphase, cytokinesis initiates to divide the cytoplasm and other organelles between the two daughter cells. Cytokinesis involves the formation of a cleavage furrow in animal cells or a cell plate in plant cells, leading to the physical separation of the cell into two distinct daughter cells. In summary, anaphase precedes cytokinesis in the process of cell division.

A microtubule organizing center, also known as a centrosome, is a structure found in cells that helps to organize and separate the microtubules during cell division. It is responsible for the formation of the spindle fibers that attach to the chromosomes and help in their movement during mitosis. In both plants and animals, a microtubule organizing center is indeed located at each pole of the dividing cell to ensure proper cell division and distribution of genetic material. Therefore, the statement is true.