Question

By means of what process do populations of bacteria or archaea increase their size? a. mitosis b. meiosis c. conjugation d. transduction e. none of the above

Short answer

The correct answer is e. None of the above. The process by which bacteria and archaea increase their size is called binary fission, which is not listed among the options.

Step-by-step solution

Understand the Terms

Mitosis is a cell division process in eukaryotic cells, Meiosis is also a cell division process but results in four daughter cells each with half the number of chromosomes of the parent cell, mostly occurring in sexual reproduction. Conjugation is a process of genetic material transfer between two bacterial cells. Transduction is a process of transferring genetic material from one bacterium to another by a virus. It's important to understand that none of these processes answer the question how bacteria and archaea increase their population size.

Identify the Correct Answer

Considering that bacteria and archaea are prokaryotes and divide by binary fission, none of the provided options is the correct answer. Binary fission, which is not listed among the alternatives, is the main way by which bacteria and archaea replicate. In this process, one cell divides into two cells of equal size.

Confirm the Answer

After analyzing all the options, the conclusion is that none of the processes provided in options a, b, c, or d is correct for the method by which bacteria and archaea multiply. Therefore, option e which states 'None of the above' is the correct answer.

Key concepts

Binary Fission

Binary fission is the process by which bacteria and archaea, which are prokaryotic organisms, replicate and increase their population size. Unlike more complex eukaryotic cells, prokaryotic cells do not undergo mitosis or meiosis. Instead, binary fission involves a single, relatively simple series of steps that ensure the bacterial cell divides into two identical daughter cells.

During binary fission, the bacterial cell first duplicates its genetic material — the singular, circular chromosome found within prokaryotes. The cell then begins to enlarge, and the duplicated chromosome is allocated to opposite sides of the cell. Eventually, a septum, or dividing partition, forms in the middle of the cell, and it pinches inwards, separating the cell into two new cells, each containing a copy of the original chromosome.

This process is rapid and efficient, which explains the exponential growth rates seen in bacterial populations. A crucial advantage of binary fission is its simplicity and speed, which can allow bacteria to double in number every 20 minutes under optimal conditions! The significance of understanding this process extends beyond academic curiosity — it's fundamental in medicine and environmental biology where control of bacterial growth is often necessary.

Prokaryotic Cell Division

Prokaryotic cell division in bacteria predominantly occurs through binary fission, as previously explained. This mode of replication is essential to the survival and proliferation of prokaryotic organisms. Prokaryotic cells are simpler than eukaryotic cells in many ways: they lack a nucleus, have a simpler structure, and have fewer chromosomes, which is usually just one circular DNA molecule.

In the context of cell division, these simplifications mean that cell division can occur without the complex machinery required for mitosis or meiosis found in eukaryotes. Instead of a spindle apparatus to distribute chromosomes, prokaryotes rely on the cell membrane attachment points to ensure the separated DNA molecules move to opposite ends of the cell.

Growth Rate

Bacterial growth and replication rates are influenced by environmental factors like temperature, nutrient availability, and pH. When conditions are favorable, some species can divide every 20 to 30 minutes, resulting in a logarithmic increase in population size. On the other hand, harsh conditions can severely inhibit or stop cell division entirely, illustrating the importance of the environment on prokaryotic life cycles.

Bacterial Reproduction

Bacterial reproduction is primarily asexual, with binary fission being the most common method of reproduction. However, bacteria possess mechanisms for genetic variation without the sexual reproduction seen in eukaryotes. These mechanisms include:

• Conjugation: a process where two bacterial cells form a physical connection and exchange genetic material through a structure called a pilus. This can result in new genetic combinations.
• Transformation: the uptake of genetic material from the environment, which can incorporate into the bacterial chromosome or plasmid, enabling the acquisition of new traits.
• Transduction: the process by which a bacteriophage, a virus that infects bacteria, transfers genetic material between bacteria.

While these methods do not result in the formation of new bacterial cells, they play crucial roles in genetic diversity and adaptation within bacterial populations. This genetic variation can lead to the evolution of new strains and can be integral in the development of antibiotic resistance, which is a major concern in public health. Students studying bacterial growth should, therefore, understand that while binary fission is the means by which bacterial numbers increase, other processes contribute to their genetic diversity and ability to adapt to changing environments.