Chapter 20 Biology Test

A virus is a microscopic particle that contains nucleic acids, proteins, and lipids. It is unable to reproduce on its own and can only replicate by infecting living cells. Once inside a host cell, the virus takes over the cellular machinery to produce more copies of itself. This process often damages or kills the host cell. Viruses can infect a wide range of organisms, including animals, plants, and even bacteria.

Prokaryotes are single-celled organisms that lack a nucleus. They are characterized by their simple cell structure, with genetic material floating freely in the cytoplasm instead of being enclosed within a membrane-bound nucleus. Prokaryotes include bacteria and archaea, and they are distinct from eukaryotes, which have a true nucleus. The term "prokaryotes" refers to this group of organisms in general, while "Prokaryotes" likely refers to the specific category or classification of prokaryotes.

Flagella are whip-like appendages that bacteria use for movement. They are long, thread-like structures that protrude from the surface of the bacteria and rotate like propellers, allowing the bacteria to swim through liquid environments. The flagella provide the bacteria with the ability to move towards favorable conditions, such as nutrients or away from harmful substances. Therefore, the correct answer is flagella.

Antibiotics are drugs that can attack a bacterial infection. They work by either killing the bacteria or preventing their growth and reproduction. Antibiotics can be prescribed by a healthcare professional to treat various bacterial infections such as respiratory tract infections, urinary tract infections, and skin infections. The correct answer is antibiotics.

Prokaryotes are simpler than most eukaryotic cells because they lack a true nucleus and membrane-bound organelles. Prokaryotes are single-celled organisms that have a simple structure, with their genetic material floating freely in the cytoplasm. In contrast, eukaryotic cells have a true nucleus that houses their genetic material and various membrane-bound organelles, such as mitochondria and endoplasmic reticulum. This distinction in complexity is a fundamental difference between prokaryotes and eukaryotes.

A typical virus enters a cell by injecting its genetic material, either DNA or RNA, into the host cell. This genetic material then takes control of the cell's machinery, forcing it to produce more viruses. Therefore, the statement that a typical virus gets into a cell by injecting DNA into it is true.

The statement "All prokaryotes move" is false. Prokaryotes are single-celled organisms that lack a nucleus and membrane-bound organelles. While many prokaryotes are capable of movement, not all of them possess this ability. Some prokaryotes, such as bacteria, have structures like flagella or pili that enable them to move, while others are immobile and rely on external factors like water currents for dispersal. Therefore, it is incorrect to say that all prokaryotes move.

The correct answer is "different cell wall." Prokaryotic cells have a cell wall that provides protection and support to the cell. The cell wall of prokaryotes differs from that of eukaryotes, which makes it a unique feature that helps protect the cell from injury. The cell wall acts as a barrier, preventing harmful substances from entering the cell and also helps maintain the shape and structure of the cell.

Pathogens are disease-causing bacteria. They are microorganisms that can cause illness or infection in a host organism. Pathogens can enter the body through various means such as inhalation, ingestion, or direct contact. Once inside the body, they can multiply and disrupt normal bodily functions, leading to the development of diseases. Pathogens can include bacteria, viruses, fungi, and parasites. It is important to identify and understand pathogens in order to prevent and treat diseases effectively.

This statement is true because the majority of bacteria do not cause harm to humans. In fact, many bacteria are beneficial and necessary for various biological processes. Only a small percentage of bacteria are pathogenic and can cause diseases. Therefore, it can be concluded that most bacteria are harmless.

E. coli is an example of Eubacteria because it is a type of bacteria that is commonly found in the intestines of humans and animals. Eubacteria are a large group of bacteria that have a wide range of shapes and sizes, and they are found in various environments such as soil, water, and the human body. They are prokaryotic organisms, meaning they lack a nucleus and other membrane-bound organelles. Eubacteria are known for their diverse metabolic capabilities and play important roles in various ecological processes.

Bacteriophages are viruses that specifically infect bacteria. They attach to the surface of bacterial cells and inject their genetic material, taking over the bacterial machinery to produce more phages. This eventually leads to the destruction of the bacterial cell and the release of new phages to infect other bacteria. Bacteriophages are important in controlling bacterial populations and have potential applications in medicine, such as using them as an alternative to antibiotics. The terms "bacteriaphages" and "bacteriophages" are both correct and can be used interchangeably to refer to these viruses.

Nitrogen fixers are organisms that have the ability to convert atmospheric nitrogen into a form that plants can use. This process is called nitrogen fixation. These organisms, such as certain bacteria and some types of plants, play a crucial role in the nitrogen cycle by making nitrogen available to other organisms in the ecosystem. By converting nitrogen into a usable form, nitrogen fixers contribute to the overall fertility of the soil and promote plant growth.

Cocci is the correct answer because cocci are bacteria that have a spherical shape. They can be found in various arrangements such as pairs (diplococci), chains (streptococci), or clusters (staphylococci). The other options, bacilli, spirilla, and rods, describe bacteria with different shapes and structures.

AIDS and influenza are both caused by viruses. AIDS is caused by the human immunodeficiency virus (HIV), which attacks the immune system and weakens the body's ability to fight off infections. Influenza, commonly known as the flu, is caused by the influenza virus. Both viruses can be transmitted from person to person through various means, such as sexual contact or respiratory droplets. Treatment for these diseases mainly focuses on managing symptoms and preventing complications, as there is currently no cure for either AIDS or influenza.

Gangrene (clostridium) is caused by endotoxin. Clostridium is a type of bacteria that can cause gangrene, a condition where body tissues die due to lack of blood supply. Endotoxins are toxins that are released when the bacteria are killed or break down, causing damage to the surrounding tissues and leading to the development of gangrene. Exotoxins, on the other hand, are toxins that are released by living bacteria and can cause various other diseases, but not specifically gangrene. Therefore, the correct answer is endotoxin.

Prions are particles that only contain proteins. Unlike other options such as retroviruses, cancer cells, and bacteriophages, prions do not contain genetic material like DNA or RNA. Prions are misfolded proteins that can cause other proteins to misfold as well, leading to the development of various neurodegenerative diseases. This unique characteristic of prions differentiates them from the other options provided.

Tuberculosis and measles are caused by viruses. These viral infections affect the respiratory system and are highly contagious. Tuberculosis is caused by the bacterium Mycobacterium tuberculosis, while measles is caused by the measles virus. Both diseases can be transmitted through respiratory droplets, making close contact with an infected individual a common mode of transmission. Vaccines are available for both tuberculosis and measles, which have been instrumental in reducing the global burden of these diseases.

Eubacteria are known for their ability to thrive in various environments, including extreme conditions. They can be found in soil, water, air, and even inside the bodies of other organisms. This adaptability allows them to survive in harsh conditions such as extreme temperatures, high levels of acidity or salinity, and even in the presence of toxins. Therefore, it is true that eubacteria can live anywhere, including harsh conditions.

Bacteria do not reproduce sexually through conjugation. Conjugation is a form of horizontal gene transfer in bacteria where genetic material is transferred between two cells through a pilus. It is a method of genetic exchange but not a form of sexual reproduction. Bacteria primarily reproduce asexually through processes such as binary fission, where a single bacterium divides into two identical daughter cells. Therefore, the statement that bacteria reproduce sexually with conjugation is false.

Lysogenic infection does not cause the host cell to burst. In lysogenic infection, the viral DNA integrates into the host cell's DNA and remains dormant, without causing immediate damage to the host cell. It can later enter the lytic phase, where the host cell bursts and releases new viral particles. However, the initial lysogenic phase does not result in cell bursting.

Conjugation is the correct answer because it is a type of bacteria reproduction that occurs when conditions are poor. During conjugation, two bacteria cells come together and exchange genetic material through a bridge-like structure called a pilus. This process allows for the transfer of beneficial genes that can help the bacteria survive and adapt to the poor conditions. Conjugation is a form of horizontal gene transfer and is commonly observed in bacteria when resources are scarce or the environment is unfavorable.

The given options are all components that are typically found in bacteria. However, the term "capsid" refers to the protein coat that surrounds the genetic material of viruses, not bacteria. Therefore, capsid is not part of the structure of bacteria.

Gram staining is a method used to differentiate between two different types of eubacteria by using dyes. It involves the application of crystal violet dye, followed by iodine, ethanol, and safranin, which helps to distinguish between Gram-positive and Gram-negative bacteria based on the differences in their cell wall composition. Gram staining is an essential technique in microbiology and is widely used in the identification and classification of bacteria.

The endosymbiotic theory explains the relationship between archaebacteria and eukaryotes. According to this theory, eukaryotic cells evolved from a symbiotic relationship between archaebacteria and other prokaryotic cells. It suggests that mitochondria and chloroplasts, which are organelles found in eukaryotic cells, were once free-living prokaryotes that were engulfed by ancestral eukaryotic cells. Over time, these prokaryotes became integrated into the host cell and formed a mutually beneficial relationship, leading to the development of eukaryotic cells. Therefore, the endosymbiotic theory provides an explanation for the origin and evolution of eukaryotes.

Methanogens are a group of microorganisms that thrive in the digestive systems of cows. They play a crucial role in the digestion process of cows by breaking down complex carbohydrates and producing methane gas as a byproduct. This gas is then released through the cow's burps. Therefore, it can be inferred that methanogens live in cows.

Exotoxins do not break down tissue for food. Exotoxins are toxic substances secreted by certain bacteria, which can cause damage to the host's cells or tissues. They can disrupt cellular processes and lead to various symptoms or diseases. However, their primary function is not to break down tissue for food, but rather to aid in the bacteria's survival or colonization within the host.

Syphilis is a correct answer because it is a sexually transmitted disease that can be transmitted from a mother to her fetus during pregnancy. This is known as congenital syphilis and can occur when a pregnant woman with syphilis passes the infection to her unborn baby through the placenta. If left untreated, congenital syphilis can lead to serious health problems for the baby, including birth defects, developmental delays, and even death. Therefore, it is important for pregnant women to be screened and treated for syphilis to prevent transmission to their babies.

The correct answer is eubacteria because eubacteria, also known as true bacteria, are the larger group of prokaryotes. Prokaryotes are single-celled organisms that lack a nucleus and other membrane-bound organelles. Eubacteria are the most common and well-known type of prokaryotes, and they can be found in various environments including soil, water, and the human body. They play important roles in nutrient cycling, decomposition, and some can cause diseases.

Archaebacteria lack peptidoglycan (starch) and their membrane lipids are different from those of eubacteria.

Chlamydia is considered a "silent epidemic" because it often does not cause any symptoms, especially in women. This means that many people may be infected without realizing it, leading to the spread of the infection unknowingly. Chlamydia can have serious health consequences if left untreated, such as pelvic inflammatory disease and infertility, making it important to raise awareness about testing and prevention.

Bacteria have various positive uses in different fields. Fermentation in food is one such use where bacteria are used to convert sugars into alcohol or acids, resulting in the production of food products like yogurt, cheese, and bread. Genetic engineering involves the manipulation of bacteria to produce desired traits or products, such as the production of antibiotics or biofuels. Bacteria are also used in the production of insulin, a hormone used to treat diabetes. Lastly, bacteria play a crucial role in digestion by breaking down complex food molecules into simpler forms that can be absorbed by the body.

Oncogenic viruses are viruses that have the ability to cause cancer. These viruses can integrate their genetic material into the host cell's DNA, leading to the disruption of normal cell growth and division. This can result in the development of tumors and the progression of cancer. The correct answer is "Oncogenic, oncogenic, oncongenic" as all three variations refer to viruses that have the potential to cause cancer.