Question

1. A Gram stain is made of a fixed smear from a culture of Escherichia coli. Which of the following microscopes would be most suitable for observing this bacterium?

Bright field microscope

Phase-contrast microscope

Transmission electron microscope

Dark-field microscope

Scanning electron microscope

2. True or False. Molecular phylogenetics aims to classify organisms based on observable traits, such as morphological, biochemical and physical characteristics.

3. Which of the following is NOT true concerning the plasma membrane of a cell?

               A. it is the interface between the cytoplasm and the external environment

B. it is a semi-permeable selective barrier to movement of molecules in and out of the cell

C. its chief structural components are hydrophilic proteins and negatively charged sugars

D. it is a hydrophobic bilayer of phospholipids with embedded proteins and other components

4. All microbial cells _________ but only some microbial cells are able to _________

            A. metabolize, grow                   

            B. move, metabolize

            C. evolve, communicate  

            D. differentiate, communicate   

5. Mitochondria evolved from _______ .

phototrophic bacteria

heterotrophic bacteria

chemolithotrophic bacteria

auxotrophic bacteria

20. Consider the following statements: I. Most bacterial species do not cause disease. II. Infectious diseases are the leading cause of death in the US today.

Only statement I is correct.

Only statement II is correct.

Both statements I and II are correct.

Neither statement I nor II is correct.

________ 21. Scotophobotaxis refers to the ability of an organism to sense __________

scotophobes.

light.

extremes in pH.

darkness.

None of the above

58. A species of insect that lives solely on pine sap was found to contain a bacterial symbiont. Genome sequencing of both the host and the symbiont revealed that the symbiont lacked many genes required for energy production, and the host lacked genes for biosynthesis of several essential amino acids. What is/are the most likely mechanism(s) that caused the loss of these genes?

A) coevolution

B) horizontal gene transfer

C) increased mutation rate

D) horizontal gene transfer and increased mutation rate

PLEASE I NEED HELP WITH THESE QUESTIONS, THANK YOU!!!

Answer 1

• A general laboratory bright-field microscope is suitable for visualizing Gram-stained Escherichia coli cells. An oil immersion objective of 100x is generally used for studying its cell morphology.
• The given statement is false. The molecular phylogenetics is utilized in order to trace the evolutionary history of micro-organisms and establish a relationship between closely related phylogenetic neighbors. The classification based on phenotypic, physiological, or biochemical characteristics should support the results obtained by phylogenetic analysis. In prokaryotic taxonomy, such type of classification is often referred to as a polyphasic approach.
• In given statements regarding the plasma membrane of a cell, option "C" is incorrect. The chief structural components of a plasma membrane are phospholipids bearing hydrophilic head and hydrophobic tail components. Along with them, other components such as cholesterol, glycolipids make the plasma membrane more unique. In all, lipids, protein, and carbohydrates are collectively essential for the integrity of the plasma membrane.
• All microbial cells evolve but only some microbial cells are able to communicate. The process of evolution is not restricted to characteristics. It applied to all life forms on the planet Earth. The process of cellular communication is an advanced stage of evolution and is based on the type of micro-organism one is discussing. So option C is correct.
• Mitochondria are developed from purple non-sulfur bacteria which are a type of photoheterotrophs. So, it is worthwhile to mention that phototrophic bacteria contributed to the evolution of mitochondria.
• Ans 20). Both statements I and II are correct. It is true that most of the bacterial species don't cause disease. The human body is a reservoir to trillions of bacteria. If our immunity compromised, we may become their victim. Also, it is true that infectious diseases are the leading cause of death in the United States, as most of them are from nosocomial infections.
• Ans 21). The phenomenon of scotophobotaxis refers to the ability of an organism to sense light. It is a type of phototaxis where an organism responds to the illuminated light and such a phenomenon can be studied under a light microscope.
• Ans 58). The correct answer to this question is option A i.e. coevolution. An insect feeding only on pine sap is living with symbiotic bacteria. The process of symbiosis involves mutual benefits to host and symbiont. The bacteria are well known to manufacture several essential amino acids that may be useful for the host. While by-products of many biological reactions might be utilized by symbiont as a direct substrate so there is no need of investing energy for their biosynthesis. So this is a perfect case of co-evolution where certain demands are fulfilled by mutual interaction. During the course of evolution, the genes responsible for manufacturing essential amino acids could have lost from host DNA. While genes for energy production could have lost from symbiont bacterium. I don't think that there could be any role played by horizontal gene transfer and increased mutation rate. Because they are not only limited to genes for energy production and manufacturing of essential amino acids.