Q3. The answer is retroviruses.
Retroviruses have single-stranded RNA. However, RNA cannot be incorporated into the host cell genome. To incorporate their genome, viruses first must produce DNA from their RNA genome inside of the host cell. This is actually the reason they are called RETROviruses. After that, DNA can be incorporated into the host cell genome.
-The other choices cannot be correct because: prophage is a genome of a bacteriophage which is a virus that infects bacteria while capsid is a protein that coats the genetic material of viruses.
Q4. The answer is Archaebacteria do not have peptidoglycan in their cell walls, but Eubacteria do.
Two bacteria kingdoms - Archaebacteria and Eubacteria have many in common. However, the main difference between these two kingdoms and the characteristic that best helps distinguish the kingdoms is the makeup of their cell walls. Eubacteria have cell walls made of peptidoglycan while Archaebacteria have cell walls made of uncommon lipids and lack in peptidoglycan.
Q5. Some bacteria provide nutrients and raw materials for organisms in an ecosystem.
<span>Since plants are not able to directly use atmospheric nitrogen, it must be converted into different form through a nitrogen cycle. Thanks to nitrogen fixing bacteria which converts atmospheric nitrogen into ammonium, nitrogen in the form of ammonium is now available to plants. </span>Also, bacteria are decomposers. After the death of producers and consumers, decomposers eat dead organisms and release carbon, nitrogen, and other elements into the environment.
Q6. The answer is acting as a pathogen.
A pathogen is a microorganism that can cause a disease. Among different groups of organisms, some bacteria can be pathogens. Some species are pathogenic and are able to cause diseases such as tuberculosis, tetanus, cholera, etc. This pathogenic role of bacteria cannot be beneficial for humans. On the other hand, usage of bacteria in genetic engineering for production of some vitamins or hormones, such as insulin that lack in diabetic patients, can be of a great benefit to humans.
Q7. The answer is releasing toxins.
Bacteria can produce toxins that can promote an infection and cause a disease. Bacterial toxins can be endotoxins and exotoxins. EXOtoxins are after secretion released out of the cell. ENDOtoxins remain as the part of the bacteria and they are released only if bacteria are killed by the immune system of the organism. The organism will response to the presence of endotoxins and usually, inflammation occurs.
