Biological Classification Test - 15

The first living things to invade such an area and establish themselves in it are known as pioneer organisms. A typical pioneer organism populating bare rock is lichens. Some lichens grow on rocks without soil, so can be considered among the first of life forms. They break down rock into the soil that facilitates the growth of other plants. 
Thus, the correct answer is option A. 

Saprophytes- Decomposition of dead organic materials
Parasites - Grow on/in living plants and animals
Lichens - Symbiotic association of algae and fungi
Mycorrhiza - Symbiotic association of fungi with plant roots.

Methanogens are the primitive bacteria belonging to archaea which are able to produce methane. These organisms can utilise the carbon dioxide and hydrogen gas to form methane. These organisms are found in marshy areas, swamps and in the stomach of certain animals. These organisms are responsible for methane production in the stomach of cattle like cows and buffaloes. The anaerobic breakdown of the complex molecules help in digestion. 

Lichens are composed of algae and fungi living together in a symbiotic relationship. Sulfur dioxide, is a pollutant which when mixed with rainwater or air can damage lichens and does not allow them to grow due to which they act as natural indicators of air pollution. Therefore the absence of lichens indicates that the area is heavily polluted with sulfur dioxide. Thus, the correct answer is option D.

Infective constituent of the virus is not the protein coat, but it the nucleic acid, either DNA or RNA

• An organism that does not possess a true nucleus (nucleus with nuclear membrane) and membrane-bounded organelles are called as prokaryotes. 
•  Monerans are prokaryotes. Eg. bacteria (Mycobacterium), cyanobacteria (Nostoc and Oscillatoria). 
•  Saccharomyces belong to Kingdom Fungi which possess a true nucleus and membrane-bounded organelles i.e., eukaryotic. 

Thus, the correct answer is option B.

The fungal cell wall is predominantly composed of carbohydrate polymers called chitin. Chitin is thought to mostly add structural strength to the cell wall. Hence the correct option is A.

• Adenoviruses are a group of viruses that typically cause respiratory illnesses, such as a common cold, conjunctivitis (infection in the eye),  bronchitis, or pneumonia. In children, adenoviruses usually cause infections in the respiratory tract and intestinal tract.
  
• The Potato spindle tuber viroid was the first viroid to be identified. It is a small, single-stranded circular RNA molecule, infecting potatoes and tomatoes.
  
• Tobacco mosaic disease is caused by the bacteriophage  Tobacco mosaic virus, a single stranded RNA virus. It infects a wide range of plants, especially tobacco and other members of the family Solanaceae. The infection causes characteristic patterns, such as "mosaic"-like mottling and discoloration on the leaves.
• A prion is a type of protein that can trigger normal proteins in the brain to fold abnormally, leading to diseases like Alzheimer's disease and Creutzfeldt-Jakob disease (CJD).
  

• Antibiotics or antibacterials are medications that destroy or slow down the growth of bacteria.
• The antibiotics have no effect on viruses because viruses show no metabolism of their own. Viruses are non-living entities and as such do not inherently have their own metabolism.
  
• Hence the antibiotics have no effect on viruses because viruses show no metabolism(ability to collect and use energy) of their own.
• So, the correct answer is 'viruses show no metabolism of their own'