Biological Classification Test - 81

Prions are highly resistant glycoprotein particles which function as infectious agents. Prions can also act as catalyst converting normal protein into prion state. Prions are not affected by proteases, nucleases, temperature upto $$800^oC$$, UV radiations and formaldehyde.

Methanogens are microorganisms that produce methane as a metabolic byproduct in hypoxic conditions. They are prokaryotic and belong to the domain of archaea. They are common in wetlands, where they are responsible for marsh gas, and in the digestive tracts of animals such as ruminants and humans, where they are responsible for the methane content of belching in ruminants and flatulence in humans. In marine sediments the biological production of methane, also termed methanogenesis, is generally confined to where sulfates are depleted, below the top layers. Moreover, the methanogenic archaea populations play an indispensable role in anaerobic wastewater treatments. Others are extremophiles, found in environments such as hot springs and submarine hydrothermal vents as well as in the "solid" rock of the Earth's crust, kilometers below the surface.

• Plasmogamy is a stage in the sexual reproduction of fungi, in which the cytoplasm of two-parent cells (usually from the mycelia) fuses together without the fusion of nuclei, effectively bringing two haploid nuclei to close together in the same cell. 

The property of being divisible into symmetrical halves on either side of a unique plane is bilateral symmetry. Example, humans

• Capsid is the protein shell of a virus. It is also known as the envelope of a virus. It is made up of protomers.
•  It encloses the genetic material of a virus and protects it from the environment. 
• It also contains special sites on its surface which allow its attachment to a host cell. 

Lichens are association (mutually beneficial) between fungus and alga. The fungal partner is mycobiont and algal partner is phycobion. The mycobiont is usually an ascomycete and phycobiont is usually green algae Lichens can grow in extremely inhospitable conditions In many ecosystems they are the pioneer species. The role of mycobiont is providing body structure and anchorage and absorption of minerals and water. The role of phycobiont is mainly in providing food through photosynthesis. So, the correct answer is 'Fungus and algae'.

A heterotroph is an organism that cannot produce its own food and rely on others for its food requirement. Most animals fall in the category of heterotrophs. They are not able to synthesize their own food. They usually eat autotrophs (plants) to obtain the energy. The types of heterotrophs include herbivores, those who eat plants; carnivores, those who eat other animals; omnivores, those who eat both plants and animals. 

• Comma-shaped bacteria - e.g. Vibrio cholera.
  
• Spherical-shaped bacteria (Cocci) - e.g. Staphylococcus and Streptococcus.
• Rod-shaped bacteria (Bacilli) - e.g. E.Coli and Salmonella.
• Spiral-shaped bacteria (Spirilla) - e.g. Treponema and Borellia.
• So, the correct answer is 'Cocci are spherical shaped'.

Lichens are a symbiotic partnership of fungus and algae. The dominant partner is the fungus, which gives the lichen the majority of its characteristics from its thallus shape to its fruiting bodies. So, thallus is foliose in lichens. Lichens occur in one of four basic growth forms. crustose, squamulose, foliose and fruticose. So, the correct answer is 'Lichens'.