All questions of Domains and Kingdoms for Grade 9 Exam

Mycoplasma does not has cell wall

Blue green algae

Nitrogen Fixation in Legume Roots
Nitrogen fixation is a crucial biological process that converts atmospheric nitrogen (N2) into ammonia (NH3), a form usable by plants. In legumes, this process primarily occurs in symbiotic relationships with specific bacteria.
Key Players in Nitrogen Fixation:
- Rhizobium Bacteria: The primary bacteria involved in nitrogen fixation in legume roots are from the genus Rhizobium. These are heterotrophic bacteria that thrive in the root nodules of legumes.
- Symbiotic Relationship: Legumes, such as peas, beans, and lentils, form nodules on their roots where these bacteria reside. The plant provides carbohydrates and a suitable environment for the bacteria, while the bacteria convert nitrogen gas from the atmosphere into ammonia.
- Mutual Benefits: This mutualistic relationship benefits both partners. The bacteria gain nutrients and a habitat, while legumes receive essential nitrogen, which is vital for their growth and development.
Process of Nitrogen Fixation:
- Root Nodule Formation: When legumes are exposed to Rhizobium, the bacteria invade the root hairs, leading to nodule formation.
- Nitrogen Conversion: Within these nodules, the Rhizobium bacteria utilize the enzyme nitrogenase to convert atmospheric nitrogen into ammonia, which the plant can then assimilate.
- Impact on Soil Fertility: This process not only supports the growth of legumes but also enhances soil fertility, benefiting subsequent crops planted in the same soil.
Conclusion:
In summary, nitrogen fixation in legume roots is primarily performed by heterotrophic bacteria, specifically Rhizobium, establishing a vital symbiotic relationship that plays a significant role in agriculture and ecosystem health.

On the basis of their energy source, organisms are classified as organotrophic and lithotrophs. Most prokaryotes and all non-phototrophic eukaryotes use organic compounds as their energy source and thus, are referred to as organotrophs. They oxidise organic compounds during cellular respiration and the produced oxygen as a byproduct. But some Cyanobacteria and Archaea use inorganic compounds as an electron donor in electron transport chain and are referred to as lithotrophs, none of the eukaryotes falls in this category. Virus act as non-living outside the cell. It becomes active when it enters the host cell and derives the cellular protein from the host.

Unicellular
- Cyanobacteria can be either unicellular or multicellular, depending on the species.
- Some species exist as single cells, while others form colonies or filaments.

Colonial or filamentous
- Cyanobacteria are known to form colonies or filaments, which allows them to thrive in various habitats.
- These colonies or filaments can be seen as slimy masses in water bodies or on surfaces.

Form blooms in polluted water bodies
- Cyanobacteria are notorious for forming blooms in polluted water bodies.
- These blooms can be harmful to the environment and aquatic life due to the toxins they produce.

Only marine algae
- This statement is incorrect, as cyanobacteria are not exclusive to marine environments.
- Cyanobacteria can be found in various habitats, including freshwater, soil, and even extreme environments like hot springs.
Overall, cyanobacteria possess the features of being unicellular or colonial/filamentous, forming blooms in polluted water bodies, and can thrive in a wide range of environments beyond just marine habitats.

Understanding the Three-Domain System
The three-domain system, proposed by Carl Woese, classifies all living organisms into three primary domains: Archaea, Bacteria, and Eukarya. This classification is based on genetic and biochemical differences.

Organisms in the Kingdom Monera
The Kingdom Monera historically included all prokaryotic organisms, which are unicellular and lack a membrane-bound nucleus. In the context of the three-domain system, Monera is divided into two distinct domains:

• Bacteria: This domain includes common bacteria, characterized by peptidoglycan in their cell walls. They play essential roles in various ecosystems, including decomposition and nutrient cycling.
• Archaea: This domain includes extremophiles, such as methanogens and halophiles, which can survive in extreme environmental conditions. Their cell membranes and biochemistry differ significantly from those of bacteria.

Conclusion
Thus, organisms from the Kingdom Monera belong to two domains: Bacteria and Archaea. The classification emphasizes the fundamental differences between these groups, leading to the conclusion that the correct answer is option 'B'—two domains.