Biological Classification Test - 7

Lichens are peculiar dual organisms produced by the intimate association of two organisms: a fungus and an alga. The association between the two organisms is symbiosis. Both the organisms are mutually benefitted in this association and are dependent on each other. The algal cell photosynthesizes with the help of chloroplast. Therefore lichens are autotrophic. A part of these manufactured carbohydrates are used by the alga in its nutrition, the rest is supplied to the fungal partner. The fungus in turn provides water and nutrients which it absorbs from the soil using the rhizoidal hyphae. Thus both the partners get benefitted from each other. The algal partner is called phycobiont and the fungal partner is called mycobiont.

Gobar gas is mixture of methane (CH₄​), carbon dioxide (CO₂​), hydrogen (H₂​) and hydrogen sulphide (H₂​S) with methane as major component (65%). Methanogens are anaerobic, autotrophic, eukaryote that converts carbon dioxide and hydrogen into methane gas. The hydrogen serves as electron donor for reduction of carbon dioxide. Thus, methogens produce gober gas by anerobic fermentation of biomass in presence of water. The chemolithotrophic bacteria that reduce the organic nitrogen into ammonia are termed as ammonifying bacteria. The chemolithotropic bacteria that converts ammonia NH_3​ into nitrates, NO_3​-, are termed as nitrifying bacteria; it includes Nitrosomonas and Nitrobacter. The chemolithotrophic bacteria that reduce the nitrates into nitrogen are termed as denitrifying bacteria. Ammonifying, nitrifying and denitrifying bacteria are component of nitrogen cycle and do not serve in gober gas (methane) production.

Lichens are found in Artie Tundra region where no other plant can grow. Lichens prefer to grow in pollution free environment. They are often used as a indicator of pollution and also they are very sensitive to S0₂. They are first to die in a polluted environment (more SO,).

Heterotrophic nutrition involves digesting organic compounds. There are three main types of heterotrophic nutrition.

Holozoic nutrition: Complex food is taken into a digestive system and broken down into small pieces to be absorbed. This process consists of 5 stages, ingestion, digestion, absorption, assimilation and egestion.

Saprophytic: Organisms feed on dead organic remains of other organisms.

Parasitism: Organisms getting food from other living organisms (the host), with the host receiving some kind of illness from the parasite. As Fungi shows all the three patterns of nutrition they are perfect example of heterotrophic nutrition.

• Chemosynthetic bacteria do not require sunlight to grow since they use light to create their meal.

• They get their energy from inorganic molecules, which they then convert into organic compounds.

• They get their energy by oxidising organic molecules.

In Amoeba and Paramoecium, osmoregulation occurs through contractile vacoule. Osmoregulation is a phenomenon in which contractile vacuole plays an important role in maintaining the water balance of the cell. Paramoecium contains two contractile vacuoles which have fixed position. One contractile vacuole is present near the anterior end while another is present towards posterior end of the body. Each contractile vacuole is surrounded by 5-12 radial canals. Excess of water is transferred from the cytoplasm to the radial canals. The latter pour water into the contractile vacuole. The contractile vacuole expels water outside the body. Thus the contractile vacuoles and radial canals are for osmoregulation. In Amoeba the endoplasm, at its posterior end, contains a single, clear rounded and pulsating contractile vacuole, filled with a watery fluid and enclosed by a unit membrane. Surrounding this membrane is a region containing many tiny feeder vacuoles and mitochondria. It helps in the osmoregulatory and excretory activities of the animal.

In sexual reproduction, syngamy and meiotic division takes place but in bacteria, during sexual reproduction there is no formation of gametes hence no syngamy and reduction division occurs, bacteria lack alternation of generation. Conjugation and exchange of genetic material takes place in bacteria.

The breeding places of mosquito is ponds, marshes, swampy areas etc. So, if all the ponds and puddles are destroyed mosquitoes are killed. Plasmodium completes its life cycle within the mosquito and hence they are also killed.

The citric acid (2-hydroxy-propane-1,2,3-tricarboxylic acid) is a tricarboxylic acid which contains three carboxylic functional groups. It is a primary metabolic product formed in the tricarboxylic acid (or Krebs) cycle. Citric acid is the most important organic acid produced in tonnage and is extensively used in food and pharmaceutical industries. It is produced mainly by submerged fermentation using Aspergillus niger or Candida sp. from different sources of carbohydrates, such as molasses and starch-based media.

Blue green algae (BGA) also known as cyanobacteria are photosynthetic prokaryotes. Many of them form symbiotic association with fungi and green plants. According to Bergey's classification they are oxygenic phototrophic bacteria. Many members have the ability to fix the atmospheric nitrogen in the soil. BGA are the source of food to several aquatic animals Spirulina is cultivated for a source of protein rich animal feed.