Chapter 2: Biological Classification

Ans: Biological categorization is the scientific method of grouping organisms into hierarchical groups and subgroups based on their similarities and differences. Scientists have developed various classification systems, which have undergone several revisions over time. Previously, Aristotle developed an artificial classification system that classified animals and plants according to their habitat. Aquatic (fish, whales), terrestrial (reptiles, cattle), and aerial (birds) are examples (e.g., bat, birds). Morphology, anatomy, physiology, reproduction, ontogeny, cytochemistry, and other factors were used to classify organisms back then. Following that, creatures were categorized using a phylogenetic framework based on evolutionary links. It uses cytotaxonomy, chemotaxonomy, numerical taxonomy, and cladistic taxonomy to classify organisms.

Ans: Some heterotrophic bacteria are decomposers; they are used as natural scavengers, decomposing dead bodies and organic wastes to release raw resources, allowing organic matter to be reused. They also assist with sewage disposal, manure production, and other tasks.

• Symbiotic bacteria aid in nitrogen-fixing in the atmosphere.

• Bacteria are used in the manufacturing of lactic acid, curd, cheese, butter, vinegar, and other industrial products. Pseudomonas, Xanthomonas, and other bacteria are utilized in the production of serum, vaccines, vitamins, enzymes, antibiotics, and other products.

Archaebacteria:

• Archaebacteria are used to produce gobar gas from manure and sewage, and they cause cellulose fermentation in ruminants.

• Archaebacteria can be found in the guts of ruminants like cows and buffaloes, and they aid in digestion.

Ans: Diatoms' cell walls are known as frustules. The cell wall is primarily made up of cellulose that has been impregnated with glass, similar to silica. It is made up of two overlapping halves (or theca) that fit together like the two halves of a soapbox or a petri dish. Epitheca refers to the upper half (lid), whereas hypotheca refers to the lower half (case). Fine patterns, pits, pores, and ridges can be found on the outer layer. Diatoms' siliceous frustules are resistant to degradation. They generate large mounds of diatomite or diatomaceous earth at the bottom of water reservoirs. It may extend for hundreds of meters in some regions, from which it can be mined.

Ans: An algal bloom is a fast growth in populations of algae and other phytoplankton, particularly cyanobacteria, in organically rich water bodies. The creatures’ density may prevent light from reaching lower depths in the water body. A rise in nitrate levels, a mineral ion required for algal and bacterial growth, causes algal blooms. Agricultural fertilizers, which are leached — into water systems from the soil, or sewage effluent could be the source of increasing nitrate. Because of the high concentration of photosynthetic accessory pigments, red tides are generated by a sudden, often dangerous growth of marine phytoplankton, particularly dinoflagellates, which color the seared, brown, or yellowish. Some dinoflagellates, such as Gonyaulax, create toxins that can harm fish and invertebrates or accumulate in the food chain, providing a risk to humans who consume shellfish and other seafood. These phytoplanktonic blooms are thought to be caused by nutrient-rich inputs from the land, upwelling oceanic waters, and the activation of cyst-like structures on the seabed.

Ans: Viroids are the tiniest known infectious disease pathogens, consisting of a single-stranded RNA molecule. They don't have a capsid and don't have any proteins attached to them. Only plants are infected by viruses. Viruses, on the other hand, have genetic material that is protected by a protein or lipoprotein coat. Viruses have four forms of genetic material: double-stranded DNA, double-stranded RNA, single-stranded DNA, and single-stranded RNA. They can infect both plants and mammals.

Ans: Protozoans are all heterotrophic, meaning they exist as predators or parasites. Animal relatives are thought to be their ancestors. Based on locomotory organelles, they are divided into four classes.

(i)Amoeboid Protozoans: Amoeboid protozoans are creatures that dwell in freshwater, seawater, or moist soil. As in Amoeba, they move and seize their prey by generating pseudopodia (fake feet). Some of them are parasites, such as Entamoeba.

(ii) Flagellated Protozoans: This group includes both free-living and parasitic protozoans. For locomotion, they have flagella. The parasitic forms, such as Trypanosoma, cause disorders like sleeping sickness.

(ii) Ciliated Protozoans: Ciliated protozoans are aquatic, actively moving organisms with thousands of cilia. They have a cavity (gullet) on the cell surface that opens to the outside. Water packed with food, such as paramecium, is directed into the gullet by the coordinated movement of rows of cilia.

(iv) Sporozoans are parasitic organisms that go through a life cycle that includes an infectious spore stage. There are no locator organs. N. Plasmodium has a bad effect on the human population because it causes malaria.

Ans: Plants that eat insects, such as Drosera, Nepenthes, and Utricularia, are somewhat heterotrophic. The nitrogen content of these plants is low, although they are otherwise autotrophic. They capture a variety of insects to get nitrogen from them. The rest of the food, namely carbohydrates, is produced by the photosynthesis process.

Ans: A lichen is a structurally organized object made up of a fungus and an alga that is permanently associated. Mycobiont refers to the fungal component of lichen, while phycobiont refers to the algal component. Both mycobiont and phycobiont are part of a symbiotic relationship in which the fungus is the dominant partner and the algae are the submissive. The fungus provides the structural covering that protects alga from adverse conditions like drought, heat, and other environmental factors. It also absorbs moisture from the air and binds the lichen to rock, tree bark, leaves, and other similar structures. By converting carbon dioxide into organic food, the alga prepares organic food. Cyanobacteria (blue-green algae) can fix atmospheric nitrogen in addition to preparing food if the algal component is cyanobacteria (blue-green algae).

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Ans: The most fascinating species are the euglenoid flagellates, which combine animal and plant features. The following are the distinguishing characteristics:

• They are flagellates with only one cell.

• There is no defined cellulose cell wall in these protists. Instead, a thin membrane known as a pellicle protects the cells. Protein, fat, and carbs make up the pellicle.

• These protists have one or two flagella, which aid them in swimming. If there are two flagella, one is long and the other is short. They have two longitudinal rows of fine hairs and are tinsel-shaped. Each flagellum has its granule at the base. A bulge known as the paraflagellar body connects the two flagella.

• The cell's anterior end has an eccentric mouth, or cytostome, that leads into a flask-shaped chamber, such as the gullet or cytopharynx. The gullet is a big basal reservoir that opens up.

• The cytoplasm of one end of the reservoir has an orange-red stigma (eyespot). The eyespot is a curving plate that contains the red pigment astaxanthin and is covered with orange-red granules. Photoreceptors are found in both the paraflagellar body and the eyespot.

• A contractile vacuole with several feeding channels can be detected just below the reservoir. Osmoregulation is aided by the contractile vacuole. It expands and pumps the contents of its fluid into the reservoir.

• Euglenoids are either holophytic or photoautotrophic in their feeding.

• Ectoplasm and endoplasm are two types of cytoplasm. The nucleus is big and located in the center of the cell. During cell division, the envelope and nucleolus remain.

• Each chloroplast is made up of a granular matrix with 10-45 dense bands running through it and a three-membraned envelope. Chlorophyll –b is a photosynthetic pigment found in them. Carbohydrates are stored in the form of paramylon bodies, which are dispersed throughout the body. Carbohydrates are stored as paramylon bodies, which are dispersed throughout the cytoplasm.

• Longitudinal binary fission is used in asexual reproduction. Before cell division, the flagellum is replicated.

• When conditions are unfavorable, the euglenoids produce cysts to prolong the dry period.

• There is no evidence of sexual reproduction.