Biological Classification Taxonomy Class 11 Full Chapter 2 in Gist

In life on Earth, every organism, from the tiniest microbe to the mightiest mammal, is intricately interconnected. How do we organize and categorize them? The answer lies in biological classification taxonomy. Biological classification, also known as taxonomy, organizes living organisms into hierarchical groups based on shared characteristics.

Definition of Biological Classification Taxonomy:

• Biological classification taxonomy is a scientific discipline concerned with organizing and categorizing living organisms based on their shared characteristics and evolutionary relationships. It provides a systematic framework for naming, classifying, and studying the vast diversity of life forms on Earth.
• Through biological classification taxonomy, organisms are grouped into hierarchical categories, from the most specific (species) to the most general (kingdom), allowing scientists to understand and communicate about the relationships between different species and groups.
• This biological classification taxonomy system helps researchers uncover patterns of evolutionary history, biodiversity, and ecological interactions, ultimately contributing to our understanding of the natural world.

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Biological Classification Taxonomy of Five Kingdom Classification:

Characters	Monera	Protista	Fungi	Plantae	Animalia
Cell Type	Prokaryotic	Eukaryotic	Eukaryotic	Eukaryotic	Eukaryotic
Cell Wall	Noncellulosic (Polysaccharide amino acid)	Present in some	Present with chitin	Present (cellulose)	Absent
Nuclear Membrane	Absent	Present	Present	Present	Present
Body organization	Cellular	Cellular	Multiceullar/ loose tissue	Tissue/ organ	Tissue/organ/ organ system
Mode of nutrition	Autotrophic (chemosynthetic and photosynthetic) and Heterotrophic (saprophytic/parasitic)	Autotrophic (Photosynthetic) and Heterotrophic	Heterotrophic (Saprophytic/ Parasitic)	Autotrophic (Photosynthetic)	Heterotrophic (Holozoic/ Saprophytic etc.)
Examples	Bacteria (e.g., Escherichia coli, Bacillus subtilis) Archaea (e.g., Methanogens, Halophiles)	Amoeba (e.g., Amoeba proteus) Euglena (e.g., Euglena gracilis) Paramecium (e.g., Paramecium caudatum) Diatoms (e.g., Navicula, Cyclotella)	Mushrooms (e.g., button mushrooms, chanterelles) Yeasts (e.g., Saccharomyces cerevisiae) Molds (e.g., Penicillium, Aspergillus) Lichens (symbiotic organisms consisting of fungi and algae or cyanobacteria)	Trees (e.g., oak, pine, maple) Flowers (e.g., roses, sunflowers, tulips) Grasses (e.g., wheat, rice, corn) Ferns (e.g., maidenhair fern, Boston fern)	Humans (Homo sapiens sapiens) Lions (Panthera leo) Dogs (Canis lupus familiaris) Insects (e.g., bees, ants, butterflies)

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Salient Features and Classification of Monera:

In biological classification taxonomy, Monera is one of the five kingdoms of biological classification, encompassing a diverse group of organisms that are characterized by their simple cellular structure and prokaryotic nature. These organisms play crucial roles in various ecosystems, from the decomposition of organic matter to nitrogen fixation.

Salient Features:

1. Prokaryotic Cells: Monera are comprised of prokaryotic cells, which lack a true nucleus and membrane-bound organelles. Instead, their genetic material is contained within a single circular chromosome, typically located in the nucleoid region of the cell.
2. Cellular Structure: Monerans exhibit a wide range of cellular morphologies, including cocci (spherical), bacilli (rod-shaped), and spirilla (spiral-shaped). Some species may also form colonies or filaments.
3. Cell Wall Composition: The cell wall of Monera is primarily composed of peptidoglycan, a unique polysaccharide structure that provides structural support and protection to the cell. However, some species may lack a cell wall entirely.
4. Metabolism: Monerans display diverse metabolic capabilities, including autotrophic and heterotrophic modes of nutrition. Autotrophic species can synthesize their own organic molecules from inorganic sources, while heterotrophic species rely on organic compounds for energy and carbon.
5. Reproduction: Monerans reproduce asexually through binary fission, where a single cell divides into two identical daughter cells. Some species may also exchange genetic material through processes such as conjugation, transformation, or transduction.

Classification:

In biological classification taxonomy, the classification of Monera is primarily based on genetic, biochemical, and morphological characteristics. Traditionally, Monera has been divided into two main groups:

1. Bacteria (Eubacteria): Bacteria are the most abundant and diverse group of Monerans, inhabiting virtually every environment on Earth. They exhibit a wide range of metabolic diversity, including aerobic and anaerobic respiration, nitrogen fixation, and fermentation. Bacteria are further classified based on their shape, staining characteristics (Gram-positive or Gram-negative), and metabolic properties.
2. Archaea (Archaebacteria): Archaea are ancient prokaryotic organisms that thrive in extreme environments such as hot springs, salt flats, and deep-sea hydrothermal vents. They exhibit unique biochemical and genetic features distinct from bacteria and are classified into multiple phyla based on phylogenetic analysis.

Recent advancements in molecular biology and genomics have led to revisions in the classification of Monera, with ongoing efforts to elucidate the evolutionary relationships and diversity within this kingdom. New techniques such as metagenomics, which involve the sequencing of environmental DNA, are providing insights into the vast diversity of microbial life on Earth.

Salient Features and Classification of Protista:

In biological classification taxonomy, Protista is a diverse kingdom of eukaryotic organisms that includes a wide variety of unicellular, colonial, and multicellular organisms. These organisms exhibit a range of morphological, physiological, and ecological characteristics, making them essential components of various ecosystems.

Salient Features:

1. Eukaryotic Cells: Protists are characterized by the presence of eukaryotic cells, which contain membrane-bound organelles including a true nucleus. This distinguishes them from prokaryotic organisms, such as bacteria and archaea.
2. Cellular Diversity: Protists exhibit a wide range of cellular morphologies, including spherical (coccoid), rod-shaped (bacillar), spiral (spirillar), and amoeboid shapes. Some protists may form colonies or multicellular structures.
3. Nutritional Modes: Protists display diverse modes of nutrition, including autotrophic, heterotrophic, and mixotrophic strategies. Autotrophic protists, such as algae, can photosynthesize to produce their own food, while heterotrophic protists obtain nutrients by ingesting organic matter. Mixotrophic protists exhibit a combination of autotrophic and heterotrophic characteristics.
4. Habitats: Protists inhabit a wide range of aquatic and terrestrial environments, including freshwater and marine habitats, soil, and symbiotic relationships with other organisms. Some protists are free-living, while others are parasitic or symbiotic.
5. Reproduction: Protists reproduce through a variety of mechanisms, including binary fission, multiple fission, budding, fragmentation, and sexual reproduction. Many protists have complex life cycles involving both sexual and asexual phases.

Classification:

In biological classification taxonomy, Protists are a diverse and polyphyletic group, meaning they do not share a common ancestor and are instead classified based on evolutionary relationships inferred from molecular, morphological, and ecological data. The classification of protists is constantly evolving as new information becomes available. However, protists are traditionally grouped into several major taxonomic groups:

1. Algae: Algae are photosynthetic protists that can range from unicellular to multicellular forms. They are found in diverse habitats, including freshwater, marine environments, and moist terrestrial habitats. Examples include diatoms, dinoflagellates, green algae, brown algae, and red algae.
2. Protozoa: Protozoa are heterotrophic protists that obtain nutrients by ingesting organic matter. They exhibit a wide range of morphologies and locomotion mechanisms, including flagella, cilia, and pseudopodia. Examples include amoebas, paramecia, euglenas, and ciliates.
3. Slime Molds: Slime molds are protists that exhibit both unicellular and multicellular stages in their life cycles. They are often found in damp, decaying organic matter and play important roles in decomposition and nutrient cycling.
4. Water Molds: Water molds, or oomycetes, are protists that resemble fungi in their filamentous morphology and mode of nutrition. They are often found in aquatic environments and are important decomposers and pathogens of plants and animals.
5. Other Groups: In addition to the major taxonomic groups mentioned above, protists include a diverse array of organisms with unique characteristics and ecological roles. These may include colonial protists, mixotrophic organisms, and symbiotic associations such as lichens.

Salient Features and Classification of Fungi:

In biological classification taxonomy, Fungi constitute a diverse kingdom of eukaryotic organisms that play critical roles in ecosystems as decomposers, symbionts, and pathogens. They exhibit unique morphological, physiological, and ecological characteristics, making them distinct from other kingdoms of life.

Salient Features:

1. Eukaryotic Cells: Fungi are composed of eukaryotic cells, meaning they have a true nucleus and membrane-bound organelles such as mitochondria and Golgi apparatus. This distinguishes them from prokaryotic organisms like bacteria.
2. Heterotrophic Nutrition: Fungi are heterotrophs, meaning they obtain their nutrients by absorbing organic matter from their environment. They secrete enzymes that break down complex organic molecules into simpler forms, which are then absorbed through their cell walls.
3. Cell Wall Composition: Fungi have cell walls primarily composed of chitin, a complex polysaccharide that provides structural support and protection. This sets them apart from other eukaryotic organisms, such as plants and animals, which have cell walls made of cellulose or other materials.
4. Morphological Diversity: Fungi exhibit a wide range of morphologies, including multicellular filamentous structures called hyphae, which collectively form a network known as mycelium. Some fungi produce specialized reproductive structures such as mushrooms, while others exist as yeasts or single-celled forms.
5. Reproduction: Fungi reproduce through a combination of sexual and asexual means. Sexual reproduction involves the fusion of specialized reproductive structures called gametes, while asexual reproduction occurs through the production of spores, which are dispersed and germinate to form new fungal colonies.

Classification:

In biological classification taxonomy, the Fungi are classified into several major taxonomic groups based on their morphological characteristics, reproductive strategies, and genetic relationships. The classification of fungi is complex and continues to evolve with advances in molecular biology and phylogenetics. However, the major taxonomic groups include:

1. Phylum Zygomycota: Zygomycetes are characterized by their production of thick-walled resting structures called zygospores, which result from the fusion of specialized hyphae. They include bread molds and other saprophytic fungi.
2. Phylum Ascomycota: Ascomycetes, or sac fungi, produce sexual spores called ascospores within sac-like structures called asci. They include diverse organisms such as yeasts, molds, truffles, and morels.
3. Phylum Basidiomycota: Basidiomycetes, or club fungi, produce sexual spores called basidiospores on specialized club-shaped structures called basidia. They include mushrooms, puffballs, rusts, and smuts.
4. Phylum Glomeromycota: Glomeromycetes form arbuscular mycorrhizal symbioses with the roots of most terrestrial plants, playing essential roles in nutrient uptake and plant health.
5. Phylum Chytridiomycota: Chytrids are aquatic or soil-dwelling fungi characterized by their flagellated reproductive cells. Some chytrid species are parasites of plants, algae, or animals, while others are saprobes.
6. Phylum Mycetozoa: Mycetozoans, or slime molds, are unique fungi that exhibit both animal-like and fungus-like characteristics. They include plasmodial slime molds and cellular slime molds.

Let’s Visualize The Chapter Biological Classification Taxonomy

Kingdom Plantae:

• In biological classification taxonomy, the kingdom Plantae encompasses all eukaryotic organisms containing chlorophyll, commonly referred to as plants.
• Some members of this kingdom exhibit partial heterotrophy, such as insectivorous plants or parasites. Examples of insectivorous plants include bladderwort and Venus flytrap, while Cuscuta serves as a parasite.
• Plant cells display a eukaryotic structure characterized by prominent chloroplasts and a cell wall primarily composed of cellulose.
• Plantae comprises algae, bryophytes, pteridophytes, gymnosperms, and angiosperms.
• The life cycle of plants involves two distinct phases: the diploid sporophytic and the haploid gametophytic phases, which alternate with each other.
• The duration of these phases and whether they are independent or reliant on other organisms vary among different plant groups. This phenomenon is known as alternation of generations.

Kingdom Animalia:

• In biological classification taxonomy, this kingdom comprises multicellular heterotrophic eukaryotic organisms whose cells lack cell walls.
• They rely directly or indirectly on plants for sustenance, digesting their food internally and storing reserves as glycogen or fat.
• Their nutritional mode is holozoic, involving the ingestion of food.
• These organisms follow a defined growth pattern, reaching adulthood with distinct shapes and sizes.
• Higher forms exhibit sophisticated sensory and neuromotor mechanisms, with many capable of locomotion.
• Sexual reproduction in this kingdom occurs through the copulation of male and female individuals, followed by embryonic development.

Lichens, Viruses, and Viroids:

In this living world, there exist microorganisms that defy conventional classification and challenge our understanding of biological diversity. Lichens, viruses, and viroids are three such entities that hold profound significance in ecology, medicine, and molecular biology.

Lichens

Lichens are remarkable organisms that often go unnoticed in the natural world, yet they play crucial roles in various ecosystems and have captivated scientists and nature enthusiasts alike for centuries. In this article, we will delve into the salient features and classification of lichens, shedding light on their fascinating biology and diversity.

Salient Features of Lichens:

1. Symbiotic Nature: One of the most distinctive features of lichens is their symbiotic relationship between a fungus (the mycobiont) and a photosynthetic partner (the photobiont), typically green algae or cyanobacteria. This symbiosis allows lichens to thrive in a wide range of environments, from barren deserts to harsh polar regions.
2. Thallus Structure: Lichens exhibit a variety of growth forms, collectively known as thalli, which can range from crustose (crust-like) to foliose (leaf-like) and fruticose (shrub-like). These growth forms are adapted to different environmental conditions and play important roles in nutrient acquisition, water retention, and reproduction.
3. Environmental Tolerance: Lichens are known for their remarkable tolerance to extreme environmental conditions, including drought, high levels of ultraviolet radiation, and pollution. They are often the first organisms to colonize bare rock or soil, initiating the process of primary succession in ecosystems.
4. Chemical Defense: Lichens produce a variety of secondary metabolites, including pigments, acids, and antibiotics, which serve as chemical defenses against herbivores, pathogens, and competing organisms. These compounds also contribute to the diverse colors and textures observed in lichens.
5. Reproductive Strategies: Lichens reproduce through a combination of sexual and asexual means. Sexual reproduction involves the formation of fungal spores or algal cells, which can fuse to form a new lichen thallus. Asexual reproduction occurs through fragmentation, where portions of the thallus break off and establish new colonies.

Classification of Lichens:

Lichens are classified based on the dominant fungal partner (the mycobiont) and the growth form of the thallus. The most common groups of lichens include:

1. Crustose Lichens: These lichens have a crust-like thallus that is tightly attached to the substrate, such as rocks or bark. Examples include species of the genera Lecanora and Caloplaca.
2. Foliose Lichens: Foliose lichens have a leaf-like thallus with distinct upper and lower surfaces. They are often loosely attached to the substrate and can be easily detached. Examples include species of the genera Parmelia and Lobaria.
3. Fruticose Lichens: Fruticose lichens have a shrub-like or branching thallus that is typically erect or pendant. These lichens can be found growing on soil, rocks, or other substrates. Examples include species of the genera Usnea and Cladonia.
4. Squamulose Lichens: Squamulose lichens have a thallus composed of small, scale-like structures called squamules. They are often found growing on soil or rocks in arid or semi-arid environments. Examples include species of the genera Psora and Cladia.

Ecological Significance:

Lichens play vital roles in ecosystems as pioneers in primary succession, contributing to soil formation, nitrogen fixation, and habitat creation. They serve as food sources for a variety of organisms, including insects, birds, and mammals, and are important indicators of environmental health and air quality.

Examples of Lichens:

1. Reindeer Lichen (Cladonia rangiferina): Found in Arctic and subarctic regions, this lichen forms dense mats resembling reindeer antlers. It is an important food source for caribou and reindeer during harsh winters.
2. British Soldier Lichen (Cladonia cristatella): Named for its red caps resembling British soldiers’ uniforms, this lichen is commonly found on tree bark and rocks in forests across North America.
3. Old Man’s Beard (Usnea spp.): This distinctive lichen hangs from tree branches like grayish-green beards, giving it its common name. It is found in various habitats worldwide and is used in traditional medicine.
4. Pixie Cup Lichen (Cladonia pyxidata): Recognizable by its cup-shaped fruiting bodies, this lichen grows on soil, rocks, and tree bark in forests and heathlands. It is widespread across Europe and North America.
5. Powdered Sunshine Lichen (Xanthoria spp.): This bright yellow or orange lichen is commonly found on rocks, tree bark, and man-made structures in sunny, exposed habitats. It is tolerant of pollution and is often used as an indicator of air quality.

Viruses

Viruses are fascinating microorganisms that straddle the line between living and non-living entities. Despite their simplicity, they wield immense power in shaping ecosystems and influencing the course of life on Earth.

Salient Features of Viruses:

1. Submicroscopic Size: Viruses are incredibly small, ranging in size from 20 to 300 nanometers. They are not visible under a light microscope and require specialized techniques such as electron microscopy for visualization.
2. Genetic Material: Viruses contain genetic material, either DNA or RNA, surrounded by a protein coat called a capsid. Some viruses also possess additional structures such as an envelope derived from the host cell membrane.
3. Host Dependence: Viruses are obligate intracellular parasites, meaning they can only replicate inside host cells. They lack the cellular machinery necessary for metabolism and reproduction and must hijack the host cell’s machinery to replicate.
4. Diverse Shapes: Viruses exhibit a wide range of shapes, including helical, icosahedral, and complex structures. Their morphology is determined by the arrangement of viral proteins and genetic material within the capsid.
5. Modes of Transmission: Viruses employ diverse strategies for transmission, including direct contact, respiratory droplets, fecal-oral route, and vector-borne transmission by arthropods. Understanding the mechanisms of viral transmission is crucial for controlling and preventing viral outbreaks.

Classification of Viruses:

Viruses are classified based on various criteria, including their genetic material, structure, mode of replication, and host specificity. The International Committee on Taxonomy of Viruses (ICTV) classifies viruses into several orders, families, genera, and species. Common taxonomic groups of viruses include:

1. DNA Viruses: These viruses contain DNA as their genetic material and include families such as Herpesviridae, Adenoviridae, and Papillomaviridae.
2. RNA Viruses: RNA viruses contain RNA as their genetic material and are further classified into positive-sense RNA viruses (e.g., Picornaviridae, Flaviviridae), negative-sense RNA viruses (e.g., Paramyxoviridae, Orthomyxoviridae), and double-stranded RNA viruses (e.g., Reoviridae).
3. Retroviruses: Retroviruses contain RNA as their genetic material but replicate through a reverse transcription process to produce DNA. Examples include Human Immunodeficiency Virus (HIV) and Human T-cell Leukemia Virus (HTLV).

Examples of Viruses:

1. Influenza Virus: The influenza virus belongs to the Orthomyxoviridae family and is responsible for seasonal flu outbreaks worldwide. It exhibits high mutation rates, leading to the emergence of new strains and the need for annual vaccination.
2. Human Immunodeficiency Virus (HIV): HIV is a retrovirus that causes Acquired Immunodeficiency Syndrome (AIDS), a condition characterized by the progressive weakening of the immune system. Despite advances in treatment, HIV/AIDS remains a significant global health challenge.
3. Herpes Simplex Virus (HSV): HSV belongs to the Herpesviridae family and is responsible for oral and genital herpes infections. It establishes latent infections in nerve cells, leading to recurrent outbreaks of painful sores.
4. Hepatitis B Virus (HBV): HBV is a DNA virus that infects the liver, causing acute and chronic hepatitis. It is transmitted through contact with infected blood or bodily fluids and can lead to severe liver damage, including cirrhosis and liver cancer.
5. Ebola Virus: Ebola virus belongs to the Filoviridae family and causes severe hemorrhagic fever in humans and non-human primates. It is transmitted through direct contact with infected bodily fluids and has a high mortality rate during outbreaks.

Viroids

Viroids are intriguing entities in the realm of microbiology, representing a unique group of infectious agents with a minimalistic structure and significant implications for plant health and agriculture.

Salient Features of Viroids:

1. Minimalistic Structure: Viroids are small, circular RNA molecules that lack a protein coat (capsid). They typically range in size from a few hundred to over a thousand nucleotides and are among the smallest infectious agents known to science.
2. No Protein Coding Capacity: Unlike viruses, viroids do not encode any proteins and rely entirely on host cellular machinery for replication and propagation. They contain a single-stranded RNA genome that folds into complex secondary structures critical for their biological activity.
3. Pathogenic Potential: Viroids are pathogens of plants, causing a variety of diseases characterized by stunting, leaf curling, yellowing, and necrosis. They infect a wide range of plant species, including crop plants such as potatoes, tomatoes, citrus, and avocado, leading to significant economic losses in agriculture.
4. Mechanism of Infection: Viroids enter plant cells through wounds or natural openings and replicate in the nucleus or chloroplasts using host enzymes. They induce changes in gene expression, disrupt cellular processes, and trigger immune responses in infected plants.

Classification of Viroids:

Viroids are classified into two families based on their structure, sequence homology, and host range:

1. Pospiviroidae: This family includes viroids with a rod-like secondary structure and conserved central regions. Examples of pospiviroids include Potato spindle tuber viroid (PSTVd) and Tomato chlorotic dwarf viroid (TCDVd).
2. Avsunviroidae: Avsunviroids have a branched secondary structure with conserved central regions and variable terminal regions. The type species in this family is Avocado sunblotch viroid (ASBVd).

Examples of Viroids:

1. Potato Spindle Tuber Viroid (PSTVd): PSTVd is one of the best-characterized viroids and causes spindle tuber disease in potatoes. It is transmitted through infected tubers and leads to reduced yields and tuber quality.
2. Citrus Exocortis Viroid (CEVd): CEVd infects citrus trees and is responsible for citrus exocortis disease, characterized by stunted growth, bark scaling, and reduced fruit yield. It is transmitted through grafting and mechanical contact.
3. Tomato Chlorotic Dwarf Viroid (TCDVd): TCDVd infects tomato plants and causes chlorotic dwarfism, leaf curling, and reduced fruit size. It is transmitted through mechanical contact and seed transmission.
4. Apple Scar Skin Viroid (ASSVd): ASSVd infects apple trees and leads to the development of scarred lesions on fruit skins, reducing their marketability. It is transmitted through infected budwood and grafting.
5. Hop Stunt Viroid (HSVd): HSVd infects hop plants and causes stunting, chlorosis, and reduction in cone production. It is transmitted through infected plant material and contributes to economic losses in the hop industry.

The biological classification taxonomy serves as a foundational tool in our exploration and understanding of the intricate web of life on Earth. By systematically organizing and categorizing living organisms based on their shared characteristics and evolutionary relationships, taxonomy provides a roadmap for navigating the complexities of biodiversity.

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