Explain – Biological Classification (NCERT Class 11 Chapter 2 Biological Classification).
The living world is a complex network of interconnected organisms that engage in metabolism, reproduction, and response to environmental cues. We are aware of how intricately connected everything in the living world is. The diversity of living forms on earth gives it a wonderful environment to liveRead more
The living world is a complex network of interconnected organisms that engage in metabolism, reproduction, and response to environmental cues. We are aware of how intricately connected everything in the living world is. The diversity of living forms on earth gives it a wonderful environment to live and thrive. The abundance of diversity suggests the presence of numerous species with unique characteristics. The fact that an organism is either a living thing or a non-living entity is its most striking characteristic. As a result, in order to distinguish between a living item and a non-living one, we first need to define what a “living being” actually is.
What is ‘Living’?
Any organism that breathes and moves is considered ‘Living’. Any life form that exhibits or possesses the qualities of life or being alive is referred to as a living thing. The basic traits include having an organized structure, requiring energy, reacting to stimuli and changing their surroundings, and having the ability to reproduce, grow, move, metabolize, and die. The three Domains that make up the current classification of living things are Bacteria, Archaea, and Eucarya.
Characteristics of Living World
All living organisms grow and increase in mass and number of individuals. Growth, reproduction, ability to sense the environment and mount a suitable response is unique features of living organisms. Given below are some characteristic features of the Living world:
Respiration
- Aerobic respiration: Aerobic respiration is a chemical process in which oxygen is used to make energy from sugars. Aerobic respiration is also known as aerobic metabolism and cell respiration.
- Anaerobic respiration: Anaerobic respiration takes place in the absence of oxygen. examples include alcohol fermentation and lactic acid fermentation.
Nutrition
- Autotrophic Nutrition: It is a type of nutrition in which plants make their own food .they are interdependent on themselves. example- plants. Autotrophic nutrition is of two types: phototrophic, and chemotrophic.
- Heterotrophic Nutrition: It is a type of nutrition in which an organism is dependent on another organism for food. example -humans. Heterotrophic nutrition is of three types: herbivorous, carnivorous, and omnivorous.
Excretion
The process of moving out waste material from the body is known as excretion.
Locomotion/Movement
Locomotion is a term used to describe a movement of an organism from one place to another.
Reproduction
- Asexual Reproduction: A process where a single gamete is responsible for reproduction to take place i.e., new offspring is produced from a single parent. Examples: hydra and paramecium.
- Sexual Reproduction: Process where both the gametes take part in reproduction. Examples: fishes, and mammals.
Structural Organisation
- Unicellular: It is also known as a single-celled organism and only single cells perform all the functions needed for an organism to live. example- protozoa and Protista.
- Multicellular: Multicellular organisms consist of many cells to perform different functions. example-Dogs, cows.
Diversity
A large variety of anything is known as diversity. Diversity is a vast term to include different species, genes, and ecosystem levels. Thomas Lovejoy introduced the term biological diversity in 1980.
Biodiversity
A large variety of organisms or terms used to refer to the number of varieties of plants and animals on earth is termed biodiversity. there are three types of biodiversity: genetic, species, and ecological diversity. There are over 15 Lakh species in the world of which 10 Lakh are animals(8 Lakh of insects and 2 Lakh of others) and 5 Lakh of plants.
Nomenclature
The scientific naming of organisms is known as nomenclature. Nomenclature is defined as the language of sculpture. The scientific name of mango is written as Mangifera indica.
Rules of Nomenclature
- Latinised names are used.
- The first word represents the genus and the second word is the species name.
- Printed in italics, if handwritten then underline separately.
- The first word starts with a capital letter while the species name is written in small letters.
ICBN International Code of Botanical Nomenclature (This is for giving scientific names to plants).
ICZN International Code of Zoological Nomenclature(This is for giving scientific names to animals).
Classification
Grouping organisms into categories on the basis of similarities and differences is known as classification. classification is the process by which anything is grouped into systematic categories based on some easily observable characteristics. For example, we easily recognize groups such as plants or animals, dogs or cats, insects, or reptiles.
Need of Classification
Classification is done to organize the vast number of plants and animals into categories that could be named, remembered, studied, and understood. classification avoids confusion among the different varieties of organisms. Moreover, it makes the study of organisms easier.
Given below are some scientist’s contributions to biology
- Carolus Linnaeus (Father of Taxonomy): He gives the 2 kingdoms system.
- Hackel: He gave the 3 kingdom systems.
- Copeland: He gave the 4 kingdom systems.
- R.H Whittaker: He gave the 5 kingdom system which is the popular one.
- Carl Woese: He gave the 6 kingdom system and is the latest.
Taxonomy
The study of principles and procedures of classification is termed taxonomy. Based on characteristics, all living organisms can be classified into different taxa. This process of classification is taxonomy.
Taxonomic Categories
A. P. Candolle is credited with coining the term “taxonomy,” which refers to the seven main taxonomic categories. It is the listing of categories from the top-most kingdom to the bottom-most species, either in ascending or declining orders. There are two kinds in the hierarchy: intermediate and mandatory. From kingdoms to species, Obligate is rigidly adhered to, yet Intermediate is the exact reverse.
- Species: The smallest and most fundamental distinction in classification is the species. It describes a population that is comparable in terms of form, shape, and reproductive characteristics. Similar reproductive characteristics can lead to the formation of fertile siblings.
- Genus: This is the grouping of a number of closely related species that share linked features and are thought to have shared ancestors. For instance, the genus Panthera is where the leopard and cat belong.
- Family: Families are associations of connected genera. The vegetative and reproductive characteristics are used to categorize the families. The Felidae family includes animals like tigers and lions as examples.
- Order: It is the combination of one or more common families, which is regarded as a higher category. Felidae family members participate in the Carnivora order.
- Class: A class designates a division in a phylum made up of one or more orders. All mammals, including gorillas, monkeys, humans, and gibbons, are included in the Mammalia class.
- Phylum: It contains a group of related classes. Mammalia, along with reptiles, fish, amphibians, and birds, make up the phylum Chordata.
- Kingdom: The highest taxonomic classification known as a kingdom is given to every animal that belongs to various phyla. The kingdom Animalia and Plantae encompasses all living things, including both plants and animals. A taxon is a classification that identifies an organismal group based on external characteristics.
FAQs on Living World
Q1: Define the following terms: Phylum, and Class.
Answer:
- Phylum– Classes comprising animals like fishes, amphibians, reptiles, and birds along with mammals constitute the higher category called phylum. All these, based on the common features like the presence of notochord and dorsal hollow neural system, are included in phylum Chordata.
- Class– This category includes related orders. For example- the order primate comprising monkey, gorilla, and gibbon is placed in class Mammalia along with the order Carnivora which includes animals like tiger, cat, and dog.
Q2: How is a key helpful in the identification and classification of organisms?
Answer:
The key is defined as the taxonomical aid used to identify and classify plants and animals based on their similarities and differences. Keys are generally analytical in nature.
Q3: Define a taxon.
Answer:
Taxon is plural of taxa, it is the taxonomic unit of any rank. ARISTOTLE is known as the father of taxonomy.
Q4: Why are living organisms classified?
Answer:
See lessLiving organism are classified due to the following reasons:
- To make study of organism easy.
- To avoid confusion.
- To learn the interrelationship among the various organisms.
Notes for NCERT Class 11 Chapter 2 Biological Classification: Biological classification is the process by which biologists group living organisms which, are classified on the basis of their similarity. Classification is essential for the convenient study of living organisms. It is required to identiRead more
Notes for NCERT Class 11 Chapter 2 Biological Classification: Biological classification is the process by which biologists group living organisms which, are classified on the basis of their similarity. Classification is essential for the convenient study of living organisms. It is required to identify different varieties of organisms. It helps in the correct identification of many organisms. It leads to the evolution of organisms. It also establishes phylogenetic relationships among organisms. Carolus Linneuas was one of the scientists to classify organisms.
NCERT Class 11 Biology Chapter 02 Biological Classification: The practice of classifying organisms based on shared characteristics is known as biological classification. Linnaeus proposed two areas of classification. He divided organisms into two kingdoms: the animal kingdom (Animalia) and the plant kingdom (Plantae). The classification of the two kingdoms had some disadvantages, such as the impossibility of distinguishing between eukaryotes and prokaryotes, unicellular and multicellular species, and photosynthetic and non-photosynthetic organisms. As a result, the field continued to grow and served as a primary example of R.H. Whittaker’s classification of the five domains or kingdoms.
Biological Classification
Two Kingdom Classification
Two kingdom classification was given by a biologist, Carolus Linnaeus. He classified organisms into two kingdoms, i.e. Plantae (included all plants) and Animalia (included all animals).
Disadvantages of Two Kingdom Classification
This system didn’t distinguish between the following types of organisms-
Five Kingdom Classification
In 1969, R.H. Whittaker proposed the five-kingdom classification. He classified those five kingdoms as Monera, Protista, Fungi, Plantae, and Animalia. He primarily used the following criteria for classification:
Kingdom Monera
Bacteria are the main members of this kingdom. Kingdom Monera is further divided into:
Archaebacteria
They are special bacteria as they can withstand extreme environmental conditions because of their different cell wall structure. They can be:
Eubacteria or True Bacteria
They have rigid cell walls and flagellum (locomotion), if motile. They can be photosynthetic autotrophs, chemosynthetic autotrophs and heterotrophs.
Heterocyst
Reproduction in Bacteria
They reproduce by asexual mode- binary fission, sexual mode- transfer of DNA and spore formation in unfavourable conditions.
Mycoplasma
They are the smallest organisms which lack cell walls. They can survive in the absence of oxygen (anaerobic). They cause diseases (pathogens).
Kingdom Protista
They are single-celled eukaryotes. They include:
plasmodium differentiates and forms fruiting bodies (spores inside)
Types of Protozoans and their Features/ Diseases Caused
Kingdom Fungi
Fungi are multicellular and the how heterotrophic mode of nutrition (saprophytes/parasites/symbiotic- mycorrhiza). Some fungi are unicellular, e.g. yeast.
Some Useful Fungi
Mushrooms and yeast are the most valuable fungi. Mushrooms are edible and are a good source of proteins. Yeast is used to make bread and cheese. Penicillium fungi are used to produce antibiotics.
Some Harmful Fungi
Some fungi cause diseases in both plants and animals, e.g. wheat rust disease is caused by Puccinia fungus.
Reproduction in Fungi
There are three modes of reproduction in fungi, i.e. vegetative, asexual and sexual.
Stages of Sexual Reproduction in Fungi
In ascomycetes and basidiomycetes, the dikaryotic stage (n + n, i.e., two nuclei per cell) is formed, known as dikaryon and the phase is dikaryophase.
Four Major Groups of Fungi
mould fungi) and Albugo (parasitic fungi
on mustard)
fungus), Mushrooms, bracket fungi, puffballs
Kingdom Plantae
All eukaryotic organisms that contain chlorophyll, usually known as plants, are classified as Plantae. A few species, like parasites and plants that feed on insects, are partially heterotrophic. Insectivorous plants include bladderwort and Venus fly traps, and parasites like Cuscuta feed on them. The eukaryotic structure of plant cells has large chloroplasts and a cell wall comprised primarily of cellulose. Algae, bryophytes, pteridophytes, gymnosperms, and angiosperms are all part of the plant kingdom.
Alternation of Generation
The haploid gametophytic and the diploid sporophytic phases of a plant’s life cycle alternate with one another. Various plant families have different haploid and diploid phase lengths and whether they are independent or reliant on others.
Kingdom Animalia
They are multicellular and heterotrophic (show the holozoic mode of nutrition) eukaryotes. They lack cell walls. Almost, all the animals show locomotion. Sexual reproduction occurs by the fusion of male and female gametes which give rise to an embryo followed by repeated cell divisions.
Viruses, Viroids, Prions And Lichens
The differences between viruses, viroids and prions are given below:
Bacteriophage
Bacteriophages are also known as phages. These are the viruses which infect and replicate in the bacterial cells.
Tobacco Mosaic Virus
The tobacco mosaic virus (TMV) consists of single-stranded RNA. It infects tobacco plants and members of the family Solanaceae. The infection can cause some patterns like a mosaic, which shows mottling and discolouration on the surface of the leaves.
Lichens
The close association of fungus and algae form lichens. They are found in a pollution-free environment. Lichens are used in deodorant, pH papers, insense-sticks, toothpaste and perfumes. The fungal component is known as mycobiont and the algal component is known as phycobiont.
FAQs on Biological Classification
Q1: What are the Commercial Applications for Heterotrophic Bacteria and Archaea?
Answer:
Q2: Write Some Plant like and Animal-like Features of Euglena.
Answer:
Q3: What Function Do Fungi Play in Our Daily Lives?
Answer:
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