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Q. What are the classifications of living organisms?
Ans. Living organisms are classified into five main kingdoms: Monera, Protista, Fungi, Plantae, and Animalia, based on characteristics such as cell structure, mode of nutrition, and reproduction.
Q. Who introduced the classification of living things?
Ans. Carl Linnaeus, a Swedish botanist, introduced the classification of living things in a systematic way, laying the foundation for modern taxonomy.
Q. What is the classification of living things?
Ans. The classification of living things organizes organisms into hierarchical categories based on shared traits. The primary levels include Domain, Kingdom, Phylum, Class, Order, Family, Genus, and Species.
Q. What are the 7 categories of biological classification?
Ans. The 7 primary categories are Kingdom, Phylum, Class, Order, Family, Genus, and Species, arranged from the most general to the most specific.
Q. Who is the father of taxonomy?
Ans. Carl Linnaeus is known as the father of taxonomy for his development of a formal system for classifying organisms.
Classification of Living Organisms, Definition, Levels, and Kingdoms
Classification of Living Organisms, This article aims to provide a detailed article on the classification of living organisms including two and five kingdom systems.
Krati Saraswat4 Jun, 2025
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Classification of living organisms is a key concept in biology, helping students understand the diversity of life forms on Earth. By organizing species into groups based on shared characteristics, classification makes it easier to study and understand complex relationships between organisms. For the NEET Exam , classification is an important topic as it provides a foundational understanding of biological diversity, essential for both theoretical and practical applications in biology .
Definition of Classification of Living Organisms
Classification is the process of organizing living organisms into categories based on their similarities and differences. This scientific grouping helps biologists systematically study various organisms, making it easier to identify, name, and understand their evolutionary relationships. Classification also helps in understanding how different species interact with each other and adapt to their environments.
Levels of Classification (Taxonomic Hierarchy)
Classification follows a taxonomic hierarchy, which organizes organisms from the most general level to the most specific. Here are the main taxonomic ranks:
Kingdom: The broadest level, grouping organisms into large categories, such as plants and animals.
Phylum: Divides kingdoms into groups based on major body plans or structural similarities.
Class : Groups organisms within each phylum based on additional features (e.g., mammals in the animal kingdom).
Order: Classifies organisms within each class into smaller groups.
Family: A group within each order that includes related genera (plural of genus).
Genus : Groups of species that are closely related and share similar characteristics.
Species : The most specific level, refers to individual organisms that can breed and produce fertile offspring.
Two-Kingdom Classification
The Two-Kingdom Classification System was introduced by Carl Linnaeus, a Swedish botanist, who categorized all living organisms into two main kingdoms: Kingdom Plantae and Kingdom Animalia. This classification system was a significant advancement for its time, though it had limitations that later led to the development of more comprehensive systems.
Kingdom Plantae : This kingdom includes organisms that are primarily autotrophic (able to produce their own food via photosynthesis ) and have a cell wall.
Examples : Mosses, ferns, algae, and flowering plants.
Kingdom Animalia: This kingdom consists of heterotrophic organisms (those that obtain food by consuming other organisms) and lacks a cell wall.
Examples : Mammals, birds, insects, and fish.
Five-Kingdom Classification
The Five-Kingdom Classification system, introduced by Robert Whittaker in 1969, divides life into five main kingdoms based on cell structure, mode of nutrition, and other characteristics. This system includes Monera, Protista, Fungi, Plantae, and Animalia, covering both prokaryotic and eukaryotic life forms.
Kingdom Monera
Kingdom Monera includes all prokaryotic organisms, which are single-celled organisms that lack a true nucleus and membrane-bound organelles. The sole members of this kingdom are bacteria, making them the simplest and most abundant microorganisms on Earth. General Characteristics of Kingdom Monera
Cell Wall Composition : Most members of Monera have a cell wall made of peptidoglycan, with some exceptions like archaea and mycoplasma that lack this structure.
Genetic Material : The genetic material in Monera is in the form of naked DNA without a nuclear envelope.
Organelles : All membrane-bound organelles, such as mitochondria, chloroplasts, and the endoplasmic reticulum, are absent.
Ribosomes : Bacteria contain 70S ribosomes, which are smaller than those found in eukaryotic cells.
Respiration : Since mitochondria are absent, respiratory enzymes are associated with the plasma membrane in structures called mesosomes.
Nutrition: Bacteria can be either autotrophic (making their own food through chemosynthesis or photosynthesis) or heterotrophic (obtaining food from other sources, either as saprophytes or parasites).
Reproduction : Bacteria reproduce asexually, typically through binary fission. Though there is no true sexual reproduction, bacteria can exchange genetic material through processes like conjugation or transduction.
Types of Bacteria Based on Shape Bacteria in Kingdom Monera are categorized based on their shape:
Coccus (pl. Cocci) – These are spherical-shaped bacteria. Example: Streptococcus
Bacillus (pl. Bacilli) – These bacteria have a rod-shaped structure. Example: Escherichia coli (E. coli)
Spirillum (pl. Spirilla) – These are spiral-shaped bacteria. Example: Spirillum volutans
Vibrio (pl. Vibrios) – These bacteria have a comma shape. Example: Vibrio cholerae
Kingdom Protista
Kingdom Protista comprises unicellular eukaryotic organisms, which means that they possess a true nucleus and membrane-bound organelles, unlike prokaryotes. This kingdom is diverse and includes organisms that display a mix of characteristics similar to plants, animals, and fungi, making it a crucial link between these kingdoms. General Characteristics of Kingdom Protista
Unicellular Eukaryotes : All members of Protista are unicellular, meaning they consist of only one cell, but they are eukaryotic with a well-defined nucleus and other membrane-bound organelles.
Unclear Boundaries: The boundaries of this kingdom are not well-defined because Protista includes a wide range of organisms with varying characteristics, making it a complex and diverse group.
Aquatic Habitat: Most protists are primarily aquatic, living in water bodies such as ponds, lakes, and oceans. They can also be found in moist environments.
Link to Other Kingdoms: Kingdom Protista acts as a link between other kingdoms, sharing traits with plants, animals, and fungi. Some protists have plant-like chloroplasts for photosynthesis, while others show animal-like mobility and feeding habits.
Locomotion : Protists exhibit various methods of locomotion, moving with the help of structures like flagella, cilia, or pseudopodia (false feet).
Reproduction: Protists reproduce both asexually (through simple cell division) and sexually. Sexual reproduction in protists involves cell fusion and the formation of a zygote, leading to genetic variation among offspring.
Kingdom Fungi
Kingdom Fungi consist of a unique group of heterotrophic organisms that cannot make their own food. Unlike plants, fungi lack chloroplasts and rely on external sources of organic matter for nutrition. Fungi display remarkable diversity in both form and habitat, occupying various environments across the globe. General Characteristics of Kingdom Fungi
Heterotrophic Nutrition: Fungi are heterotrophs , which means they depend on other organisms or organic matter for their nutrients. They absorb nutrients from dead organic material or live as parasites on other living organisms.
Morphology and Habitat : Fungi exhibit a wide range of morphological forms and can be found in diverse habitats. They are cosmopolitan, meaning they can live almost anywhere, from soil and water to surfaces like leather, wood, and bread, especially in warm and humid environments. Some fungi are parasitic, living on plants, animals, and even in the human body.
Structure : With the exception of yeasts, which are unicellular, most fungi are filamentous. They consist of hyphae — long, slender thread-like structures that form a network called mycelium.
Cell Wall Composition : The cell wall of fungi is made of chitin and polysaccharides, providing them structural support and protection.
Types of Fungi Based on Nutrition Source: Saprophytic Fungi, Parasitic Fungi, and Symbiotic Fungi.
Kingdom Plantae
Kingdom Plantae comprises eukaryotic, chlorophyll-containing organisms that are commonly known as plants. This kingdom includes a wide variety of organisms, from tiny algae to massive trees, all of which play a crucial role in the Earth's ecosystems by producing oxygen and serving as a primary food source for various life forms. General Characteristics of Kingdom Plantae
Eukaryotic and Photosynthetic: Plants are eukaryotic organisms, meaning they have a well-defined nucleus and membrane-bound organelles. They contain chlorophyll, which allows them to carry out photosynthesis and produce their own food.
Cell Structure : Plant cells have prominent chloroplasts that house chlorophyll for photosynthesis. They also possess a cell wall, primarily made of cellulose, which gives the cells structural support and rigidity.
Diverse Groups : Kingdom Plantae includes several groups of plants, such as: Algae, Bryophytes, Pteridophytes, Gymnosperms, and Angiosperms.
Kingdom Animalia
Kingdom Animalia includes multicellular, heterotrophic eukaryotes commonly known as animals. These organisms display a vast array of forms, sizes, and behaviors, ranging from simple invertebrates like sponges to complex mammals, including humans.
General Characteristics of Kingdom Animalia
Multicellular and Eukaryotic: Animals are multicellular eukaryotic organisms, meaning they consist of multiple cells with a well-defined nucleus and other membrane-bound organelles.
Absence of Cell Walls: Unlike plants and fungi, animal cells lack cell walls. This feature contributes to their flexibility and mobility.
Heterotrophic Nutrition : Animals are heterotrophic, meaning they cannot produce their own food and must obtain it by consuming other organisms, directly or indirectly relying on plants.
Holozoic Mode of Nutrition : Animals typically consume solid food through ingestion, a form of nutrition known as holozoic nutrition. They digest their food in an internal cavity and store reserves in the form of glycogen or fat.
Locomotion: Most animals are capable of movement at some stage of their lives, enabling them to find food, escape predators, and seek mates.
Sexual Reproduction : Reproduction in animals is primarily sexual, involving the union of male and female gametes, leading to embryological development in higher organisms. This process involves distinct stages, from fertilization to the development of the organism’s adult form.
MCQs of Classification of Living Organisms
Q1. A kingdom system of classification was given by _____ in _____.
Whittaker, 1822
Aristotle, 1969
Aristotle, 1822
Whittaker, 1969
Q2. The kingdom system of classification suggested by R.H. Whittaker is NOT based on; (2014)
complexity of body organization.
the presence or absence of a well-defined nucleus.
mode of reproduction.
mode of nutrition.
Q3. The kingdom present in both two kingdoms & five-kingdom system of classification is;
Protista
Monera
Fungi
Plantae
Answers of MCQs of Classification of Living Organisms
Ans1 . Whittaker, 1969, Ans2. Presence or absence of a well-defined nucleus., Ans3 . Plantae Physics Wallah (PW) offers the Best NEET Online Coaching in India, designed to make quality education accessible to all aspiring medical students.
