The Living World: Composition, Characteristics & Taxonomy

The living world is a diversity of living organisms which are made of inorganic and organic matter. The main components of the living world are organic and inorganic substances. 

• The living world contains all kinds of life, plants and animals that we may or may not see. 
• Organic matter includes amino acids, proteins, lipids, etc. 
• Inorganic materials include water and minerals. 
• Living things have many characteristics, including the ability to grow and reproduce. 
• Mammals are one of them. 
• Some living things live close to the surface of the water. 
• Since activities are mostly powered by sunlight, water, carbon dioxide and oxygen.
• The living world includes development, body-organization, adaptation and energy utilization.
• Organisms are named according to their functions.

Read More: The Living World: Important Questions

Key Terms: The Living World, Living Organisms, Biomolecules, Plants, Animals, Carbon Dioxide, Carbohydrates, Amino Acid, Proteins, Scientific Name, Genus, Species, Phylum, Family, Order, Phylogeny

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What is Living?

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Living is a form of breathing and movement cycle in an organism. There are millions of organisms living on Earth, which vary from place to place. An organism that possesses the characteristics of being alive is known as a living thing.

• The organisms are capable of eating, breathing, growing and moving.
• It includes an organized structure and required energy level.
• Bacteria, Archaea, and Eucarya are three types of living organisms.
• Living possesses the characteristics of cellular organization and consciousness.

The Living World

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Composition of the Living World

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Living organisms are composed of a number of organic and inorganic biomolecules. The inorganic components include water and mineral substances, whereas, the organic substances include carbohydrates, amino acids, proteins, lipids, nucleic acids etc. 

Role of Water

The human body is comprised of 70-90% liquid water. It helps in many life processes. metabolic activities and no living entity is possible without water.

Role of Oxygen

Oxygen is compulsory for aerobic respiration to produce plenty of energy required for different metabolic activities.

Role of NaCl

The ionic forms of sodium chloride (Na, Cl) plays an important role in various metabolic activities of the body.

Role of Proteins

Proteins is very long chains of amino acid molecules that are connected by peptide bonds. They play an essential role in forming the physical structure of the organism. They will be broken down with the release of a huge amount of energy.

Role of Lipids

Lipids are polymers of alcohol and fatty acids in the organic world. They are fats and oils. They perform several functions in living systems.

Read More: Living World MCQs

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Characteristics of Living Organisms

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There are different characteristics of living organisms as mentioned below:

Reproduction

The organisms need to grow and reproduce to form new offspring for the continuity of species. This is possible through both asexual and sexual reproduction. It increases the number of cells. They are divided into two categories, which are as follows:

Sexual Reproduction

Sexual reproduction involves the mating of two organisms. The process is initiated when both the gametes take part in reproduction.

Asexual Reproduction

Asexual reproduction does not require the mating of two organisms. The newly reproduced offspring will possess the same DNA composition as the parent organisms.

Reproduction

Read More: Principles of Inheritance and Variation

Growth and Adaptation

Living organisms grow and adapt to their surrounding environments. To survive in a new environment with favourable and unfavourable factors, the organisms must adapt to their surroundings.

• The unfavourable factors are water deficiency, soil nutrient availability and soil and water pH level.
• It results in the increase of mass and number of cells.
• In the case of plants, the process of cell division takes place throughout their life.

Homeostasis

In living systems, the maintenance and control of internal states are required by a process called homeostasis. This involves balancing the internal pH level, temperature and water quantity. 

• The term was coined by French physiologist Clause Bernard.
• It offers resistance to the external environment, which is essential for the survival of all living organisms.
• Receptor, Control center, and Effector are three components of Homeostasis.

Read More: Chromosome Theory of Inheritance

Respiration

All living organisms need respiration. In this process, energy is released from the breaking down of food. This energy is useful in growth and development. 

• Respiration transfers oxygen to the outside environment to cells in the tissues.
• It is a biological process that eliminates the need for carbon dioxide.

Respiration is divided into two categories, which are as follows:

Aerobic Respiration

Aerobic respiration is a type of respiration in which oxygen is used to make energy for living organisms. It is also known as aerobic metabolism and involves the breaking of glucose into carbon dioxide.

Anaerobic Respiration

Anaerobic respiration is a type of respiration that takes place in the absence of oxygen. It involves breaking of glucose into into ethyl alcohol, carbon dioxide and energy.

Read More: Multicellular Organisms

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Nomenclature

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The plants and animals are known by their local or vernacular names. The names vary from place to place within a country. This creates confusion in identifying and studying different species.

• Therefore, it must be called by its scientific name.
• The process of giving scientific names to an organisms is called nomenclature.
• It is given universally with a genus and a species name. 

Advancement of Systems of Classification

Scientific study is an ever-going process. New species and organisms are often discovered and added. The primitive classification system was based on organisms' habits and habitat. 

• Later, external morphology became a basis for the category. 
• After this, the external morphology and seed embryology are taken into account.
• It is followed by the phylogenetic (hereditary) relationship and the cell biology of the organism. 
• Modern-day uses of biochemical and other techniques classify organisms based on their nucleic acid components and other macromolecules.

Read More: Botanical Name and Biological Classification

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Diversity in the Living World

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Diversity is defined as the measure of the range of certain features within the required population set. It is based on intra-population interactions and environmental factors.

• It includes species, genes, and ecosystem levels. 
• The term was introduced by Thomas Lovejoy in 1980.
• The different types of plants and animals living on Earth are known as biodiversity.
• Ecological, genetic, and species diversity are three types of diversity.
• It is based on the distribution of attributes based on the population of interest.

Diversity in the Living World

Read More: Morphology of Flowering Plants

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Taxonomy

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A taxonomy is the level of hierarchy in the system of classifying living organisms. A. P. Candolle was the person behind the creation of the term taxonomy. In this, organisms are arranged on the basis of their characteristic.

• Taxonomy is based on behavioural, genetic and biochemical variations. 
• It includes the study of nomenclature, classification, history and identification.
• Carolus Linnaeus is called the father of taxonomy.

Taxonomy is divided into various categories, which are as follows:

Phylum

It is a taxonomical hierarchy below Kingdom and above class. It is a taxon with classes of organisms with similar features.

Read More: Animal Morphology

Class

Class is a taxonomical hierarchy higher than Order and lower than Phylum. Class includes related orders of similar organisms. Example: Presence of notochord in the body of mammals.

Family 

Family has a group of related genera with fewer similarities than genus and species. For example, fox and dog belong to the same family, Canidae. It is a group of organisms below Order and above Genus.

Order

Order is a taxon below higher than Family and lower than class. It is the group of families which exhibit a few similar features.

Genus

Genus comprises a group of related species with more features than species of other genera. For example, Lions, tigers, and leopards are classified under the genus Panthera (carnivores, cat family). It is above that of a species and below a family.

Kingdom

In this category, key is a taxonomic aid that can be used to identify organisms based on similarities and dissimilarities. It represents the choice between two opposite or contrasting characters. 

• This is useful for identifying contrasting characters of related organisms. 
• When there are two contrasting characters, species, family, or genera are identified. 
• If the organism is not recorded, efforts will be made to verify and reconsider its discovery before naming it. 
• Therefore, each organism will be classified as it is known or unknown.

Taxa at Hierarchical Level

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Things to Remember

• The living world is composed of inorganic and organic substances.
• External morphology became a base for classification.
• The living world includes seed embryology, phylogenetic (hereditary) relationships, and the cell biology of the organism.
• Class is a taxonomical hierarchy which is higher than Order and lower than Phylum.
• Order is a taxon below higher than Family and lower than class.
• There are many ranks in the organism's hierarchy, which are called taxa and taxonomic categories.