The Living World- NEET Biology Essential Notes

The Living World is the study of life and living organisms, their characteristics, and their interconnections within ecosystems. This chapter provides the foundation for understanding the diversity of life on Earth and how living organisms are classified and organised. Understanding the fundamental properties of life is crucial for students preparing for the NEET exam.

Key Features of Living Organisms

• Growth- The increase in size and complexity of an organism over time.

• Reproduction- The ability to produce offspring, ensuring the survival of species.

• Metabolism- Chemical reactions that occur within cells to maintain life.

• Sensation and Response to Stimuli- The ability to perceive environmental changes.

• Mortality- All living organisms have a life span, ending in death.

• Self-organisation- Organisms can maintain structure and function through regulation.

Huxley’s Protoplasmic Theory

The protoplasm is the physical basis of life. It is the site where all cellular processes occur, representing the living matter of cells.

Biodiversity- The Heart of The Living World

What is Biodiversity?

Biodiversity refers to the variety of life forms on Earth, from the smallest microorganisms to the largest mammals. It includes genetic diversity, species diversity, and ecosystem diversity. Biodiversity is essential for maintaining the balance of nature and the survival of ecosystems.

Classification of Living Organisms

Living organisms are categorised based on shared characteristics, which make it easier to understand and study the vast array of life forms. This process of classification involves

• Nomenclature- The system of naming organisms using scientific terms. Carolus Linnaeus introduced the binomial nomenclature system, which assigns each organism a two-part Latin name (e.g., Homo sapiens).

Rules of Nomenclature

1. Each organism has a two-word name, the genus and the species.

2. Scientific names are italicised in print and underlined when handwritten.

3. Latin is used for the scientific names, and the genus name begins with a capital letter, while the species name is lowercase.

• Taxonomy- This is the science of classifying organisms. Taxonomy involves the identification, nomenclature, and classification of living organisms based on their characteristics and evolutionary history.

• Systematics- The branch of biology that studies the evolutionary relationships among organisms. It involves organising life forms into a natural classification system.

Taxonomic Hierarchy- Organising Life Forms

Organisms are classified into a hierarchical structure known as the taxonomic ranks, from the broadest (Kingdom) to the most specific (Species). This system helps scientists organise and categorise organisms based on shared characteristics.

The taxonomic categories are as follows

• Kingdom- The highest rank in the classification system, which includes all organisms (e.g., Animalia, Plantae).

• Phylum/Division- A division in plants and a phylum in animals.

• Class- Groups related orders.

• Order- Groups related families.

• Family- Groups related genera.

• Genus- A group of closely related species.

• Species- The most specific level, which refers to individuals that can interbreed and produce fertile offspring.

Taxonomic Aids- Tools for Identification

Taxonomic aids are essential for identifying and classifying organisms accurately. Some common tools and methods include

• Herbarium- A collection of dried plant specimens that are mounted on sheets and used for reference in identifying plant species.

• Museum- A repository for preserved specimens of both plants and animals. Museums help in studying organisms and understanding biodiversity.

• Botanical Gardens- Collections of living plants used for identification and study. Plants are labeled with their scientific names, helping visitors learn about different species.

• Zoological Parks- Conservatories for animal species that offer opportunities to study wildlife behavior, conservation, and breeding.

• Keys- Dichotomous keys help identify organisms based on their characteristics by providing a series of choices.

Famous Figures in Taxonomy and Biology

Throughout history, many notable figures have contributed to the field of taxonomy and biology

• Carolus Linnaeus- Known as the Father of Taxonomy, he developed the system of binomial nomenclature.

• H. Santapau- The Father of Indian Taxonomy.

• William Roxburgh- Father of Indian Botany and Indian Herbaria.

• Lamarck- Proposed that species evolve based on environmental changes (the dynamic concept of species).

• A.P. de Candolle- Coined the term "taxonomy."

The Concept of Species in Biology

The term “species” refers to a group of organisms that can interbreed and produce fertile offspring. However, the concept of species is dynamic, meaning species can evolve and change over time due to various factors such as environmental pressures, mutations, and natural selection.

Types of Species

• Sympatric Species- Species that live in the same geographical area.

• Allopatric Species- Species that are geographically isolated from each other but may share a common ancestor.

• Monotypic Species- A species without any subspecies.

• Polytypic Species- A species that has multiple subspecies.

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