What is Living?

• Biology is the science of life forms and living processes
• The living world comprises an amazing diversity of living organisms

What is ‘Living’?

• Living beings are characterized by attributes like growth, reproduction, metabolism, ability to sense environment, and self-organize
• Growth, reproduction, and ability to sense environment are exhibited by living beings.
• Growth, reproduction, and metabolism cannot be regarded as defining features of life because non-living objects can also 'grow' by accumulation of material on the surface.
• Reproduction is also not seen in infertile humans, mules, sterile worker bees and hence cannot be regarded as defining features of life
• Metabolism, cellular organization, consciousness and interactions are defining properties of living organisms
• All living phenomena are due to underlying interactions. Properties of tissues are not present in the constituent cells but arise as a result of interactions among the constituent cells.
• Life is defined as the sum total of all metabolic activities occurring inside a living organism

Diversity in the Living World

• Biodiversity refers to the variety of living organisms present on Earth
• Nomenclature is the standardized process of naming living organisms, ensuring each organism has a unique and universal name.
• Identification involves accurately recognizing the characteristics of an organism and matching it with existing classifications.
• Binomial nomenclature, proposed by Carolus Linnaeus, assigns each organism a scientific name composed of two words: the genus and the specific epithet.
• Taxonomic categories form a hierarchical classification system, including kingdom, phylum/division, class, order, family, genus, and species.

Taxonomic Categories

• Taxonomy is the science of classification
• Systematics considers evolutionary relationships between organisms

Species

• Species are a group of individual organisms with similar characteristics and can interbreed to produce fertile offspring.
• For example, Mangifera indica (mango), Solanum tuberosum (potato), and Panthera leo (lion). All the three names, indica, tuberosum and leo, represent the specific epithets, while the first words Mangifera, Solanum and Panthera are genera.

Genus

• A genus comprises a group of related species that share common ancestry.
• For example, Panthera includes lion (Panthera leo), leopard (P. pardus), and tiger (P. tigris). Solanum includes species like nigrum and melongena.

Family

• Families are categories defined by a group of related genera (plural of genus), sharing several common characteristics.
• For example, the family Solanaceae includes the genera Solanum, Petunia, and Datura. In animals, for example, the genus Panthera, comprising lion, tiger, leopard is put along with genus Felis (cats) in the family Felidae.

Order

• Order: An order is an assemblage of families exhibiting a few similar characteristics.
• For example, the order Polymoniales includes the families Convolvulaceae and Solanaceae
• The animal order Carnivora, includes families like Felidae and Canidae.

Class

• Class: Class is a category comprising one or more related orders.
• For example, the class Mammalia includes the orders Primata and Carnivora.

Phylum or Division

• Phylum or Division: Phylum (in animals) and division (in plants) are categories comprising one or more related classes.
• For example, the phylum Chordata includes the class Mammalia, Aves, Reptilia, and Amphibia.

Kingdom

• Kingdom is the highest taxonomic category
• All plants are included in the kingdom Plantae.
• All animals are included in the kingdom Animalia.

Taxonomic Aids

• Taxonomic aids are tools and methods used to identify and classify organisms.
• Herbarium is a collection of preserved plant specimens, that are dried, pressed, and mounted on sheets, arranged according to a recognized classification system, and serve as reference material.
• Botanical gardens are specialized gardens that have collections of living plants for reference, identification, and study.
• Museum have collections of preserved plant and animal specimens for study and reference. Specimens are often preserved in formalin or other chemical preservatives.
• Zoological parks are facilities where wild animals are kept in protected environments under human care, enabling the study of their behavior and ecology.
• Key is a taxonomic aid used for identification of plants and animals based on similarities and dissimilarities. The keys are based on the contrasting characters generally in a pair called couplet. Each statement in the key is called lead.
• Flora provides information about plants found in a particular area
• Manuals contain information for identification of names of species found in an area.
• Monographs contain comprehensive accounts of a single taxon.