Classification of Living Things

Taxonomy is the branch of science concerned with classification, specifically of organisms. The term comes from Greek 'taxis' (arrangement) and 'nomia' (method). Astronomy studies celestial bodies, and anatomy deals with body structure.

In biological classification hierarchy, the order is: species → genus → family → order → class → phylum → kingdom. A group of related families makes an order, just as related genera make a family.

In biological classification, different classes with common characteristics constitute a phylum in animals or division in plants. The phylum is a high-ranking taxonomic rank below kingdom.

Species is the fundamental unit of biological classification. A species is a group of organisms that can interbreed and produce fertile offspring, representing the most specific level in the taxonomic hierarchy.

  Viruses and euglena are the organisms of doubtful classification.

Cryptogams are flowerless and seedless plants that reproduce via spores. The term comes from Greek 'crypto' (hidden) and 'gamos' (marriage), referring to their hidden reproduction. They include algae, fungi, bryophytes, and pteridophytes.

Dicotyledons (dicots) are plants with two seed leaves (cotyledons) in their embryos. This distinguishes them from monocotyledons (monocots) which have only one seed leaf. Common examples include beans, peas, and most trees.

The three main groups of cryptogams (flowerless, seedless plants) are Thallophyta (simple plants like algae), Bryophyta (mosses and liverworts), and Pteridophyta (ferns). They all reproduce via spores rather than seeds.

Spermatophyta (seed-bearing plants) are divided into two major groups: Gymnosperms (naked seeds like conifers) and Angiosperms (covered seeds in flowering plants). Angiosperms are the more advanced and diverse group.

The calyx is the collective term for all sepals of a flower. Sepals are the outermost whorl of flower parts, typically green and leaf-like, protecting the flower bud. The corolla is the petals, carpel is the female part, and stamen is the male part.

Perennials are plants that live for more than two years, flowering and producing seeds multiple times. Mango trees and pine trees are classic examples of long-lived perennials, while mustard, sunflower, carrot, and radish are typically annuals or biennials.

Bryophytes like mosses and liverworts bear spores in capsules called sporangia. These spore-containing capsules are a distinguishing feature of non-vascular plants. Cycas and Nephrolepis are vascular plants, while lichen and mushroom are fungi.

Evergreen trees retain their leaves throughout the year and maintain foliage in all seasons, unlike deciduous trees which shed leaves annually. Pine and guava are classic examples that stay green regardless of season.

Bryophytes such as mosses and liverworts possess rhizoids that resemble roots but lack true vascular tissues, earning them the description of having false roots. These are among the simplest non-vascular plants.

Lichens are composite organisms formed from a symbiotic partnership between fungus and algae (or cyanobacteria). The fungal partner provides structure while the photosynthetic partner produces food through photosynthesis.

In botanical terminology, leaves that emerge directly from the root-stock or ground level are called radical leaves (radicals). These form a basal rosette at the plant's base rather than growing on an elevated stem.

Sunflowers are classic annual plants - they complete their entire life cycle in one growing season. They germinate, grow, flower, produce seeds, and die within a single year. Mango is a perennial tree, while carrot and radish are typically biennials (though some radish varieties can be annual).

Shrubs are woody perennial plants typically growing 10-15 feet tall, intermediate between herbs (soft-stemmed) and trees (much taller). They have multiple stems arising from the base rather than a single trunk.

 Monocot roots are characterised by the absence of cambium.

Pollination is the transfer of pollen grains from the male anther to the female stigma, enabling fertilization. This can occur within the same flower (self-pollination) or between flowers (cross-pollination). It is distinct from fertilization (fusion of gametes) and photosynthesis.

In biological classification hierarchy, kingdom is the highest and most comprehensive category. All phyla (for animals) or divisions (for plants) are grouped into kingdoms. The hierarchy from broadest to most specific is: Kingdom > Phylum/Division > Class > Order > Family > Genus > Species.

Gymnosperms are classified into cycadales and coniferales.

The plant kingdom is traditionally divided into two main groups: cryptogams (plants with hidden reproductive structures like algae, fungi, bryophytes, pteridophytes) and phanerogams (plants with visible reproductive structures). Phanerogams include gymnosperms and angiosperms (also called spermatophyta).

 Angiosperms are further divided based on the number of cotyledons that form the seed.

A genus is a taxonomic category that groups species sharing similar characteristics, especially in their reproductive organs. Species within the same genus are closely related and can often hybridize. Genus ranks above species but below family in the classification hierarchy.