Samacheer Class 11 Bio Botany - Taxonomy and Systematic Botany

National botanical gardens play a multi-faceted and crucial role in conserving biodiversity. Firstly, they serve as living museums, maintaining extensive collections of diverse plant species, including rare, endangered, and endemic ones, thereby acting as ex-situ conservation sites. These collections provide a genetic reservoir that can be vital for future restoration efforts or scientific research. Secondly, many botanical gardens have significant aesthetic value, attracting a large number of visitors. This public engagement helps in raising awareness about plant diversity, conservation issues, and the importance of plants in ecosystems. For example, the Great Banyan Tree (Ficus benghalensis) in the Indian Botanical Garden at Kolkata is a major attraction that educates visitors about botanical wonders. Thirdly, these gardens are indispensable for botanical research, offering a wide range of taxonomic material for studies on plant morphology, anatomy, genetics, and ecology. Researchers can access diverse species in a controlled environment, facilitating advancements in plant science. Fourthly, botanical gardens are vital centers for education and demonstration. They provide opportunities for self-instruction, formal education programs, and practical demonstrations for students, researchers, and the general public, fostering a deeper understanding of plant life and conservation principles. Lastly, many gardens are actively involved in seed banking, propagation of rare species, and reintroduction programs, directly contributing to the preservation of threatened plant populations.

Plants that contain two cotyledons are classified under the Class Dicotyledoneae. Within the classification system, particularly Bentham and Hooker's system, the presence of a cup-shaped thalamus is a distinctive feature used to further categorize dicotyledonous plants. Specifically, plants exhibiting a cup-shaped thalamus are placed under the Subclass Polypetalae, which is characterized by free petals. Furthermore, within Polypetalae, they belong to the Series Thalamiflorae. This series is distinguished by flowers with a prominent, often conical or cup-shaped, thalamus (receptacle) on which the floral parts are inserted. Therefore, a plant with two cotyledons and a cup-shaped thalamus would be classified as: Class Dicotyledoneae, Subclass Polypetalae, Series Thalamiflorae. This hierarchical classification helps in systematically organizing and identifying plants based on their key morphological characteristics.

Molecular taxonomy utilizes molecular markers such as RAPDs (Random Amplified Polymorphic DNA), RFLPs (Restriction Fragment Length Polymorphisms), and other DNA-based techniques to establish relationships between organisms at the genetic level. These molecular markers work by analyzing variations in DNA sequences and patterns among different organisms, which reflect their evolutionary divergence and relatedness. By comparing DNA sequences and genetic differences between members of different taxonomic groups, scientists can determine how closely related organisms are to each other and trace their evolutionary pathways. This approach is particularly powerful because it provides direct evidence of genetic similarity and difference, which is more objective than morphological comparisons alone. Molecular markers help unlock the evolutionary history of organisms by revealing the timing and pattern of evolutionary divergence, identifying common ancestors, and constructing accurate phylogenetic trees that show how different species have evolved and diversified over time. This molecular approach has revolutionized our understanding of plant evolution and taxonomy by providing insights that are independent of physical characteristics.

JSolanaceae (Dicot) Morphology
Liliaceae (Monocot) Morphology
Bulbous stem / rhizome / corm absent but stem tuber present eg. Solarium tuberosum
Bulbous Stem – Lilium
Rhizome -Polygonatum
Corm – Colchicum Occur
Radical leaves Cariscup } Absent from roots
Radical leaves present eg. Lilium
Leaves alternate & exstipulate
Slipules absent exstipulate fleshy and hollow
Flowers – Pentamerous
Flowers – Trimerous
Calyx_ – Persistent -Solanum melongena
Calyx, Corolla – Absent
Corolla of various shapes present
Perranth is only present
Stamens – 5 – Epipetalous
Stamens – 6 – In a whorl of three each apostamenous
Carpels:
* Ovary superior
* bicarpellary, bilocular
Carpels oblipuely placed bicarpellary later become tetra carpellary due to the formation of false septa
Ovary superior tricarpellary trilocular
Fruits – Berry / capsule
Fruits – Loculierdal capsula
Anatomy:
Bi-collateral Vascular Bundles occur
Cambium present Secondary growth present
Anatomy:
Conjoint collateral Vascular bundles
Cambium absent
No secondary growth
Part – B
11th Bio Botany Guide Taxonomy and Systematic Botany Additional Important Questions and Answers
Choose the correct answer:

The correct matching of the Common name to its Botanical name is as follows: (i) Rosewood refers to Dalbergia latifolia (B). (ii) Red Sandalwood is Pterocarpus santalinus (D). (iii) Padauk is Pterocarpus dalbergioides (A). (iv) Vengai is Pterocarpus marsupium (C). Therefore, the correct sequence is B D A C. Rosewood, specifically Indian Rosewood, is botanically known as Dalbergia latifolia, prized for its dark, dense timber. Red Sandalwood, distinct from white sandalwood, is Pterocarpus santalinus, known for its deep red wood and medicinal properties. Padauk refers to several species, but Pterocarpus dalbergioides is a common species known by this name, particularly Andaman Padauk. Vengai, or Indian Kino Tree, is botanically identified as Pterocarpus marsupium, valued for its timber and medicinal gum.

The gynoecium of Pisum sativum (pea plant) and Datura metal (thornapple) exhibit distinct differences in their structural organization. In Pisum sativum, the gynoecium is monocarpellary, meaning it is composed of a single carpel. It is unilocular, possessing a single chamber, and the ovules are arranged on marginal placentation, where they develop along the fused margins of the carpel. The stigma is typically feathery, adapted for capturing pollen. In contrast, the gynoecium of Datura metal is bicarpellary, formed from two fused carpels. It is tetralocular, meaning it has four chambers due to the formation of false septa within the ovary. The ovules are borne on axile placentation, where they are attached to the central axis of the ovary. The stigma is bilobed, providing a larger receptive surface for pollen. These differences reflect adaptations to their respective reproductive strategies and evolutionary paths.

Taxonomical Aids are essentially tools and techniques that facilitate the study of taxonomy, aiding in the identification, classification, and nomenclature of organisms. These aids are crucial for accurate and systematic biological research. There are various types of taxonomical aids, including keys, floras, revisions, monographs, catalogues, herbaria, and botanical gardens. Each type serves a specific purpose in the taxonomic process. For instance, a Flora is a comprehensive document that lists and describes all plant species found in a particular geographical area. It provides detailed information on the habitat, distribution, and characteristics of each species, often including keys for identification. Floras can be categorized based on the extent of the area they cover. A Local Flora covers a limited geographical region, such as a state, country, city, or a specific mountain range; an example is the Flora of Thiruvannamalai District. A Regional Flora encompasses a larger geographical area, like the Flora of Tamilnadu Carnatic by K.M. Mathew. A Continental Flora covers an entire continent, such as the Flora Europaea by D.A. Web. In modern taxonomy, Electronic Floras, which are digital versions of floras published online, are increasingly common, offering easy accessibility and searchability, like the E-Flora of China. These aids are indispensable for botanists, ecologists, and conservationists in understanding plant diversity and its conservation.

• Population of organism closely resemble each other
• Descend from common ancestor
• They sexually interbreed freely producing fertile offspring
• They have morphological resemblance in asexually reproducing organism
• In fossil organisms they are identified by their morphological & anatomical resemblance

ICN’s second principle is that a specimen must be associated with a scientific name known as nomenclatural type (specimen, or its illustration)
Eg. Herbarium sheet: –
There are 7 types
* Holotype:
The original Protologue of the author is a definite source of identity
Citation & submission of it is one of the criteria for valid publication of a botanical name
* Isotype: Duplicate of Holotypes
* Same person on the same date with same field number
* Reliable duplicates of holotype – to be distributed to various herbaria of various region
* Lectotype: Specimen selected from original material may serve as Lectotype when holotype is missing or destroyed
* Syntype: When the author cites more than one specimen in his Protologue without designating Holotype.
* Neotype: Specimen from the non-original collection when original
* Paratype: holotype missing or destroyed: specimen other than Holo, Iso, or Syntype
* Epitope: Specimen or illustration serves as an interpretive type when all the above types are ambiguous.

Species is indeed considered the lowest or most fundamental taxon in biological classification. It is precisely defined as a group of individuals that are closely resembling each other in morphological, anatomical, biochemical, and genetic characteristics, and, crucially, are capable of interbreeding among themselves under natural conditions to produce fertile offspring. This ability to interbreed and produce fertile progeny is a key criterion for delineating a species, particularly in sexually reproducing organisms. Individuals within a species share a common gene pool and are reproductively isolated from other species. This concept helps to organize the vast diversity of life into discrete, manageable units, providing a basis for understanding evolutionary relationships and biodiversity. For example, all humans belong to the species Homo sapiens, as they can interbreed and produce fertile offspring.

• Commonly used & accepted for phylogenetic classifications.
• Produces a hypothesis about the relationship of organisms to predict the morphological characteristics of an organism.
• Help to elucidate the mechanism of evolution.

Binomial Nomenclature is a standardized system for naming organisms, where each species is given a scientific name consisting of two parts. This system was initially introduced by Gaspard Bauhin, but it was rigorously implemented and popularized by Carolus Linnaeus, who is often regarded as the 'Father of Modern Taxonomy'. According to this system, the scientific name of a plant, or any organism, comprises two words. The first word represents the genus name, which is always capitalized. The second word represents the species epithet, which is written in lowercase. Both parts of the name are typically italicized when typed or underlined when handwritten, to distinguish them from the surrounding text. For example, in the scientific name Mangifera indica, 'Mangifera' is the genus name, and 'indica' is the species epithet. This two-part naming system provides a unique and universally recognized name for each species, eliminating ambiguity that can arise from common names, which vary geographically and linguistically. It ensures clarity and precision in scientific communication worldwide.

The systematic position of the Pea family, also known as Fabaceae or Leguminosae, can be understood through different classification systems. According to the Angiosperm Phylogeny Group (APG) Classification, the Pea family belongs to the Kingdom Plantae, Clade Angiosperms, Clade Eudicots, Clade Rosids, and Order Fabales. The family itself is Fabaceae. In contrast, Bentham & Hooker’s Classifications place the Pea family in the Kingdom Plantae, Class Dicotyledonae, Subclass Polypetatae, Series Calyciflorae, and Order Rosales. The family remains Fabaceae in this system as well. These classifications highlight its placement within the flowering plants, specifically among the dicotyledons, and its close relationships with other plant groups based on morphological and genetic characteristics.

• Most recent classification of flowering plants
• Done in last decade of 20th century
• All these provide data with respect to DNA seqences of 2 chloroplast genes (extrachromosomal) (atp B and r bcL) and one nuclear gene (nuclear ribosomal 18 s DNA).

Taxonomy and Systematics are closely related but distinct fields within biology. Taxonomy is primarily concerned with the theory and practice of classifying organisms into hierarchical groups called taxa. It involves the processes of naming organisms (nomenclature), describing their characteristics, identifying them, and preserving specimens for future study. Essentially, taxonomy can be summarized as the combination of classification and nomenclature. Systematics, on the other hand, is a broader field that encompasses taxonomy and also studies the diversification of species and their evolutionary relationships. It aims to understand the evolutionary history (phylogeny) of organisms and their phylogenetic relationships. Therefore, systematics includes not only the principles of taxonomy but also incorporates evolutionary biology to establish a comprehensive understanding of biodiversity. It can be seen as the integration of taxonomy and phylogeny.

• Collection of collected, pressed and dried plant specimens preserved, then mounted on a sheet of paper is referred to as Herbarium.
• It also refers to the Institution where many such Herbaria are preserved.
• Eg. Royal Botanical garden Kew London.

Biosystematics is a specialized approach to studying life forms that integrates experimental, ecological, and cytotaxonomic methods to define their relationships. It moves beyond traditional morphological comparisons by incorporating data from various biological disciplines. The primary aims of biosystematics are multifaceted. Firstly, it seeks to accurately delimit naturally occurring biotic communities of plant species, providing a more precise understanding of species boundaries. Secondly, a crucial aim is to establish the evolutionary history and phylogenetic trends of a group of taxa, thereby elucidating their evolutionary pathways. Thirdly, biosystematics emphasizes the involvement of diverse data types, moving beyond solely morphological and anatomical observations to include modern concepts such as genetic, biochemical, and ecological data. Finally, it aims to recognize and categorize various groups into distinct biosystematic categories, such as ecotypes (populations adapted to specific ecological conditions), ecospecies (groups of ecotypes that can interbreed), cenospecies (groups of ecospecies that can hybridize but produce sterile offspring), and comparium (a group of cenospecies that can hybridize).

Linnaeus's classification system is often referred to as the sexual system of classification because its primary basis for grouping plants relies heavily on the characteristics of their sexual organs, specifically the stamens and carpels. Carl Linnaeus developed this artificial system in the 18th century, categorizing plants into classes and orders based on the number, union, length, and distribution of stamens (male reproductive parts), as well as the characteristics of the carpels (female reproductive parts). For example, plants with a certain number of stamens would be placed in one class, while those with a different number or arrangement would be in another. This emphasis on reproductive structures, particularly the sexual characters, led to its designation as the sexual system of classification, despite its artificial nature compared to modern phylogenetic systems.

International herbariums are major repositories of preserved plant specimens used for botanical research and reference. The Museum National d'Histoire Naturelle in Paris, France, established in 1635 with acronym P and PC, houses approximately 10,000,000 specimens and is one of the oldest herbarium collections. The New York Botanical Garden in Bronx, New York, USA, established in 1891 with acronym NY, contains about 7,200,000 specimens. The Komarov Botanical Institute in St. Petersburg (formerly Leningrad), Russia, established in 1823 with acronym LE, holds approximately 7,160,000 specimens. The Royal Botanic Gardens at Kew, England, UK, established in 1841 with acronym K, preserves about 7,000,000 specimens. These institutions serve as essential centers for plant taxonomy, identification, and botanical research worldwide.

The Fabaceae family exhibits various types of habits and growth forms. Herbaceous forms include erect herbs such as Crotalaria verrucosa and prostrate herbs like Indigofera enneaphylla, with other herbaceous examples including Indigofera and Crotalaria species. Shrubby forms are represented by Cajanus cajan. Small trees in this family include Sesbania species. Climbing forms are diverse, ranging from herbaceous climbers like Clitoria species to woody climbers such as Mucuna. Large trees in Fabaceae include important timber species like Pongamia and Dalbergia. Additionally, some members like Aeschynomene aspera are hydrophytes adapted to aquatic or wetland environments. This diversity of habits reflects the wide ecological adaptation and distribution of the Fabaceae family across different habitats and climatic zones.

• Provides resource material for systematic research & studies
• A place for the orderly arrangement of voucher specimens
• Voucher specimen serves as a reference for comparing doubtful Newly collected fresh specimen
• Voucher specimens play a role in
• Studies like floristic diversity
• Environmental assessment
• Ecological mechanisms &
• Survey of unexplored area
• provides an opportunity for documenting biodiversity and studies related to the field of ecology & conservation biology.

• Increased knowledge of chromosomes Have been used for extensive biosystematic studies & resolving many taxonomic problems.
• Cytological especially chromosomal characters such as number, size, morphology and behaviour during meiosis are of taxonomic value.

The androecium, which refers to the male reproductive part of a flower consisting of stamens, in the Family Fabaceae (Pea family) exhibits interesting variations. One common arrangement is diadelphous, where the ten stamens are typically arranged into two bundles. Often, this takes the form of nine stamens united at their filaments to form a tube, with the tenth stamen remaining free. Another diadelphous arrangement can involve stamens grouped into two bundles of five each, though this is less common than the 9+1 configuration. Additionally, some members of the family display a monadelphous but dimorphic androecium. In this case, all ten stamens are united into a single bundle, but they are dimorphic, meaning they exhibit two distinct forms. For instance, five stamens might have longer filaments and larger anthers, while the other five have shorter filaments and smaller anthers, contributing to specialized pollination mechanisms.

• Study of various chemicals available in plants help to solve the certain taxonomical problem
• Chemotaxonomy scientific approach of classification of plants on the basis of their biochemical constituents
• Proteins – (more controlled by genes less subjected to natural selection)
• So used at all hierarchical level of classification starling from variety to division.
• Other chemicals studied are – Amino acids, nucleic acids – peptides

Regional Flora and Continental Flora are terms used to describe botanical works that document the plant life of specific geographical areas, differing primarily in the scale of the region covered. Regional Flora refers to a comprehensive account of the plant species found within a large, defined geographical area or a specific botanical region. These floras typically provide detailed descriptions, keys for identification, distribution information, and sometimes ecological notes for all native and naturalized plants within that region. An example would be the "Flora of Madras Presidency," which documents the plant diversity of a specific administrative and geographical area within India. In contrast, Continental Flora encompasses the plant life of an entire continent. These works are much broader in scope and often involve collaborative efforts from numerous botanists across different countries within that continent. They aim to provide an exhaustive inventory of all plant species found across the vast expanse of a continent, such as the "Flora Europaea," which covers the diverse plant kingdom found throughout the continent of Europe.

• Conserved molecular sequences helped to identify
• DNA data help in – investigation of evolutionary patterns
• DNA taxonomy – play vital role in, understanding
• phytogeography – help in genome mapping & bio deversity Conservation
• DNA based Molecular markers – used for designing DNA based molecular probes

Ornamental plants are cultivated for their aesthetic appeal and are distributed across various plant families. From the family Fabaceae, Butea frondosa, commonly known as the Flame of the forest, is prized for its brilliant orange-red flowers, and Clitoria ternatea, known as the Sangu flower, is valued for its attractive blue flowers. From the family Solanaceae, Cestrum diurnum, the day jasmine, produces fragrant white flowers, and Petunia hybrida, the garden petunia, offers a wide range of flower colors and is extensively cultivated as an ornamental. From the family Liliaceae, Tulipa suaveolens, the tulip, is renowned for its elegant cup-shaped flowers in various colors, and Agapanthus africanus, the African lily, displays attractive blue or white flowers in spherical clusters. These ornamental plants are selected for cultivation based on their flower color, form, fragrance, and overall aesthetic value in gardens and landscaping.

• A scanner like the UPC of supermarket things, – DNA barcoding is a taxonomical device to distinguish one species from another.
• A very short genetic sequence from a standard part of a genome is used as a DNA tag or barcode to identify a plant
• Paul Hebert proposed it and so-known as the Father of barcoding.

• Helps in the identification and classification organism
• Aids in the mapping the extend of bio-diversity
• Eventhough it require a large data base of sequences for comparison & prior knowledge of the barcoding region, it is helpful tool to determine the authenticity of botanical material in whole, cut or powdered form.

• In Arachis hypogea after fartilization, the stipe of ovary become meristematic and grows down into the soil.
• The ovary gets buried into the soil and so we call the fmit as groundnut.

Stipules, stipels, and pulvini are three distinct structures associated with compound leaves in the Fabaceae family. Stipules are green, scale-like structures that originate from the base of the petiole and from which the entire compound leaf arises. They are typically paired and may be leafy or membranous in nature. Stipels are small, scaly structures that occur at the base of individual leaflets within the compound leaf, serving as miniature stipule-like appendages for each leaflet. The pulvinus is a swollen, cushion-like region found at the junction of the rachis and petiole, as well as at the base of individual leaflets. This swollen condition of the pulvinus is an important adaptation that allows for leaf movements, particularly in response to light and touch stimuli, enabling the characteristic sleep movements observed in many Fabaceae plants. These three structures represent different levels of leaf organization and have distinct structural and functional roles in the compound leaf architecture of Fabaceae.

Habit – Twining climber
Root – Branched tap root system
Stem – Aerial weak stem, twiner
Leaf – Imparipmnately compound, Petcolate, Alternate, stipulate,
Leaf lets stipellate, stipels are pulvinate reticulate venation
Inflorescence – Solitary and Axillary
Flower -Zygomorphic Bracteate, Bracteolate (large) Bisexual complete
Dichlamydeous – Pedicellate, Pentarnerous & Hypogynous
Calyx – 5 sepals synsepalous valvate aestivation odd sepal anterior in position
Corolla – 5 petals apopetalous
1 standard petal -(Vexillum)
2 wing petals -(aiea)
2 keel petal(carina) – united at the base in descendingly imbricate aestivation
Androecium – 10 stamens diadeiphous
(9) + 1 (i.e.) nine united one free in 2 + bundleš
Anther – Dithecous, basifixed introse and devisce by Longitudinal Division
Gynoecium – Made up of ovary style & stigma
Ovary – Superior with a prominent stipe monocarpellary, unilocular with many ovules on marginal placentation
Style – simple incurved
Stigma – feathery
Fruit – Legume
Seed – non endospermous reniform

Phylloclade and cladode are both modifications of aerial stems in the Liliaceae family, but they differ in their structural characteristics and examples. A phylloclade is a branch that has been modified to assume the form and function of a leaf, with the leaves themselves being reduced to scales. In phylloclade, the entire aerial stem or branch is flattened and photosynthetic, as seen in Ruscus species. A cladode, also referred to as an aerial stem or branch modification, similarly has leaves reduced to scales, but the modification involves the development of flattened stem segments that function as leaves, as exemplified by Asparagus species. While both structures represent adaptations for photosynthesis in plants with reduced leaves, the distinction lies in the specific morphological nature of the modification and the degree to which the stem assumes leaf-like characteristics. Both adaptations are significant xerophytic features that reduce water loss while maintaining photosynthetic capacity.

Habit – Large erect, stout, herb
Root – Branched tap root system
Stem – Hollow, herbaceous strong odour
Leaf – Simple, alternate, petiolate, entire or deeply lobed glabrous, exstipulate unicostate reticulate venation
Inflorescence – Solitary & Axillary cyme
Flower – Actinomorphic, (Regular) Bracteate, Bracteolate, Bisexual Complete Dichlamydeous Pentamerous, sessile & hypogynous
Calyx – 5 sepals synsepalous
Valvate aestivation persistant
Corolla – 5 petals synpetalous plicate 10 lobed Twisted aestivation funneishaped
Androecium – 5 stamens – epipetalous altemi petalous.
Anther – dithecous, basifixed, introse longitudinal dehiseence
Gynoecium – Superior – bicarpellary bilocular,
Ovary – syncarpous basically bilocular later become tetralocular due to the formation of false septa Carpels obliquely placed ovules on swollen axile placentation
Style – simple long flu form
Stigma – bibbed
Fruit – Spinesent capsule opening by four apical valves persistent calyx
Seed – Endospermous

Chemotaxonomy is a field that utilizes chemical compounds found within organisms as taxonomic characters to aid in classification and to understand evolutionary relationships. The aims of chemotaxonomy are significant in refining our understanding of plant diversity. Firstly, a primary aim is to develop novel taxonomic characters based on the presence, absence, or concentration of specific chemical substances. These chemical markers can provide additional, often more stable and less environmentally influenced, data compared to purely morphological features, thereby improving existing systems of plant classification and resolving ambiguities. Secondly, chemotaxonomy aims to enhance our current knowledge of the phylogeny of plants. By analyzing the distribution of various secondary metabolites, proteins, nucleic acids, and other biochemical compounds across different plant groups, scientists can infer evolutionary pathways and relationships, contributing to a more accurate and robust understanding of plant evolution.

Habit – Perrennial herb with bulb
Root – Fibrous adventitious root system
Stem – Underground bulb
Leaf – Radical leaves cylindrical fleshy with sheathing leaf bases & parallel venation
Inflorescence – scafrigerous, pedicels of equal length arising from apex of peduncle
Flower – Small white
Actinomorphic,
Bracteate, eBracteolate Bisexual Complete
Monochiamydeous.
Trimerous – hypogynous
Flowers – Protandrous
Perianth – 6 Tetals in 2 whorls of 3 each syntepalous Valvate acstivatíon
Androecium – 6 stamens in a whorls of 3 each epipelatous
apostamenous
Anther – Dithecous basifixed, introse and longitudinal dehiscence
Gynoecium
Ovary – Superior, tricarpellary trilocular 2 ovules in each locule on axile
placentation
Style – simple, slender
Sligma – simple
Fruit – loculicidal capsule.