BSc Botany Diversity & Classification of Plants Notes 2024 .DETAIL OF COURSES. FOR BS (4 – YEAR) IN BOTANY. 1st Year 1st Semester. Diversity of Plants. Credit Hours: 4 (3+1).In the first and second year the students begin by taking Botany as a with the diversity of plant life, an outline of the classification of plants.

What are the 7 classifications of plants?

Plant species can be classified based on their life cycle.

• Annuals. These are plants that complete their life cycle during a single season
• Biennials. These are plants that require two years to complete their life cycle
• Perennials
• Coniferophyta (Gymnosperms)
• Anthophyta (Angiosperms)

Plant taxonomy or classification is the science of naming organisms and placing them in a hierarchical structure, each level being given a name (e.g., kingdom, division (phylum), class, order, family, genus, species).

Diversity in Plant Life (With Diagram)

Plants are multi-cellular and mostly photosynthetic organisms which found essentially everywhere, both in water and on land.

The aquatic plants include red, brown and green algae and the land plants include mosses, ferns, gymnosperms and angiosperms.

The angiosperms or flowering plants are dominate the earth the last 70 million years.

There are over 3, 00,000 angiosperm species growing on the earth which show enormous diversity in size and form. In India there are about 45,000 plant species are that represent about 7% of the world’s flora. Nearly, 4900 species of angiosperms are endemic to India.

I. Diversity on The Basis of Habitat:

Plants grow in a variety of habitats.

On the basis of habitat, plants may be classified into following groups:

1. Hydrophytes:

The plants growing near water or submerged under water are hydrophytes. Such plants have poor root system, soft stem and poor vascular tissue. The bulk of the tissue is spongy provided with air spaces.

These plants may be:

(i) Submerged (e.g., Vallisneria, Hydrilla, Potamogeton etc.),

(ii) free-floating and fixed-floating (e.g., Wolffia, Utricularia, Salvinia, Ceratophyllum, Lemna, Pistia, Eichornia, Trapa, Azolla Nymphaea etc.), and

(iii) amphibious (only partly submerged, e.g., Ranunculus aquatilis, Alisma plantago, Sagittaria, Limnophylla etc.).

Two angiosperms are also marine, e.g., Zostera and Thalassia.

2. Hygrophytes:

These plants grow in moist and shady habitats. Their stem and roots are soft and spongy and show stunted growth. The leaves are well-develop, provided with stomata. Common examples are Ferns, Begonias, Aroid and certain grasses.

3. Halophytes:

These plants grow in saline soil or saline water. They can tolerate a relatively high concentration of salts (Nacl, MgCl₂, and MgSO4). They have characteristic negatively geotropic breathing roots called pneumatophores. Common examples are mangrove vegetations like Rhizophora, Ceriops, Avicennia, Sonneratia etc.

4. Mesophytes:

The majorities of angiosperms grows in places of moderate water supply and are as mesophytes. They are usually large and fast growing. They have well developed roots and leaves. There stem may be herbaceous or woody. There are certain mesophytes, such as deciduous trees (viz., shedding leaves at a certain season), which are mesophytic during the summer and xerophytic during the winters.

5. Xerophytes:

The plants which grow in xeric or dry conditions or where water availability is negligible, are as xerophytes, e.g., Euphorbia, Acacia, Argemone, Amaranthus, calotropis, Nerium, Ziziphus etc. some xerophytes store water in their stem (opuntia), leaves (Aloe. Agava, Bryophyllum) or in roots (Asparagus) and are call as Succulents.

Xerophytes may be further divide into following types:

i. Lithophytes – Plants growing on rocks

ii. Psammophytes – Plants growing in sandy soils

iii. Oxylophytes – Plants growing on acidic soil.

6. Epiphytes:

Are the plants that grow on the trunk or branches of other plants, e.g., an orchid or lichen growing-as an epiphyte on a mango branch. The epiphytes are consider as space parasites. However, the interaction between the orchid (a commensal) growing on a tree (host) would be an example of commensalism where the host is unharm, while the commensals benefits,

7. Parasitic plants:

These plants live on other plants as parasites, e.g. Cuscuta, Striga (grows on roots of jowar)

II. Diversity On The Basis Of Habit:

On the basis of habit (i.e., shape, size and form), angiosperms are classified into four groups:

1. Herbs (Herbaceous):

The stem of those plants is green, delicate and short. Usually their life is short e.g., wheat (Fig 1.2A), gram. In some herbaceous plants, the underground part of stem is greatly reduce but the aerial branch with flowers at the top arises from underground parts at the time of reproduction. Such a stem is call scape e.g. onion (fig. 1.2B)

2. Shrubs (= Shruby or Fruticose):

These plants are woody, branched and larger than herbs. Usually with several stems but no main axis e.g., China rose, rose, henna. (Fig 1.2C).

3. Trees (Arborescent):

The plants are longer or larger than shrubs, hard and woody, very well developed and thick. Possess a prominent trunk.

These are of the following types:

(a) Caudex:

The stem is un-branch and usually bears a crown of leaves at the apex e.g., Date-palm (Fig. 1.3A).

(b) Excurrent:

The lower part of the stem is thicker which gradually tapers above. The plant appears conical due to acropetal arrangement of branches on the main stem (Fig. 1.3B).

(c) Deliquescent:

The apical bud of the main stem dies after some time and branches and sub- branches spread in different directions e.g., Tamarindus, Ficus.(Fig. 1.3C).

4. Culms:

In these plants, nodes and internodes are extremely prominent, lnternodes of such plants are usually hollow: These plants are grasses but cannot be consider as herbs or shrub or tree, e.g., Bamboo. (Fig. 1.4)

III. Diversity of Angiosperms on The Basis of the Nature of Stem:

On the basis of the nature of stem, the angiosperm plants may be classified as given below:

1. Erect:

These plants grow upright. Most trees, shrubs and some herbs have strong stem (axis) and thus can stand erect on the soil.

2. Creepers:

These plants have trailing stem having roots throughout its length. Since these plants have weak, long and thin stem they creep on the surface of the soil. Leaves emerge from nodes, from the axil of which branches arise. Adventitious roots arise from nodes throughout the length of the stem, e.g., Oxalis; Cynodon (doob grass) etc.

3. Trailers:

Stem sprawling on the ground with the help of adventitious roots. These plants are like creepers with the difference that here adventitious roots do not arise from nodes. A trailer may be procumbant or decumbent. In procumbent trailer, the stem lies completely horizontal (e.g., Basella), while in decumbent, the apical part of the stem is raise above the ground (e.g., Lindenbergia).

4. Climbers:

These plants with weak stem climb on some support by means of tendrils, petioles, spines, adventitious roots etc., e.g., pea, betel etc.

IV. Diversity on The Basis of Life-Span:

On the basis of life-span, angiosperms are classified into following four groups:-

1. Ephemerals:

Such plants complete their life span within a very short period before the approach of actual dry conditions. These are not true xerophytes, and often called as drought evaders or drought escapers, e.g., Argemon mexicana, Solanum xanthocarpum, Cassia tora, Artemesia etc.

2. Annuals:

They complete their life-cycle within one year and die after producing seeds, e.g., wheat, rice, gram.

3. Biennials (or Biannuals);

These plants complete their life-cycle in two years. During first year they show only vegetative growth, and during second year they develop flowers, fruits and seeds. These plants are usually herbs, e.g., Radish, Turnip, and Carrot.

4. Perennials:

These plants have long life, and once established continue to live for many years. The great banyan tree (Ficus bengalensis) in the Botanical Garden, Kolkata is more than 200 years old. The Bodhi tree (ficus religiosa) at Gaya is about 2500 years old.

Most perennials, after attaining maturity, bear flowers and fruits in a particular season of each year.Some perennials (e.g., Bamboos, Agave) are monocarpic i.e., they bear fruits only once in their life. All annuals and biennials are monocarpic.

V. Diversity on The Basis of Size:

The angiospermic plants show great variation in their size. The smallest angiosperm is a rootless aquatic Wolffia. It has a diameter of 0.1 mm. Aquatic Lemna has a diameter of 0.1 cm. The tallest angiosperm plant it is Eucalyptus regnans. It is over 100 meter tall. Some of the Eucalyptus trees attain a height of 130 meter. The largest-sized plant is Banyan tree (Ficus bengalensis). It can spread over an area of 2 – 5 acres with more than 200 prop roots.

VI. Diversity on The Basis of Nutrition:

On the basis of mode of nutrition, plants are classified as follows:-

1. Autotrophic plants or autotrophs. Most of the plants are autotrophs as they are green and manufacture their own organic food from inorganic raw materials (viz. CO₂ and H₂O).

2. Heterotrophic plants or heterotrophs. These plants obtain a part or whole of their nourishments from outside sources. Heterotrophs may be parasites, saprophytes, symbionts and insectivorous.

The Classification Of Plants

All living organisms in the ecosystem are classified into kingdoms and sub-kingdoms based on their characteristics. Similarly, plants are also classified into different sub-kingdoms based on certain characteristic features.

• Botanical type
• Geographical or ecological communities

DIVESITY OF PLANTS

Different plants have different morphology, physiology, cytology and anatomy. It produces diversity among plants. Diversity includes classification and nomenclature of plants.

SCOPE AND CLASSIFICATION OF PLANT KINGDOMS

The study of systematics gives the order and relationships among the organism. This order and relationship arise from evolutionary processes. These studies also give description of the new species. It organizes the animals into groups (taxa). This grouping is based on degree of evolutionary relatedness.

A. TAXONOMIC HIERARCHY

(a)        Taxonomic hierarchy based on morphology

The modern classification system has been give by Carolus Linnaeus. This system of classification is still use today. Carolus Linnaeus believed that different species could be group into same

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– Diversity of Plants: Introduction

categories on the basis of similarities between them. The group of animal with similar characteristics forms a taxon. For example, Amaltas (cassia fistula) shows similarities with other cassia specie (cassia senna). Both have compound leaves and produce bean. Therefore, all such plants are place in the same taxon. Moreover. Cassia also shares characters with Bauhinia verigata (Kachnar). So they are place in the same family.

Carolus Linnaeus recognized five taxa. Modern taxonomists use eight taxa including earlier five taxa. It means arrangement of classification from broad to specific. These taxa are: Kingdom, Phylum, Class, Order, Family, Genus, and Species.

(b)      Taxonomic hierarchy based on evolution

Carolus Linnaeus did not accept evolution. But still many of his groupings show evolutionary relationships. Morphological similarities between two plants have a genetic basis. It gives rise common evolutionary history. Thus the plants are group according to similar characteristics. Carolus Linnaeus grouped them according to their evolutionary relationships. The members of the same taxonomic group are more closely related to each other than the members of different taxa.

KINGDOMS OF LIFE

(a) Kingdom classification system

In 1969, Robert H. Whittaker described a system of classification. This classification forms five kingdoms. This basis of classification of Whittaker is:

(a)Cellular organization

(b)Mode of nutrition.

There are following five kingdoms:

1. Monera: The members of this kingdom are prokaryotes. The kingdom Monera contains bacteria and the cyanobacteria.
2. Protista Members of the kingdom Protista are eukanjotic. They consist cf single cells or colonies of cells This kingdom includes Amoeba. Paramecium, etc.
3. Plantae: Members of the kingdom Plantae are eukaryotic, multicellular, and photosynthetic. Plants have walled cells. They are usually non,motile.
4. Fungi: Members of the kingdom Fungi are also eukaryotic and multicellular. They also have walled cells and are usually non‑10Master Success Text Book of Botany Amotile. Mode of nutrition distinguishes fungi from plants. Fungi are decomposers. Fungi digest organic matter outside the body and absorb the broken products.5. Animalia: Members of the kingdom Animalia are eukaryotic and multicellular. They feed by ingesting other organisms or parts of other organisms. Their cells lack walls and they are usually motile.

BSc Botany 1st Year Diversity & Classification of Plants Notes 2024

1. Domain classification systemThe systematists have concluded on the basis of studies of ribosomal RNA that all life shares a common ancestor. They find that there are three major evolutionary lineages. Each of these lineages is call a domain. The domain is present above the kingdom. There are three domains:
   1. Arcbaea: These are prokaryotic microbes. They live in extremeenvironment such as high temperature rift valleys on ocean floor, or high-salt or acidic environments. All members of the Archaea inhabit anaerobic environments. These environments show the conditions on the earth at the time of origin. The Archaea are the most primitive life form. Ancient Achaeans gave rise to two other domains of organisms.

BSc Botany 1st Year Diversity & Classification of Plants Notes

1. Eubacteria: These include true bacteria. These are include prokaryotic microorganisms.
   2. Eukarya: The Eukarya include all eulcaryotic organisms. The Eukarya diverged more recently than the Eubacteria from the Archaea. Thus, the Eukarya are more closely to Archaea than the Eubacteria. It includes the other four kingdoms of eukaryotes: Protista (Protoctista), fungi, Plantae and Animalia.Classification of PlantsPlant biologists use the term division for the major plant groups within the plant kingdom. Division is equal to phylum. Divisions are further subdivide into classes, orders, families, and genera.The classification scheme used in this text recognizes twelve divisions within the kingdom Plantae. These divisions are: Nonvascular nlants
   3.  Division BryopsidaMosses
   4.  Division HepaticopsidaLiverworts
   5.  Division Anthocero ,sidaHornworts

Classification of Plants

Classification Of Plants

However, from a biological perspective, plants can be classified as:

Classification based on Life Cycle

Plant species can be classified based on their life cycle.

Annuals

These are plants that complete their life cycle during a single season. They are normally herbaceous. Examples like corn, rice, wheat, and pulses are annuals plant.

Biennials

These are plants that require two years to complete their life cycle. They are normally herbaceous. For example, carrot, cabbage, onions, and beetroot are biennials plant.

Perennials

These are plants that have a long lifespan – typically more than two years. They are characteristically woody or herbaceous. Rose, lavender, dianthus, and lilies are prominent examples of perennials.

Taxonomic Classification Of Plants

Taxonomy is a system for classifying plants based on their genetic and evolutionary relationship. Plant Taxonomy is a branch of science continues to change as new species are being almost every day.

Plants are classified into a separate kingdom called the Kingdom Plantae. This current system of classification of plants is based on the evolutionary relationship amid other plants.

Coniferophyta (Gymnosperms)

It is a group of plants which is primarily evergreen and are native to the temperate zone.They are vascular, non-flowering plants which produce seeds without the production of flower and fruits. Some common examples of gymnosperm include pines, cycads, cedars, etc.

Anthophyta (Angiosperms)

They can grow into big trees as well as small shrubs, bushes and herbs. The angiosperms are distribute all over the world (>250,000 species). Most of the plants that we see around are group under this division.

Angiosperms are by the seeds that are fully enclose in fruits. They are subdivide into- Monocotyledonous and Dicotyledonous. Some common examples of angiosperms include mango trees, roses, jasmine, marry gold, etc.

Monocotyledons

Monocotyledonous plants are commonly refer to as monocot plants. They are flowering plants with seed containing one cotyledon. The venation pattern of their leaves is parallel-veine. Some common examples of monocot plants are rice, corn, sugarcane, tulips, onion, etc. There are around 50,000 species of monocotyledonous plants discover to date.

Dicotyledons

Dicotyledonous plants are commonly refer to as dicot plants. They are flowering plants, mostly grown as herbs, shrubs, and trees with the seed containing two cotyledons. The venation pattern of their leaves radiates from a central main vein. Some common examples are figs, eucalyptus, potato, tomato, hibiscus, etc. There are around 200,000 species of dicotyledonous or dicots plants.

Importance of Plant Classification

The main purpose of classifying plants is to ensure that the right plants are correctly name, group and identify.

Plants are classified based on these 3 characteristics:

1. The evergreen plants are plants that retain leaves at all times (all year round).
2. Woody plants can also be group as deciduous or evergreen.
3. Deciduous plants are seasonal plants which shed its leaves at the end of the growing season, either during the winter season in the temperate climate or during the dry season in the tropical climate.

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Frequently Asked Questions on The Classification Of Plants

What are vascular plants?

The vascular plants are a large group of terrestrial plants, which have specialized tissues for conducting water and nutrients to different parts of plants. All plants including the members of the Phylum Pteridophyta, Gymnosperms, and Angiosperms are classified as vascular plants.

What are Gymnosperms?

Gymnosperms refer to those plants which have naked seeds. Overall, there are about 600-650 different types of gymnosperm plants.

What are the examples of Angiosperms?

Mustard plants, oak trees, pea plant and lilies are the best examples of Angiosperms.

List out the classification of plants based on their life cycle?

Based on their life cycle, plants are further classified into:
Annuals
Biennials
Perennials.

What are the examples of Monocotyledonous?

Monocotyledonous plants are also refer to as the monocot plants. There are around 40 to 50,000 species of monocotyledonous plants. Examples of monocot plants are corn, onion, sugarcane, tulips, rice, etc.

What are the examples of Flowering and Non-flowering Plants?

Rose, Tulips, Jasmine, Marigold are examples of flowering plants. Cedars, Redwoods, Pines are examples of non-flowering plants.