Class 11 Biology Introduction to Floral Density Notes

Biodiversity

Biodiversity can be defined as the variety and variability of living organisms which exist in a particular area or on the earth.

Types of Biodiversity

1) Species Diversity

Species diversity can be defined as the variety of species found within a particular area.

2) Genetic Diversity

Genetic diversity can be defined as the variation found among the population of a single species due to variation in genes.

3) Ecosystem Diversity

Ecosystem diversity can be defined as the variety of habitats, biotic communities and variety in the composition and structure of organisms.

Floral Diversity in Nepal

The variety and variability found among the plants of a particular geographical area is known as floral diversity. The source notes state that Nepal is very rich in floral diversity and list the following occurrences of plant groups in Nepal.

Plant group	Record written in the scan
Lichens	Miehe et al. (2015) reported 856 species of lichens in Nepal.
Fungi	Adhikari (2014) reported 2467 species of fungi in Nepal.
Algae	Prasad (2013) reported 1001 species of algae in Nepal.
Bryophytes	Pradhan (2016) listed 1213 species of bryophytes in Nepal.
Pteridophytes	Jenkins et al. (2018) reported 580 species of pteridophytes in Nepal.
Gymnosperms	Shrestha et al. (2007) reported 41 species of gymnosperms in Nepal.
Angiosperms	Groombridge and Jenkins (2002) reported 6973 species of flowering plants in Nepal.

Source note: Names, dates and species counts above are transcribed from the supplied handwritten scan.

Scope of Biodiversity

It helps to find out different foods and drinks for human consumption.
It helps in finding new medicines.
It helps in finding new raw materials for industries and other domestic uses.
It helps in maintenance of natural beauty.
It helps in conservation of nature, plants and animals.
It helps in controlling natural calamities.
It has great importance as a direct source of income and economic development.

Concept of Taxonomy

Taxonomy is the branch of biology that deals with identification, nomenclature and classification of organisms according to their characteristics. It is also known as systematic biology or systematics.

A Swedish naturalist, Carolus Linnaeus (1707–1778), is known as the father of taxonomy.

Classification

Classification is the system of arrangement of organisms into different groups on the basis of their morphology and relationship between the organisms.

The source discusses the following systems of classification:

Artificial system of classification
Natural system of classification
Phylogenetic system of classification

Systems of Classification

1) Artificial System of Classification

Artificial system of classification was developed by Carolus Linnaeus. In this system organisms are classified into different groups on the basis of one or a few visible characters. It is basically based on superficial characters of plants.

According to this system, unrelated organisms may be kept in one group while related organisms may be separated. Therefore, the source describes this system as not logical.

2) Natural System of Classification

Natural system of classification was proposed by Bentham and Hooker. This system is based on natural relationships between organisms. It considers external as well as internal features of organisms.

Characteristics such as morphology, anatomy, cytology, embryology, biochemistry, etc. are considered. Related organisms are kept in the same group and unrelated organisms are separated; therefore, the source describes the system as logical.

3) Phylogenetic System of Classification

Phylogenetic system of classification was proposed by Engler and Prantl. It is based on the evolutionary relationship of organisms. Many characteristics and fossil records are considered. The source states that this system reflects the true relationship among organisms and their evolution.

Artificial

One or a few visible / superficial characters.

Natural

Many external and internal characters.

Phylogenetic

Evolutionary relationships and fossil records.

Binomial Nomenclature

The system of giving two names to organisms is called binomial nomenclature. It was developed by Carolus Linnaeus.

Binomial nomenclature consists of two names:

Generic name
Specific name

The generic name begins with a capital letter.
The specific name begins with a small letter.
Both generic and specific names are underlined while writing.
They are italicized while printing.
The name of the author or scientist may be written in abbreviated form at the end of the specific name.

Examples Given in the Scan

Zea mays

Solanum tuberosum

Triticum sativum

Pisum sativum

The scientific-name examples are retained as written in the supplied scan.

Advantages of Binomial Nomenclature

The scientific name of an organism is universal and is used throughout the world.
One organism has only one scientific name; therefore there is no confusion in recognition of organisms.
The nomenclature shows evolutionary relationships among various species under the same genus.
It helps in recognition or identification of newly discovered organisms.
It indicates a relationship between different varieties of species.

Difference Between Artificial and Natural Systems of Classification

Artificial System	Natural System
It is based on one or a few characters.	It is based on a number of characters.
It uses superficial characters such as habit, habitat or external characters like presence or absence of wings.	It uses characters pertaining to morphology, anatomy, physiology, cytology, biochemistry and genetic similarities.
It leads to heterogeneous assemblage of unrelated groups.	It leads to homogeneous groups of related and naturally interbreeding populations.
It does not reflect phylogenetic or evolutionary relationship of organisms.	It reflects the phylogenetic or evolutionary relationship of organisms.
It was arbitrary, so it was discarded.	It is logical and is being used at present, as written in the scan.
It does not convey much information about organisms.	It gives detailed information about organisms.
Homology is not used as a criterion.	Homology is used as an important criterion to determine similarity.

Species and Genus

Species

A species is a group of organisms which can interbreed freely and can reproduce offspring of their own kind.

Genus

A genus is a group of species having common characteristics. The source notes state that all species of a genus evolved from a common ancestor.

Taxonomic Category and Taxon

Taxonomic Category

Taxonomic categories are the different hierarchical ranks in the system of classification. Kingdom is the highest taxonomic category while species is the lowest taxonomic category.

Taxon

A taxon can be defined as a group of organisms belonging to a particular taxonomic category. For example, family is a taxonomic category and Cruciferae is a taxon.

Taxonomic Hierarchy

The arrangement of groups of organisms into different taxonomic categories according to their rank is called the hierarchical system of classification.

Classification of Mustard Plant Given in the Scan

KingdomPlantae

Sub-kingdomPhanerogamae

DivisionAngiospermae

ClassDicotyledonae

Sub-classPolypetalae

SeriesThalamiflora

OrderParietales

FamilyCruciferae

GenusBrassica

Speciescampestris

Two-Kingdom System of Classification

The system of classifying all living organisms into two kingdoms, namely plant kingdom and animal kingdom, is known as the two-kingdom system of classification. It was developed by Carolus Linnaeus. The source states that this system was based on a few characteristics of organisms.

Plant Kingdom

Kingdom Plantae

Animal Kingdom

Kingdom Animalia

Drawbacks of the Two-Kingdom System

Prokaryotic organisms such as bacteria and cyanobacteria were placed with eukaryotic plants in kingdom Plantae.
Unicellular protozoans and multicellular animals were placed in the same kingdom Animalia.
Autotrophic algae and heterotrophic fungi were placed in the same kingdom.
Organisms such as Euglena, showing characters of both plants and animals, created confusion.
Viruses were not classified.

Five-Kingdom System of Classification

Due to drawbacks of the two-kingdom system, American taxonomist R. H. Whittaker (1969) developed the five-kingdom system of classification.

Principles Used in the Five-Kingdom System

Complexity of cellular structure – prokaryotic or eukaryotic.
Complexity of organisms – unicellular or multicellular.
Mode of nutrition – autotrophic or heterotrophic.

The Five Kingdoms

Kingdom	Characteristics written in the scan	Examples written in the scan
Monera	Prokaryotic, unicellular, autotrophic or heterotrophic.	Cyanobacteria and bacteria
Protista	Eukaryotic, unicellular and heterotrophic.	Amoeba, Euglena, Plasmodium
Plantae	Eukaryotic, multicellular and autotrophic.	Algae
Animalia	Eukaryotic, multicellular and heterotrophic without cell wall.	—
Mycota	Eukaryotic, multicellular and heterotrophic with cell wall.	Fungi

1MoneraProkaryotic

2ProtistaEukaryotic • unicellular

3PlantaeEukaryotic • multicellular • autotrophic

4AnimaliaEukaryotic • multicellular • heterotrophic

5MycotaEukaryotic • multicellular • heterotrophic

Memory aid in the source: the handwritten page ends with an abbreviated mnemonic based on the initials M, P, P, A, M. It is preserved here as the five-kingdom order: Monera → Protista → Plantae → Animalia → Mycota.