Importance of Biodiversity


Biodiversity: The term “biodiversity” has been derived from ‘bio’ and ‘diversity’.  Biodiversity is a measure of the variety of organisms present in different ecosystems or earth surface.

Flora: Diversity of plants in an ecosystem is called flora.

Fauna: Diversity of animals in an ecosystem is called flora.

Kinds of organisms inhabiting the earth: At least 10 million kinds of organisms inhabit the Earth but less than one third of these have been studied and catalogued (put in record) by biologists.

Origin of life?

The origin of life is not well known to science, though limited evidence suggests that until 600 million years ago, all life consisted of bacteria and similar unicellular organisms.


Importance of Biodiversity: Biodiversity provides food for humans for example some vegetable plants, fruits, etc. A significant proportion of drugs are derived, directly or indirectly, from biological sources. For example some anti-cancerous drugs are obtained from Taxus bacata . A wide range of industrial materials e.g. building materials, fibers, dyes, resins, gums, adhesives, rubber and oil are derived directly from plants.

Biodiversity plays important role in making and maintaining ecosystems. It plays a part in regulating the chemistry of our atmosphere and water supply. Biodiversity is directly involved in recycling nutrients and providing fertile soils.

Biological Classification – Biodiversity


Taxonomy: The branch of biology deals with the identification, nomenclature and classification of living organisms is called taxonomy.

Classification: The arrangement of organisms into groups and sub groups on the basis of similarities is called classification.

Systematic: The branch of biology that deals with classification and also traces the evolutionary history of organisms is known as systematic.

Need and importance of Biological classification keeping in view its historical background: There is a large collection of very dissimilar forms of organisms, found on Earth. Over 1.5 million types of animals and over 0.5 million types of plants are known to biologists and these are only a small percentage of the total types estimated to live on Earth. They range in complexity from small and simple bacteria to large and complex human beings. Some of them live in sea, some on land; some walk, others fly, and still others are stationary. Each has its own way of life i.e. getting food, avoiding unfavorable environmental conditions, finding a place to live, and reproducing its kind. When there are so many diverse kinds of organisms, it becomes difficult to learn about the characteristics of each.

To study such a large collection, biologists classify the organisms into groups and subgroups and for this task they require some system. Biological classification is a method by which biologists divide organisms into groups and subgroups.

Aims and Objectives: –

The aims and objectives of classification are as under: –

  1. i) Determine similarities and differences between organisms so that they can be studied easily.
  2. ii) Arrange organisms according to similarities and differences.

iii) Identify the organisms on the basis of structure and prominent features.

  1. iv) Finds out inter relationship of organisms.
  2. V) To find the evolutionary relationships among organisms.

Basis and Principles of Classification

The classification of organisms is based on such features or characters, which are similar in one kind of organisms and different in different kind of organisms. These characters may be about internal morphology, (anatomy), external morphology, physiology, cell structure, especially the number of chromosomes and chemical composition (especially of proteins) and embryology of the organisms. These characters help in study of intra specific (within the same species) and intra specific (between different) species differences. The presence of similar characters in different organisms indicates their common ancestry. This similarity because of common ancestral origin is called Homology e.g. arm of a monkey, flipper of a whale and wing of a bat show homology. They are dissimilar apparently but their internal structure (arrangement of bones and muscles) is same. These organs are called homologous organs. Due to this homology, we can, say that monkey, whale and bad had common ancestors and are placed in same large group “vertebrate”. This homology is proved to be very helpful in classification.


Taxonomic Hierarchy: The groups into which organisms are classified are known as taxonomic categories or taxa (singular “taxon”).   “OR”  Any group in the taxonomic categories or taxanomic classification is termed as taxon. A ladder like structure formed by taxanomic categories is known as Taxanomic hierarchy. All organisms are divided into five kingdoms. So kingdom is the largest taxon. On the basis of similarities, each kingdom is further divided into smaller taxa in the following way:



  • Phylum (Division: for plants and fungi): A phylum is a group of related classes.
  • Class: A class is a group of related orders.
  • Order: An order is a group of related families.
  • Family: A family is a group of related genera.
  • Genus: A genus is a group of related species.
  • Species: A species consists of similar organisms.


Members of lower taxon resemble one another more than the members of a higher taxon. Table below illustrates the classifications of humans (Homo sapiens) and pea (Pisum sativum).



Simple classification of two organisms.

Taxa Human Pea
Kingdom Animalia Plantae
Phylum Chordata Magnoliophyta
Class Mammalia Magnoliopsida
Order Primates Fabales
Family Hominidae Fabaceae
Genus Homo Pisum
Species H. sapiens P. sativum


Species – The Basic Unit of Classification

Species is the basic unit of classification. “A species is a group of organisms which can interbreed freely among them and produce fertile offspring, but are reproductively isolated from all other such groups in nature.” Each species possesses its own distinct structural, ecological and behavioral characteristics.

The criteria of interbreeding cannot be used for species recognition in organisms who reproduce asexually and do not interbreed with one another (for example many unicellular organisms).

In the definition of species we must emphasize “in nature” because two organisms related to two different but closely related species can cross-breed under artificial conditions. In such unnatural crosses they produce infertile offspring. For example, a cross between a male donkey and a female horse produces an infertile offspring i.e. Mule.

History of classification systems: The earliest known system of classification of organisms comes from the Greek philosopher Aristotle. He classified all living organisms known at that time as either in the group ‘plantae’ or in ‘animalia’.

In 700s, Abu-Usman Umer Aljahiz described the characteristics of 350 species of animals in his book. He wrote a lot about the life of ants. In 1172, Ibn Rushd (Averroes)translated Aristotle’s book “de Anima (On the Soul)” in Arabic. In the end of 15th century, many biologists had started work on classification methods.

Biologists prefer such a system that can provide maximum information about the basic differences and similarities among different organisms. According to earlier classification system, organisms were classified into two kingdoms but now taxonomists agree on five-kingdom classification system.

Andrea Caesalpino

(1519-1603 AD)

Divided plants into fifteen groups and called them “genera“.
John Ray

(1627-1705 AD)

Published important works on plants classification.
Augustus Rivinus

(1652-1723 AD)

Introduced the taxon of “order“.

(1656-1708 AD)

Introduced the taxa of “class“ and “species“.
Carolus Linnaeus

(1707-1778 AD)

Grouped species according to similar physical characteristics.


Carolus Linnaeus divided nature into three kingdoms: mineral, vegetable and animal. Linnaeus used five ranks in classification: class, order, genus, species, and variety. Linnaeus is best known for his introduction of the method still used to formulate the scientific name of every species.



It is the oldest system of classification put forwarded by Aristotle, the father of biology.

  • kingdom plantae: All organisms that can prepare food from simple inorganic materials and thus can store energy, are autotrophs and are included in kingdom plantae. According to this system, bacteria, fungi and algae were included in kingdom plantae.
  • Kingdom Animalia: Organisms that cannot synthesize their food and depend on autotrophs or others are heterotrophs and are included in kingdom animalia.

Drawbacks of two kingdom system of classification:

Some taxonomists found this system unworkable because; many unicellular organisms like Euglena have both plant-like (presence of chlorophyll) and animal-like (heterotrophic mode of nutrition in darkness and lack of cell wall) characters. So there should be a separate kingdom for such organisms. This system also ignores the difference between organisms having prokaryotic and those having eukaryotic cells.



In 1866, Ernst Hackel solved the first objection and proposed a third kingdom i.e. protista to accommodate euglena-like organisms. He also included bacteria in kingdom protista. In this system, fungi were still included in the kingdom plantae.

Drawbacks of three kingdom system of classification: This system did not clear the difference between prokaryotes and eukaryotes. Some biologists disagreed about the position of fungi in kingdom plantae. Fungi resemble plants in many ways but are not autotrophs. They are special form of heterotrophs that get their food by absorption. They do not have cellulose in their cell walls rather possess chitin.


In 1937, E-Chatton suggested the terms of, “Procariotique” (prokaryotic) to describe bacteria and “Eucariotique”(eukaryotic) to describe animal and plant cells. In 1967, Robert Whittaker introduced the five-kingdom classification system. This system is based on;

Basis for establishing five kingdoms of classification:

  • The levels of cellular organization i.e. prokaryotic, unicellular eukaryotic and multicellular eukaryotic.
  • The principal modes of nutrition i.e. photosynthesis, absorption, and ingestion.

On this basis, organisms are classified into five Kingdoms: monera, protista, fungi, plantae and animalia.

In 1988Margulis and Schwartz modified the five-kingdom classification of Whittaker. They considered genetics along with cellular organization and mode of nutrition in classification. They classified the organisms into the same five kingdoms as proposed by Whittaker.



The general characteristics of the five kingdoms are as follows ;

  1. Kingdom monera:It includes prokaryotic organisms i.e. they are made of prokaryotic cells. Monerans are unicellular, although some types form chains, clusters, or colonies of cells. Prokaryotic cells are radically different from eukaryotic cells. Most are heterotrophic but some perform photosynthesis because they have chlorophyll in their cytoplasm. Within this kingdom, there are two different kinds of organisms i.e. bacteria and cyanobacteria.
  2. Kingdom protista:It includes eukaryotic unicellular and simple multicellular organisms. There are three main types of protists.
  • Algae are unicellular, colonial or simple multicellular. They resemble plant cells with cell walls and chlorophyll in chloroplasts. Simple multicellular means that they do not have multicellular sex organs and do not form embryos during their life cycles.
  • embryos during their life cycles.
  • Protozoans resemble animals whose cells lack chlorophyll and cell walls.
  • Some protists are fungi-like.
  1. Kingdom fungi:It includes eukaryotic multicellular heterotrophs which are absorptive in their nutritional mode e.g. mushrooms. Most fungi are decomposers. They live on organic material, secrete digestive enzymes and absorb small organic molecules formed by the digestion by enzymes.
  2. Kingdom plantae:It includes eukaryotic multicellular autotrophs. Plants are autotrophic in nutritional mode, making their own food by photosynthesis. They have multicellular sex organs and form embryos during their life cycles. Mosses, ferns and flowering plants are included in this kingdom.
  3. Kingdom Animalia:It includes eukaryotic multicellular consumers. Animals live mostly by ingesting food and digesting it within specialized cavities. They lack cell wall and show movements.

Distinguishing characters of the five kingdoms of life.

Kingdom Cell Type Nuclear Envelope Cell Wall Mode of Nutrition Multi-Cellularity
Monera Prokaryotic Absent Non-cellulose


plus amino acids)


or heterotroph

Protista Eukayrotic Present Present in some forms, various types Photosynthetic or heterotroph, or combination Absent in most forms
Fungi Eukaryotic Present Chitin Absorptive


Present in most forms
Plantae Eukaryotic Present Cellulose and other


Photosynthetic Present in all forms
Animalia Eukaryotic Present Absent Ingestive




Viruses Place in Biodiversity and Systems of Classification


Status of Viruses: Viruses are at the borderline of living and nonliving. They show characteristics both like living and non living.

Living characteristics of viruses: **They have nucliec acids (DNA OR RNA).

** They show reproduction.

** show sensitivity.

Non-Living characteristics: **They can be crystallized.

** In non living environment they show no sensitivity.

** They are A-cellular.


Prions are composed of protein only and Viroids are composed of circular RNA only. Both these particles cause infectious diseases in certain plants. These are excluded from five kingdom system of classification due to both living and non-living characteristics.

Position of virus in five kingdom system or why viruses are excluded from five kingdom system of classification: viruses are excluded from five kingdom system of classification due to both living and non living characteristics.

Binomial Nomenclature and Biodiversity


Nomenclature: A system of naming organisms is called nomenclature.

BINOMIAL NOMENCLATURE; A system of giving two word name to an organism is called Binomial nomenclature.

Explanations: Carolus Linnaeus(1707-1778 AD) first introduced and adopted the system of binomial nomenclature. As the word “binomial” suggests, the scientific name of a species consists of two names: the first is genus name and the second one is the name of species.

Rules, Bases and Principles for assigning scientific names: some rule for assigning scientific names are as follows.

  • Scientific names are usually printed in italics, such as Homo sapiens. When handwritten they are underlined.
  • The first term (generic name) always begins with capital letter, while species name is never capitalized (even when derived from a proper name).
  • The scientific name is generally written in full when it is first used. But when several species from the same genus are being listed, it may then be abbreviated by just using an initial for genus; for example Escherichia coli becomes E. coli.

Aims and Significance of Binomial nomenclature:

In biological research, common names cause many problems. Different regions have different names for the same organism. For example; common name of onion in Urdu is ‘Piyaz’ but in different regions of Pakistan it is also known as ‘ganda’ or ‘bassal’ or ‘vassal’. In other countries, it has other sets of names. In science, it is known with a single name as Allium cepa. In some cases, different organisms are called by the same common name. For example; the name ‘black bird’ is used for crow as well as for raven.

Common names have no scientific basis. For example; a fish is a vertebrate animal with fins and gills. But several common names of ‘silver fish’, ‘cray fish’, ‘jelly fish’, and ‘star fish’ do not fit the biologist’s definition of a fish. To avoid all these confusions, organisms are given scientific names by using binomial nomenclature . The value of this system is due to its widespread use and the stability of its names. In binomial nomenclature, every species can be unambiguously identified with just two words. Same name can be used all over the world, in all languages, avoiding difficulties of translation.



Common Name Scientific Name
Onion Allium cepa
Common sea star (starfish) Asterias rubens
House crow Corvus splendens


Sometime organisms are named in honor of the research workers who described and classified them. For example; the Orchid tree (Mountain-ebony) was named as Bauhinia variegata after the Swiss botanists Bauhin. Bauhinia variegata is an ornamental tree found in southeast Asia.


Conservation of biodiversity: Conservation is the protection, preservation, management and restoration of wildlife and natural resources such as forests and water.

Types of Conservation: There are two types of conservation.

  • Insitu conservation: Conservation of habitats, species and ecosystems where they naturally occur.
  • Ex-situ conservation: The conservation of elements of biodiversity out of their natural refered to as ex-situ conservation. Zoo and Botanical gardens are example of this type of conservation.


Answer: EXTINCT SPECIES: A species is called extinct when there is no doubt that the last individual of that species has died in that ecosystem. E.g, Dinosaur.

ENDANGERED SPECIES: A species is called endangered when it is at risk of extinction in near future. Examples of endangered animal species are lion, tiger, Asiatic cheetah, Indian one-horned rhinoceros, swamp deer, Indian wild ass, hangul, black buck etc.


Interesting information:

Hot spots: A region of high conservation patriority is known as hot spot.

Keystone species: Species that play a key rule in functioning of a habitat and their loss would lead to greater than average change in other species population or ecosystem processes are known as keystone species.

Flagship species: Species that are threatened and are easily conserved as compared to other threatened species are known as flagship species.

Question#16) briefly describe about importance of forests?

Answer: Importance of Forests: Forests support considerable biodiversity. The utilization of forest products, including timber and fuel wood, have played a key role in human societies. Today, developed countries continue to utilize timber for building houses and wood pulp for making paper. The forest products industry is a large part of the economy in developed and developing countries. Short-term economic gains made by conversion of forest to agriculture often leads to loss of long-term income.

Forests extract carbon dioxide and pollutants from the air, thus contributing to biosphere stability. Forests are also valued for their aesthetic beauty and tourist attraction.

IMPACTS OF HUMAN BEINGS ON BIODIVERSITY: Human beings effect biodiversity by different ways. Some are as follows.

  • Deforestation: Cutting down or removal of the forests is known as deforestation.

Causes of Deforestation: forests can be cleared due to poverty, buildings developments, fuel, etc. Poverty is the main cause of deforestation. Poor people go to forests and cut down trees to meet their needs. Forest fire is also a major cause.

Affects of deforestation: Deforestation affects the amount of water in soil and moisture in atmosphere. When there are no trees to keep soil in place, there are more chances of soil erosion. Heavy rainfall washes soil into rivers . Essential nutrients are washed out of soil. Rivers become choked up with mud and silt, which can cause floods. The silted water gets stored in dams and it reduces their water storage capacity. Deforestation also contributes to decreased transpiration, which reduces cloud formation. This ultimately reduces the sources of rains.

More than 260,000 people are added to the world population each day, or more than 180 each minute!


Habitat loss is probably the greatest threat to biodiversity on Earth today.



Sea star (starfish) eats mussels. If sea stars are removed from a region in ocean, mussels rapidly increase in number. Large number of mussels prey on small animals and become dangerous for their existence.


Eucalyptus plants were imported from Australia and introduced in Pakistan. These plants consume more water and have disturbed the water table (level of underground water). It harms other small plants that grow near Eucalyptus trees.


The race to produce cash through fruits, spices, sugar, tobacco, soap, rubber, paper, and cloth has stimulated many to get them by using soil and by destroying the forests.
In developing countries, almost 3 billion people rely on wood for heating and cooking.


These important aspects of forests are also harmed due to deforestation. In Pakistan too, deforestation is a great threat to biodiversity. In the province Khyber Pakhtunkhwa, the closed canopy forests are shrinking at approximately 1% per year.


Over-hunting has been a significant cause of the extinction of hundreds of species and the endangerment of many more such as whales, ibex, urial, markhor (the national animal of   Pakistan) etc. Commercial hunting, both legal and illegal, is the principal threat.


STEPS FOR THE CONSERVATION OF BIODIVERSITY: Conservation of biodiversity has become a global concern. Biologists urge the national policy makers to state a set of rules necessary to protect a species. They demand that laws should define species which are threatened by extinction and must be protected. Though rich in biodiversity, Pakistan today faces severe threats to its animal and plant species. The greatest concern is the loss of natural habitats. Main causes of this loss are rapid growth in human population and the prevailing poverty in rural areas of Pakistan. In addition, low literacy rate is also a reason for the failure of conservation measures taken so far.

The International Union for the Conservation of Nature and Natural Resources (IUCN) and the World Wildlife Fund-Pakistan (WWF-P) work in close coordination with Pakistan’s Ministry of Environment and other government and non-government institutions. The IUCN has prepared the first national Red List (list of endangered or threatened species).


Following are a few examples of environmental work that has been carried out in Pakistan in order to conserve species and associated habitats.

  1. National Conservation Strategy:In 1980’s, IUCN and the government of Pakistan formulated the National Conservation Strategy for Pakistan for the conservation of Pakistan’s biodiversity.
  2. UN Convention on Combating Desertification (CCD):This is an international treaty against damage and poverty in dry-lands. Pakistan signed this in 1997.
  3. Himalayan Jungle Project (HJP):It started in 1991 in the Palas Valley, in Khyber Pakhtunkhwa (KP). It aimed at protecting one of the richest areas of biodiversity in Pakistan.
  4. Conservation of biodiversity of the Suleiman Range, Balochistan:Suleiman Range Chilghoza Forest is the largest Chilghoza forest in the world. In 1992, the WWF-P started its conservation program.
  5. Northern Areas Conservation Project: The northern areas of Pakistan serve as a habitat for a number of wildlife species. The survival of these species is under threat. The NACP is a project of WWF-P which is successful in implementing a ban on the hunting of these species.
  6. Conservation of migratory birds in Chitral, KP: Chitral lies on the migratory route of several important bird species. These birds face enormous hunting pressure. WWF-Pakistan initiated efforts to reduce the hunting pressure in 1992. The efforts proved successful.
  7. Conservation of Chiltan Markhor:Hazarganji National Park is located close to Quetta and is the only remaining habitat of Chiltan Markhor in the country. WWF- Pakistan developed the management plan of the park.
  8. Ban on games:Foreigners visit the northern areas and play many games in which bears are used. WWF Pakistan has been successful in imposing a ban on this illegal practice.


The threat to biodiversity is among the hot topics discussed at the UN World summits.



Due to human activities, the biodiversity in Pakistan is facing a great loss. Here are a few examples of endangered species in Pakistan.


Indus dolphin

According to WWF-P, only 600 animals of the species of Indus dolphin are left today in the Indus River. The population of this species declined due to water pollution, poaching, and destruction of habitat.


The northern areas provide habitats to Musk deer, Snow leopard, Astore markhor and Himalayan ibex, Woolly flying squirrel and the Brown bear.


It is estimated that about 200,000 of the one million migratory birds passing through Chitral are killed during migration.



The herders capture the bear cubs and sell them to the trainers who train them and sell to the foreigners.

Marco Polo sheep

Marco Polo sheep are mostly found in the Khunjerab National Park and nearby areas. Their numbers have been rapidly decreasing in the last two decades and WWF-P has started projects for its conservation.

Houbara bustard

This bird flies to Pakistan in winter season from former Soviet territory and settles in Cholistan and Thar deserts. The decline in its population is due to hunting by foreigners and destruction of its habitats.

Mode of nutrition of animals is ingestive heterotrophic while that of fungi is absorptive heterotrophic.

Question) It is difficult to use the criterion of interbreeding to define species of unicellular organisms. Why?

Answer: It is difficult to use the criterion of interbreeding to define species of unicellular organisms because most of the unicellular organisms do not show sexual reproduction, instead they reproduces by asexual methods.

Question) What are the contributions of Whittaker, Margulis and Schwartz in taxonomy?

Answer: Whittaker proposed the five kingdom system of classification while Margulis and Schwartz modify it.

Question) Define the following terms?


  • A-cellular OR A cellular bodies: Living creatures not consisting of cells are called a-cellular bodies. These particles show some characteristics of the cell or living organisms but also show characteristics of non living.
  • Soil erosion: The washing away of the top layer of soil is called soil erosion.
  • Taxon: Any of the category in the taxonomic hierarchy or classification system is called taxon.
  • Viroid: An infectious agent similar to a virus but consisting of only a short, single strand of RNA without a protein coat is called viroid. Viroids cause infections in plants.
  • WWF: World wildlife fund(WWF) is the world largest conservation organization that protect natural resources, specially organisms and their habitat from various impacts.

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