Basics of Biodiversity

Biodiversity

Biodiversity is defined as ‘the variability among living organisms from all sources, including terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are a part; this includes diversity within species, between species and of ecosystems (United Nations Earth Summit (1992))

State of a species being native to a single defined geographic location, such as an island, state, nation, country or other defined zone is called Endemism.

More than 70 per cent of all the species recorded are animals, while plants (including algae, fungi, bryophytes, gymnosperms and angiosperms) comprise no more than 22 percent of the total. Among animals, insects are the most species rich taxonomic group, making up more than 70 per cent of the total. Maximum biodiversity on earth is observed in the Amazon rainforest. India accounts for nearly 7% of recorded species.

BASIC CONCEPTS

Plant classification:

• Herb is defined as a plant whose stem is always green and tender with height of not more than 1 metre.

• Shrub is defined as a woody perennial plant differing from a perennial herb in its persistent and woody stem. It differs from a tree in its low stature and its habitat of branching from the base. Not more than 6 metres in height.

• Tree is defined as a large woody perennial plant having a single well defined stem with a more or less definite crown.

• Parasites an organism that draws a part or whole of its nourishment from another living organism. These plants do not draw moisture and mineral nutrients from the soil. They grow on some living planet called host and penetrate their sucking roots, called haustoria, into the host plants. Total parasite draws whole of its nourishment. Partial parasite draws a part of its nourishment.

• Epiphytes grow on the host plant but are not nourished by the host plant as they don’t draw food from the host plant. They only take the help of the host plant in getting access to light. Their roots perform two functions. While changing roots establish the plant on the branches of the host plant, aerial roots draw moisture from the air Eg : Vanda.

• Climbers herbaceous or woody plant that climbs up trees or other support by twining round them or by holding on to them by trendrills, hooks, aerial roots or other attachments.

Classification of Life Forms :

Classification of life forms is closely related to evolution. The living organisms which have evolved from the same ancestor would tend to stay in the same group during classification. Various biologists have tried to classify all living organisms into broad categories called the kingdom.

The classification, Robert whittaker (1969) proposed is widely used and has five kingdoms:

1. Monera
2. Protista
3. Fungai
4. Plantae
5. Animalia

The number of kingdoms were expanded to 7 in 2015 by Ruggerio. These are monera, archaea, protozoa, chromista, fungi, plants and animals. The classification also has two super kingdoms (prokaryote and eukaryote). In 1990, three domain system (archaea, bacteria and eukaryote) of biological classification was introduced by Carl worse.

The above groups have been formed based on the cell structure, mode and source of nutrition and body organization.Further classification is done by naming the subgroups at various levels as  given in the following scheme:

1. Kingdom
2. Phylum (for animals) division (for plants)
3. Class
4. Order
5. Family
6. Genus
7. Species

Humans:

1. Kingdom: Animalia
2. Phylum: chordate
3. Class: Mammalia
4. Order: primates
5. Family: Hominidae
6. Crenus: homo
7. Species: homosapiens.

Thus, by separating organisms on the basis of a hierarchy of characteristics into smaller and smaller groups, we arrive at a basic unit of classification which is a species. Broadly, a species includes all organisms that are similar enough to breed and perpetuate. (gene pool and  fertile offsprings)

1. Monera and Archaea :

• All prokaryotes are found in this kingdom.
• Don’t have a defined nucleus or organelles
• Don’t show multicellular body design.
• Show diversity based on other characteristics.
• Cell walls- some have, some not.
• Autotrophic or heterotrophic.

This kingdom is divided into two sub-kingdoms- Archaebacteria (ancient) and Eubacteria (true). Monerans are important decomposers and mineralizers in the biosphere. They also live in extreme habitats such as hot springs, deserts, snow and deep oceans where very few other life forms can survive. Many of them live in or on other organisms as parasites.

The organism may be unicellular as in eubacteria and filamentous as in cyanobacteria. Eg. Bacteria, blue green algae or cyanobacteria (it is considered a bacterium and the term algae is reserved for eukaryotes organisms only, it is autotrophic), mycoplasma (lacks a cell wall around their cell membrane).

The cyanobacteria (also referred to as blue-green algae) have chlorophyll similar to green plants and are photosynthetic autotrophs. The cyanobacteria are unicellular, colonial or filamentous, freshwater/marine or terrestrial algae. The colonies are generally surrounded by a gelatinous sheath. They often form blooms in polluted water bodies. Some of these organisms can fix atmospheric nitrogen in specialised cells called heterocysts,  e.g. Anabaena, Nostoc, Oscillatoria, and Spirulina, etc.

2. Protista (or protozoa)

It is a group made up of protozoa, unicellular algae (but eukaryotic) and slime moulds. The heterotrophic portion is protozoa. It is the hodgepodge category i.e it consists of organisms that don’t fit in any of the other categories. Protists are eukaryotic organisms that cannot be classified as a plant, animal or fungus. Mostly unicellular, but some like algae are multicellular (e.g seaweed is a large multicellular protists – it lacks the cellular characteristics of plants and hence not classified as plants.

• Can be autotrophic or hetero trophic (eg amoeba)
• Primarily live in water (some in moist soil). Can be found anywhere on earth where there is liquid water (even in humans)
• Some of these organisms use appendage such as hair like cilia or whip like flagella for moving around.

Unicellular algae, diatoms (major group of algae and among most common type of phytoplankton) and protozoa. Plasmodium falciparum (a protozoa) cause malaria in humans.

3. Fungi

• These are heterotrophic, eukaryotic organism.
• They use decaying organic material as food and are therefore called saprophytes.
• Many of them have the capacity to become multicellular organisms at some stage of life.
• They have cell walls made by tough complex sugar called chitin.

Eg : i) yeast ,mushrooms etc.

Some fungal species live in permanent mutually dependent relationships with blue green algae (or cyanobacteria) such relationships are called symbiotic. Their symbiosis life forms are called lichens.

The uses of fungi are as follows:

1. Fungi are used in the production of antibiotics, medicines such as penicillin, streptomycin.
2. Mushrooms that are highly proteinaceous belong to fungi that are consumed in the form of food.
3. In the bakery yeast is used in all the products and also in the food and beverages industries.

4. Plantae :

• Multicellular eukaryotes with cell walls.
• They are autotrophs and use chlorophyll for photosynthesis.

 Thus, all plants are included in this group.

Floral diversity : plant kingdom : In terms of plant diversity, India ranks tenth in the world and fourth in Asia. India represents nearly 11%  of the world’s know floral diversity

Thallophyte ( commonly called algae): Plants that don’t have well differentiated body design fall in this group. The plants in this group are commonly called algae. The plants are predominantly aquatic. Eg : spirogyra, Ulothrix , Cladophora , Ulva, Chara etc.

Bryophytes : No vascular tissues. They have differentiated body parts like stems and leaves. However, no specialised tissue for conduction of waters and other substances from one part of the plant body to another. Reproduction through spores (not seeds). All bryophytes reproduce through spores and not seeds. Eg:  moss (Funaria) Marchantia, liverwort, hornworts, mosses) They cannot circulate rain water through their stems and leaves but must absorb it from the environment that surrounds them. The plant body is differentiated into a small stem and simple leaves, but true roots are absent. Usually grow in moist places.

Bryophytes are the second largest group of green plants in India distributed largely in eastern Himalayas, North eastern India, Western Himalaya and the Western ghats. Mosses consist of the major component of Indian bryo flora followed by liverworts and hornworts.

Pteridophyte :  They are the most basic vascular plants having a simple reproductive system lacking flowers and seeds. Vascular plants have specialised tissues for conduction of water and other substances from one part of the plant body to another. (xylem & phloem) Well differentiated body parts : well differentiated plant body into roots, stem and leaves. Reproduction through spores. Produce neither flowers nor seeds, so they are referred to as cryptogams. Most of them are terrestrial plants flourishing well in moist and shady places, and some of them are aquatic. This group of vascular cryptogams like club mosses, horsetails and ferns which are universally distributed all over the world

In India, the north eastern region (including eastern Himalaya) is rich in pteridophyte diversity, followed by South India (including eastern and western ghats)and North India (including Western Himalayas).

Note : the thallophytes, the bryophytes and the pteridophytes have naked embryos that are called spores. The reproductive organs in all these three groups are very inconspicuous and they are therefore called cryptogams or those with hidden reproductive organs.

Gymnosperms (seed not enclosed) eg. Conifers : Group of seed producing plants that include conifers, cycads, ginkgo and gnetales (origin of word : Greek gymnos: naked, sperma : seed). This is named so after the enclosed condition of their seeds. The naked condition of seeds of gymnosperm stands in contrast to the seeds and ovules of flowering plant (angiosperms) which are enclosed within an ovary.  In gymnosperms ovules are present on the surface of the megasporophylls and are directly pollinated by the pollen grains. There is nothing like ovary, style and stigma and naturally there is not fruit.

Angiosperms (seed enclosed) eg. Flowering plants. The word is made from two Greek words: angio means covered and sperma means seed. Angiosperms, the flowering plants are the most diverse group of land plants. Angiosperms are the seed producing plants like the gymnosperms and can be distinguished from the gymnosperms by characteristics including flowers, endosperm within the seeds, and the production of fruits that contains the seed.

These are the most highly developed plants which bear flowers having conspicuous accessory and essential whorls. Carpels have the ovary, style and stigma. With the stimulus of fertilisation the ovary generally develops into fruit and the ovules in seeds thus, the seed remains within the fruit. Plant embryos in seeds have structures called cotyledons. Cotyledons are called seed leaves because in many instances they emerge and become green when the seed germinates. Thus, cotyledons represent a bit of pre- designed plant in the seed.

The angiosperms are divided into two groups on the basis of the number of cotyledons present in the seed. Monocotyledons / monocots: plants with seeds having a single cotyledon (embryonic leaf). They are generally grass and grass like flowering plants  Eg: wheat, rice, maize etc are a monocotyledons). Other economically important monocotyledons include palms, banana, ginger, turmeric, onion, garlic etc.  Dicots: plants with seeds having two.

5. Animal kingdom: Animalia

 These are organisms which are eukaryotic, multicellular, heterotrophic. They can be broadly classified as vertebrates and invertebrates. Vertebrates are animals with backbone and spinal columns i.e. these animals have a true vertebral column and internal skeleton, allowing for a complete by different distribution of muscle attachment points to be used for movement.

Vertebrates are bilaterally symmetrical triploblastic (derived from three embryonic cell layers- ectoderm, mesoderm and endoderm) coelomic and segmented with complex differentiation of body tissues and organs.  All chordates( phylum) possess the following features :

• Have a notochord.
• Have a dorsal nerve cord.
• Are triploblastic.
• Have paired gill pouches.
• Are coelomates.

Vertebrates are the most advanced organisms on earth. Although they represent a very small percentage of all animals, their size percentage of all animals, their size and mobility often allow them to dominate their environment. Vertebrates can further classified into 5 groups :

• Fishes
• Amphibians
• Reptiles
• Birds
• Mammals

Invertebrates: Invertebrates are animals without backbones; more than 98% animal species in the world are invertebrates. Invertebrates don’t have an internal skeleton made of bone. Many invertebrates have fluid filled, hydrostatic skeletons, like the jelly fish or worm. Others have a hard outer shell, like insects and crustaceans. It can be classified as:

• Porifera
• Coelenterate (cnidaria)
• Planty helminths
• Nematoda
• Annelida
• Arthropods – can be further divided into Insects, Crustaceans, Arachnids
• Mollusks
• Echinoderms
• Protochordate

Porifera :  The word porifera means organism with holes. These are holes or pores all over the body. These lead to a canal system that helps in circulating water throughout the body to bring food and oxygen. These animals are covered with a hard outside layer or skeleton. The body design involves very minimum differentiation and division into tissues. They are commonly called sponges and mainly found in marine habitats.

Coelenterate (cnidaria) : Animals living in water. They show more body design differentiation. The body is made of two layers of cells.One makes up the cells on the outside of the body, and the other makes the inner lining of the body. Some of the species live in colonies (corals), while others have a solitary life span (hydra) Jellyfish and sea anemones are common examples.

Platyhelminthes: More complex than porifera and coelenterata. The body is bilaterally symmetrical, meaning that the left and the right half of the body has the same design. There are three layers of cells from which differentiated tissues can be made which is why such animals are called triploblastic. This allows outside and inside body linings as well as some organs to be made. There is thus some degree of tissue formation.

However, there is no true internal body cavity or coelom, in which well developed organs can be accommodated. The body is flattened dorsiventrally meaning from top to bottom which is why these animals are called flatworms. Either free living or parasitic. Some examples: Planarians, or parasitic animals like liver flukes.

Nematoda : The nematoda body is also bilaterally symmetrical and triploblastic. However the body is cylindrical rather than flattened. There are tissues but no real organs, although a sort of body cavity or a pseudo coelom is present.  These are very familiar, as parasitic worms causing diseases such as the worms causing elephantiasis (filarial worms) or the worms in the intestine. (roundworms or pinworms)

Annelids : They are defined as triploblastic, bilaterally symmetrical, metamerically segmented, a coelomate worm with a thin flexible cuticle around the body. They are mostly aquatic, marine or freshwater, some are terrestrial borrowing. Body organisation is that of an organ grade system.

Arthropoda : Probably the largest group of animals. These animals are bilaterally symmetrical and segmented. They have jointed legs (the word arthropod means jointed legs). They make up 75% of the world’s animal species. Have limbs with joints that allow them to move. They also have an exoskeleton which is a hard, external skeleton. They include cockroaches, crabs, butterflies, beetles, scorpions, shrimp, spider, lobster, ticks, termites, potato bugs, mites and sea monkeys.

• Arthropods include animals such as insects, crustaceans and arachnids. Largest group of arthropods are the insects. The next large group are crustaceans, including lobsters and crabs. The arachnids include spiders and ticks. Insects are the largest group of arthropods very adaptable, living almost everywhere in the world. Exoskeleton that covers their entire body. The Insect’s body consists of three parts: the heads, thorax and abdomen. Eg: beetle, butterfly, moth, dragonfly, bee etc.

• Crustaceans live mostly in oceans or other waters. Hard external shells which protect their body. Eg crab, lobster and barnacle

• Arachnids: spiders, ticks and scorpions Like other arthropods, the arachnids have a hard exoskeleton and jointed appendages for walking. Most have four pairs of legs. Unlike other arthropods, arachnids do not have antennae. Eg: spider, scorpion etc.

Mollusks : In the animals of this group, there is bilateral symmetry. The coelomic cavity is reduced, little segmentation is present. There is an open circulatory system and kidney like organ for excretion. There is a foot that is used to move around. Most mollusks have a soft, skin-like organ covered with a hard outside shell. Some live on land such as snails or slugs. Other mollusks live in water, such as the oyster, mussel, clam, squid, octopus etc.

Echinoderms : Exclusively free living marine animals. They are triploblastic and have a coelomic cavity. Most have arms that radiate from the centre of their body. Centre body contains organs and mouth for feeding.

Protochordates : They are an informal category of animals named mainly for convenience to describe invertebrate animals that are closely related to vertebrates. These animals are bilaterally symmetrical triploblastic and have a coelom. In addition, they show a new feature of body design, namely a notochord, at least at some stages during their lives. The notochord is a long rod-like support structure( chord = string) that runs along the back of animals  separating the nervous tissues from the gut. It provides a place for muscle to attach for ease of movement. Protochordates may not have a proper notochord present at all stages in their lives or for the entire length of the animal. They are marine animals. Eg Balanoglossus, Herdmania and amphioxus.

SPECIES-RELATED TERMINOLOGIES

Species Richness : Species Richness is the number of different species represented in an ecological community, landscape or region. Species richness is simply a count of species, and it does not take into account the abundances of the species or their relative abundance distributions. It is a measurement of the relative frequency of each species.

Species evenness :  refers to how close in numbers each species in an environment is. Mathematically it is defined as a diversity index, a measure of biodiversity which quantifies how equal the community is numerically. So, if there are 40 foxes and 1000 dogs, the community is not very even. It is a number of species found in said environment.

Species diversity of an environment is essentially a combined measurement of richness and evenness. Sometimes, it is called the Shannon Diversity Index.

 Important Terms Related to Ecosystem

• Biopiracy: Practice in which indigenous knowledge of nature, originating with indigenous peoples, is used by others for profit, without authorization or compensation to the indigenous people themselves.

• Bioprospecting: Systematic and organised search for useful products derived from bioresources including plants, microorganisms, animals, etc., that can be developed further for commercialization and overall benefits of the society.

• Biomining: Process of using microorganisms (microbes) to extract metals of economic interest from rock ores or mine waste. Biomining techniques may also be used to clean up sites that have been polluted with metals.

• Bioassay: A test in which organisms are used to detect the presence or the effects of any other physical factor, chemical factor or any other type of ecological disturbance. It is very common in pollution studies; the aim is to detect lethal concentration or effective concentration causing mortality or other effects.

Levels of Biodiversity :

• Genetic Diversity : It is concerned with the variation in genes within a particular species. Genetic diversity allows species to adapt to changing environments. This diversity aims to ensure that some species survive drastic changes and thus carry-on desirable genes. Genetic diversity gives us beautiful butterflies, roses, parakeets or coral in a myriad hues, shapes and sizes.

• Species Diversity : It refers to the variety of living organisms on earth. Species differ from one another, markedly in their genetic makeup, do not interbreed in nature. Closely related species however have in common much of their hereditary characteristics. It is the ratio of one species population over the total number of organisms across all species in the given biome. Zero would be infinite diversity, and one represents only one species present.

Species diversity refers to the variety in number and richness of the species in any habitat. The number of species per unit area at a specific time is called species richness, which denotes the  measure of species diversity. The Western Ghats have greater amphibian species diversity than the Eastern Ghats. The more the number of species in an area the more is the species richness

The three indices of diversity are – Alpha, Beta and Gamma diversity.

1. Alpha diversity: It is measured by counting the number of taxa (usually species) within a particular area, community or ecosystem.

2. Beta diversity: It is species diversity between two adjacent ecosystems and is obtained by comparing the number of species unique to each of the ecosystems.

3. Gamma diversity: It refers to the diversity of the habitats over the total landscape or geographical area.

• Ecosystem/ Community Diversity : Community diversity refers to the different types of habitats. A habitat is the cumulative factor of the climate, vegetation and geography of a region. There are several kinds of habitats around the world. Corals, grasslands, wetland, desert, mangrove and tropical rain forests are examples of ecosystems.

• Pattern Diversity : Diversity resulting from the differences due to zonation, periodicity, stratification, food webs, patchiness and habitat condition is referred to as pattern diversity . It is environmentally induced diversity.

Magnitude of biodiversity:

Biodiversity is often quantified as the number of species in a region at a given time. The current estimate of different species on earth is around 8-9 million. However, we really don’t know the exact magnitude of our natural wealth. This is called the ‘The Taxonomic impediment’. So far about 1.5 million species of microorganisms, animals and plants have been described. Each year about 10-15 thousand new species are identified and published worldwide, of which 75% are invertebrates. The number of undescribed species is undoubtedly much higher.

India is very rich in terms of biological diversity due to its unique bio-geographical location,

diversified climatic conditions and enormous eco-diversity and geo-diversity. According to world biogeographic classification, India represents two of the major realms (The Palearctic and Indo-Malayan) and three biomes (Tropical humid forests, Tropical Dry/ Deciduous forests and Warm Deserts/Semi deserts).

With only about 2.4% of the world’s total land surface, India is known to have over 8% of the species of animals that the world holds and this percentage accounts for about 92,000 known species. India is the seventh largest country in the world in terms of area. India has a variety of ecosystems, biomes with its varied habitats like, hills, valleys, plateaus, sea shores,

mangroves, estuaries, glaciers, grasslands and river basins. It also reflects different kinds of climates, precipitation, temperature distribution, river flow and soil. India is one of the 17 mega biodiversity countries of the world and has ten biogeographic zones with characteristic habitat and biota.

“The world is currently undergoing a very rapid loss of biodiversity comparable with the great mass extinction events that have previously occurred only five or six times in the earth’s history.” – World Wildlife Fund

 Patterns of biodiversity distribution :

The distribution of plants and animals is not uniform around the world. Organisms require different sets of conditions for their optimum metabolism and growth. Within this optimal range (habitat) a large number and type of organisms are likely to occur, grow and multiply. 

Latitudinal and altitudinal gradients : Temperature, precipitation, distance from the equator (latitudinal gradient), altitude from sea level (altitudinal gradient) are some of the factors that determine biodiversity distribution patterns.

The most important pattern of biodiversity is latitudinal gradient in diversity. This means that there is an increasing diversity from the poles to the equator. Diversity increases as one moves towards the temperate zones and reaches the maximum at the tropics. Thus, tropics harbour more biodiversity than temperate or polar regions, especially between the latitudes of 23.5⁰N and 23.5⁰S (Tropic of Cancer to the Tropic of Capricorn).

Harsh conditions exist in temperate areas during the cold seasons while very harsh conditions prevail for most of the year in polar regions. Columbia located near the equator (0⁰) has nearly 1400 species of birds while New York at 41⁰N has 105 species and Greenland at 71⁰N has 56 species. India, with much of its land area in the tropical latitudes, is home for more than 1200 species of birds.

Thus, it is evident that the latitude increases the species diversity. Decrease in species diversity occurs as one ascends a high mountain due to drop in temperature. (temperature decreases @ 6.5⁰C per Km above mean sea level)

The reasons for the richness of biodiversity in the Tropics are:

• Warm tropical regions between the tropic of Cancer and Capricorn on either side of the equator possess congenial habitats for living organisms.

• Environmental conditions of the tropics are favourable not only for speciation but also for supporting both variety and number of organisms.

• The temperatures vary between 25⁰C to 35⁰C, a range in which most metabolic activities of living organisms occur with ease and efficiency.

• The average rainfall is often more than 200 mm per year.

• Climate, seasons, temperature, humidity, photoperiods are more or less stable and encourage both variety and numbers.

• Rich resource and nutrient availability.

Significance of Biodiversity:

Biodiversity is the variety of life on earth. That is, it is the number of different species of flora and fauna including microorganisms. These organisms can inhabit different ecosystems with varying conditions like the Rainforests, Coral reefs, Grasslands, Deserts, Tundra and the Polar ice caps. This variety (Biodiversity) is essential for the wellbeing of our planet and sustenance of life as a whole.

Ecologist Paul Ehrlich proposed the ‘Rivet Popper Hypothesis’ for better understanding the loss of each species in the ecosystem. He compared each species of an ecosystem with rivets in the body of an aeroplane. Thousands of rivets (species) join all the parts of an aeroplane (ecosystem). If every passenger travelling in the aeroplane starts taking rivets home (loss of species), initially it may not affect flight safety (proper functioning of the ecosystem). However, the plane becomes dangerously weak over a period of time, when more and more rivets are removed. Moreover, which rivet is removed is also important. When the key rivets (removal of keystone species) on the wings of the aeroplane are removed, undoubtedly it poses a serious threat to the flight safety. Thus we understand the role of every species for the hormonal function of an ecosystem.

The importance of biodiversity can be viewed and measured as :

• Ecosystem services.
• Biological resources.
• Social benefits of biodiversity

The major functional attributes are:

• Continuity of nutrient cycles or biogeochemical cycles. (N2, C, H2O, P, S cycles)

• Soil formation, conditioning or maintenance of soil health (fertility) by soil microbial diversity along with the different trophic members.

• Increases ecosystem productivity and provide food resources.

• Act as water traps, filters, water flow regulators and water purifiers. (forest cover and vegetation)

• Climate stability (forests are essential for rainfall, temperature regulation, CO2 absorption, which in turn regulate the density and type of vegetation)

• Forest resource management and sustainable development.

• Maintaining balance between biotic components.

• Cleaning up of pollutants – microbes are the biggest degraders of molecules including many anthropogenic ones which are present in effluents, sewage, garbage and agro-chemicals.

• Ecological stability – the varieties and richness of species contribute to ecological stability and survival of species. Bio diverse regions are reservoirs of biological resources like food resources, gene pool, genetic resource, and medicinal resources, bio-prospecting.

• To provide unique aesthetic value and hot spots for Ecotourism. Along with forest resources and wildlife it has commercial significance.

• An indicator of the health of the ecosystem. Endemism is a crucial indicator of richness.

Threats to biodiversity:

Even though India is one of the 17 identified mega diverse countries of the world, it faces lots of threats to its biodiversity. Apart from natural causes, human activities, both directly and indirectly are today’s main reason for habitat loss and biodiversity loss. Fragmentation and degradation due to agricultural practices, extraction (mining, fishing, logging, harvesting) and development (settlements, industrial and associated infrastructures) leads to habitat loss and fragmentation leads to formation of isolated, small and scattered populations and as endangered species.Some of the other threats include specialised diet, specialised habitat requirement, large size, small population size, limited geographic distribution and high economic or commercial value.

Large mammals by virtue of their size require larger areas to obtain the necessities of life – food, cover, mates than do smaller mammals. Individual home range of Lion can be about 100 square Km. Mammals have specialised dietary needs such as carnivores, frugivores and the need to forage over much larger areas than general dietary herbivores and omnivores. Mammals also have low reproductive output other than small rodents.

Causes of biodiversity loss : The major causes for biodiversity decline are :

• Habitat loss, fragmentation and destruction. (affects about 73% of all species)
• Pollution and pollutants. (smog, pesticides, herbicides, oil slicks, GHGs)
• Climate change.
• Introduction of alien/exotic species.
• Over exploitation of resources (poaching, indiscriminate cutting of trees, over fishing, hunting, mining)
• Intensive agriculture and aquaculture practices.
• Hybridization between native and nonnative species and loss of native species
• Natural disasters (Tsunami, forest fire, earthquake, volcanoes.
• Industrialization, Urbanization, infrastructure development, Transport – Road and Shipping activity, communication towers, dam construction, unregulated tourism and monoculture are common areas of specific threats.
• Co-extinction.