8 Concepts, Types and Distribution of Biodiversity

Saleha Jamal

     

    1. Introduction

1.1 Elements of Biodiversity

1.2 Types of biodiversity

1.2.1 Ecosystem or ecological diversity

1.2.2 Species diversity

1.2.3 Genetic diversity

1.3 Important Values of biodiversity

1.3.1 Direct values

1.3.2 Indirect values

1.4   Distribution of biodiversity

1.4.1 Terrestrial Biomes

1.4.2 Aquatic Ecosystems

1.5 Major biodiversity threats

1.6 Conclusion

Objectives

At the end of this module the student should be able to:

• Explain the concept and definition of biodiversity
• Recognize different elements of biodiversity
• Explain the difference between ecosystem, species, genetic diversity
• Learn distribution of biodiversity
• Recognize major biodiversity threats

1. Introduction

The term biodiversity has been commenced by Walter Rosen in 1986. Biological diversity is abbreviated as biodiversity which refers to the sum total of species, populations, communities and ecosystems. It may also be defined as the variety and variability among the living organisms (aunicellular fungi, protozoa, bacteria, and multi cellular organisms such as plants, fishes, and mammals) and the ecological complexes (including gens, habitats, and ecosystem) in which they occur. Biological diversity or Biodiversity is defined as the

     1.1 Elements of Biodiversity

Ø  Ecosystem Difference: is described by various types of ecosystems having certain sets of environmental conditions together with biological population, in fact, ecosystem diversity refers to number of ecosystems and different ecological processes operating in a certain area.

Ø  Temporal difference: refers to variation in time duration in terms of sequential progress of biotic communities. The biodiversity of an area is always measured in terms of temporal factor i.e. the condition of biological communities in the past, at the present time and in future. Here we also learn the course of development and destruction of species and their future standing.

Ø  Genetic difference: which establishes richness of biological variety of a specified ecosystem because genetic difference within and between the populations of species of a ecosystem verifies the nature and course of reproduction of species, productivity, adaptability to particular or composite environmental conditions and changes there in capability, mutualism etc.

Ø  Species difference: refers to variety of species of biological population including species of plants, animals and micro-organisms of a particular ecosystem. Species diversity determines number of different species that are represented in a given community (a dataset) which incorporates both species richness and the evenness of species’ abundances.the richer the variety of species the larger and more complex is the food chains and abundance is the biodiversity and more stable ecosystem.

     1.2 Types of biodiversity

   Biodiversity can be divided into following three levels;

i. Ecosystem or ecological diversity

ii. Species diversity

iii. Genetic diversity

1.2.1  Ecosystem or ecological diversity

Biodiversity is considered at ecosystem level as it determines the variety and number of species in particular ecosystems through the different habitats for biological communities and biological processes operating in each natural ecosystem. A region may have numerous ecosystems, or it may have one. Vastnesses of oceans or deserts are examples of regions with small ecological diversity while a mountain area which may have lakes, forests and grasslands will have greater biodiversity. A region with numerous ecosystems may be able to provide more resources to help indigenous species to survive, particularly when one ecosystem is exposed by drought or disease. Ecosystem diversity is often assessed through the relative richness of diverse species and considering types of species.

Ecosystem diversity has three outlooks;

a) Alpha (α) Diversity : It is the biodiversity within a particular region, community or ecosystem. It is usually expressed by the number of species in that ecosystem. This can be calculated by including the number of distinct groups of organisms (taxa) within the ecosystem (Families, genera and species).

b) Beta (β) Diversity: Beta diversity is a measure of biodiversity which works by matching up the species diversity between ecosystems or along environmental pitches. This involves matching the number of taxa that are exclusive to each of the ecosystems. It depicts a range of communities due to substitution of species which takes place due to the occurrence of diverse microhabitats, niches and environmental conditions.

c) Gamma (γ) Diversity: It illustrates diversity of habitat over a total geographical area. It is a productof component ecosystems (alpha diversity) and the between component ecosystems (beta diversity). Gamma diversity can be expressed in terms of the species abundance of component communities as follows;

γ  = s1 + s2 – c

s1 = the total number of species recorded in the first community

s2 = the total number of species recorded in the second community c = the number of species common to both communities

     1.2.2 Species diversity

Species is a fundamental unit of classification and is described as largest group of organisms in which two individuals can mate and produce fertile offspring, typically by sexual reproduction and thus, share a common ancestry. The numbers of species of flora and fauna that are present in an area comprise its species diversity. This diversity is seen both in natural ecosystem and in agricultural ecosystems. Some areas are richer in species than others. Every ecosystem contains a unique set of species, all interacting with each other while some ecosystems could have numerous species than another. In some ecosystems, a particular species has grown so large that it takes over the natural community. A great number of species can assist an ecosystem to pull through from environmental threats, even if some species go extinct. The natural world contains about 8.7 million species, according to a new estimate described by scientists as the most accurate ever (Richard Black,2011). Various scientist groups are currently studying both species-rich groups and regions in order to give a reliable depiction of species richness patterns and a base for calculating the number of species on Earth.

The natural world in numbers

§    Animals: 7.77 million (12% described)

§    Fungi: 0.61 million (7% described)

§    Plants: 0.30 million (70% described)

§    Protozoa: 0.04 million (22% described)

§    Chromists: 0.03 million (50% described)

1.2.3    Genetic diversity

Genetic diversity refers to the variation of genes within a population or species. The genetic variation is vital for a vigorous breeding population of a species. Each and every individual of any animal or plant species varies widely from other individuals in its genetic makeupdue to the huge number of grouping possible in the genes that give every individual specific characteristic. Thus, for example, each and every human being is very different from all others.

Genetic diversity can be measured using a variety of DNA-based and other techniques. The genetic material of microorganisms, plants and animals contain information that determines the characteristics of all species and individuals that make up the diversity of the living world. Thus, genetic diversity refers to the differences in genetic make- up between distinct species and to genetic variations within a single species. In simple terms, genetic material dictates whether we have blue or brown eyes, blond or black hair and are tall or short. It also determines whether an individual animal or plant has the ability to survive in a particular habitat or under particular environmental conditions, some plants, for example, are able to grow in saline water as a result of genetic variation. New genetic variation is produced in populations of organisms that can be reproducing sexually by recombination and in individuals by gene and chromosome mutations. The large differences in the amount and distribution of genetic variation can be attributed in part to the enormous variety and complexity of habitats, and the different ways organism obtain their living (Benny Jseph, 2009).

Functional Biodiversity

Number of scientists also identifies the fourth level of biodiversity as functional biodiversity .Here the way species act, obtain food and utilize the natural resources of an ecosystem is known as functional diversity. Generally a species-rich ecosystem is supposed to have high functional diversity, as there are numerous species which also varies in their behaviours. Studying an ecosystem’s functional diversity can be helpful to environmentalist trying to preserve or restore the damaged , because understanding the behaviours and functions of species can point to gaps in a food cycle or ecological niches that are lacking species.

1.3 Important Values of biodiversity

Values related to biodiversity can be grouped into two categories as below:

i. Direct values and

ii. Indirect Values

1.3.1     Direct values

The direct values iclude (i) Consumptive use value and (ii) Productive use value.

Consumptive use value: here the biodiversity2 products are consumed directly for example food (plants, fishes), fuel (wood, coal, petroleum, natural gas) and drugs (Quinine, Penicillin, Tetracycline, vinblastin and vincristine)

Productive use values: In productive use the product is commercially sold in national and international marke like textile, leather, silk, paper and pulp industry etc.

1.3.2    Indirect values

Indirect values include social and cultural values, ethical values, aesthetic values, option values and environment service values.

Social and cultural value: Some of the plants and animals are considered holy and sacred particularly in India like Tulsi, peepal, cow, snake etc

Ethical values: As all species have a right to exist independent of our need for them and valuable for the susteinance of human race so are related to conservation of biodiversity laying ethical issue of conservation and preservation.

Aesthetic value: There is a great aesthetic value which is attached to biodiversity. The natural landscapes provides prospects for leisure activities like bird watching, photography etc. promoting eco-tourism from zoological, botanical gardens, national parks, wild life conservation etc.

Option values: unidentified potentials of biodiversity include option values.

Environment service values: This is one of the important benefits of biodiversity which maintains environment services and includes:

• Carbon dioxide fixation.
• Maintaining of essential nutrients by carbon (C), oxygen (O), Nitrogen (N), Sulphur (S), Phosphorus (P) cycles.
• Maintaining water cycle
• recharging of ground water.
• Soil formation and protection from erosion.
• recycling moisture into the atmosphere.
• Detoxification and decomposition of waste.

1.4  Distribution of biodiversity

Uneven Biodiversity Distribution across the Earth

Due to the tilt on its axis relative to the sun and curvature of the Earth, different areas of the planet vary in amount of sunlight energy received throughout the year. Because of this the duration of different seasons (warm, cold, wet, and dry) in different areas, as well as other environmental factors (temperature, humidity etc.) varies. Due to this variation the distribution of biodiversity varies establishing different hotspots.

One of the most important outcomes of different affecting factors in different regions on the planet has created particular sets of environmental settings, which results in variation in predominant vegetation. The species living in different regions are distinguished by the adaptations which allow survival under the particular set of environmental conditions of the region and establishes biomes. A biome is a biological population of organisms related with particular climactic and geographic conditions (deserts, grasslands, and tropical rainforests) .These regions can be broadly classified into terrestrial biomes and aquatic ecosystems in which the biodiversity distribution varies.

Factors affecting distribution of biodiversity

• Climate
• Topography
• Soil
• Type of other species present
• geological age
• habitat size
• Latitude
• Taxon

1.4.1 Terrestrial Biomes

Terrestrial biomes are related to land, while aquatic biomes include both ocean and freshwater biomes. Terrestrial Biomes are principally distinguished by climactic and geographic factors where temperature and humidity plays important role in determining the type of species that can survive in a habitat. Warm and constant temperatures provide a more generous environment for different species survival. Thus, it is seen that as one move away from the equator toward the poles, or increase in elevation, causes decrease in average temperatures and in turn decreasing the biodiversity of the habitat.The terrestrial biomes can be divided into four broad categories:

i.  Forest

ii. Desert

iii. Savanna/grassland

iv.  Tundra.

 Forests-

Areas having large number of trees are termed as forest or more simply it can be said as forest biomes dominated by trees. On the basis of the types of organisms that populate them and variation in temperature and precipitation, forest biomes can be divided into three distinct types

i. tropical

ii. temperate

iii. boreal

while depending on the type of trees in that areas forests can be further classifed into five main categories.

• coniferous forest
• deciduous forest
• mixed leaved forest
• Mediterranean forest
• tropical rainforests.

   Ø Nearly one-third of Earth’s land area is sheltered by forests that hold 70% of the carbon present in living things.

Ø Forest biomes are very important in safeguarding climate change as they eliminate carbon dioxide from the atmosphere during photosynthesis.

Ø Tropical forests support the highest biodiversity of all biomes.

Ø Boreal forests in Russia, Asia, and North America are currently threatened by climate change and as a result of rising temperatures, influx of native pest species like the mountain pine beetle are on the rise because soils in which these beetles occur during winter no longer freeze.

Ø Deforestation is a significant problem in this biome and is occurring rapidly for a number of reasons: logging of particular tree species, clearing land for farming or cattle production; oil drilling and mining, fuel wood, building materials, and as a source of wood pulp to make paper.

Ø Many of the land covered in deciduous forest in the United States and elsewhere today contain regrown, secondary forests. Thus, an important natural control of these pests has been lost and their populations have increased greatly, causing deforestation to the trees and a cascading negative effect on the Taiga food web.

Deserts

Deserts cover about one fifth of the Earth’s land surface and occur where rainfall is less than 50 cm a year. There are four main types of desert in this biome – hot and dry, semiarid, coastal, and cold. They are all able to inhabit plant and animal life that are able to survive there. Deserts are the driest landscapes on Earth and sustain the least amount of life. Biodiversity is lowest in these biomes. Most deserts occur along latitudes of 30○N and 30○S and therefore have generally hot climates. Most deserts have a considerable amount of specialized vegetation as well as specialized vertebrate and invertebrate animals in the desert the biodiversity is not what you would think in the hot desert, the birds rely on the plants. There are surprisingly water in the desert that support 20 species of fish. There are also 5 to 6 thousand desert plants in the desert that adapted to the heat and low water sources. Reptiles are the most common animals in the desert. There are also about 20 species of birds in the desert. (Jamila Cross, 2014)

     Interesting facts:

Ø  the daytime temperatures of the desert biome are very hot, they can get very cold at night.

Ø The Sahara Desert is the largest desert in the desert biome. It covers over 300 million square miles.

Ø desert biome can only accommodate small animals, rodents, and reptiles as the vegetation does not grow very tall.

Ø Most of the desert animals tend to be nocturnal (sleeping during the day and coming out at night).

Ø plants that are able to grow in the desert biome store water in their stem and grow far apart so that their roots can expand and find water.

Ø Plant and animals have many adaptions to survive in the desert like-

–  Camel stores all its body fat in its hump to retain heat.

–  Cacti spines protect from being eaten by animals and their waxy outer covering keeps moisture from escaping.

Ø The driest desert on Earth receives on average 1 centimeter of rainfall every 5 to 20 years.

Ø The desert biome can be found on every continent except Europe.

Savanna & Grassland

The most dominant vegetation in both savanna and grassland biomes is perennial grasses and non-woody forbs. Enough rainwater is available in Savannas to support scattered trees, whereas grasslands do not. Thus, Savannas are generally found in more tropical climates while grasslands occur in temperate climates with hot summers and cold winters having deep soil rich in organic matter. The abundant grasses of savannas and grasslands support large herds of herbivores, like the Wildebeest, bison zebras, gazelles, The American bison of U.S. grasslands was nearly hunted to extinction in the 1800s. A concerted conservation effort has put this species back on track to recovery.

Tundra

Tundra is the coldest biomes, with average winter temperatures of -34˚ C and summer temperatures between 3-12° C. The warmer growing season lasts only 50 – 60 days. Here very few plants grow due to the lack of nutrients and because the ground is frozen beneath the top layer of soil. The only vegetation that grows there are shrubs, sedges, mosses, lichens, grasses, and a couple of birch trees and willow trees. Nearly, there are 48 different species of land mammals (hares, rodents, wolves, bears, foxes, and deer, carabou, oxen, polar bears, and wolverines etc) in the tundra. Mostly found insects in the tundra include black flies, deer flies, and mosquitoes. The mosquitoes have adapted to the cold environment by replacing the water in their bodies with glycerol to keep themselves from freezing.

1.4.2 Aquatic Ecosystems

Water is the common link among the aquatic ecosystems and it makes up the largest portion of the biosphere. This is where life began billions of years ago. Without water, organisms would be unable to sustain themselves. Aquatic ecosystems support highly diverse groups of organisms and are classified into two broad categories: freshwater and saltwater or marine.

Aquatic biodiversity can be defined as the variety of life and the ecosystems that make up the freshwater, tidal, and marine regions of the world and their interactions. Aquatic biodiversity encompasses freshwater ecosystems, including lakes, ponds, reservoirs, rivers, streams, groundwater, and wetlands. It also consists of marine ecosystems, including oceans, estuaries, salt marshes, seagrass beds, coral reefs, kelp beds, and mangrove forests. Aquatic biodiversity includes all unique species, their habitats and interaction between them. It consists of phytoplankton, zooplankton, aquatic plants, insects, fish, birds, mammals, and others.(Grishma Tewari and Akansha Bisht)

Interesting facts:

Ø nearly 45% of all fish species, rely on either fresh or brackish water habitats. The other 55% are marine species.

Ø The Amazon River, for example, which runs on or near the equator supports 2,000 to >5,000 species of fish.

Ø Eight of Australia’s top 15 biodiversity ‘hotspots’ can be found in Western Australia: one in the South-west and the other on our North-west Shelf which contains more marine species than in any other region of the world.

Ø Australia is one of 17 countries described as ‘megadiverse’. This group of countries has less than 10% of the global surface, but support more than 70% of the biological diversity on earth.

Ø  The Abrolhos Islands form the southern-most extensive coral reef system in the Indian Ocean and one of the highest latitude coral reefs in the Southern Hemisphere.

Ø Some 200 species of coral and 600 species of fish inhabit the Abrolhos. It is also estimated that 50 per cent of the eggs produced by the rock lobster breeding populations every year come from the islands.

Ø marine and freshwater biodiversity is under threat from a wide range of environmental factors including increasing population and movements, a changing climate, coastal developments, and aquatic pests.

Ø the International Union for Conservation of Nature (IUCN) has a Red List of threatened species including:

• all the world’s known species of reef-building corals (845 species)
• sharks, rays and chimaera (1,046 species)
• groupers (161 species)
• seabirds (349 species)
• marine mammal (whales, dolphins, porpoises, seals, sea lions, walruses, sea otter, marine otter, manatees, dugong and the polar bear (134 species))
• marine turtles (7 species)
• seagrasses and mangrove.

    Note:

Known Species on Earth

Total: 1.5–2 × 106 species

Insecta: 751 × 103 species

Planta: 250,000 species

Aves: 9,000 species

Mammalia: 4,000 species

Source: Brook Milligan,2009

1.5 Major biodiversity threats

i. Habitat destruction

ii. Extension of agriculture, shifting agriculture3

iii. Filling up of wetlands

iv. Pollution

v. Conversion of rich bio-diversity site for human settlement and industrial development

vi. Destruction of coastal areas

vii. Poaching

viii. Introducing exotic species

ix. Uncontrolled exploitation of resources

x. Diseases

References:

11. Benny Joseph, Environmental Studies (second edition-2009):,Tata Mc Graw-Hill Publishing Company Limited, New Delhi
12. Biodiversity hotspot – ScienceDaily, https://www.sciencedaily.com/terms/biodiversity_hotspot.htm
13. Brook Milligan, (2009): How is Biodiversity Distributed? Department of Biology New Mexico State University Las Cruces, New Mexico 88003 [e-mail] Fall
14. Grishma Tewari and Akansha Bisht, aquatic Biodiversity : Threats and Conservation, Department of Fishery Biology, College of Fisheries, G. B. Pant University of Agriculture and Technology, Pantnagar, Uttarakhand, India
15. http://healingearth.ijep.net/biodiversity/geographic-distribution-biodiversity
16. http://www.biodiversity.ru/coastlearn/bio-eng/introduction.html
17. http://www.environmentalpollution.in/essay/biodiversity-types-importance-and-conservation-methods-with-diagram/311 by Kumar
18. http://www.fish.wa.gov.au/Sustainability-and-Environment/Aquatic-Biodiversity/Pages/default.aspx
19. (http://www.biologydiscussion.com/biodiversity/biodiversity-concept-types-and-other-details-with-diagram/7132)
20. Jamila Cross, Biodiversity in the desert, (2014): Created By: Cross, Pollock, Ketron
21. Richard Black, Environment correspondent, BBC News, 23 August (2011): From the section Science & Environment)