Biodiversity itself is a combination of two words, Bio (life) and diversity (variety). In simple terms, biodiversity is the number and variety of organisms found within a specified geographic region. It refers to the varieties of plants, animals and micro-organisms, the genes they contain and the ecosystems they form. It relates to the variability among living organisms on the earth, including the variability within and between the species and that within and between the ecosystems.
Biodiversity can be discussed at three levels: Genetic diversity, Species diversity and Ecosystem diversity.
Genetic Diversity
Genetic biodiversity refers to the variation of genes within species. Groups of individual
organisms having certain similarities in their physical characteristics are called species. Human beings genetically belong to the homo-spines group and also differ in their characteristics such as height, colour, physical appearance, etc., considerably. This is due to genetic diversity. This genetic diversity is essential for a healthy breeding of population of species.
Species Diversity
This refers to the variety of species. It relates to the number of species in a defined area. The diversity of species can be measured through its richness, abundance and types. Some areas are more rich in species than others. Areas rich in species diversity are called hot spots of diversity.
Patterns of Biodiversity
1. Biodiversity as we have today is the result of 2.5-3.5 billion years of evolution. The number of species globally varies from 2 million to 100 million, with 10 million being the best estimate. Biodiversity is not found evenly on the earth. It is consistently richer in the tropics. Tropical forests are very rich in bio-diversity. As one approaches the
Polar Regions, one finds larger and larger populations of fewer and fewer species. The distribution of biodiversity can be discussed as under:
Latitudinal gradients: In general, species diversity decreases as we move away from the equator towards the poles. With very few exceptions, tropics (latitudinal range of 23.5° N to 23.5° S) harbour more species than temperate or polar areas. Forest in a tropical region like Ecuador has up to 10 times as many species of vascular plants as a forest of equal area in a temperate region like the Midwest of the USA. Decline in richness with latitude may be faster in the Northern than in the Southern Hemisphere and the peaks in richness may not lie actually at the Equator itself but some distance away.
What is so special about tropics that might account for their greater biological diversity?
Speciation is generally a function of time, unlike temperate regions subjected to frequent glaciations in the past, tropical latitudes have remained relatively undisturbed for millions of years and thus, had a long evolutionary time for species diversification.
Tropical environments, unlike temperate ones, are less seasonal, relatively more constant and predictable. Such constant environments promote niche specialisation and lead to a greater species diversity.
There is more solar energy available in the tropics, which contributes to higher productivity; this in turn might contribute indirectly to greater diversity.
2. Species-Area relationships: Within a region species richness increases with increasing explored area, but only up to a limit. In fact, the relation between species richness and area for a wide variety of taxa (angiosperm plants, birds, bats, freshwater fishes) turns out to be a rectangular hyperbola.
Importance of Biodiversity
Biodiversity has contributed in many ways to the development of human culture and, in turn, human communities have played a major role in shaping the diversity of nature at the genetic, species and ecological levels. Biodiversity plays the following roles:
Ecological Roles
Species of many kinds perform some or the other function in an ecosystem. Nothing in an
ecosystem evolves and sustains without any reason. That means, every organism, besides
extracting its needs, also contributes something useful to other organisms. Species capture and store energy, produce and decompose organic materials, help to cycle water and nutrients throughout the ecosystem, fix atmospheric gases and help regulate the climate. These functions are important for ecosystem function and human survival.
The more diverse an ecosystem, better are the chances for the species to survive through
adversities and attacks, and consequently, is more productive. Hence, the loss of species would decrease the ability of the system to maintain itself. Just like a species with a high genetic diversity, an ecosystem with high biodiversity may have a greater chance of adapting to environmental change. In other words, the more the variety of species in an ecosystem, the more stable the ecosystem is likely to be.
Economic Role
Biodiversity is an important resource in day-to-day life. One important part of biodiversity is ‘crop diversity’, which is also called Argo-biodiversity. Biodiversity is seen as a reservoir of resources to be drawn upon for the manufacture of food, pharmaceutical, and cosmetic products. This concept of biological resources is responsible for the deterioration of biodiversity. Some of the important economic commodities that biodiversity supplies to
humankind are: food crops, livestock, forests, fish, medicinal resources, etc.
Scientific Role
Biodiversity is important because each species can give us some clue as to how life evolved and will continue to evolve. Biodiversity also helps in understanding how life functions and the role of each species in sustaining ecosystems of which we are also a species.
Loss of biodiversity
Since the last few decades, growth in human population has increased the rate of consumption of natural resources. It has accelerated the loss of species and habitation in different parts of the world. The accelerated rates of species extinctions that the world is facing now are largely due to human activities. The major causes for biodiversity loss are discussed below.
Causes of Biodiversity losses
1. Habitat loss and fragmentation: This is the most important cause driving animals and
plants to extinction. The most dramatic examples of habitat loss come from tropical
rain forests. Once covering more than 14% of the earth’s land surface, these
rain forests now cover no more than 6%.
Besides total loss, the degradation of many habitats by pollution also threatens the
survival of many species. When large habitats are broken up into small fragments due
to various human activities, mammals and birds requiring large territories and certain
animals with migratory habits are badly affected, leading to decline of population.
2. Over-exploitation: Over-hunting, over-fishing or over-collecting of a species can quickly
lead to its decline. Changing consumption patterns of humans is often cited as the key
reason for this unsustainable exploitation of natural resources. Many species
extinctions in the last 500 years (Steller’s sea cow, passenger pigeon) were due to
over exploitation by humans.
3. Alien species invasions: When alien species are introduced unintentionally or
deliberately for any purpose, some of them turn invasive, and cause decline or
extinction of indigenous species.
4. Co-extinctions: When a species becomes extinct, the plant and animal species
associated with it in an obligatory way also become extinct. When a host fish species
becomes extinct, its unique assemblage of parasites also meets the same fate.
5. Global climate change: Both climate variability and climate change cause biodiversity
loss. Species and populations may be lost permanently , if they are not provided with
enough time to adapt to changing climatic conditions.
Next Article-Biodiversity Conservation,Megadiverse countries..........
Awesomely made. Thanks :)
ReplyDelete