Species on the earth and their diversity

Introduction to species diversity

Earth is a space housing a diverse range of plants, animals, microorganisms and, insects. The exact period when the first organism appeared on the earth is still unclear. Scientists reckon that approximately 15 million to 45 million species currently live on the Earth. Each year, approximately 13,000 new species are added to the list. Nevertheless, many species are close to the brim of extinction and some of them are completely disappeared. Robert May –an ecologist, evidently argued that approximately 7 million species live on the earth, but sadly, the rate of extinction is faster than the rate of influx of new species. The pie chart below conveys an idea of the diversity of species in the world. India encompasses about 8% of the global biodiversity despite its compact geographic situation ( just 2% of the earth’s surface).  It is one of the 12 mega-diversity countries in the world,.The urbanisation and the progress in the technology is becoming a threat to the habitats of many organisms. Out of 1.75 million species globally identified,1,26,188 varieties are from India. The flowering plants, fish population, mammals, birds, amphibians and reptile population equals 17.3% of the total species population. Fungi and insects make up for almost 60% of all species and the remaining 26.7% fall under miscellaneous species.




Plant species 

A variety of  Fungi, Algae, Mosses, Angiosperms, Ferns and Allies makes up the majority of the plant species. The pi-diagram below shows the approximate distribution of different types of flora across the world. India is the proud owner of a variety of flowers. This is connected to the wide variation in the climate, geography and plant-friendly habitats across our country. Over 18,000 species of flowering plants have been identified in India constituting around 6-7 % of the world’s flora. Total plant species in India are 50,000 including a variety of endemics. 



Vertebrates and invertebrates species-The animal kingdom 

The animal kingdom can be classified as vertebrates and invertebrates. Vertebrates are the animals having their backbone and are usually inland species. However, oceans, rivers, forests, mountains and even in deserts do have vertebrate population. On the other hand, animals with no backbone are called invertebrates; 97% of the animal kingdom are invertebrates observed in lands, ponds, oceans and other water bodies. There are 6 types of invertebrates; Annelids, Molluscs, Arthropods, Arachnids, Echinoderms, and Protozoa. The following pie chart is the presentation of the proportion of the global distribution percentage of invertebrates.



Patterns of Biodiversity


Because biodiversity is a significant component, it must be measurable, well-defined and explainable. Many biologists and ecologists have found that though organisms are highly diverse, they are distributed systematically based on the geographic and climatic factors. There 2 patterns of biodiversity distribution pattern namely, latitudinal gradients and Species-area relationships.


1. Latitudinal gradient 

Latitude is an angular distance of a place from it`s North or South Pole expressed in degrees. Latitudinal gradient is the most popular method of explaining the pattern of biodiversity on earth. Latitudinal gradient, a parameter helps to quantify the ways in which various taxonomic, phylogenetic, genetic and functional aspects of plants and animals have been distributed across the equator and Polar Regions. The equator region(central part) has a maximum diversity but as we move towards the poles, the diversity gradually diminishes. But the exception is that some of the climate-specific indigenous species like polar beer dominate in the polar regions than the others.  

2. Species-area relationships 

This represents the direct mathematical relationship between the habitat with that of the number of species in a given area. Literally saying, larger the area/s greater the numbers of species and vice-versa. Species-area relationships are applicable for a single type of organism, for example, all vascular plants or all the species at a specified trophic level of the geographic boundary. German geographer by the name Alexander von Humboldt has explained the concept of species-area relationship for the first time. He noticed that plant and animal diversity has increased as the geographic area has increased. He has explained the phenomenon by using a mathematical formula S = log C + Z log A where, S = richness of species, C = Y-intercept, Z = regression coefficient and A = Area. The following illustration explains the concept clearly. You can see that as the area increases, the richness (S) takes an exponential move.



Climate and species 

When compared to the temperate regions, tropic areas are very much favourable for the growth and development of species because of its stable climate. In a tropical area, there is the least fluctuation of weather condition resulting in high sustainability of all the species. On the contrary, temperate regions with their massive glaciations  could slide, or create a harsh and intolerant temperature zones.  For the plants, tropical regions are good because of the availability of rich solar energy to produce food and enhance growth through photosynthesis. This may not be the case in temperate regions.


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