Species on the earth and their diversity

Introduction to species diversity

Earth is a space sheltering a diverse range of plants, animals, microorganisms, insects etc. The precise time of when the first organism appeared on the earth is still a debatable topic. Scientists estimate that approximately 15 million to 45 million species currently live on the Earth. Each year, approximately 13,000 new species are added to the species,  many are close to extinction and a lot of species have completely undergone extinction. Robert May –an ecologist, evidently argues that the global species are approximately 7 million, unfortunately, the rate of extinction is faster than the rate of introduction of new species bringing a huge imbalance in the standards. The following pie chart gives an idea of the global diversity of species. India encompasses about 8% of the global biodiversity despite its geographic area is just 2% of the earth’s surface.  It is one of the 12 mega-diversity countries in the world, surprisingly, the urbanisation is becoming a threat to the habitats of many organisms. Out of 1.75 million species globally identified,1,26,188 species are from India. Various species like 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.

Table Of Contents

1.Introduction to species diversity

2. Plant species 

3. Vertebrates and invertebrates species-The animal kingdom 

4. Patterns of Biodiversity

    4.1. Latitudinal gradient 

    4.2. Species-area relationships 

5. Climate and species 




Plant species 

Some of the Lichens, Fungi, Algae, Mosses, Angiosperms, Ferns and Allies makes up the plant species. The pi-diagram below shows the approximate distribution of flora across the world. Flora in India is one of the richest in the world. This is connected to the wide of variation in the climate, geography and plant-friendly habitats in our country. Over 18,000 species of flowering plants have been identified in India which constitutes 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. Animals with no backbone are called invertebrates; 97% of the animal kingdom are invertebrates that found 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

Since biodiversity is a big component, it must be measurable, defined and must have a particular pattern to explain. Many biologists and ecologists have found that though organisms are highly diverse, their distribution has a uniform pattern. 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 parameter helps to quantify the ways in which various taxonomic, phylogenetic, genetic and functional aspects of plants and animals have been distributed between the equator and Polar Regions.  The species diversity is be based on a particular pattern from one extreme to another extreme. 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.  In general, the species richness in plants and animals is high at the equator. Being in a tropical region, India has a rich heritage of species across its coldest to the hottest regions.

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 is 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 

Tropical regions are very much favourable for the growth and development of species because of its stable climate when compared to the temperate areas. There is no rapid fluctuation of weather conditions in a tropical region resulting in high sustainability of all the species. On the contrary, temperate regions have glaciations that could slide, or create a harsh and intolerant temperature zones that might kill the species or at least make them struggle to exist. 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.




Course List