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Species Diversity is the number of different species present in an ecosystem. It is the relative abundance of each species in a given ecosystem. Species diversity is one of the three constituents of biodiversity.
- The vital role that a species plays in its ecosystem is known as its ecological niche.
- Species that normally live and survive in a particular ecosystem are native species.
- Species that migrate deliberately or accidentally to an ecosystem are called non-native or invasive species.
Each plant and animal species play an important role in an ecosystem. A number of methods have evolved over the years to preserve different species in the biosphere.
Read More: NCERT Solutions for Class 12 Biology Biodiversity and Conservation
| Table of Content |
Key Terms: Biodiversity, Species Diversity, Ecological Diversity, Ecosystem, Native Species, Invasive Species, Keystone Species
What is Biodiversity?
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The term “Biodiversity” refers to the kind of heterogeneity present in the biosphere or a microhabitat. Biodiversity has three constituents:
- Species Diversity: The existence of a variety of species and their abundance.
- Genetic Diversity: It is the variability in genetics present within the species.
- Ecological Diversity: A variety of organisms present within a geographical area in an ecosystem.
Read More:
| Relevant Concepts | ||
|---|---|---|
| Biodiversity Hotspot | Biodiversity in Plants and Animals | Loss of Biodiversity |
| Endemic Species | Diversity in Living Organisms | Conservation of Plants & Animals |
What is Species Diversity?
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Species diversity is the number of different organisms of the same species present in an ecosystem and the relative abundance of each of those species.
There are two constituents of species diversity:
- Species Richness: It is the number of species present in an ecosystem.
- Species Evenness: It is the relative abundance of individuals of each species.
Species diversity varies in different geographical locations on the earth, with the tropics having the highest diversity and it declines as we move towards the poles. Species richness increases with an increase in the explored area.
Read More: Biodiversity and Conservation
Importance of Species Diversity
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The importance of species diversity is listed as follows:
- In a healthy ecosystem, a diverse but balanced number of species exist to maintain the balance in an ecosystem.
- In an ecosystem, all the species and organisms depend on each other directly or indirectly.
- Generally, a more diverse ecosystem tends to be more productive.
- Greater species richness and productivity make an ecosystem more sustainable and stable.
- The more diverse the ecosystem, the greater the ability to withstand environmental stresses.
- Species richness makes an ecosystem able to respond to any catastrophe or danger.
- Humans get a lot of resources like fruits, vegetables, cereals, millet, dyes, medicines, antibiotics, etc.
- Bacteria and plants in the nitrogen cycle and earthworms contribute to soil fertility.
Diversity in Living Organisms
Read More: Importance of Ecosystem
Types of Species
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Each plant and animal species plays an important role in an ecosystem.
- Generalist Species: These species have broad niches and can live in many places and can consume a variety of nutrients. They can survive in rapidly changing environmental conditions also. Examples are cockroaches, flies, humans, etc.
- Specialist Species: These species have a narrow niche, are found in only one type of habitat, and feed on a few types of food items. These species are more prone to disturbances in environmental conditions and cannot tolerate small changes and environmental stress. The giant panda of China is said to be endangered because of its low reproductive rate, disturbances in its fragile habitat, and its specific diet which is bamboo.
- Native Species: Species that normally live and survive in a particular ecosystem are native species.
- Non-native Species (Invasive or Alien Species): Species that migrate deliberately or accidentally to an ecosystem are invasive species. Invasive species compete with other native species for food, sunlight, and space. If the indigenous species are unable to compete with invasive species, they are forced to leave or die.
- Indicator Species: These species serve as biological smoke alarms. These peculiar species provide early warnings of damage to an ecosystem. Many bird species are an excellent biological indicator of their habitat loss and fragmentation and the use of chemical pesticides.
- Keystone Species: Keystone species play an important role in maintaining species diversity and the integrity of an ecosystem. They have a high impact on the types and abundance of species in an ecosystem. These species play a very critical role in helping certain species to survive as well as to check the overpopulation of other species to become overly dominant.
- Foundation Species: These species play an important role in creating and enhancing some habitats. For example, elephants topple or uproot trees to open up forest areas in grasslands and woodlands of forested Africa, promoting the growth of grass varieties and other foliage trees required for small grazing species like antelope.
Ecosystems with High Species Diversity
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Following are the examples of the ecosystem with high Species Diversity:
Tropical Rainforests
- These forests contain half of the world’s biological species.
- There are nearly 5-10 million insect species present.
- 40% of the world’s 2,75,000 species of flowering plants are present in these tropical forests.
- 30% of total bird species are present in tropical forest zones.
Tropical Rainforests
Coral Reefs
- Many colonies of tiny coral animals (Cnidarians) build their large coral reef ecosystems here.
- The clear water in the coral reef systems allows the sunlight to penetrate deep.
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It results in a high level of net photosynthetic rate in the algae present inside the coral.
Coral Reefs
Read More: Biodiversity and Conservation Important Questions
Threats to Species Diversity
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The world’s biosphere is facing an accelerated rate of extinction of species mostly due to human activities. The four major causes of loss of diversity are commonly called “The Evil Quartet”.
- Habitat Loss and Fragmentation: It is generally due to pollution, urbanization, and various other destructive human activities. For example, the Amazon rainforest is a habitat for millions of species that are being cut and cleared for various purposes.
- Over-Exploitation: Indiscriminate and over-exploitation of natural resources lead to the extinction of many fragile species. For example, Steller’s sea cow, passenger pigeon, and many marine fishes are overharvested.
- Alien Species Invasions: When alien species are introduced intentionally or unintentionally, some of them become invasive, leading to the extinction of indigenous native species. For example, the extinction of cichlid fish in Lake Victoria due to the introduction of the Nile perch.
- Co-extinctions: When any species becomes extinct, the species that are associated with it also become extinct. For instance, when a host fish in a region goes extinct, the parasite on it will also go extinct.
Read More: Biodiversity and Conservation MCQs
Conservation of Species Diversity
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Every species has an important role to play in an ecosystem. So, it is important to conserve species diversity because once it gets extinct, we can not get it back. There are many means and ways to conserve biodiversity:
In-situ Conservation
- Biodiversity-rich regions can be protected as biosphere reserves, national parks, and sanctuaries.
- It involves the protection of many endangered species like the royal Bengal tiger, olive ridley sea turtles, mangrove species, etc.
Ex-situ Conversation
- Threatened and endangered species are identified, taken out, given full protection, and kept in special reserves like protected forests, botanical gardens, wildlife safaris, etc.
- Gametes and pollen grains of threatened species are preserved by cryopreservation techniques.
- Seeds of commercially and ecologically important plants are kept in the seed banks.
Read More:
| Related Topics | ||
|---|---|---|
| Difference Between Species, Population, and Community | Red Data Book | Flagship Species |
| What is a Natural Ecosystem? | Difference between Environment and Ecosystem | Productivity in Ecosystem |
Things to Remember
- Species Diversity is the number of different organisms of the same species present in an ecosystem.
- Generalist species, Specialist species, Native species, Alien species, Keystone species, and Foundation species are a few types of species.
- Tropical Rainforests and Coral Reefs are ecosystems with high species diversity.
- Habitat Loss and Fragmentation, Over Exploitation, and Alien species invasions are some threats to species diversity.
- In-situ conservation and Ex-situ conversation are the two ways to conserve biodiversity.
Previous Years’ Questions
- Amongst vertebrates, the species diversity is the maximum in…
- India’s share in global species diversity is around…
- Biodiversity refers to the number and variety of organisms…
- Hotspots of biodiversity mean… (DUET 2010)
- Species can be identified on the basis of… (JIPMER 2011)
- The most biodiversity-rich zone in India… (Himachal Pradesh PMT 2005)
- Choose the wrong statement… (KEAM)
- Read the two statements A and B. Statement A: Diversity… (KCET 2006)
- Alpha diversity is biodiversity present…
- The impact of the loss of biodiversity includes…
Sample Questions
Ques. An exotic variety of prickly pear introduced in Australia turned out to be an invasive species. How was it brought under control by the scientists? (1 Mark)
Ans. An exotic variety of prickly pear introduced in Australia was controlled by introducing a cactus-feeding predator (a moth) from its own natural habitat.
Ques. Write the level of biodiversity represented by mangrove plants. Give another example falling in the same level of ecological niche. (2 Marks)
Ans. Mangrove plants represent ecological diversity. The same level of biodiversity is also shown by many rainforests, coral reefs, wetlands, estuaries, and alpine meadows.
Ques. Name the type of biodiversity represented by the categories:
(i) 50,000 different strains of rice available in India.
(ii) Estuaries and alpine meadows found in India. (2 Marks)
Ans. (i) 50,000 different strains of rice available in India are examples of genetic diversity. (ii) Estuaries and alpine meadows found in India show ecological diversity
Ques. Name the type of biodiversity represented by the following things:
(i) 1000 varieties of mango fruits in India.
(ii) Variations in terms of potency and concentration of reserpine in Rauwolfia vomitoria plant growing in different regions of the Himalayas. (2 Marks)
Ans. (i) 1000 varieties of mango fruits in India show genetic diversity.
(ii) Rauwolfia vomitoria plants growing in different regions of the Himalayas show genetic diversity.
Ques. Why is the tropical environment able to support greater species diversity in the world? (2 Marks)
Ans. Tropical environments, unlike temperate environments, are less seasonal, relatively more constant, and predictable. Such constant environments always promote niche specialization and lead to greater species diversity in the ecosystem.
Ques. Mention the kind of biodiversity of more than a thousand varieties of mango fruits in India. How is it possible in nature? (2 Marks)
Ans. Genetic diversity or single species shows high diversity at the genetic level. Single species show high diversity at the genetic level over their distributional range or different varieties grow in different geographical areas/climatic conditions, breedings, or mutations.
Ques. State the importance of
(a) IUCN Red Data List
(b) Hot Spots in the Conservation of Biodiversity. (2 Marks)
Ans. (a) It provides information regarding the extinction of species
(b) Regions with very high levels of species richness, high degree of endemism or species confined to a particular region and not found anywhere else are identified that need to be conserved on a priority basis.
Ques. Where would more species diversity be expected in tropical regions or in polar regions? Give reasons. (3 Marks)
Ans. Tropics generally have more species biodiversity than polar regions. The maximum biodiversity in tropical regions is due to the following important reasons:
- Prolonged Evolutionary Time: The tropics had remained undisturbed in the past and therefore evolved more species diversity.
- High Productivity: There is more solar energy available in tropical regions which contributes directly to more productivity, and population sizes and also indirectly to greater species diversity.
Ques. With the help of one example, explain how alien species invasion causes biodiversity loss in nature. (3 Marks)
Ans. When alien or exotic species are introduced, some of them become invasive, compete with the native species and cause the extinction of indigenous or native species. For example,
- Parthenium (Congress grass), Lantana (shrub), and Eichhornia are the exotic species of plants that have invaded India and caused environmental damage in new locations. They pose threats to the survival of many native species in nature.
- Introduction of African catfish (Clarias gariepinus) for aquaculture purposes by business people is posing a threat to our indigenous catfish Clarias batrachus.
Ques. List any important two causes of biodiversity loss and explain any one of them. (3 Marks)
Ans. Important causes of biodiversity losses are
- Habitat loss and fragmentation
- Over-exploitation
- Alien species invasions
- Co-extinctions
Co-extinctions: When an ecological species becomes extinct, the plant and animal species associated with it in an obligatory way may also become extinct. For instance, when a host fish species becomes extinct, its unique assemblage of parasites also meets the same bad fate.
Ques. Indiscriminate human activities such as alien species invasion, fragmentation, habitat loss, etc. have accelerated the loss of biodiversity. Justify by taking one example for each. (5 Marks)
Ans. (a) When some alien species are introduced unintentionally or intentionally for whatever purpose, some of them turn invasive and decline or make extinction of indigenous native species. Examples of the same are
- The introduction of African catfish or Clarias gariepinus (for aquaculture purposes) poses a great threat to indigenous catfishes in our Indian rivers.
- The Nile perch introduced into lake Victoria in East Africa led to the extinction of more than 200 species of Cichlid fish in the same lake.
- Carrot grass or Parthenium, Lantana, Water hyacinth, or Eichhornia poses a great threat to indigenous species.
(b) Fragmentation: When large habitats are broken down into small fragments due to various human activities. Mammals or birds requiring large territories and certain animals with migratory habits are badly affected by fragmentation.
(c) Habitat Loss: The Amazon rainforest in South America is being cut and cleared for cultivating commercial crops like soybeans and conversion of grasslands for raising cattle.
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