What is Biodiversity?
Biodiversity is the variation among living organisms from all sources, including terrestrial, marine and other aquatic ecosystems, and the ecological complexes of which they are part. It encompasses diversity within species, between species and of ecosystems.
The term biodiversity was coined in 1985. Biodiversity describes the richness and variety of life on Earth - it is a fundamental and complex feature of the biosphere. It includes the number of different organisms, their relative frequencies in an ecosystem and the organisation of living forms at different levels.
Biodiversity has both ecological and economic significance. It provides food, fuel, fibre, medicines and raw materials; supports ecosystem services such as pollination and nutrient cycling; contributes to cultural and recreational values; and underpins livelihoods and economic activity such as tourism.
Types (Levels) of Biodiversity
Biodiversity is generally described at three hierarchical levels. These three levels together capture genetic variability, the variety of species, and the diversity of ecosystems.
- Genetic diversity
- Species diversity
- Ecological (ecosystem) diversity
Genetic Diversity
- Definition: Variation in the genetic composition among individuals of a species and among populations of the same species.
- Every individual of a species differs in its genetic constitution, which is why individual members show differences in appearance, physiology and behaviour. Examples include different varieties of rice, wheat, maize and barley, and variation in human blood groups and skin colour.
- Genetic diversity is the raw material for adaptation and evolution. It allows populations to respond to changing environments, resist diseases and sustain long-term survival.
Species Diversity
- Definition: The variety of species within a region or a particular habitat. It is the most commonly recognised level of biodiversity.
- Species diversity is measured by two components: species richness (the number of species present) and species evenness (how evenly individuals are distributed among those species).
- Examples include all plant species, animal species and microorganisms present in a forest, pond or agricultural field. No two individuals of a species are exactly identical; for example, humans show considerable diversity among themselves.
Ecological (Ecosystem) Diversity
- Definition: The variety of ecosystems or habitats in a region and the complex interactions among organisms and their physical environment.
- It includes diversity among ecosystems such as deserts, grasslands, tropical rainforests, mangroves, coral reefs and wetlands. Ecological diversity reflects differences in ecological processes, species interactions (food chains and food webs), and ecosystem functions.
- Healthy ecosystem diversity increases resilience to environmental changes because different ecosystems respond differently to disturbances and provide complementary services.
Question for Biodiversity: Types, Importance, Patterns and Loss of Biodiversity
Try yourself:What is the feature of the biosphere?
Explanation
The diversity observed at the species level is known as the species diversity. It is the number and abundance of each species in a particular area. Species diversity is one of the important features of the biosphere.
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The Importance of Biodiversity
- Biodiversity is crucial for the stability and health of ecosystems. Different species contribute to various ecosystem functions, such as nutrient cycling, pollination, and pest control.
- A diverse range of species ensures that ecosystems can adapt to changes and disturbances, such as climate change or natural disasters. Ecosystems with higher biodiversity are generally more resilient and can recover from disturbances more quickly.
- Biodiversity also provides a wide range of resources for humans, including food, medicine, and raw materials. Many of these resources come from wild species or traditional agricultural varieties, highlighting the importance of conserving genetic diversity.
- Furthermore, biodiversity contributes to cultural and recreational values, as natural areas with diverse species attract tourism and provide spaces for outdoor activities.
Threats to Biodiversity
- The current rate of biodiversity loss is alarmingly high, primarily due to human activities. Habitat destruction, pollution, overexploitation of resources, invasive species, and climate change are the main drivers of this decline.
- Habitat loss, particularly in tropical rainforests, wetlands, and coral reefs, is the most significant threat. These habitats are being cleared for agriculture, urban development, and infrastructure projects, leading to the extinction of many species.
- Pollution from industrial, agricultural, and urban sources degrades ecosystems and poses direct threats to species. For example, plastic pollution in oceans harms marine life, while pesticides can impact non-target species and disrupt ecosystems.
- Overexploitation of resources, such as overfishing, logging, and poaching, reduces populations of targeted species and disrupts ecological balance. Sustainable management practices are essential to prevent overexploitation.
- Invasive species, introduced either intentionally or accidentally, can outcompete native species for resources, leading to declines or extinctions. Managing and preventing the spread of invasive species is a critical aspect of conservation.
- Climate change alters habitats and affects species distributions, life cycles, and interactions. Species that cannot adapt quickly enough to changing conditions face a higher risk of extinction.
Conservation Efforts
- Conservation efforts aim to protect and restore biodiversity through various strategies. Establishing protected areas, such as national parks, wildlife reserves, and marine protected areas, is a fundamental approach to conserve critical habitats and species.
- Restoration ecology focuses on rehabilitating degraded ecosystems, reintroducing native species, and removing invasive species to restore ecological balance.
- Sustainable resource management practices, such as sustainable forestry, fisheries, and agriculture, help balance human needs with biodiversity conservation.
- Community involvement and awareness are crucial for successful conservation. Engaging local communities in conservation efforts and promoting awareness of biodiversity's importance can lead to more effective and sustainable outcomes.
- Policy and legal frameworks play a vital role in biodiversity conservation. Implementing and enforcing laws and regulations that protect endangered species, habitats, and ecosystems are essential for preventing further biodiversity loss. International agreements, such as the Convention on Biological Diversity, also facilitate global cooperation in conservation efforts.
In conclusion, biodiversity is fundamental to ecosystem stability, resilience, and the resources it provides. However, human activities pose significant threats to biodiversity, leading to rapid declines in species and ecosystems. Conservation efforts are crucial to protect and restore biodiversity, ensuring a sustainable future for all living beings on Earth.
Question for Biodiversity: Types, Importance, Patterns and Loss of Biodiversity
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What is genetic diversity?Explanation
Genetic diversity refers to the differences in the genetic composition among individuals of a species. This variation is why individual members show differences in appearance and behavior.
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How Many Species are there on Earth and How Many in India?
Known species versus actual species on Earth
Scientists maintain published records of species that have already been discovered, described, and named. Based on these records, we can say with certainty how many species are known so far. However, determining the actual total number of species on Earth is extremely difficult.
According to the International Union for Conservation of Nature (IUCN) (2004), a little over 1.5 million plant and animal species have been formally described. This figure represents only the species that science has documented; it does not include the vast number of species that remain undiscovered, unnamed, or poorly studied.
The uncertainty exists because:
Many regions of the world, especially dense forests and oceans, are still insufficiently explored.
A large number of organisms are very small, rare, or short-lived.
Many species go extinct before they are ever discovered.
Why estimates of total species vary widely
Since we cannot directly count undiscovered species, scientists rely on statistical estimation methods. These estimates vary widely, from 20 million to 50 million species, because they are based on assumptions rather than direct observation.
One commonly used method involves:
Studying a well-documented group (usually insects) in both temperate and tropical regions.
Comparing the species richness between these regions.
Extrapolating this ratio to other groups of plants and animals.
Because tropical regions are much richer in species than temperate regions and are still underexplored, scientists believe that the majority of undiscovered species are located in the tropics.
A more conservative and scientifically robust estimate was proposed by Robert May, who suggested that the total number of species on Earth is approximately 7 million. This estimate is widely accepted in biology textbooks and research.
Composition of Earth’s biodiversity
Based on currently available species inventories, Earth’s biodiversity shows clear patterns:
a. Dominance of animals
Over 70 percent of all recorded species are animals.
Plants, including algae, fungi, bryophytes, gymnosperms, and angiosperms, make up no more than 22 percent.
b. Insects: the most diverse groupAmong animals, insects are by far the most species-rich group.
More than 70 percent of all animal species are insects.
This means 7 out of every 10 animals on Earth are insects.
Reasons for the enormous diversification of insects include:
Ability to fly, allowing wide dispersal
High reproductive rate
Short life cycles
Adaptation to almost every habitat
Co-evolution with flowering plants
c. Fungi diversity
An interesting and often overlooked fact is that: The number of fungal species exceeds the combined total of fishes, amphibians, reptiles, and mammals. This highlights how human perception tends to underestimate microorganisms and less visible life forms.
The missing data: prokaryotes
Current biodiversity estimates do not include prokaryotes (bacteria and archaea) in any reliable way.
This is because:
Traditional taxonomy depends on visible structure and reproduction, which are poor criteria for microbes.
Many microbial species cannot be cultured in laboratory conditions.
If biochemical or molecular methods (DNA-based identification) are used, the number of prokaryotic species alone could run into millions.
This means global biodiversity may be far greater than even the most liberal estimates.
India as a mega-diverse country
Although India occupies only 2.4 percent of the world’s land area, it harbours about 8.1 percent of global species diversity. This disproportionately high biodiversity places India among the 12 mega-diversity countries of the world.
Currently recorded species in India include:
Around 45,000 plant species
About 90,000 animal species
The reasons for India’s rich biodiversity include:
Wide range of climates (tropical to alpine)
Diverse ecosystems such as forests, wetlands, deserts, mountains, and coastal regions
Long evolutionary history and geographical isolation of certain regions
Undiscovered species in India
If we apply Robert May’s estimate that only 22 percent of Earth’s species have been discovered so far, the implication for India is striking:
Estimated undiscovered species in India:
More than 1,00,000 plant species
More than 3,00,000 animal species
This suggests that the majority of India’s biological wealth remains unknown to science.
Challenges in completing biodiversity inventories
Completing a full inventory of species is extremely challenging due to:
Shortage of trained taxonomists
Time-consuming nature of species identification and description
Limited funding and infrastructure
Rapid habitat destruction and climate change
Many species are disappearing before they are even discovered.
The burning library metaphor
The statement “Nature’s biological library is burning even before we catalogued the titles” is a powerful metaphor. It emphasizes that:
Each species is like a book containing unique genetic, ecological, and evolutionary information.
Extinction destroys this information permanently.
Humanity is losing irreplaceable biological knowledge at an unprecedented rate.
This underscores the urgent need for biodiversity conservation, documentation, and sustainable use of natural resources.
Patterns of Biodiversity
(i) Latitudinal Gradients : Species diversity is generally higher in tropical regions (23.5° N to 23.5° S) compared to temperate and polar areas. For example, Colombia near the equator has almost 1,400 bird species, while places like New York and Greenland have significantly fewer. Tropical forests, such as the Amazon, are among the richest in biodiversity, housing thousands of species.
(ii) Species-Area Relationships : Species richness tends to increase with area, but only up to a certain limit. The relationship between species richness and area is often a rectangular hyperbola. On a logarithmic scale, it appears as a straight line, with a slope (Z) typically ranging from 0.1 to 0.2. In large areas, like continents, the slope can be much steeper, indicating a higher species-area relationship.
Question for Biodiversity: Types, Importance, Patterns and Loss of Biodiversity
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What do patterns of biodiversity help us understand?Explanation
Patterns of biodiversity show how different forms of life are organized and interact. Understanding these patterns helps us learn more about life on Earth.
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Importance of Species Diversity to the Ecosystem
Species diversity plays a crucial role in the stability and functioning of ecosystems. While ecologists have debated the exact relationship between species richness and ecosystem stability, there is evidence suggesting that communities with more species tend to be more stable. Stability in this context refers to the ability of a community to maintain consistent productivity, resist disturbances, and fend off invasions by non-native species. David Tilman's Experiments
- Long-term Studies: Tilman's outdoor experiments tracked biomass production in plots with varying species richness over time.
- Findings: Plots with more species exhibited less variation in total biomass from year to year and higher overall productivity.
- Implications: These results suggest that species diversity contributes to the stability and productivity of ecosystems.
The Rivet Popper Hypothesis
- Analogy: Paul Ehrlich's analogy compares an ecosystem to an airplane held together by rivets (species).
- Concept: Removing rivets (species) may not immediately affect flight safety (ecosystem functioning), but as more are removed, the plane becomes weaker.
- Key Point: Some rivets (key species) are more critical than others, and their loss poses a greater threat to ecosystem stability.
Loss of Biodiversity
Introduction
- Biodiversity, which includes all living organisms and their natural habitats, is facing a severe decline due to human activities.
- The extinction of species is occurring at an unprecedented rate, with current estimates being 100 to 1,000 times faster than in pre-human times.
- This rapid loss of biodiversity is often referred to as the "Sixth Extinction."
Historical Context
- Throughout Earth's history, there have been five major episodes of mass extinction long before humans existed.
- However, the current rate of species loss is alarming and is primarily attributed to human actions.
Recent Extinctions
- The IUCN Red List has documented the extinction of 784 species in the last 500 years, including vertebrates, invertebrates, and plants.
- Some well-known recent extinctions include the dodo, quagga, thylacine, and Steller's Sea Cow.
Vulnerability and Threats
- Certain groups, like amphibians, are more susceptible to extinction.
- Currently, over 15,500 species worldwide are at risk of extinction, including significant percentages of bird, mammal, amphibian, and gymnosperm species.
Consequences of Biodiversity Loss
- Decline in plant production.
- Reduced resistance to environmental changes such as drought.
- Increased variability in ecosystem processes like plant productivity and pest cycles.
Causes of Biodiversity Loss
The current rapid rate of species extinctions is primarily caused by human activities. There are four major factors contributing to this loss, collectively known as "The Evil Quartet."
(i) Habitat Loss and Fragmentation:
- Habitat loss and fragmentation is the most significant driver of extinction for animals and plants.
- Tropical rainforests, once covering over 14% of the Earth's land, now account for only about 6% and are being destroyed at an alarming rate.
- For example, the Amazon rainforest, often referred to as the "lungs of the planet," is being cleared for soy cultivation and cattle ranching.
- In addition to total loss, habitat degradation due to pollution also threatens many species.
- Fragmentation of large habitats into smaller pieces negatively impacts mammals and birds that require large territories, as well as migratory species, leading to population declines.
(ii) Over-Exploitation:
- Over-exploitation occurs when human dependence on natural resources shifts from "need" to "greed."
- Historical examples of over-exploitation leading to extinction include Steller's sea cow and the passenger pigeon.
- Currently, many marine fish populations are being overharvested, putting commercially important species at risk.
(iii) Alien Species Invasions:
- The introduction of alien species, either unintentionally or deliberately, can lead to invasive species that threaten indigenous species.
- For instance, the introduction of the Nile perch into Lake Victoria resulted in the extinction of over 200 unique species of cichlid fish.
- Invasive weed species like carrot grass (Parthenium), Lantana, and water hyacinth (Eichhornia) also pose significant threats to native species.
- Additionally, the illegal introduction of the African catfish (Clarias gariepinus) for aquaculture is threatening indigenous catfish populations in rivers.
(iv) Co-Extinctions:
- Co-extinctions occur when a species becomes extinct along with the plant and animal species that are obligately associated with it.
- For example, the extinction of a host fish species leads to the extinction of its unique parasites.
- Similarly, in co-evolved plant-pollinator relationships, the extinction of one species invariably results in the extinction of the other.
Question for Biodiversity: Types, Importance, Patterns and Loss of Biodiversity
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What does loss of biodiversity mean?Explanation
Loss of biodiversity refers to a decrease in the number of different species in an area. This means there are fewer different species present, which can lead to imbalances in the ecosystem.
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