Biodiversity is a term used to describe all aspects of biological diversity, especially including species richness, ecosystem complexity, and genetic variations. In this chapter we study to find answers of some of questions such as: Why are there so many species? Did such great diversity exist throughout earth's history? How did this diversification come about? How and why is this diversity important to the biosphere? Would it function any differently if the diversity was much less? How do humans benefit from the diversity of life?
Question 1: What is biodiversity ?
Answer: The diversity found in the living organism is called bio diversity . This term was given by Edward Wilson . There are three types of biodiversity in nature:
- Genetic diversity: Diversity at the gene level is called genetic diversity. Ex: Rauwolfia vomitoria growing in Himalayan ranges shows genetic diversity in terms of potency and concentration of reserpine chemical .
- Species diversity: Diversity at the species level is called species diversity. Ex: Western Ghats have a greater amphibian species diversity than the Eastern Ghats .
- Ecological diversity: Diversity at the ecosystem level is called ecosystem diversity. Ex: India nation has a rich ecological diversity as it has deserts, rain forests, mangroves, wetlands, coral reefs, etc.
Alfa, Beta and Gamma Diversity
- Alfa Diversity (niche Diversification): Alpha diversity indicates diversity within the community. It refers to the diversity of organisms sharing the same community or habitat.
- Beta Diversity (habitat diversification): Beta diversity indicates diversity between communities. It is due to replacement of species with change in the habitat.
- Gamma Diversity (regional diversification): Gamma diversity refers to the diversity of the habitats over the total landscape or geographical area.
Question 2: What is longitudinal gradient and factors effecting it?
Answer : Longitudinal gradient : Species diversity as we move from equator region to polar region . Tropical region has more diversity than temperate or polar region, because of following factors which effect it are:
- Speciation: Is a function of time, tropical region remain undisturbed for millions of the years, so have long time for speciation which results in rich biodiversity. Temperate region is subjected to frequent glaciations so, less time for speciation which results in less biodiversity.
- Tropical region is more constant and more predictable than temperate region , thus constant environment promote more biodiversity.
- Tropical region revives more solar energy , thus have higher productivity which results in more biodiversity.
Question 3: What is species area relationship ?
Answer : Species area relationship was given by Alexander Von Humboldt , within a region species richness increases with increase in area explored only up to limit . The relation between species richness and area explored turns out to be a rectangular hyperbola . On a logarithmic scale the relationship is straight line and described by the equation :
Log S = Log C + Z Log A .
Where S = species richness
A = area explored
Z = slope of the line
C = Y – intercept .
The value of Z lies in the range of 0.1 to 0.2 . The slope of the line is more steeper if the value of z is upto 1.6 , in large are like tropical area like tropical rain forest which has rich biodiversity .
Question 4: What is importance of species diversity to the ecosystem ?
Answer : The Importance of species diversity to the ecosystem are :
- Community more species are more stable
- Community with more species show resistant or resilient to occasional disturbances
- Community with more species are resistance to invasion by alien species
- Stable community do not show too much variation in the productivity from year to year
Note : Experiment by David Tilman shows increased diversity contributed to higher productivity .
Question 5: What is Rivet Popper Hypothesis ?
Answer : It was given by Paul Ehrlich. He compared aeroplane with ecosystem and rivets with species. According to him if every passenger starts popping a rivet from aeroplane, it may not effects flight safety initially but as more and more numbers of rivets are removed , the flight of aeroplane becomes dangerous for the ecosystem functioning.
Similarly , species extinction at initial level does not effect functioning initially but later on it may become dangerous for the functioning of ecosystem . Loss of rivets on the wings (Key stone species that drive major ecosystem function) is more dangerous for the flight (ecosystem ).
Question 6: What are causes of biodiversity losses (The Evil Quartet) and effects of loss of biodiversity ?
Answer : The causes of biodiversity losses are:
- Habitat loss and fragmentation: When the habitat of flora and fauna is damaged, biodiversity decreases. Tropical rain forest covers more than 14% of the land surface but now only 6% due to deforestation. Amazon rain forest (lungs of the planet Earth as it releases 20% of oxygen ) is cut and cleared for cultivation of soybeans or converted to grasslands for raising beef cattle.
- Over Exploitation: Human need turns to greed leads to over exploitation of the natural resources. Ex: Stellar sea cow , passenger pigeon were extinct due to over exploitation by humans.
- Aliens species invasion: When species become invasive after their introduction, decline or extinct many native species. Ex: Carrot grass (parthenium), Lantana, and water hyacinth are invasive species .
- Co-extinction: When a species become extinct, the plant and animals species associated with it also become extinct. Ex: When a host fish become extinct all parasites dependent on it become extinct.
The effects of loss of biodiversity are:
- Decline in plant production.
- Lowered resistance to environmental perturbations such as droughts.
- Increased variability in certain ecosystem processes such as plant productivity, water use and pest-disease cycle.
Question 7: What are methods of biodiversity conservation ?
Answer: Two methods of biodiversity conservation are:
In situ conservation: This is the conservation of biodiversity in their natural habitat, so along with biodiversity the habitat is also protected. Types of in situ conservation are:
- Biodiversity hotspot: 34 (25 + 9) hotspots in the world. Hotspots are bio geographical region with rich biodiversity which are declared sensitive due to direct or indirect influence of the human activities. They have endemic (species confined to that region and not found anywhere else ) species. Eastern Himalayas and western Ghats are hotspots of India.
- Protected areas: India has 14 biosphere reserves, 90 national parks and 448 wildlife sanctuaries . Jim Corbett National Park was the first to be established in India.
- Ramsar sites: There are 26 ramsar sites in India. Ramsar sites are protected wetlands areas. Ex: Sambhar lake, chilika lake are protected wetlands.
- Scared groves: Groves are protected by the native people due to their diversity and cultural importance. Ex: Khasi and jantia hills in Meghalaya , Aravali hills in Rajasthan, western Ghats of Karnataka and Maharashtra and Sarguja, Chand bastar areas of Madhyapradesh
- Ex situ conservation: (off site conservation ) It is the conservation of selected threatened plants and animals species in place outside their natural habita . Ex: Botanical gardens, Zoological parks, gene banks, etc.
Note: By using cryopreservation (preservation at -1960C in liquid Nitrogen) techniques sperm, eggs, animal cells, tissues and embryos can be stored for long period in gene bank, seed bank etc.
Question 8 : Why do we conserve biodiversity ?
Answer : We should conserve biodiversity due to following utilities :
- Narrow Utility : Humans get economic benefits from nature like food, firewood, fibre, tannins, dyes, medicines (25% of drugs from plants) and many more uses.
- Broad utility : Biodiversity plays an important role in many ecosystem services that nature provides us like oxygen (Amazon forest produces 20% of the total oxygen in atmosphere through photosynthesis), pollination, etc.
- Ethical Utility : Philosophically and spiritually every species has an intrinsic value so we have moral duty to take care of them and pass them to next generation in good condition .
- Cultural Utility : Biodiversity has cultural value, it is a source of inspiration to poets, and writers. It gives cultural identity in terms of festivals and rituals .
- Religious Utility : Some plants like tulsi and peepal some animals like cow, monkey have religious importance described in scriptures .
Question 9 : state use of biodiversity in modern agriculture ?
Answer : Agrochemicals cause pollution of soil and water and are too expensive. Genetic modification has made crops more tolerate to abiotic stresses like cold , heat, salinity,etc . It has reduced the dependence of crops on chemical pesticides as they are pest resistant .
Question 10 : What are exotic species ?
Answer : Species that are not naturally found in the habitat , they are mostly introduced in a habitat from outside and they may become invasive too.
Question 11 : What are the specific objectives of conservation of wildlife ?
Answer : The objectives of conservation of wildlife are :
- To maintain essential ecological processes and life supporting systems (air , water and soil )
- To preserve the diversity of species for their continuous use for future generations.
Question 12 : Which type of conservation measures, in situ or ex situ will help the larger number or species to survive ? Explain .
Answer : In in situ conservation species are conserved in their natural habitats so the entire ecosystem along with other organism , biotic and abiotic component of the ecosystem associated with the target species are also conserved so in situ will help the larger number of species to survive .
Question 13 : There are many animals that have become extinct in the wild but continue to be maintained in zoo,
1. What type of biodiversity conservation is observed in this case ?
2. Explain two ways which help in this type of conservation ?
Answer : 1. It is an example of ex situ conservation, in which threatened plants and animals are take out of their natural habitat and placed in to suitable and given given special care.
2. Cryopreservation and tissue culture are two ways that help in ex situ conservation. In cryopreservation, gametes of threatened species are preserved in viable and fertile condition at sub zero temperatures, which help in preserving these cells for longer time. In tissue culture plants are propagated from a small mass of tissue called callus.