Notes
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Topics to be Learn : Part-1
Topics to be Learn : Part-2
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Introduction :
Diversity is variety.
Biodiversity :
- Biodiversity refers to the variety of life on Earth, which includes a wide range of species such as microorganisms, viruses, algae, fungi, plants, and animals found in various habitats.
- Diversity is seen in shape, colour, form, mode of nutrition, habitats, reproduction, motility, duration of life cycle, life span, etc. All of these adaptations help in the survival of species and hence diverse forms are seen.
- Walter Rosen (1982) coined the term biodiversity, but it was popularised by sociologist Edward Wilson to describe combined diversity at all levels of biological organisation.
- Definition : Biodiversity is the part of nature that includes differences in genes between individuals of a species, a variety of animal and plant species in various habitats, regions, countries, and the world that form different types of ecosystems within a defined area.
- The biodiversity we see today is the result of over 3.5 billion years of evolutionary history, primarily influenced by natural processes and, more recently, by human influence.
Levels of Biodiversity: Various levels at which diversity can be seen ranging from molecular to ecosystem levels The three main levels, which form a hierarchy and interrelation : Genetic diversity, specie diversity (community) and ecosystem diversity (Ecological diversity). Genetic diversity : Examples of genetic diversity: Species diversity : Ecological or ecosystem diversity :
Patterns of biodiversity :
There are two patterns viz, Latitudinal and Altitudinal gradient and species-area relationship.
Latitudinal species diversity: There is greater species richness at lower latitude which steadily declines towards the poles.
This is called as distribution of diversity along the latitudes.
Overall stability of tropical regions, lesser annual climatic changes, availability of plenty of sunlight, lesser drastic disturbances like periodic glaciations, lesser migrations causing reduced gene flow, normal temperature and higher annual rainfall are all the factors which cause more diversity in these regions.
Altitudinal species diversity: The diversity is more at lower altitude, but at higher altitudes it declines due to change in climatic conditions and drastic seasonal variations.
Species area relationship : Number of species present in any area is directly proportional to the size of this area. Species richness increases with increase in area up to certain limit this was observed by Alexander wan Humboldt.
Alexander von Humboldt‘s views about species richness and area relationship :
Scientists have tried to establish relationship between species diversity and the size of the habitat. It is considered that number of species present is directly proportional to the area.
- It is understood that larger areas may have more resources that can be distributed amongst the inhabitant species.
- Alexander von Humboldt observed that species richness does increase with the increase in area but only till a certain limit.
- For many species this curve is a rectangular hyperbola.
- If we consider S to be species richness, A as area under study, C as the Y intercept and Z as the slope of the line, this relationship can be described by the equation, log S = log C + Z log A.
- On logarithmic scale this relationship is a straight line, as observed in the figure above.
- For smaller areas, value of Z ranges between 0.1 to 0.2 regardless of species or region under study.
- But for the larger areas like the entire continents, slopes are closer to vertical axis i.e. steeper.
- This observation indicates that in very large areas, number of species found, increase faster than the area explored.
Importance of species diversity to the ecosystem :
- A stable community has fairly constant average biomass production over a particular time period. It withstands the disturbance and recovers quickly and also resists the invasive species.
- Productivity stability hypothesis (David Tillman) : Rich diversity leads to lesser variation in production of biomass over a particular time period.
- Rivet Popper hypothesis (Paul Ehrlich): Relationship between diversity and Wellbeing of ecosystem is not linear. When key species are lost there is threat in very short span of time which affects food chain, food web, energy flow and natural cycles resulting into imbalance of ecosystem.
Biodiversity current scenario :
Loss of biodiversity :
Imbalance in the ecosystem occurs if the biodiversity is lost. Extinction of species means threat to biodiversity.
Three types of extinctions are :
- Natural extinction : Occurring due to natural causes such as forest fires, earthquakes, volcanic eruptions, etc.
- Mass extinction : Great impact causing major loss of species.
- Manmade or Anthropogenic extinction : Habitat destruction, hunting, settlement, overexploitation, reclamation are man-made causes of extinction.
There were five mass extinctions during different stages of history of Earth.
The sixth extinction is taking place now which is hundred to thousand times faster than that occurred in pre-human times.50% of diversity is said to be lost and this loss of biodiversity can alter environmental processes such as plant productivity and disease cycles.
Causes of biodiversity losses : Four major causes of biodiversity loss, known as evil quartet. (i) Habitat loss and fragmentation : (ii) Over exploitation : (iii) Alien species invasion : (iv) Co-extinctions :
Extinct species : The species which are totally eliminated from the Earth.
E.g. Dinosaurs
Endangered species : The species having dwindling numbers.
The international union for conservation of nature and natural resources (IUCN) maintains red data Book or red list to record the conservation status of plant and animal species.
Categories of species according to IUCN :
Conservation and biodiversity
Protection, upliftment and scientific management of biodiversity so that it can remain at optimum level and give us sustainable benefits is called conservation of biodiversity.
Reasons for conservation of biodiversity : The conservation of biodiversity can be done in utilitarian way or for ethical reasons. Utilitarian reasons are further classified into narrowly utilitarian and broadly utilitarian reasons : Narrowly utilitarian reasons : Broadly utilitarian reasons : Oxygen supply, seed dispersal, pollination, extra aspects that nature gives us free. Ethical reasons : Humans share earth with all the other diverse life forms and all of them have equal right to survive. Therefore, ethically we should not finish them for our prospective economic use.
Conservation of biodiversity :
In situ conservation :
- In situ conservation refers to the preservation of an organism in its natural environment or habitat.
- In situ conservation is a onsite conservation.
- It is done in natural environment.
- National parks. Sanctuaries, biosphere reserve, etc. are set up for in-situ conservation.
- It is a dynamic process. Cheap and convenient to conduct.
- In India, 34 biodiversity hotspots with high species densities and richness are strategically protected through in situ conservation.
- This method also preserves varieties that have been used for farming and horticulture in the past.
- Captive breeding is not successful in all cases of in-situ conservation method.
- Western Ghats, Indo-Burma and Eastern Himalayas are 3 world’s biodiversity hotspots located in India.
- In India, there are 14 biosphere reserves, 90 national parks, 448 wildlife sanctuaries, sacred groves are also type of in situ conservation in which flora and fauna are protected in the name of God.
- Sacred groves are found in Khasi and Jaintia hills in Meghalaya, in Western Ghats of Maharashtra (especially Sindhudurg district), and Karnataka, Aravalli hills of Rajasthan and Bastar, Chanda and Sarguja areas in Madhya Pradesh.
Ex-situ conservation :
- Critically endangered species are protected in captivity, which is called ex-situ conservation.
- Ex-situ conservation is done outside the habitat of plants and animals.
- Plant and animal species are conserved in artificial or manmade place.
- In ex-situ conservation living beings are protected in wildlife safari parks, zoological parks, botanical gardens, etc.
- Seed banks, tissue culture, cryopreservation, etc. are modern techniques which are used in this conservation method.
- It is static process. Its expensive and commercial process.
- Captive breeding is successful and can help in increasing the number of endangered organisms.
Biological Diversity Act 2002 : The main objectives for proposing this act are There is three tier system in India, comprising of
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