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Others Notes And Questions Class 12 Biology Revision Notes
Class 12 Biology students should refer to the following concepts and notes for Others Notes And Questions in standard 12. These exam notes for Grade 12 Biology will be very useful for upcoming class tests and examinations and help you to score good marks
Others Notes And Questions Notes Class 12 Biology
Chapter-15: BIODIVERSITY AND CONSERVATION
IMPORTANT SCIENTISTS AND THEIR CONTRIBUTION
Biodiversity is defined as the totality of genes, species and ecosystems of a given region, It is the variety and variability of life form (all animals, plants and microbes on earth) and the ecological complexes in which they occur. The term was popularized by the American sociobiologist Edward Wilson(1988)
Hierarchial levels of Biodiversirty:
2)Genetic Diversity and.
Refer Fig no.15.1,Pie chart representing global Biodiversity
Patterns of Biodiversity:
1) Latitudinal gradients – species diversity decreases, from equator to poles. Tropics (23.50N -23.50S) show richest species diversity. Speciation is generally a function of time. Temperate region is subjected to glaciations. Tropical regions remained relatively undisturbed for millions of years and thus had a long evolutionary time for species diversification. Tropical environments are less seasonal, relatively more constant and predictable. Constant environment facilitates niche specialisation and lead to greater species diversity. Tropical latitudes also get huge solar radiations which promote higher productivity.
SPECIES – Area relationships :
This is reflected in the quantitative formula S = cAz, in which S represents the species richness and A the size of the area. The constant c represents y intercept ,.z is regression coefficient.
ALEXANDER VON HUMBOLDT observed within a region species richness increased with increasing explored area but only up to a limit. The relation between species richness and area for a wide variety of taxa turns out to be a rectangular hyperbola. On a logarithmic scale the relationship is a straight line described by the equation
LogS = logC +Z log A Where S= species richness, A = Area, Z = slope of the line(regression coefficient),C = Y- intercept.It has been noted that regardless of the taxonomic group or region the slope of the regression line are amazingly similar. However, for a very large area like the entire continent the slope of the line is steeper.
Refer Fig. No.15.2,graph pertaining to Species-area relationship
Loss of biodiversity:
Loss of biodiversity in a region may lead to
1) decline in plant production
2) lowered resistance to environmental changes such as drought.
3) increased variability in certain ecosystem processes such as plant productivity, water use, pest & disease cycles.
Major causes of biodiversity loss:
--- Habitat loss and fragmentation
----- Over exploitation
----- Alien species invasions eg •The Nile perch was introduced to Lake Victoria in Africa and causedthe extinction of more than 200 endemic fish
---- Overexploitation ,
Biodiversity conservation Reasons for conservation can be grouped into three categories:
------ narrow utilitarian-for deriving direct economic benefit from nature.
------- broad utilitarian-as biodiversity plays a major role in many ecosystem services.
------- ethical-we need to realise that every species has an intrinsic value and we need to pass on our biological richness to future generations.
How to conserve biodiversity:
In-situ Conservation– Threatened /endangered plants and animals are provided with urgent measures to save from extinction within their natural habitat ( in wildlife sanctuaries, national parks & biosphere reserves, sacred groves / lakes-i.e. in protected areas)
Biodiversity hotspots – regions with very high levels of species richness and endemism. Norman- Myers developed the concept of hotspots in 1998 to designate priority areas for insitu conservation. They are the most threatened reservoir of biodiversity on earth. In India 2 hotspots are there, eg.Western ghats, and the Eastern Himalayas.
Ex-situ Conservation –Threatened animals& plants are taken out from their natural habitat& placed in a setting where they can be protected and given care as in botanical gardens, zoological gardens, seed/pollen/gene banks etc.
Efforts to conserve biodiversity:
Convention on Biological Diversity(CBD)
THE EARTH SUMMIT- HELD IN RIO DE JANEIRO
THE WORLD SUMMIT—HELD AT JOHANNESBURG
Q1. Define Biodiversity.
Ans-totality of genes, species and ecosystems of a given region
Q2.What is ecosystem diversity?
Ans.-No. of habitats or ecosystem in a given region of the biosphere.
Q3.Expand the term IUCN.
Ans. International Union for Conservation of Nature and Natural resources.
Q4.Who popularized the term biodiversity?
Ans .Edward Wilson
Q5.Can you mention the estimated number of species so far identified on earth?
Ans 1.7 to1.8 million
Q6. Establish the relationship between species richness and explored area
Ans-.(comment on the species – area relationship curve).
Q7.”Plots with more species showed less year to year variation in total biomass”-who showed this?
Ans- (David Tilman)
Q8.Who proposed the ‘Rivet popper hypothesis’? Comment on the major postulate of this hypothesis.
Ans- (Paul Ehrlich)
Q9.Mention the major causes behind biodiversity loss.
Ans-refer study material
Q10. Why should we conserve biodiversity?
Ans- (comment on the broad/narrow utilitarian and ethical value of biodiversity)
Q11.What do you mean by the term ‘ecosystem services’?
Ans- refer NCERT Text book
Q12. What is meant by the term ‘endemism’?
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