BIODIVERSITY AND CONSERVATION

 

BIODIVERSITY AND CONSERVATION

• Biodiversity: the term biodiversity refers to the totality of genes, species, and ecosystems of a region.
• Types of biodiversity described by Edward Wilson:
  • Genetic diversity: A single species might show high diversity at the genetic level over its distributional range.
    • Medicinal plant Rauwolfia vomitoria of Himalayan range produces active chemical reserpine shows genetic variation.
    • India has more than 50000 different strain of rice.
    • 1000 varieties of mango.
    
    
• Species diversity: different species of a single animal like frog.
• Ecological diversity: diversity in the ecosystem level like desert, rain forest, mangroves, coral reef, wetlands, estuaries etc.

How many species are there on Earth and How many in India?

• According to IUCN (2004), 1.5 million of plants and animals are in our biosphere.
• Robert May places global species diversity at about 7 millions.
• More than 70 percent of all the species recorded are animals.
• All plants constitute about 22 percent.
• Among animals insects constitute 70 percent.
• India has only 2.4 percent of the world’s land area; its share of global species diversity is impressive 8.1 percent.
• India is considered one of the mega diversity countries of the world.

Pattern of Biodiversity:

Latitudinal gradients:

• Species diversity decreases as we move away from the equator towards the pole.
• Tropic (23.5^o N to 23.5^o S) harbors more species than temperate and pole
• The largely tropical Amazonian rain forest in South America has the greatest biodiversity on earth:
• 40,000 species of plants.
• 3000 species of fishes.
• 1300 of birds.
• 427 amphibians
• 378 reptiles
• More than 1, 25,000 invertebrates.

Why tropical rain forest has greater biodiversity:

• Unlike temperate regions subjected to frequent glaciations in the past, tropical latitudes have remained relatively undisturbed for millions of years and thus, had a long evolutionary time for species diversification.
• Tropical environments. Unlike temperate ones, are less seasonal, relatively more constant and predictable, promotes niche specialization and lead to greater species diversity.
• There is more solar energy available in the tropics, which contribute to higher productivity.

Species area relationship:

• 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 describe 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.

Importance of species diversity to the Ecosystem:

• Community with more species generally tends to be more stable than those with less species.
• A stable community should not show too much variation in productivity from year to year; it must be resistant or resilient to occasional disturbances (natural or man-made)
• Stable community must be resistant to invasion by alien species.
• David Tillman’s long-term field experiment finds that:
  • Plots with more species showed less year to year variation in biomass
  • Increased diversity contributed to higher productivity.
  
  
• The rivet popper hypothesis:
  • In an airplane (ecosystem) all parts are joined together by thousands of rivets (species).
  • If every passenger starts popping a rivet to take home (species extinct), it may not affect flight safety initially but as more and more rivets are removed the plane becomes dangerously weak.
  • Further more which rivet is removed may also be critical.
  • Loss of rivets on the wings (key species) is obviously a more serious threat to flight safety than loss of a few rivets on the seats or windows inside the plane.

Loss of Biodiversity:

• The IUCN Red List (2004) documents the extinction of 784 species.
• Recent extinction includes:
  • Dodo (Mauritius).
  • Quake (Africa)
  • Thylacine (Australia)
  • Stiller’s cow (Russia)
  • Three subspecies of tiger (Bali, Java, Caspian).
  
  
• Since the origin and diversification of life on earth there were five episodes of mass extinction of species.
• The sixth mass Extinctions in progress now.

How the’ sixth Extinction’ is different from the previous five extinctions.

• The current extinction rate is 100 to 1000 times faster.
• All others are pre-human period, this one is anthropogenic.

 

CBSE Biology (Chapter Wise) Class XII ( By Mr. Hare Krushna Giri )
Email Id : [email protected]