Biodiversity: Types, Patterns, Importance, Causes and Loss YouTube Lecture Handouts

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Biodiversity: Types, Patterns, Importance, Causes and Loss

Biodiversity – Meaning & Importance

  • Sum of different species of animals, plants, fungi and microbial organisms living on Earth and the variety of habitats in which they live.
  • Increases productivity and stable ecosystem

What Would Happen if There Are Many Lions?

  • Higher biodiversity ecosystem are more productive
  • Paul Ehlrich: Rivet Popper Hypothesis – (aeroplane as ecosystem and rivets as species) – If rivets are removed if will not affect safety in beginning but later will become weak and if wings (major species) removed there would be immediate threat
  • 50 million species of plants and animals exist
  • 1.4 million species have been identified so far
  • Term given by Walter Rosen in 1985
  • Term popularized by Edward Wilson in 1992
  • Species rich regions – Tropics and Coral reefs
  • Of total species, 70 % species are animals (amongst animals highest proportion is insects) while 22 % are plants
  • Around 15,000 new species are discovered every year (thanks to Species 2000 & Global Biodiversity Information Facility)

Levels of Biodiversity

Types of Biodiversity

Genetic Diversity: Diversity in types and number of genes and chromosomes

  • 50,000 varieties of rice & 1,000 varieties of mango – it helps in speciation and evolution of new species
  • Low diversity – uniformity and higher yield & mass scale destruction

Species Diversity: Variety in number and richness of species

2 Communities for Biodiversity
  • Richness: Number of species per unit area
  • Evenness or Equitability: Number of individuals of different species, more or less equal number of species
  • Dominance: One or more species have dominance as compared to others
  • Odum – Species diversity as number of species per 1000
  • Menhinick – Number of species as square root of total number of individuals – as Shannon Index
  • Simpson՚s reciprocal index (DI) = where N is total number of individuals collected and n is number of individuals of a species – higher values shows greater biodiversity with low competition

Ecological/Community/Ecosystem Diversity: Large variety of ecosystems

  • - Diversity: Within community and dependent on species richness and evenness
  • Diversity: Diversity between community
  • Diversity: Present as ranges of community over a landscape like desert, deciduous, forest, mangroves etc. It is given as where is species in community 1, is species in community 2 and C is common species
Alpha (Α) Diversity V/S Bita (Β) Diversity

Biogeographical Regions of India

  • India is amongst 17 mega diversity regions of world with 8.1 % genetic resources
  • Classified in 10 regions by Wildlife Institute of India
  • Largest – Deccan (42 %) area
  • Most diverse – Western Ghats & NE States
  • Endemic species – NE, NW, Western Ghats, A & N Islands
10 Biogeographic Zones of India

Biodiversity witness latitudinal and altitudinal gradient (master gradient) – very less biodiversity at poles (harsh condition) and maximum at equator (maximum at tropical rainforest of Amazon)

Biodiversity decrease with altitude as temperature drops and seasonal variability increases

Why Tropics are good?

  • Ample sunlight
  • Ample resources
  • Less competition due to favorable environment
  • Low rate of extinction
  • Poles witnessed glaciation but tropics were undisturbed

Species-Area Relationship -

Humboldt: Richness of species increases with area but upto certain limit as rectangular hyperbola

Causes of Biodiversity Loss

Evil Quartet

  • Habitat Loss and Fragmentation – overpopulation, industrialization and urbanization – tropical rainforests have decreased from 14 % to 6 %
  • Alien Species Invasion – exotic species harmful to local species, water hyacinth introduced to check population clogged water bodies and lead to death of aquatic animals
  • Nile Perch (predator fish) in Lake Victoria of South Africa killed Cichlid fish
  • Over exploitation – Dodo, passenger pigeon are know extinct, commercially important species become extinct
  • Co-extinctions – mutualistic relationships exist, removal of one will lead to threat to another (e. g. , Pronuba yuccaselles and Yucca)

Other Causes

  • Disturbance and degradation – natural or manmade
  • Pollution – biomagnification of pesticides, runoff of fertilizers causes nutrient enrichment and eutrophication – lead and heavy metals in body of animals
  • Intensive agriculture – HYV – increase vulnerability of crops to attack of pathogens
  • Forestry – grow trees in pure strands drives away other species and pure strands are liable to pathogen attack

Loss of Biodiversity

Caused by extinction or elimination of species

It will lead to

  • Decline in ecosystem productivity
  • Reduced resistance to environmental perturbations
  • Drastic change in ecosystem process

Which species are more susceptible to Extinction?

  • Large body size
  • Small population size
  • Low reproductive potential
  • Higher status of trophic level
  • Fixed migratory route
  • Narrow range of distribution
  • Island species
  • Lack of genetic variability
  • Inability to switch to alternate foods

Types of Extinction

Natural/Background Extinction: Slow process with better adopted species replacing others, extinction vertex is combination of genetic and demographic factors

Mass Extinction

Mass Extinction
  • Permian Period: Shallow invertebrates disappeared
  • B/w Cretaceous and Tertiary - dinosaurs disappeared (K-T Boundary)

Anthropogenic Extinction – by settlement, hunting, overexploitation and habitat destruction

  • Colonization leads to extinction of native species
  • 6th mass extinction is considered anthropogenic (tropical forest losing at 2 - 5 species/hour)

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