NEET Biology Notes – Biodiversity And Conservation

Biodiversity And Conservation Introduction

The occurrence of different types of genes, gene pools, species, habitats, and ecosystem in a particular place and various parts of the earth is called biodiversity (term popularized by Edward Wilson).

Currently, the number of predescribed species of all plants and animals is slightly more than 1.5 million.

Robed May estimated global species diversity at about 7 million (means only 22% of total diversity has been recorded so far).

Estimates Of Species Number On Earth And In India

• Of the total estimate, more than 70% are animals while plants (including fungi) comprise no more than 22%. The most species-rich taxonomic group is insect (70% of animals).
• The number of fungal species in the world is more than the combined total of fishes, amphibians, reptiles, and mammals.
• No estimations are available for prokaryotes as consell giventional taxonomic methods are not suitable, and many of them are not culturable. We may accept bio-chemical/molecular criteria of estimation of diversity in this group.
• India has 2.4% of world’s land, with 8.1% of global diversity. So, India is among 12 mega-diverse countries.
• Nearly 45,000 plant species and twice as many animal species have been recorded from India.
• Applying May’s method, more than 1,00,000 plant and 3,00,000 animals species are yet to be discovered and described.
• Approximately 15,000 new species are discovered every year.

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Levels Of Biodiversity

There are three types of biodiversity:

• Genetic diversity
  • It is a measure of variety in genetic information contained in the organism, e.g., 10-150 genes in virus, 450-700 genes in Mycoplasma, and 32,000-50,000 genes in Oryza sativa.
  • It enables a population to adapt to its environment, e.g., Rauwolfia vomitoria in Himalayan ranges.
  • It helps in the formation of ecotype.
  • It plays a key role in the process of speciation. It maintains diversity at the community level.
• Species diversity
  • It is the variety of species within a region, e.g., Western Ghats are more diverse than Eastern Ghats.
  • Species richness is the number of species present within a unit area.
  • Species diversity is the product of species richness and species evenness.
  • Maximum/taxonomic diversity occurs where the species of taxonomically different groups occur in almost equal abundance.
  • Species evenness is the proportionate number of individuals of different species.
• Community or ecosystem diversity

It is of three types (Whittaker):

• • a-diversity (within community diversity): It is also called local diversity. It is diversity within a community.
  • B-diversity (between community diversity): It is calculated by dividing y by a diversity. It is diversity between two communities.
  • y-diversity: It is also called regional diversity. It represents the total richness of species in all the habitats found within a region, geographical area, or landscape. For example, India is more diverse than Norway.

Patterns of Biodiversity

• The degree of biodiversity shows two master gradients: latitudinal and altitudinal.
• Biodiversity increases from high to low latitudes, i.e., from the poles to the equator.
• Biodiversity is minimum in arctic, moderate in temperate, and maximum in tropical regions. With very few exceptions, tropics (latitudinal range of 23.5° N to 23.5° S) harbor more species than temperate or polar areas. Colombia located near the equator has nearly 1,400 species of birds while New York at 41° N has 105 species and Greenland at 71° N has only 56 species.
• India with much of its land area in the tropical latitudes has more than 1200 species of birds. A forest in a tropical region such as Equador has up to 10 times as many species of vascular plants as in a forest of equal area in a temperate region such as the Midwest of the USA. The largely tropical Amazonian rain forest in South America has the greatest biodiversity on the earth.
• It is home to more than 40,000 species of plants, 3000 of fishes, 1300 species of birds, 427 species of mammals, 427 species of amphibians, 378 species of reptiles, and more than 1,25,000 species of invertebrates. Scientists estimate that in these rain forests, there might be at least 2 million insect species waiting to be discovered and named.
• Tropics show greater diversity because of the following reasons:
  • Speciation is generally a function of time. 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 are less seasonal, are relatively more constant and predictable, can promote niche specialization, and lead to a greater species diversity.
  • Species-area relationships: Alexander Humboldt observed that within a region, species richness increased with increasing explored area, but only up to a limit. In fact, the relation between species richness and area for a wide variety of taxa (angiosperm plants, birds, bats, freshwater fishes) turns out to be a rectangular hyperbola.
    The relationship is a straight line described by the equationlog S = log C + Z log Awhere S is species richness, A is area, Z is the slope of the line (regression coefficient), and C is the Y-intercept.

• Ecologists have discovered that the value of Z lies in the range of 0.1 to 0.2, regardless of the taxonomic group or region. If we analyze the species area relationships among very large areas such as the entire continents, the slope of the line will be much steeper (Z values in the range of 0.6 to 1.2). For frugivorous (fruit-eating) birds and mammals in the tropical forests of different continents, the slope is found to be 1.15.
• Diversity decreases from lower to higher altitudes on a mountain, i.e., it is maximum at the base.
• Conditions favoring growth do not induce biodiversity or speciation; it is called the paradox of enrichment.

Importance of Species Diversity to the Ecosystem

Community with more species is more stable. Stable community should not show too much variation in productivity per year and must be resistant or resilient to occasional disturbances by natural or anthropogenic agencies and alien species. Ecosystem health/balance will be severely affected if species. extinction (particularly key stone) occurs.

Biodiversity Conservation

• Narrowly utilitarian aspect:
  • Pinus, Abies, and Boswellia are major sources of paper.
  • Pine resin is obtained from Pinus while damar is obtained from Shorea robusta.
  • Gums: Kuteera gum (Stericulia urens), Bengal kino gum (Butea monosperma), salai (Boswellia serrata), dhaora (Anogeissus latifolia), gum Arabic (Acacia senegal), etc.
  • Tannin sources: Uncaria (leaves and young branches), Acacia (bark), Juglans (bark), and Caesalpinia (wood and fruits).
  • Important dyes: Cutch/kattha (heartwood of Acacia catechu), henna (leaves of Lawsonia inermis), and haematoxylon (heartwood of Haematoxylon campechianum).
  • Plants can also be used to manufacture innumerable synthetic products called botanochemicals.

• Broadly utilitarian aspect: Ecosystem services are important.
• Ethical aspect: Every species has an intrinsic value.
• Loss of Biodiversity IUCN Red List documents the extinctions of 784 species (including 338 vertebrates, 359 invertebrates, and 87 plants) in the last 500 years.
• Some recent extinctions: Dodo (Mauritius), Quagga (Africa), Thylacine (Australia), Steller’s sea cow (Russia), and three subspecies (Bali, Javan, and Caspian) of tiger.
• 27 species have disappeared in the last 20 years.
• Presently, 12% birds species, 23% of all mammals, 32% of all amphibians, and 31% of all gymnosperms in the world are facing the threat of extinction (more than 15,500 species).
• The sixth extinction is 100-1000 times faster.
• This may lead to decline in plant production, lowered resistance, and increased variability in ecosystem processes, e.g., pest and disease cycle.

Causes of Biodiversity Losses

• Important factors that cause loss of biodiversity are habitat loss, habitat fragmentation, disturbance, over exploitation, pollution, exotic species, intensive agriculture, and forestry (growing only exploitable forest plants).
• Habitat destruction or loss is the primary cause of the loss of biodiversity (tropical rain forests were once covering 14% while now they cover 6% only), Amazon valley.
• Habitat fragmentation reduces the core area and in- creases the edge area.
• Dodo of Mauritius, messenger pigeon, Steller’s sea cow, and Tasmanian wolf have become extinct due to overexploitation. Heath hen disappeared due to hunting and habitat destruction.
• Exotic (alien) species becoming invasive is considered another potent factor for the extinction of species.
• Examples of some exotic species: Water hyacinth (Eichhornia crassipes), Lantana (Lantana camera), congress grass (Parthenium hysterophorus), Nile perch, Eupatorium (Eupatorium cdoratum), and African catfish (Clarias gariepinus).
• Coextinction: For example, coevolved species.

Susceptibility to Extinction

Species more susceptible to extinction have the following population characteristics:

• Large body size (e.g., rhinoceros and lion)
• Small population size and low reproductive rate (e.g., giant panda and blue whale)
• High trophic level in food chain (e.g., bald eagle and Bengal tiger)
• Fixed habitat and migratory routes (e.g., whooping crane and blue whale)

IUCN Red List

• World Conservation Union (WCU) which was formerly known as International Union for the Conservation of Nature and Natural Resources (IUCN), headquarter at Mc-den, Switzerland, has recognized eight Red List categories of species. They are extinct, extinct in wild, critically endangered, endangered, vulnerable, lower risk, data deficient, and not evaluated.
• Critically endangered, endangered, and vulnerable species are called threatened species.
• Rare species have a small population and these are nei- ther vulnerable nor endangered but are at risk.
• A taxon is critically endangered when it is facing an extremely high risk of extinction in the wild in the immediate future.
• A taxon is endangered when it is facing a high risk of extinction in the wild in the near future.
• A taxon is vulnerable when it is facing a high risk of extinction in the wild in the medium term future.

Conservation of Biodiversity

There are two types of conservation strategies: in situ (on site) and ex situ (off site).

In situ Conservation

• Examples of protected areas: National parks, wildlife sanctuaries, and biosphere reserves.
• World Conservation Monitoring Center has recognized 37,000 protected areas.
• There are 448 wildlife sanctuaries and 90 national parks in India.
• In wildlife sanctuaries, protection is given only to animal life while in national parks, both flora and fauna are protected.
• The concept of biosphere reserves was launched under the MAB program of UNESCO (started in 1975).Total biosphere reserves in India are 14.
• A biosphere reserve is made of core, buffer, and transition zones. In core or natural zone, no human activity is allowed.
• Research and educational activities are allowed in buffer zone.
• Activities such as settlements, cropping, grazing, forestry, and tourism are allowed in transition zone.

Scared Grooves

• Sacred forests (islands of pristine forests): Examples are forests of Jaintia and Khasi (Meghalaya), Aravalli (Rajasthan), Western Ghats (Maharashtra and Karnataka), Surguja, Chanda, and Bastar area (MP).
• Sacred lakes: Examples are Pushkar lake in Rajasthan and Khecheopalri lake in Sikkim.
• Sacred plants: Examples are Ocimum sanctum (tulsi), Elaeocarpus floribundus, and Ficus religiosa.

Ex situ Conservation Strategies

• These include botanical gardens, zoological parks and wildlife safari parks, arboreta, aquaria, seed bank, DNA banks, tissue culture, horticultural trade, etc.
• Cryopreservation (at temperature 196°C) is useful for conserving vegetatively propagated crops, e.g., potato. There are two types of cryopreservation:
  • Very rapid cooling (e.g., storing seeds)
  • Gradual cooling and simultaneous dehydration (e.g., tissue culture)
• More than 1500 botanical gardens and arboreta and 800 professionally managed zoos are present around the world.

Biodiversity Hotspots

• The concept was developed by Norman Myers in 1988. Spots with accelerated habitat loss are priority areas for in situ conservation. These areas show high species richness and high endemism.
• India with 2.4% land area accounts approximately 8% species of the world.
• Initially 25 terrestrial hotspots were identified glob- ally. But now the number is raised to 34 with an area of less than 2%.
• Among 34, three (Western Ghats and Sri Lanka, Indo Burma, and Himalayas) are found in India. Eastern Himalayas are active center of evolution of many angiosperms and have many primitive angiosperms.
• The protection of these areas can reduce mass extinction by almost 30%.
• IUCN and WWF (World Wide Fund for Nature) are leading international organizations concerned with biodiversity conservation.

Some Abbreviations

• NEERI: National Environment Engineering Research Institute
• UNEP: United Nations Environment Program
• CAZRI: Central Arid Zone Research Institute (Jodhpur)
• BRP: Biosphere Reserve Program
• MAB: Man and Biosphere
• IBWL: Indian Board of Wild Life
• CITES: Convention on International Trade in Endangered Species
• CBD: Convention on Biological Diversity (The Earth Summit, 1992)

 

Assertion-Reasoning Questions

In the following questions, a statement of Assertion (A) is followed by a statement of Reason (R).

1. If both Assertion and Reason are true and the reason is the correct explanation of the assertion, then mark (1).
2. If both Assertion and Reason are true but the reason is not the correct explanation of the assertion, then mark (2).
3. If Assertion is true but Reason is false, then mark (3).
4. If both Assertion and Reason are false, then mark (4).

Question 1. Assertion: Western Ghats are included among the hot spots of biodiversity.

Reason: Western Ghats have greater amphibian diversity than Eastern Ghats.

Answer. 2. If both Assertion and Reason are true but the reason is not the correct explanation of the assertion, then mark (2).

Question 2. Assertion: Tropical regions are more diversity-rich in comparison to temperate areas.

Reason: Availability of more solar energy directly affects the presence of more species in these areas.

Answer. 3. If Assertion is true but Reason is false, then mark (3).

Question 3. Assertion: The process of extinction is random.

Reason: Any species not adapted to environmental conditions cannot survive.

Answer. 4. If both Assertion and Reason are false, then mark (4).

Question 4. Assertion: Habitat destruction is the main reason of loss of biodiversity.

Reason: This actually causes the increase in edge area and reduction in core area.

Answer. 3. If Assertion is true but Reason is false, then mark (3).

Question 5. Assertion: Pristine forests are among in situ conservation strategies.

Reason: These are sacred grooves where biota is protected on site.

Answer. 1. If both Assertion and Reason are true and the reason is the correct explanation of the assertion, then mark (1).