Jain Metaphysics and Science: 4.12 Evolution and Biodiversity

All populations of the same kind of organisms form a species. A group of individuals of the same species living together in a common area at a particular time form a population of that area. The process by which an existing species gives rise to one or more new species is called speciation. Speciation may occur by accumulation of variation, migration, natural calamity, mutation, hybridization and polyploidy.

In biology, evolution is the process by which populations of organisms acquire and pass on novel traits from generation to generation. Its action over large stretches of time explains the origin of new species and ultimately the vast diversity of the biological world. The living species of today are related to each other through common descent, products of evolution and speciation over billions of years. The modern theory of evolution is based on the concept of natural selection proposed by Charles Darwin in 1859. Natural selection is the idea that individuals who possess advantageous heritable traits are more likely to survive and reproduce. In doing so, they increase the frequency of such traits in subsequent generations.

In the 1930 scientists combined Darwinian natural selection with the theory of Mendelian heredity to create the modern evolutionary synthesis. The modern synthesis understands evolution to be a change in the frequency of alleles within a population from one generation to the next. The mechanisms that produce these changes are the basic mechanisms of population genetics: natural selection and genetic drift acting on genetic variations created by mutation, sex, and gene flow. This theory has become the central organizing principle of modern biology. It helps biologists understand topics as diverse as the origin of antibiotic resistance in bacteria, eusociality in insects, and the staggering biodiversity of the living world. Because of its potential implications for the origin of humankind, the theory of evolution has been at the center of many social and religious controversies since it was first introduced.

Evolution consists of two basic types of process; those that introduce new genetic variation into population, and those that affect the frequencies of existing variation. The mechanisms of evolution include mutation, linkage, heterozygosity, recombination, gene flow population structure, drift, natural selection, and adoption. Speciation is the creation of two or more species from one. This may take place by various mechanisms like allot speciation, sympatric speciation, peripatric speciation etc.

Biodiversity found on Earth today is the result of 4 billion years of evolution. The origin of life is not well known to science, though limited evidence suggests that life may already have been well - established a few 100 million years after the formation of the Earth. Until approximately 600 million years ago, all life consisted of bacteria and similar single- celled organisms.

The history of biodiversity during the Phanerozoic (the last 540 million years), starts with rapid growth during the Cambrian explosion - a period during which nearly every phylum of multi cellular organisms first appeared. Over the next 400 million years or so, global diversity showed little overall trend, but was marked by periodic, massive losses of diversity classified as mass extinction events.

The apparent biodiversity shown in the fossil record suggests that the last few million years include the period of greatest biodiversity in the Earth's history. However, not all scientists support this view, since there is considerable uncertainty as to how strongly the fossil record is biased by the greater availability and preservation of recent geologic sections. Some argue that corrected for sampling artifacts; modern biodiversity is not much different from biodiversity 300 million years ago. Estimates of the present global macroscopic species diversity vary from 2 million species to 100 million species, with a best estimate of somewhere near 10 million.

Most biologists agree however that the period since the emergence of humans is part of a new mass extinction, the Holocene extinction event, caused primarily by the impact humans are having on the environment. At present, the number of species estimated to have gone extinct as a result of human action is still far smaller than are observed during the major mass extinctions of the geological past. However, it has been argued that the present rate of extinction is sufficient to create a major mass extinction in less than 100 years. Others dispute this and suggest that the present rate of extinction could be sustained for many thousands of years before the loss of biodiversity matches the more than 20% losses in past global extinction events.

New species are regularly discovered (on average about three new species of birds each year) and many, though discovered, are not yet classified. Biodiversity is not distributed evenly on Earth. It is consistently richer in the tropics and in other localized regions. As one approaches polar region one generally finds fewer species. Flora and fauna diversity depends on climate, altitude, soils and the presence of other species. For example, Brazil's Atlantic Forest contains roughly 20000 plant species, 1350 vertebrates, and millions of insects, about half of which occur nowhere else in the world. The island of Madagascar possess a very high ratio of species endemism and biodiversity, since the island separated from mainland Africa 65 million years ago, most of the species and ecosystems have evolved independently producing unique species different than other parts of Africa.

Biodiversity is most closely known to the public as animals with a backbone when in fact there exist 20 times that number of insects 5 times as many flowering plants. In fact it is often estimated that less than half and perhaps less than two- thirds of earth organisms have been identified. As a soft guide, however, the number of identified modern species as of 2004 can be broken down as follows.

1. 287,655 plants, including;
   15000 mosses,
   13025 ferns,
   980 gymnosperms,
   199,350 dicotyledons,
   59300 monocotyledons;
2. 4000 bacteria
3. 80000 protists (algae, protozoa)
4. 74000-120000 fungi;
5. 10000 lichens;
6. 1250000 animals, including
   
   1. 1190200 invertebrates:
      - 950000 insects,
      - 70000 mollusks,
      - 40000 crustaceans
      - 130200 others;
      
   2. 58 808 vertebrates:
      - 29300 fish,
      - 5743 amphibians,
      - 8240 reptiles,
      - 10234 birds,
      - 5416 mammals.

However the total number of species for some phyla may be much higher

5-10 million bacteria;

1.5 million fungi

There are over 250000 species of flowering plants, Angiosperms as shown in Table 4.1

Table 4.1 Flowering Plants

During the last century, erosion of biodiversity has been increasingly observed. Some studies show that about one of eight known plant species is threatened with extinction. Some estimates put the loss at up to 140000 species per year. This figure indicates unsustainable ecological practices, because only a small number of species come into being each year. Almost all scientists acknowledge that the rate of species loss is greater now than at any time in human history, with extinctions occurring at rates hundreds of times higher than background rates. Factors contributing to loss of biodiversity are; over population, deforestation, pollution (air pollution, water pollution, soil contamination) and global warming or climate change, driven by human activity. These factors, while stemming from over population, produce a cumulative impact upon biodiversity.

The rich diversity of unique species across many parts of the world exist only because they are separated by barriers, particularly large rivers, seas, oceans, mountains and deserts, from other species of other land masses, particularly the highly fecund, ultra-competitive, generalist "super - species". These are barriers that could never be crossed by natural processes, except for many millions of year in the future through continental drift. However humans have invented ships and airplanes, and now have the power to bring into contact species that never have met in their evolutionary history, and on a time scale of days, unlike the centuries that historically have accompanied major animal migrations.

The widespread introduction of exotic species by humans is a potent threat to biodiversity. The exotic organisms may be either predator parasites, or simply aggressive species that deprive indigenous species of nutrients, water and light. As a consequence if humans continue to combine species from different eco regions, there is the potential that the world's ecosystems will end up dominated by relatively a few, aggressive, cosmopolitan "super - species".

Purebred naturally evolved region specific wild species can be threatened with extinction in a big way through the process of Genetic Pollution i.e. uncontrolled hybridization, introgression and Genetic swamping which leads to homogenization or replacement of local genotypes as a result of either a numerical and/ or fitness advantage of introduced plant or animal. These phenomena can be especially detrimental for rare species coming into contact with more abundant ones where the abundant ones can interbreed with them swamping the entire rarer gene pool creating hybrids thus driving the entire original purebred native stock to complete extinction. Some degree of gene flow may be a normal, evolutionarily constructive process, and all constellations of genes and genotypes cannot be preserved however, hybridization with or without introgression may, nevertheless, threaten a rare species existence.

In agriculture and animal husbandry, green revolution popularized the use of conventional hybridization to increase, yield many folds by creating "high-yielding varieties". Often the handful of breeds of plants and animals hybridized originated in developed countries and were further hybridized with local varieties, in the rest of the developing world, to create high yield strains resistant to local climate and diseases. Local governments and industry since have been pushing hybridization with such zeal that several of the wild and indigenous breeds evolved locally over thousands of years having high resistance to local extremes in climate and immunity to diseases etc. have already become extinct or are in grave danger of becoming so in the near future. Due to complete disuse because of un-profitability and uncontrolled intentional, compounded with unintentional cross-pollination and cross breeding (genetic pollution) formerly huge gene pools of various wild and indigenous breeds have collapsed widespread genetic erosion and genetic pollution resulting in great loss in genetic diversity and biodiversity as a whole. Genetically Modified crops today have become a common source for genetic pollution, not only of wild varieties but also of other domesticated varieties derived from relatively natural hybridization. It is being said that genetic erosion coupled with genetic pollution is destroying that needed unique genetic base thereby creating an unforeseen hidden crises which will result in a severe threat to our food security for the future when diverse genetic material will cease to exist to be able to further improve or hybridize weakening food crops and livestock against more resistant diseases and climate changes.

Monoculture, the lack of biodiversity, was a contributing factor to several agricultural disasters in history. Higher biodiversity also controls the spread of certain diseases e.g. viruses will need to adapt itself with every new species. Biodiversity provides food for humans. Although about 80% of our food supply comes from just 20 kinds of plants, humans use at least 40000 species of plants and animals a day. Many people around the world depend on these species for their food, shelter, and clothing. There is vast untapped potential for increasing the range of food products suitable for human consumption, provided that the high present extinction rate can be stopped.

A significant proportion of drugs are derived, directly or indirectly, from biological sources; in most cases these medicines cannot presently be synthesized in a laboratory setting. About 40% of the pharmaceuticals used in the USA are manufactured using natural compounds found in plants, animals and microorganisms.

Biodiversity provides many ecosystem services that are often not readily visible. It plays a part in regulating the chemistry of our atmosphere and water supply. Biodiversity is directly involved in recycling nutrients and providing fertile soils. Experiments with controlled environments have shown that humans cannot easily build ecosystems to support human needs; for example insect pollination cannot be mimicked by human- mode construction, and that activity alone represents tens of billions of dollars in ecosystem services per annum to humankind. Many cultural groups view themselves as an integral part of the natural world and show respect for other living organisms (parasparopgraho jivanama).