SPECIES DATA OF BOTANICAL GARDEN TILL MAY 2012

SANGAMNER COLLEGE 

 NOTES FOR T.Y.B.SC : TOPIC- ENDEMISM

 Endemism is the ecological state of being unique to a particular geographic location, such as a specific island, habitat type, nation or other defined zone. To be endemic to a place or area means that it is found only in that part of the world and nowhere else. The extreme opposite of endemism is cosmopolitan distribution. 

Physical, climatic, and biological factors can contribute to endemism.  Political factors can play a part if a species is protected, or actively hunted, in one jurisdiction but not another. There are two subcategories of endemism - Paleoendemism and Neoendemism.

Paleoendemism is also called contracting or retrogressive endemics, refers to a species that was formerly wide spread but is now restricted to a smaller area.

Neoendemism which is also called progressive or expanding endemics refers to a species that has recently arisen such as a species that has diverged and become reproductively isolated, or one that has formed following hybridization and is now classified as a separate species. This is a common process in plants especially those which exhibit polyploidy.

Pseudo endemics :-Sometimes mutants appear and vanish without being able to compete with parental species, and are called pseudo-endemic.

Endemic types or species are especially likely to develop on biologically isolated areas such as islands because of their geographical isolation. This includes remote island groups, such as Hawaii, the Galápagos Islands, and Socotra, and biologically isolated but not island areas such as the highlands of Ethiopia, or large bodies of water like Lake Baikal.

Endemics can easily become endangered or extinct if their restricted habitat changes, particularly but not only due to human actions, including the introduction of new organisms. There were millions of both Bermuda Petrels and "Bermuda cedars" (actually junipers) in Bermuda when it was settled at the start of the seventeenth century. By the end of the century, the petrels were thought extinct. Cedars, already ravaged by centuries of shipbuilding, were driven nearly to extinction in the twentieth century by the introduction of a parasite. Bermuda petrels and cedars, although not actually extinct, are very rare today, as are other species endemic to Bermuda.

Contributions of J.D.Hooker                                                   

Sir Joseph Dalton Hooker OM, GCSI, CB, FRS (30 June 1817 – 10 December 1911) was one of the greatest British botanists and explorers of the 19th century. Hooker was a founder of geographical botany and Charles Darwin's closest friend. He was Director of the Royal Botanical Gardens, Kew for twenty years, in succession to his father William Jackson Hooker and was awarded the highest honours of British science.

His Expedition work :

1)     Voyage to the Antarctic 1839–1843

2)     Geological Survey of Great Britain

3)     Voyage to the Himalayas and India 1847–1851

4)     Voyage to Palestine 1860

5)     Voyage to Morocco 1871

6)     Voyage to Western United States 1877

He as the Director of  Royal Botanical Gardens, Kew:-

By his travels and his publications, Hooker built up a high scientific reputation at home. In 1855 he was appointed Assistant-Director of the Royal Botanic Gardens, Kew, and in 1865 he succeeded his father as full Director, holding the post for twenty years. Under the directorship of father and son Hooker, the Royal Botanical gardens of Kew rose to world renown. At the age of thirty, Hooker was elected a fellow of the Royal Society, and in 1873 he was chosen its president (till 1877). He received three of its medals: the Royal Medal in 1854, the Copley in 1887 and the Darwin Medal in 1892. He continued to intersperse work at Kew with foreign exploration and collecting. His journeys to Palestine, Morocco and the United States all produced valuable information and specimens for Kew.

He started the series Flora Indica in 1855, together with Thomas Thompson. Their botanical observations and the publication of the Rhododendrons of Sikkim-Himalaya (1849–51), formed the basis of elaborate works on the rhododendrons of the Sikkim Himalaya and on the flora of India. His works were illustrated with lithographs by Walter Hood Fitch.

His greatest botanical work was the Flora of British India, published in seven volumes starting in 1872. On the publication of the last part in 1897, he was promoted Knight Grand Commander of the Order of the Star of India (being made a Knight Commander of that Order in 1877). Ten years later, on attaining the age of ninety in 1907, he was awarded the Order of Merit.

He was the author of numerous scientific papers and monographs, and his larger books included, in addition to those already mentioned, a standard Students Flora of the British Isles and a monumental work, the Genera plantarum (1860–83), based on the collections at Kew, in which he had the assistance of George Bentham. His collaboration with George Bentham was especially important. Bentham, an amateur botanist who worked at Kew for many years, was perhaps the leading botanical systematist of the 19th century.^[36] The Handbook of the British flora, begun by Bentham and completed by Hooker, was the standard text for a hundred years. It was always known as 'Bentham & Hooker'.

In 1904, at the age of 87, Hooker published A sketch of the Vegetation of the Indian Empire. He continued the compilation of his father Sir William Jackson Hooker's project, Icones Plantarum (Illustrations of Plants), producing volumes eleven through nineteen.

His various contributions are listed below.

• 1844–1859: Flora Antarctica: the botany of the Antarctic voyage. 3 vols, 1844 (general), 1853 (New Zealand), 1859 (Tasmania). Reeve, London.

• 1864–1867: Handbook of the New Zealand flora

• 1849: Niger flora

• 1849–1851: The Rhododendrons of Sikkim-Himalaya

• 1854: Himalayan Journals, or notes of a naturalist, in Bengal, the Sikkim and Nepal Himalayas, Khasia Mountains ...

• 1855: Illustrations of Himalayan plants

• 1855: Flora indica, with Thomas Thomson

• 1858: with George Bentham, Handbook of the British flora. ("Bentham & Hooker")

• 1859: A century of Indian orchids

• 1859: Introductory Essay to the Flora of Australia^[48]

• 1862–1883: with George Bentham, Genera plantarum

• 1870; 1878: The student's flora of the British Isles. Macmillan, London.

• 1872–1897: The Flora of British India

• 1898–1900: Handbook to the Ceylon flora

• 1904–1906: An epitome to the British Indian species of Impatiens

Rev. Fr. H. Santapau, S. J.

Fr. H. Santapau was born at La Galera, Tarragona, Spain on December 05, 1903. He joined the Society of Jesus at Gandia, Valencia, at the age of 16. He left for India in 1928, to serve out the period of his regency and to complete his theological studies. He abtained B. Sc. Hons. and Ph.D. degrees in Botany from the London University. He also acquired Associateship Diploma of the Royal College of Science and the Diploma of the Imperial College. After spending two years at Herbarium of the Royal Botanical Gardens, Kew, England, he joined as the teaching staff of St. Xaviers College in 1940. He was recongnised as a postgraduate teacher in Botany at the universities of Bombay, Poona, Agra and Calcutta. Among 216 scientific publications of Fr. Santapau, The Flora of Khandala in the Western Ghats of India,(1953), The Flora of Purandhar, (1958), The Flora of Saurashtra, part I, (1962), The Acacthaceae of Bombay, (1952), The Asclepiadaceae and Periplocaceae of Bombay (1962), The Orchids of Bombay (1966) are well known.

Fr. Santapau was associated with the National Institute of Sciences of India, the Linnean Society, London, the Indian Botanical Society, The Royal Asiatic Society of Bengal, The Botanical Society of Bengal, Bombay Natural History Society, Indian Science Congress Association, Phytopathological Society of India, International Society of Pythomorphology, International Association for Plant Taxonomy, International Association of Botanical Gardens, the Royal Agricultural and Horticultural Society of Bengal, etc. Fr. Santapau served on some of the committees appointed by the CSIR, ICMR and the Indian Council of Ayurvedic Research.

In 1954, the Government of India nominated Fr. Santapau as chief Botanist for one year for the revival of the Botanical Survey of India. He served as Director, BSI from 1961-67. He was asked by the Government of India to head the Indian contingent to the tenth International Botanical Congress, Edinburgh, in 1964. He was also an official delegate at the International Standards Organisation meeting in New Delhi in 1964.

For his signal services to the country in education and research Fr. Santapau received Padma Shri Award from the Government of India and the Order of Alphonsus X, the Wise Award from the Spanish Government. The First Birbal Sahani Medal was bestowed on him by the Indian Botanical Society in 1964 .

Fr. Santapau's research has unearthed a valuable treasury of scientific lore and placed it before Indian students. He has not only helped to initiate, popularize and maintain the discipline of taxonomy in India but also endeared himself to research students by latinising the names of hundreds of new specimens.

In a well deserved tribute to the memory of the late Rev. Fr. Hermenegild Santapau, S.J., who died on January 13, 1970, the Prime Minister of India, Mrs. Indira Gandhi, wrote on January 22 : “ In Rev .Fr. Santapau’s death we have lost an eminent scholar who has served education and science for over 40 years. His deep love for India urged him to become a citizen of the country. He had a great knowledge of, and concern for, our plant wealth and wrote intensively on it for experts and laymen. May his memory long continue to inspire all those interested in our flora.”

Syllabus:- Evolution

1)      Variations and speciation in plants:

sources of variations- mutations and recombination, natural selection, Allopatric and sympatric speciation, origin of deme, race and species

Evolution at molecular level.

What is a Species?

Definitions of species tend to fall into two main camps, the morphological and the biological species concepts.

Morphological species concept: Oak trees look like oak trees, tigers look like tigers. Morphology refers to the form and structure of an organism or any of its parts. The morphological species concept supports the widely held view that "members of a species are individuals that look similar to one another." This school of thought was the basis for Linneaus' original classification, which is still broadly accepted and applicable today.

This concept became criticized by biologists because it was arbitrary. Many examples were found in which individuals of two populations were very hard to tell apart but would not mate with one another, suggesting that they were in fact different species.

The morphological species concept was replaced by another viewpoint that puts more emphasis on the biological differences between species.

Biological species concept: This concept states that "a species is a group of actually or potentially interbreeding individuals who are reproductively isolated from other such groups." OR A species is an actually or potentially interbreeding population that does not interbreed with other such populations when there is opportunity to do so.

This definition was attractive to biologists and became widely adopted by the 1940's. It suggested a critical test of species-hood: two individuals belong to the same species if their gametes can unite with each other under natural conditions to produce fertile offspring.

Polytypic & Monotypic species :- Species with two or more subspecies are polytypic species and Species that are not subdivided into subspecies are called monotypic or monospecific.

 Speciation : The process of transformation of a parent species into one or several progeny species is called speciation. It can take place in two general ways. A single species may change over time into a new form that is different enough to be considered a new species. This process is known as anagenesis. More commonly, a species may become split into two groups that no longer share the same gene pool. This process is known as cladogenesis. There are several ways in which anagenesis and cladogenesis may take place. In all cases, reproductive isolation occurs.

Allopatric speciation

Allopatric (geographic) speciation is the differentiation of physically isolated populations to the point that reunion of the two populations does not occur if contact is re- established.

During allopatric (from the ancient Greek allos, "other" + Greek patrā, "fatherland") speciation, a population splits into two geographically isolated populations.

Allopatric speciation, the most common form of speciation, occurs when populations of a species become geographically isolated. When populations become separated, gene flow between them ceases. Over time, the populations may become genetically different in response to the natural selection imposed by their different environments. If the populations are relatively small, they may experience a founder effect: the populations may have contained different allelic frequencies when they were separated. Selection and genetic drift will act differently on these two different genetic backgrounds, creating genetic differences between the two new species

The isolated populations then undergo genotypic and/or phenotypic divergence as: (a) they become subjected to dissimilar selective pressures; (b) they independently undergo genetic drift; (c) different mutations arise in the two populations. When the populations come back into contact, they have evolved such that they are reproductively isolated and are no longer capable of exchanging genes.

The separate populations over time may evolve distinctly different characteristics. If the geographical barriers are later removed, members of the two populations may be unable to successfully mate with each other, at which point, the genetically isolated groups have emerged as different species. Allopatric isolation is a key factor in speciation and a common process by which new species arise.

Sympatric speciation

Sympatric speciation refers to the formation of two or more descendant species from a single ancestral species all occupying the same geographic location. Sympatric speciation is the process through which new species evolve from a single ancestral species while inhabiting the same geographic region. Sympatric speciation occurs when populations of a species that share the same habitat become reproductively isolated from each other. This speciation phenomenon most commonly occurs through polyploidy, in which an offspring or group of offspring will be produced with twice the normal number of chromosomes. Where a normal individual has two copies of each chromosome (diploidy), these offspring may have four copies (tetraploidy). A tetraploid individual cannot mate with a diploid individual, creating reproductive isolation.

Sympatric speciation is rare. It occurs more often among plants than animals, since it is so much easier for plants to self-fertilize than it is for animals. A tetraploidy plant can fertilize itself and create offspring. For a tetraploidy animal to reproduce, it must find another animal of the same species but of opposite sex that has also randomly undergone polyploidy.

Mutation as a source of variation:-

Mutation is defined as a failure to store genetic information faithfully. Changes in genetic information can be reflected in the expression of that information (i.e. in the proteins produced). In other words, mutation accounts for the variability in the genetic information. This property was necessary to explain why individuals within a population are not all genetically identical, and to explain how organisms evolve.

Mutation is therefore a double-edged sword. On one hand, mutation is necessary to introduce variation into the gene pool of a population. Genetic variation has been shown to correlate with species fitness. On the other hand, most mutations are deleterious to the individuals in which they occur. So mutation is good for the population, but generally not so good for the individual.

Types of mutations

1)    Somatic mutations -Mutations occur in regular body cells; these are somatic mutations

2)    Gametic mutations- Some mutations occur in germline cells. These cells produce the gametes; therefore, they are gametic mutations.

3)    Spontaneous mutations- Some mutations arise as natural errors in DNA replication (or as a result of unknown chemical reactions); these are known as spontaneous mutations.

4)    Induced mutations- Mutations can also be caused by agents in the environment; these are induced mutations. Agents in the environment that cause an increase in the mutation rate are called mutagens.

5)    Random mutations- Mutations do not occur in response to a stimulus

 Recombination as a source of variation:-

There is a mechanism of genetic variation other than mutation, and it involves exchange between DNA molecules with significant sequence similarity. Because the molecules must be homologous in order for recombination to occur, the process is often called homologous recombination. This process occurs in viruses, bacteria, and eukaryotes. In eukaryotes, recombination is the molecular basis of crossing over between homologous chromosomes. (For a review of crossing over, see the module on meiosis.)

Natural selection

 The term was introduced by Darwin in his influential 1859 book On the Origin of Species. Natural selection is one of the basic mechanisms of evolution, along with mutation recombination and genetic drift. It is a key mechanism of evolution.

Natural selection & Speciation

Speciation requires selective mating which result in a reduced gene flow. Selective mating can be the result of 1. Geographic isolation, 2. Behavioral isolation, or 3. Temporal isolation. For example, a change in the physical environment (geographic isolation by an extrinsic barrier) would follow number 1 a change in camouflage for number 2 or a shift in mating times (i.e., one species of deer shifts location and therefore changes its "rut") for number 3.^{[citation needed]}

Over time these subgroups might diverge radically to become different species either because of differences in selection pressures on the different subgroups or because different mutations arise spontaneously in the different populations or because of founder effects – some potentially beneficial alleles may by chance be present in only one or other of two subgroups when they first become separated. Genetic changes within groups result in increasing incompatibility between the genomes of the two subgroups, thus reducing gene flow between the groups. Gene flow will effectively cease when the distinctive mutations characterizing each subgroup become fixed. As few as two mutations can result in speciation: if each mutation has a neutral or positive effect on fitness when they occur separately but a negative effect when they occur together, then fixation of these genes in the respective subgroups will lead to two reproductively isolated populations. According to the biological species concept these will be two different species.

Deme :- It is a term for a local interbreeding population within a species. Population that is sufficiently isolated so that it can be considered an evolving unit. Deme is more typically used by evolutionary biologists

Uneven distribution can result in clusters of individuals partially isolated from other such clusters—that is, with more interbreeding within the clusters than between them—simply because of proximity. It is to such clusters that the term deme is usually applied.

If demes inhabit different local environments, natural selection can operate in different directions in these populations with the result that there may be genetic and even physical variation in the characteristics of individual demes. Other processes of evolution, such as mutation and other forms of genetic change, can also enhance these differences, depending upon the extent of demic isolation.

Subspecies

If different populations within a species occur, they vary as a consequence of evolutionary processes occurring within those populations. Consequently, it is sometimes possible to subdivide a species into identifiable subspecies. A subspecies is simply a recognizably distinct subpopulation within a species that occupies a particular geographic area. Subspecies designations are conventionally considered valid if as many as three-fourths of the individuals are recognizable as belonging to that subgroup on the basis of some morphological or biochemical characteristic. Subspecies may represent intermediate stages in the process of speciation, the formation of new species. A small amount of gene flow, interbreeding across a population boundary, slows or prevents genetic divergence between subspecies

 Botanical survey of India

 Botanical Survey of India (BSI) 

 The Botanical Survey of India (BSI) is the apex research organization under the Ministry of Environment and Forests, Govt. of India for carrying out taxonomic and floristic studies on wild plant resources of the country. It was established on 13^th February, 1890 with the basic objective to explore the plant resources of the country and to identify the plants species with economic virtues. The Botanical Survey of India has the eleven regional circles situated at different regions of the country. 

 Organisation Setup 

1. Ecology
2. Cryptogamic Botany
3. Plant Chemistry
4. Pharmacognosy
5. Flora of India
6. Publication
7. Library and documentation
8. Technical.
   
   
   
   

   	INDIAN BOTANIC GARDEN, HOWRAH: a 273 acre sprawling garden and National Orchidarium.
   	CENTRAL NATIONAL HERBARIUM, HOWRAH (Acronym: CAL): including the Palynology Unit (covering states of Bihar, Jharkhand and West Bengal).
   	CENTRAL BOTANICAL LABORATORY, HOWRAH: with Economic Botany, Cytology and  Plant Physiology and Biochemistry units.
   	INDUSTRIAL SECTION, INDIAN MUSEUM, KOLKATA

REGIONAL CIRCLES:
	1)Eastern Circle, Shillong (covering the states of Assam, Manipur, Meghalaya, Mizoram,  Nagaland and Tripura).  The circle has a National Orchidarium at Shillong and  an associated Botanic Garden at Barapani and Tissue Culture laboratory at both Shillong and Barapani.
	2)Southern Circle, Coimbatore (covering the states of Kerala and Tamilnadu and Union Terrirories of Lakshadweep & Minicoy Islands). The circle has a National Orchidarium, an associated Botanic garden and a Tissue Culuture laboratory at Yercaud.
	3)Western Circle, Pune (covering states of  Goa, Karnataka and Maharashtra and Union Terrirories of Dadra & Nagar Haveli, Daman, Diu). The circle has an associated Botanic Garden at  Mundhwa.
	4)Northern Circle, Dehra Dun (covering the the states of  Haryana, Himachal Pradesh, Jammu & Kashmir, Punjab, Uttranchal and Union Terrirories of Chandigarh. The circle has three associated Botanic Gardens at Dehra Dun, Khirsu and Pauri, one green, house one Orchidarium and one Tissue Culture laboratory at Dehradun.
	5)Central Circle, Allahabad (covering the states of Madhya Pradesh, Chattisgarh and Uttar Pradesh). The circle has an associated Botanic Garden at Allahabad.
	6)Arid Zone Circle, Jodhpur (covering the states of Rajasthan and Gujarat). The circle has an associated Desert Botanic Garden at Jodhpur.
	7)Andaman & Nicobar Circle, Port Blair (all the oceanic Islands under Andaman & Nicobar). The circle has an associated Botanic Garden at Dhanikhari.
	8)Sikkim Himalayan Circle, Gangtok (covering the states of Sikkim and Darjeeling district of West Bengal). The circle has a Green House and a Glass House at Gangtok.
	9)Arunachal Pradesh Circle, Itanagar (covering the state of Arunachal Pradesh). The circle  has an Arboretum at Sankie View, Itanagar
	10)Botanic Garden of Indian Republic, Noida (covering the National Capital Territory Region of Delhi). The Centre is currently under the development.
	11)Deccan Circle (Covering the states of Andhra Pradesh and Orissa.)    Aims & Objectives  PRIMARY OBJECTIVES Exploration, inventorying and documentation of phytodiversity (including non-flowering plants) in general and protected areas, hotspots, fragile ecosystems and sacred groves in particular; publication of National, State and District Floras. Identification of Red list species and species rich areas needing conservation; ex situ conservation of critically threatened taxa in botanical gardens. Survey and documentation of traditional knowledge (ethno-botany) associated with plants. Develop a National database of Indian plants, including herbarium specimens, live specimens, botanical paintings illustrations etc. SECONDARY OBJECTIVES Revisionary/Monographic studies on selected plant groups. Qualitative analysis of nutritive value of ethno-food plants and other economically useful species. Capacity building in plant taxonomy through refresher courses and post M.Sc. certificate course. Environment Impact Assessment of areas assigned to BSI for study. Develop and maintain Botanical Gardens, Museum and Herbaria. Preparation of Seed, Pollen and Spore Atlas of Indian Plants. Repatriation of Indian Biodiversity Information held in herbaria/museums abroad. Achievements and contribution  of Western circle(Pune) of BSI Contribution:-   PUBLICATIONS  BOOKS                   National Flora : 4               State Flora : 3               Regional Flora : 1               District Flora : 8               Miscellaneous : 4 Researchpapers                        :500 Achievements  Exploration of Plant Resources  Floristic and Taxonomic studies  Inventorisation of Endangered Plant Species  Ex-situ Conservation  Fragile Ecosystems  Protected Areas  Ethnobotanical Studies  Environmental Impact Assessment  Geobotanical Studies  National Database  Environmental Education and Awareness  Capacity Building in Plant Taxonomy  International Conventions vis-a-vis Botanical Survey of India  Miscellaneous studies  Publications

·         A radionuclide is an atom with an unstable nucleus. The radionuclide undergoes radioactive decay by emitting a gamma ray(s) and/or subatomic particles. Radio nuclides are often referred to by chemists and biologists as radioactive isotopes or radioisotopes

You can heat the substance up, subject it to high pressure or strong magnetic fields - in fact, do pretty much whatever you like to it - and you won't affect the rate of decay in the slightest.

• Alpha particles are easy to stop, gamma rays are hard to stop.

• Particles that ionise other atoms strongly have a low penetrating power, because they lose energy each time they ionise an atom. 

• Radioactive decay is not affected by external conditions.

• You need to know the information in this table:-

Biological Effect of Ionizing Radiation changes caused in the life activity and structure of living organisms under the influence of shortwave electromagnetic radiation (X rays and gamma rays) or fluxes of charged particles (alpha particles, beta radiation, protons) and neutrons. A number of general principles characterize the biological effect of ionizing radiation. (1) Profound disturbance of life activity is caused by infinitesimally small quantities of absorbed energy. Thus, the energy absorbed by the body of a mammalian animal or of a human in being irradiated with a lethal dose when converted to heat energy would raise the body temperature by only 0.001°C. An attempt to explain the “discrepancy” between the quantity of energy and the resulting effect led to formulation of the target theory, according to which radiation damage results when the energy reaches the especially radiosensitive part of the cell—the “target.’’ (2) The biological effect of ionizing radiation is not limited to the organism subjected to irradiation but may spread to succeeding generations, which is explained by the effect on the hereditary apparatus of the organism.

 scintillation counter

 measures ionizing radiation. The sensor, called a scintillator, consists of a transparent crystal, usually phosphor, plastic (usually containing anthracene), or organic liquid (see liquid scintillation counting) that fluoresces when struck by ionizing radiation. A sensitive photomultiplier tube (PMT) measures the light from the crystal. The PMT is attached to an electronic amplifier and other electronic equipment to count and possibly quantify the amplitude of the signals produced by the photomultiplier.

The scintillation counter was invented in 1944 by Sir Samuel Curran^[1][2] whilst he was working on the Manhattan Project at the University of California at Berkeley, and it is based on the earlier work of Antoine Henri Becquerel, who is generally credited with discovering radioactivity, whilst working on the phosphorescence of certain uranium salts (in 1896). Scintillation counters are widely used because they can be made inexpensively yet with good quantum efficiency. The quantum efficiency of a gamma-ray detector (per unit volume) depends upon the density of electrons in the detector, and certain scintillating materials, such as sodium iodide and bismuth germanate, achieve high electron densities as a result of the high atomic numbers of some of the elements of which they are composed. However, detectors based on semiconductors, notably hyper pure germanium, have better intrinsic energy resolution than scintillators, and are preferred where feasible for gamma-ray spectrometry. In the case of neutron detectors, high efficiency is gained through the use of scintillating materials rich in hydrogen that scatter neutrons efficiently. Liquid scintillation counters are an efficient and practical means of quantifying beta radiation.

A particle or radiation detector which operates through emission of light flashes that are detected by a photosensitive device, usually a photomultiplier or a silicon PIN diode. The scintillation counter not only can detect the presence of a particle, gamma ray, or x-ray, but can measure the energy, or the energy loss, of the particle or radiation in thescintillating medium. The sensitive medium may be solid, liquid, or gaseous, but is usually one of the first two. The scintillation counter is one of the most versatile particle detectors, and is widely used in industry, scientific research, medical diagnosis, and radiation monitoring, as well as in exploration for petroleum and radioactive minerals that emit gamma rays. Many low-level radioactivity measurements are made with scintillation counters. See also Low-level counting; Particle detector; Photomultiplier.

Scintillation counters are made of transparent crystalline materials, liquids, plastics, or glasses. In order to be an efficient detector, the bulk scintillating medium must be transparent to its own luminescent radiation, and since some detectors are quite extensive, covering meters in length, the transparency must be of a high order. One face of the scintillatoris placed in optical contact with the photosensitive surface of the photomultiplier or PIN diode (see illustration). In order to direct as much as possible of the light flash to the photosensitive surface, reflecting material is placed between the scintillator and the inside surface of the container.

Diagram of a scintillation counter.

In many cases it is necessary to collect the light fr

STUDY MATERIAL / NOTES FOR T.Y.B.SC, TOPIC- ENDEMISM , A/Y - 2012-13

 Endemism is the ecological state of being unique to a particular geographic location, such as a specific island, habitat type, nation or other defined zone. To be endemic to a place or area means that it is found only in that part of the world and nowhere else.The extreme opposite of endemism is cosmopolitan distribution. 

Physical, climatic, and biological factors can contribute to endemism.  Political factors can play a part if a species is protected, or actively hunted, in one jurisdiction but not another.

There are two subcategories of endemism - paleoendemism and neoendemism. Paleoendemism refers to a species that was formerly widespread but is now restricted to a smaller area. Neoendemism refers to a species that has recently arisen such as a species that has diverged and become reproductively isolated, or one that has formed following hybridization and is now classified as a separate species. This is a common process in plants especially those which exhibit polyploidy.

Endemic types or species are especially likely to develop on biologically isolated areas such as islands because of their geographical isolation. This includes remote island groups, such as Hawaii, the Galápagos Islands, and Socotra, and biologically isolated but not island areas such as the highlands of Ethiopia, or large bodies of water like Lake Baikal.

Endemics can easily become endangered or extinct if their restricted habitat changes, particularly but not only due to human actions, including the introduction of new organisms. There were millions of both Bermuda Petrels and "Bermuda cedars" (actually junipers) in Bermuda when it was settled at the start of the seventeenth century. By the end of the century, the petrels were thought extinct. Cedars, already ravaged by centuries of shipbuilding, were driven nearly to extinction in the twentieth century by the introduction of a parasite. Bermuda petrels and cedars, although not actually extinct, are very rare today, as are other species endemic to Bermuda.

Checklist of Endemic Plants of Maharashtra:- Checklist Stats -Number of Species: 170.

 Study Material / Notes for T.Y.B.Sc.

PHYTOGEORAPHICAL REGIONS OF INDIA

 NOTES FOR TYBSc :- Topic:- Origin of Angiosperms

Place of origin of angiosperms

The place of origion of angiosperms has no concrete suggestions and it is also not yet finally decided. There are divergent views regarding their place of origin as discussed further.

Hear (1868) recommended the polar region to be the centter of origin. This recomendation was supported by Hooker (1887), Engler(1904 and Arnold (1947). But Croziat criticised this idea .

Hallier 1912 stated that the basin of the pacific ocean to be the cradle of angiosperms. Many primitive families likeMagnoliacae etc. are concertrated about the pacific basin. This idea did not get any support from geological evidenes.

Baily !949 supported Northern`Australia , New Guania, New Caledonia, Fiji and adjecent areas are the places of origion of angiosperms as these areas shows rich assemblage of primitive forms of angiosperms. Takhtajan supported that the eastern south easternAsia, Australia and Malonesia as the birth place of angiosperms.

TIME OF ORIGION OF ANGIOSPERMS

The time of origin of angiosperms is decided mainly on the basis of available fossil record.  From middle Cretaceous onwards there is plenty of fossil record of angiosperms which suggests their great presence. Unfortunately very scanty fossil record of angisperms is available from Triassic and Jurassic period. The oldest known fossil of angisperm is Furcula granulifera which is a leaf fossil found from the late triassic rocks of Greenland. This is the direct proof of their presence in late triassic. Some of the scientists belive that angiosperms may have originated even before triassic (Permian period of mesozoic) but the conditions were not suitable for fossilization as they were dwelling to highland areas.

There are many views regarding ancestry of angiosperms. Different plant groups were proposed as ancestors to angiosperms by various workers. Three important theories of origin of angiosperms are summerised as under.

Gnetalean theory :-

According to this theory Gnetales, a order of gymnosperms is supposed to be the ancestor of angiosperms.Wettstein (1901), proposed this theory and Markgraf (1930) and Fagerlind (1947) srongly supported his views.This theory is based on the apparent (external) similarities observed between the two groups. 

1)The leaf of Gnetum with broad lamina and reticulate venation exactly looks like a typical dicot leaf. 

2)Presence of two cotyledons and vessels are other common characters between the two groups. 

3)The unisexual inflorescence of Gnetum can easily compared with the catkin of many amentiferous angiosperms. 

4)The stamens of three genera of Gnetales are apparently similar to those of angiosperms. 

5)The gametophytes in both the groups are highly reduced.

Weakness of the theory-

This theory is objected and criticized on the dissimilarities on issues like ontogeny (development) of vessels, cotyledonary characters, loss of archegonia , vascular anatomy of ovule and female gametophyte.

Bennettitalean theory

Saporta and Marion(1885), and later Arber and Parkin (1907), proposed the Bennettitales, the extinct group of gymnosperms to be the possible ancestors of angiosperms. The basis of this theory is the recemblance in structure between the srobili of the Mesozoic genus Cycadeoidea and the flowers of Magnolia.  Both these structures are bisexual and consists of an elongated axis on which the protective bracts, microsporophylls and megasporophylls are arranged successively from below upwards. 

Weakness of the theory- Detailed studies reveal that there are several differences in spite of this superficial resemblance. The microsporophylls (stamens) of magnolia are free and are spirally arranged on the axis but in bennettitales they are whorled  and mostly connate. The megasporophylls of bennettitales are greatly reduced, simplified stalk like structures, each bearing a solitary terminal ovule. Between megasporophylls there are sterile scales which appear to be sterilized megasporophylls. These are protective in function. There are no such structures in the flower of Magnolia. Further the micropylar tube formed in the ovules of bennettitales is unknown in angiosperms and the pollen grains are shed on the stigma of carpel. Again the seeds of bennettitales are non endospermic with a large embryo while those of primitive angiosperms are with copies endosperm and small embryo. Lastly the bennettitalean stem has a large pith, a thin vascular cylinder and a thick cortex while the angiosperm stem has a small pith, a thick vascular cylinder and a thin cortex. All these facts indicate that the bennettitales cannot have been the ancestors of angiosperms.  

Pteridosperms theory :-

According to this theory, Preridosperms (Cycadofilicales) commonly known as seed ferns, a extinct group of paleozoic era,is supposed to be the ancestor of angiosperms. Andrew,1947; Arnold,1949; Thomas, 1955 and Cronqist 1968 supported this view.

This theory is based on the following similarities between the two groups, pteridosperms & angiosperms.

1) Seed habit is the common feature of the pteridospermales and angiosperms. 

2) Vascular histology, stellar structure and available fossil records also favor this theory. 

3) In both groups sporangial development is eusporangiate type. 

4) Amphiphloic siphonostele is also a common feature. 

5) Some primitive angiosperms show absence of vessels in their secondary wood also goes in favor of this theory. Weakness of the theory-
It is not possible to explain the complex pteridosperm seed in terms of simple angiosperm ovule.

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