Monday, 16 April 2018

Meaning and Definitions of Statistics

(a) Statistics and Statistical Data : 

The word Statistics is used to convey two different senses and is defined differently in each case. One the plural of “statistics” referring to the numerical data collected in an orderly manner with some specific objective in view. A. L. Bowley defines Statistics as numerical statements of facts in any department of inquiry placed in relation to each oilier. however. Prof Hrace Secrist defined it as “By Statistics we mean aggregate of facts affected to a marked extent by multiplicity of causes numerically expressed. enumerated or estimated according to reasonable standards of accuracy. collected in a : systematic manner for a predetermined purpose and placed in relation to each other.”

(b) Statistics as Statistical methods or as a tool of analysis: 

When the word carries a singular sense it refers to the science of theory and techniques that are used lo co1lect represent. analyze and draw conclusions horn the data. A. L. Rowley defined Statistics as the “science of measurements of social organism. Regarded as a “hole in all its manifestation. in fact a number of definitions of statistics denoting singularity are available but perhaps the best one so far is given by Croxton and Cowden as:
“Statistics may be defined as the science of collection. presentation. analysis and interrelation of numerical data.” 
On the basis of these ideas. we can broadly summarize that Statistics is a science of
  • Collecting numerical information (data) 
  • Classification. summarization. organization and analysis of data 
  • evaluation of the numerical (data) 
  • Drawing conclusions based on evaluation of data

Applications of Statistics

There have been a tremendous growth in the last century that Statistics keeps a role to play in almost ever)’ branch of human knowledge; it may be the proper functioning of business and industry, understanding the principles of commerce and economics or the development of the various scientific theories and what not. A few of the multitudes of channels that confront statistics these days are as follows:
  • Statistics in business commerce and industry: The important areas of business or industry are ( a) Production (b) Marketing (e) Personnel (d) Finance and (e) Accounting. where the main functions of Statistics in a practical field of working are planning of operations, establishment of standards and their control. In business problems these statistical functions are conducted either : if) isolation or in mutual combinations. For example, Statistics is used for quality control in production and is employed for the analysis of sales and marketing in business. Wages and allowances of employees are fixed up on the basis of index numbers. Statistical analysis of costing and accounting data is made for ascertaining profit or loss and for knowing the financial position of the concern at a particular point. Statistical methods are very common and useful to accounts. Audits are done with speed and reliance through sampling. An estimate of the relationship between the cost and volume of production can be made through statistical studies of the past data.
  • Statistical methods: provide a valuable assistance for the study. solution and formulation of economic policies on topics like production. distribution of wealth. demand arid supply. etc. that no economist can afford to go without their exhaustive studies. The government intervention in the national economy, the growth of large scale entrepreneurial activity and introduction of scientific methods in to various parts of business administration has simulated and contributed to the rapid development of economic- statistics.
  • A student of Physics or chemistry or of any other pure science. while conducting an experience in the laboratory has necessity to rely upon the application of statistics. An experiment is repeated, its readings very and in order to reach closest lo the accurate result. one has to tabulate them and an average is calculated. In fact higher studies in every science need application of the statistical laws like correlation, Regression, dispersion, approximation probability and the tests of significance etc.
  • Innumerable illustrations can be given to show that in biology there are frequent applications of statistics Tests of significance are applied to compare the effects of two or more drugs; the law of probability is employed in irradiation when the cells in the retina of eye are exposed to he light; chart is used to study heart beats; through electrocardiograms, and the like. In agriculture; the comparison or varieties of seeds or of fertilizers is made through the principle of analyses variance based on sampling theory. The very fact that industrial, medical, agricultural, bio statistics and many more like that are now separate branch of study which speaks of the every expanding scope of statistics and its indispensability in these areas. Statistics also provides a good: device of saving time. Material and personnel in different studies. 
Statistical Applications may broadly he classified under following two disciplines : _______
  • descriptive Statics :ln descriptive statistics we summarize or describe the data set at hand and evaluate the data sets for patterns and reduce. information to a convenient from.
  • Inferential Statistics:in Inferential Statistics we use the sample data to make estimates or predictions about a large set of data (also known as population or universe) and test their suitability.

Sunday, 1 April 2018

Introduction to Fungi

Fungi are a vast assemblage of 95,000 organisms. All of them completely lack photosynthesis. They are heterotrophs that depend upon other living or dead matter for nutrition. As parasites many are serious pathogens on other plants. As saprotrophs they, along with bacteria, degrade dead organisms and release organic chemicals and nutrient elements so they can be recycled. About 13,500 fungal species have a unique association with some algal partners resulting in symbiotic structures known as lichens. The majority of higher plants possess mycorrhizal association where some species of fungi live as symbionts inside or around the roots.

Fungi are eukaryotes. They are an ancient group. Fossil evidence shows that all major fungal groups known today had already evolved by the end of the Paleozoic era, about 280 million years ago. At a time when all living things were grouped under either th animal or the plant kingdom the fungi were thought to be plants. We now place all fungi in the kingdom, Fungi (Myceate). Members of this kingdom lack plastids. They are mostly filamentous in construction. Except in one group their walls contain chum rather than cellulose. Fungi do not store starch as plants do. The filamentous structures that make up the fungal body are known as mycelia (singular. mycelium). Although the filaments are microscopic. the extensive growth of fungal mycelium can be seen as a fuzzy mass. The reproductive bodies of some fungi such as the mushrooms are made up of well defined aggregates of mycelia. Complex tissues and organs characteristic of the plants are never found among the fungi. Fungi reproduce by spores.

In spite of the many features that seem to unite the members of the fungal kingdom the fungi are a heterogeneous group. Fungi are classified into 7 divisions (Table 1.2). Relationships among these groups are shown in Fig. 2.2. The slime molds (Myxomnycota) are not true fungi. They appear to have evolved independently from some protozoan ancestors. In their vegetative phase the slime molds lack a cell wall. The wall-less cells aggregate lo form an amoeba-like mass that moves around and engulfs bacteria and other organio matter. Two groups of slime molds are known: the plasmodial slime molds with a multinucleate true plasmodium and the cellular slime molds. The vegetative body of cellular slime molds is a pseudo plasmodium where the aggregating cells retain their cell membranes and individuality. Slime molds produce motile spores. The oomycetes or water molds differ from other fungi by the possession of cellulose in their cell walls. The fungal body is diploid rather than haploid as in other true fungi. These and other features of reproduction and metabolism suggest that the oomycetes are not related to other fungal groups. They might have evolved from some green or yellow-green algal ancestors after losing their plastids.

The chytrids are simple water molds that live as parasites or saprotrophs. Because they possess motile spores they are often classified with the oomycetes. However, the ehytrids have chitin and their filaments are haploid. They are probably distantly related lo the bread molds and other true fungi.

The zygomyeetes (bread molds). Ascomycetes (sac fungi) and basidiomycetes (club fungi) are evolutionarily related as shown in Fig. 2.2. None of them produce motile cells at any stage of their life cycle. The frugal filaments do not have septa (cross walls) in the zygomyceetes. The mycelium is septate in the other two groups.

Fungi reproduce asexually and sexually. In sexual reproduction the ascomycetes produce characteristic structures known as asci (singular. ascus). Basidia are the equivalent structures among the basidiomycetes. A fungal species can he assigned to either one of these groups only when they produce an ascus or basidium. A vast number of fungi.

about 22.000 species, reproduce only asexually, or sexual cycle has not been observed yet. Because their life cycle is imperfectly known and they cannot he assigned with confidence to either one of the groups they are known as Fungi Imperfectly. The divisional name Deuteromycota is often used for this group of imperfect fungi. When the sexual life cycle is known the species is automatically assigned to-either the ascomycetes or the basidiomycetes.

fungi

Lichens are unique organisms consisting of a fungal and an algal panner. Less than 40 Introduction to Cyanobacteria.. algal or cyanobacterial species enter into this association. Yet, there are about 13,500 species of lichens! The characteristic form of each lichen appears to be determined by the fungal component. About 2% of the species have either a basidiomycete or an imperfect fungus as [he fungal panner. The remaining 98% of lichens are composed of ascomycete species. The lichens are not considered to be a separate taxonomic category. Rather, they are treated as members of the respective fungal divisions, and the name of a lichen refers co the name of its fungal partner.

In Table 2.2 the fungi are divided into 7 formal divisions. in other classifications only two divisions are recognized, the Myxomycota (slime molds) and Eumycota (true fungi). The latter is divided into subdivisions and classes etc.

Introduction to Cyanobacteria

The cyanobacteria are true bacteria (singular bacterium). They are prokaryotes and do not possess a true nucleus or membrane-bound organelles such as mitochondria or plastids. Like other prokaryotes they have 70S ribosomes. Although there are other bacteria which can photosynthesis, the cyanobacteria are unique in possessing the pigment chlorophyll a. This pigment is also present in algae and plants and is responsible for the evolution of oxygen during photosynthesis. The photosynthetic bacteria posses a different kind of pigment, bacteriochlorophyll which does not permit oxygen evolution during bacterial photosynthesis.

The term “cyan” in cyanobacteria refers to the color, blue. Cyanobacteria possess certain accessory pigments such as phycocyanin and phycoerythrin. The presence of these pigments and chlorophyll a together impart characteristic color to these organisms. It is for this reason (hat the cyanobacteria are commonly known as blue- green algae. Like true algae they also evolve oxygen during photosynthesis and often occupy habitats where algae occur, in fresh, marine and brackish water bodies and on moist soil surface. However, true algae are eukaryotic and the two are not immediately related.

Since the affinities of the cyanobacteria are with the other bacteria we must briefly examine these organisms for a more complete picture of the position of cyanobacteria in the world of living things. About 4,000 species of bacteria have been described so far. These include about 1,700 species of cyanobacteria. Although small in number of species, bacteria are the most abundant of all organisms. They are also the most ancient. (Not the amoeba, which is a eukaryote of later origin). Bacteria are known in the fossil record as far back as 3.5 billion years ago. Bacteria are morphologically and anatomically the simplest of organisms. Yet, metabolically they are very diverse. Many bacteria are identified not by the morphology of the individuals but by their characteristics in culture.

Bacteria are very small, ranging in size between I to few 11m. A most unusual discovery was made in 1993 of a bacterium living in the intestinal tracs of a surgeonfish that is 600 am in length! Bacteria vary in shape. Some are rod-shaped, others spherical and yet others spiral or even comma-shaped. Tiny as they are, bacteria are responsible for activities that strongly affect our lives. Many are agents of serious diseases of human beings, animals and plants. Others ferment food and are thus useful in making varied products such as curd or ‘idli’ as well as many industrial chemicals. Some are the . source of life-saving antibiotics.

Bergey’s Manual of Determinative Bacteriology is the standard reference for the classification of bacteria. Since sufficient information is not available to place all bacteria into a hierarchical system of classification, the Bergey’s Manual recognises 19 major groups such as the spirochetes, Gram-positive cocci, gliding bacteria, mycoplasma and actinomyeetes. Cyanobacteria is included in one such group. The classification of bacteria is an active area of research. In recent years molecular biologists have analyzed the structure of ribosomal RNA (rRNA) and the sequence of rRNA nucleotides in bacteria and other organisms. Such analysis has revealed fundamental differences among two major bacterial groups, the ARCHASBACTERIA and EUBACTERIA. Differences have also been noted in the chemical composition of the cell membranes of these two bacterial groups and the eukaryotes.

The American scientist Carl Woese considers that the differences between the archaebacteria and the eubacteria are as fundamental as between these groups and the eukaryotes. Thus, life on this planet is considered to comprise of three ancient and primary lineages. The three ancient domains are shown in Fig. 2.1. The cyanobacteria arc members of the true bacterial lineage. The archaebacteria include members that live in most unusual environments such as very hot and acidic pools or in waters with extremely high salt contents. Some members of this group live in deep sea vents several kilometers below the ocean surface. The bacteria which produce methane gas are called methanogens.

Cyanobacteria are of great evolutionary interest according to the endosymbiont theory some ancestral cyanobacterial cells became the plastids of different algal groups. The plastids of red algae resemble (he cells of 4anobacteria and both possess chlorophyll a and biliproteins. The green algae and plants possess both chlorophylls a and b. Although most cyanobacteria possess only chlorophyll a at least three organisms are known (o contain both the chlorophylls. Prochloron didevni live as symbionts in (he gut walls of sea squirts. Prochlorothrix hollandica was recently discovered in lakes in Holland. More recently Prochlorococcus was discovered as a free-floating form in open seas. All these organisms possess chlorophylls a and b, and their cells resemble die chloroplast of green algae and plants. For this reason, some authors describe them as prochlorophytes and include (he three genera in a separate division nr class. Some ancestral prochlofophyte was perhaps the endosymbiont that evolved into the green plant chloroplast.