Bacteria-Discovery,characters,shape and size

Discovery of bacteria

Bacteria were 1st discovered by a Dutch botanist,Antony von Leeuwenhoek in 1676. He observed them in a rain drop with the help of  a simple microscope designed by him He also gave illustrated account of these microscopic organism from his own teeth scum. These were called 'animalcules' by the early microbiologists. It was Linnaeus (1758) who placed them under the genus vermes.The name Bacteria was given  by a German biologist Christian G. Ehrenberg (1828).However Bacteria as a group were recognised by German botanist, Karl Wilhelm von Nageli (1857) who proposed the name Schizomycetes for this group.

Antony von Leeuwenhoek

Louis Pasteur, a French chemist, observed that bacteria are the cause of   some diseases. This fact was called 'Germ Theory of  Disease". He also discovered bacteria causing chicken cholera. Almost at the same time Robert Koch discovered  bacteria causing anthux and tuberculosis.

General characters of Bacteria

1. Bacteria are the  simplest and the most primitive organisms. They are cosmopolitan and are found in all the places wherever life is possible.
2. Bacteria are considered to be the plants because they have a rigid cell wall.
3. Bacteria are prokaryotes like blue-green algae.
4. Bacteria are strictly unicellular and generally occur singly.Some of them are founds in groups.
5. Bacteria also lack membrane bound organelles like endoplasmic reticulum, golgi bodies,mitochondria,plastids etc.
6. Bacteria lack nuclear membrane and ,therefore, distinct nucleus and nucleoli absent.
7. Most of the bacteria lack chlorophyll,hence they are heterotrophic. However, few bacteria possess chlorophyll and are autotrophic.The chlorophyll  remains scattered in the cytoplasm.
8. Genetic material is represented by histone free DNA.
9. They commonly reproduce vegetatively by  fission.
10. Variations in the genetic characters are due to genetic recombinations brought about by conjugation, transformation and transduction.Flagellated gametes are, however not produced.

Shape of  Bacteria

There are have more than 2000 species of bacteria. and there have 4 fundamental shape are present.

[I]  Bacillus or rod-shaped

These are small stick or rod-shaped bacteria. This shape is the commonest of all the bacterial shapes. Bacilli may occurs in two form.

1. Diplobacillus- In this form two or more bacilli occur in a pair.    e.g,  Corynebacterium diphtheriae.
2. Streptobacillus-In this type many  bacilli occurs in a chain,     e.g,  Bacillus tuberculosis, Bacillus anthracis, etc.

[II]  Coccus or spherical

These  bacteria are  oval or spherical in shape .Cocci are generally non-motile and are the smallest bacteria.Cocci occur in 6 forms.

1. Micrococci-In this type each coccus is a free individual;  e.g,  Micrococcus luteus.
2. Diplococcus-Here cocci remain attached, mostly in pairs,  e.g,  Diplococcus pneumoniae.
3. Streptococcus-In this type cocci form chain;  e.g,  Streptococcus lactis.
4. Tetracoccus-Here four cocci form a characteristic group,  e.g,  Neisseria.
5. Staphylococcus-Cells form irregular groups or bunches, e.g,  Staphylococcus aureus.
6. Sarcinae-This is a type where 8-64 cocci are arranged in cubes, e.g,  Sarcina lutea.

 [III]   Spiral or helical

These bacteria are helical or cork screw shaped or coiled.  e.g,  Spirillum volutans.

[IV]Some other shapes

1. Comma shaped-These are short, incomplete spirals and look like comma (,). They are also known as Vibrio.  e.g,  Vibrio cholerae.
2. Stalked road- These are rod-shaped with a distinct stalk,  e.g,  Caulobacter.
3. Branched filament- The bacterium is long and thread-like,  e.g,  Streptomyces.






4. Pleomorphic-The shape of many bacteria changes according to time, habitat and medium. This characters of existance of different shapes in the same species is called pleomorphism, e.g,  Azotobacter.

Size of Bacteria

Bacteria vary considerably in size. The average size of a bacteria cell  is 0.5-1.0 ×2.0-5.μm Beggiatoa mirabilis is the largest bacterium.(16-45  μm). Bacillus butschlii, with a length of approximately 80  μm is considered to be the longest bacterium. Dialister pneumosintes is probably the smallest bacterium (length  0.15-0.31  μm).

Cell- Defination, Discovery, types and example of cell

Cell

All living bodies on earth are composed of a complex living substance, called protoplasm, which is the physical basis of life.It is found in all living bodies in a small organised morphological form rather than in large mass.These minute organised morphological forms are termed as cells.A living organism under the microscope shows to be composed of either a single cell or numerous cells. Therefore the cells are the structural unit of living body.

The word cell is derived from the greek word kytos, which means a vessel or container.A cell is the smallest unit of life that can replicate independently and cell are often called the "building blocks of life". The science which deals with the cell is called cytology.Cytology may also defined as the branch of science which deals with the study of morphology and internal structure of cells.

Definition of a cell:

A cell may be defined as a piece of nucleated cytoplasm surrounded by a cell wall or a membrane existing singly or in group and containing structures of various kinds.

                                                                         OR

Cell consist of cytoplasm  enclosed within a membrane which contain many biomolecules such as proteins and nucleic acids.

Discovery of the cell

The speculations about the existence of cell in living bodies can be traced back to the time of ancient Greek philosophers. The possibility for a scientific approach on cell arose in the 16th century, after the discovery of microscope by Janssen and Janssen in 1590.

In the year 1665, Robert Hooke, an Englishman, was able to visualise the cells under microscope for the first time. He designed and built an improvised compound microscope and examined the section of  a bottle cork under it. He found that the cork is not a compact mass. It consisted of a number of empty vassels or cavities bounded by definite walls, and thus giving an appearance of a honey-comb.Hooke named each of these cavities as  cell, the term derived from a latin word cellula, means a little room.

Robert Hooke

Types of cell

On the basis of presence and absence of organised nucleus ,two types of cells have been recognized.These are prokaryotic cells and eukaryotic cells.

Prokaryotic cell

(Gr. pro=primitive, karyon=nucleus)

This cell have a well organised nucleus. Organism composed of prokaryotic cells are commonly referred to as prokaryotes. Prokaryotes are considered to be primitive.In prokaryotes the protoplasm is relatively rigid,usually non-vacuolate gel; relatively resistant to desiccation, osmotic shock and thermal denaturation.True nucleus is absent in prokaryotic cell. The membrane bound organelles like  Golgi bodies, plastids, mitochondria ,Endoplasmic Reticulum, etc are absent in these cells. In prokaryotes 70S type of ribosomes is present.Mostly amitotic cell division is occur in prokaryotic cell.Mitotic apparatus is absent.

Examples:Cells of mycoplasma, bacteria, blue -green algae.

Eukaryotic cell

(Gr. Eu=good, karyon=nucleus)

The cell has a well organised nucleus. Organisms made of eukaryotic cell are known as eukaryotes. Eukaryotes are phylogenetically advanced.In eukaryotes the protoplasm is tipically more fluid, generally vacuolate, more sensitive to desiccation, osmotic shock and thermal denaturation. True nucleus is present in eukaryotic cell.Organelles like Golgi bodies, plastids, mitochondira,ER, etc are present  in these cell.In eukaryotes 80S type of ribosomes is present.In these cell tipically mitotic cell division is occur.Mitotic apparatus is present.

Examples:Cells of all the higher organisms, except  mycoplasma, bacteria and blue-green algae.

Function of Nucleus

Function of the Nucleus

The Nucleus is regarded as the centre of many vital activities of the cell.

1. It is concerned with the synthesis of enzymes which catalyze many metabolic reactions.
2. The hereditary factors which influence the characters of plants exist mainly in the nucleus.
3. The nucleus plays an important role in cell division.During cell division it divides first and then the cell divides in to two.Thus by repeated divisions the number of cells increases in the plant body.
4. The nucleus is directly connected with sexual reproduction.The nuclei of male and female gametes fuse together and give rise to the zygote or oospore , from which the embryo develops.
5. Cell nucleus is to control gene expression and mediate the replication of  DNA during the cell cycle.
6. Nucleus contains all the genetic information in its chromatin.
7. Nucleus forms ribosomes  on its nucleolus.
8. The main function of the nucleus is to supports and protects the cell
9. The metabolic reaction is occur in to the nucleus.
10. The nucleus directs all the activities of the cell,controls the growth and reproduction of the cell and contains the blueprints of the cell in the DNA.

Nucleus

What is nucleus?

Nucleus is the most prominent and largest cell organelle present roughly in center of animal cell and on side in a plant cell. It is found in most eukaryotic cells, the exception being red blood cells. It is the small bright body in the head of comet.

structure

Nucleus is a spherical body present inside the cell, surrounded by the cytoplasm.It is bound by a membrane, called  the nuclear membrane, which separates the inner content of the nucleus from the cytoplasm. Nuclear membrane is a double-layered membrane made up of lipo-protein. It is not a continuous membrane as some pores are present at place. These pores are called nuclear pores.Through this pores exchange of various substances takes place  between  the nuclear content and cytoplasm. The inner content of nucleus consists of undifferentiated protoplasm and ground substance known as nuclear sap or nucleoplasm or karyolymph. Inside the nuclear sap a net work of some dark staining thread like structures are present, called the nuclear reticulum or chromatin reticulum. Each of these threads is known as chromatin or chromosome.Chromatin is a characteristic substance in the nucleus.Besides the chromosomes a deeply stained small spherical body is present inside the nucleus, called the Nucleolus.
Each chromosome has a covering,called the matrix, which encloses two identical,spirally twisted, delicate threads known as chromatids. These two chromatids lie very close to each other and are attached to each other only at some points or constriction, called the kinetochore or centromere.


Along the length of the chromatids there are some granular bodies known as chromomeres.Again each chromatids consists of fine thread like structures, called chromonemata.The chromosome is differenciated into some darker staining regions and lighter staining regions,alternating with each other along its length. The darker stained region is called the heterochromatin or the heterochromatic region. The lighter stained region is called the euchromatin or euchromatic region.

Chromosomes consists of nucelic acids and proteins. Nucleic acids are of two types; deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).When these nucleic acids combine with proteins they form deoxyribonucleo-protein and ribonucleo-protein.

Chromosomes are the bearers of all the hereditary characters, and consists of hereditary units or genes. Each gene forms a part of the DNA chain present in the chromosomes. These genes control  all the activities and characters of plants and animals. Therefore, nucleus is the vital part of the cell.
Generally one nucleus is present in each cell of a living organism.But in case of some algae and fungi more than one nucleus  are present. In bacteria and few lower plants (algae) the nucleus is not covered by any membrane and remains undifferentiated inside the protoplast. Such a nucleus is often called incipient nucleus..

cell

cytoplasm

CYTOPLASM

           Within the cell wall the inner content of the cell is the protoplast, which is differentiated in to the cytoplasm and the nucleus. Cytoplasm remains surrounding the nucleus, and thereby it is known as the extranuclear part of protoplast. Optically it appears to be clear and hyaline in nature, consisting of somewhat viscous fluid. It embeds many granular bodies known as organelles. The viscous fluid of the cytoplasm is also termed as hyaloplasm, due to its hyaline appearence. The external surface layer of the cytoplasm lying against the cell wall is called the ectoplasm,while the internal layer around the vacuoles  are called tonoplasm. The granular cytoplasmic substances inbetween these two layers are called the endoplasm.

                                                                                  
         



                  Recent studies with the help of electron microscope reveales that the outermost part of the cytoplasm  i.e, the ectoplasm from a membrane or a bounding wall, also called as plasmamembrane. It remain close to the cell wall and  thus sarves as a boundary layer inbetween  the outer non living wall and internal cytoplamic ground substance or cytoplasmic matrix. Chemically plasmamembrane is  composed of protein and phospholipid, in such a way  that a layer of phospholipid is enclosed  on either  sides by two layears of protein. This lipo-protein  composition of the membrane offers it a semipermeable nature i.e, it allows only few selective compounds to pass through it. Therefore, it is otherwise known as semipermeable membrane or selectively permeable membrane. Some authors refers it also as unit membrane, and regard that lipo-protein composition is a characteristic of all the cell membranes.
             
                The various components of the  cytoplasm distributed over  the hyaloplasm are mainly vacuoles,organelles, and other living and non-living substances.

Vacuoles

               Vacuoles are the greatly expanded cavities inside the cytoplasm, filled with watery fluid or the sap. In matured cells two or three vacuoles may be present, and their size increase with the increase of the size and age of the cell. In meristematic cells the vacuoles are minute or even absent. Each vacuole is bounded by a plasmamembrane, known as  tonoplasm or tonoplast.
                                                                                           

 Organelles or Subcellular particles

                Organelles are the living bodies of different structures having some definite functions, and found suspended inside the cytoplasm. The chief organelles present inside the plant celles are plastids, mitochondria, endoplasmic reticulum, ribosomes, golgi bodies, lysosomes, spherosomes and centrosomes.
s

branches of botany

26 branches of botany

1. Morphology (morphe=form, logos=science):Under this branch we study the form and structure of plant.That branch of morphology which is based upon the external form and  structure of plant is called External Morphology.
2. Anatomy:The study of internal structure of the plant with the help of section cutting, is called Internal Morphology.    
3. Cytology:Detailed study of the cell is called cytology. It includes structure, function of  different cell organelles, nucleus and cell inclusions.
4. Histology: The study of cell and tissues with the help of microscope is called histology.
5. Plant Physiology: This branch includes the study of various vital activities of the plant.
6. Taxonomy: In this branch the plants are classified according to their characteristics and interrelationship. With the help of taxonomy we are able to identify the plants and known their characters.
7. Ecology(Oikos=house, logos=science): The study of environment of plants and their communities and vice-versa. This branch also includes the studies of soil erosion, soil conservation and pollution.
8. Plant geography: This branch deals with the distribution of plants on the earth and reasons thereof.
9. Genetics: Study of heredity and variations. What are the laws of inheritance and why the offspring resembles or differs  for the parents are studies under this group.
10. Plant breeding: dealing with the development of improved varities of plants.
11. Embryology:Study the parental development of gametes,fertilization, and development of embryos and fetuses.
12. Paleobotany: the study of fossil plant.
13. Economic botany: The study of the relationship between people (individuals and cultures) and plant.
14. Plant pathology: The scientific study of diseases in plants caused by pathogens and environmental conditions.
15. Biochemistry: The study of chemical processes within and relating to living organisms.
16. Biophysics: This is an interdisciplinary science that applies the approaches and methods of physics to study biological systems.
17. Organic evolution: The study of the evolution of complex organisms from simple ones and the principles involved in it.
18. Microbiology: Study of microorganisms.
19. Molecular biology: Study of biochemistry at molicular level.
20. Palynology: Study of pollen grains in relation to taxonomy and evolution etc.
21. Biometrics: Statistical analysis of different results of biological experiment.
22. Genetic Engineering: Adding,removing or repairing part of genetic meterial, thereby changing the phenotype of organism and desired.
23. Agronomy: Is the science which deals with the crop plants.
24. Horticulture: Is the science which deals with the  study of  flowering fruiting plants.
25. Pharmacognosy: Dealing with the medical plants.
26. Pedology: Dealing with the  study of soils.

Diffusion

What is Diffusion?

Diffusion of gases and liquids is a very common phenomenon in nature. We see that the storms move, the cloud flies,sugar crystals dissolve in water forming solution, the fragrance of a flower spread to a distant place and so on. All these happen because of the movement of their component molecules from one place to the other, which is nothing but a process of diffusion.
 
When a solute is dissolved in a solvent it forms a solution. In a solvent the molecules or ions are having a random and spontaneous movement and when a solute is put into in the solute molecules or ions also move spontaneously. This random and spontaneous movement of ions throughout the medium is known as diffusion.Diffusion of molecules from a region of  its  higher concentration or pressure to a region of its lower concentration or pressure without the use of any external energy is a common tendency of any fluid substance.

Diffusion pressure

Diffusion pressure can be defined as a physical force of a substance by virtue of which its molecules or ions move from one place to another,if other conditions do not resist the movement.

Factors affecting Diffusion

Diffusion or the rate of movement of any molecules is dependent on following factors.

1. Temperature: Increase in the temperature increase the  speed of the molecules, and thereby,the rate of diffusion too. In a similar way at lower temperature the rate of diffusion also decreases.    
2. Kinetic Energy of the Solvent Molecules: When the amount of surrounding medium or solution of a cell is increased the kinetic energy of a solvent molecules will be considerably more. As a result there will be  more diffusion of solvent  into the cell.                                                                                             
3. Density: Density is defined as the amount of material that exists within a given volume. Regions of high density contain a  greater number of particles per unit  volume then regions of lower  density. An increase number of particles leads to a greater chance of  collisions, and this leads to an increased rate of diffusion. A lower number of particles leads to  reduced chance of collisions and this lower the rate of diffusion. Therefore high density regions have a greater rate of diffusion than low density region.                                                                                               
4. External  Pressure: External pressure also determines the direction and rate of diffusion. If the external pressure on the surrounding medium of a cell increase the  rate of diffusion of solvent molecules into the cell will also increase  and the vice-versa.                                                                  
5. Size of the Molecules: With the increase of the size of the molecules the rate of diffusion decrease. The smaller the molecules the more is the rate of diffusion.

    

introduction to biology

What is biology?

          

              Biology is the natural science that studies life and living organism, including their physical structure, chemical composition, function, development and evolution. Shortly biology is the science of life.

              It is concerned with the characteristic and behaviors of organism; how individuals come into existence, and how species evolve, and the interactions they have with each other and with their environment.

Discovery of biology

         

             The term biology is derived from the greek word- bios (life) and logia (study of) . The  latin- language  form  the term first appeared in 1736 when swedish scientist
Carl Linnaeus used biologi in his bibliotheca botanica.  The term biology was first coined by Jean-Baptiste Lamark and  Gottfried -Reinhold Treviranus in 1802.
              In 384-322 BC Aristotle dicover biology, especially important are his history of animal.Aristotle's successor at the lyceum, Theophrastus, wrote a series of books on botany in 371-287 BC.

Branches of biology

  Biological science is divided in  two types of branches; that is botany and zoology.

              Botany is also called as plant science , plant biology or phytology: is the science of plant life and a branch of biology,
that studies the plant kingdom, including structure, growth and differentiation, reproduction ,biochemistry and primary metabolism, chemical products, development ,diseases, evolutionary relationship, systematics and plant taxonomy. There are 26 branches of botany also have.
            Zoology is also called animal science or animal biology;that studies the animal kingdom, including the structure, embryology, evolution, classification, habits and distribution of all animals, both living and extinct, and how they interact with their ecosystem.