Types of Microscopes

The evolution of microscopes unlocked a world previously unseen by the naked eye. It ushered in the new field of microbiology and allowed us to study the minute facets of hidden life that exists cloaked with the limitations of our field of vision. A microscope is basically a tool which uses a medium to detect surface reflection and allow it to be visualized by humans.

Light or Optical Microscopes

Light microscope

A Light microscope

The earliest type of microscope uses light waves as the medium and our own human eyes as the receiver. Lenses amplified the amount of light reaching our eyes, as they reflect and pass through on the subject. Cells, prokaryotes, and plankton were all visualized using this type of microscope. The magnification attained was based on the lenses used and the resolution limited only by the inherent limitations of light as a medium. Magnification initially started from 10 times but can now be made to attain up to 1500x useful magnification. The resolution limit of today’s light microscopes is usually 0.2 micrometers. The outer features of cells as well as their interior can now be visualized and studied due to the optical microscope. Use of ultraviolet radiation can extend this limit somewhat at the cost of clarity.  The specimen can be viewed by peering into the eyepiece; the image can be adjusted using fine and coarse adjustment knobs; and the magnification and resolution can be changed by adjusting the revolving nosepiece.

Different types of microscope are used to study different aspects of the cell. A phase contrast optical microscope is used to study a single specimen over time, elucidating the process of the cell cycle.  The advent of technology now allows a CCD  or charged-coupled device to replace the eye as the direct receiver of light, allowing computer displays to directly output the microscopes view.

Electron Microscopes


Siemens electron microscope

During the 1960s, a new medium was tapped to exceed the magnification offered by light. The electron microscope by Ernst Ruska and Max Knoll created during the early 1930s took microscopy to a whole new level. The electron, a subatomic particle, was used to obtain magnification a thousand times more than what the naked eye can see. Instead of a light source, cathode ray tubes were used to generate streams of electrons while instead of the eye, a computer was utilized to detect the reflected electron particles and to generate a visual image. Electromagnetic lenses serve to focus the beams until they hit the sample. This allowed scientists to see the outer surface of the object (scanning electron microscope) as well as to use it in a way similar to optical microscopes (transmission electron microscope). The scanning electron microscope uses electron beams to view the outer surface, distinguishing features based on comparative elevation. The transmission electron microscope follows the same principle as the light microscope, with electrons passing through the subject used to generate images. This is called electron diffraction. Electron microscopes, due to their shorter wavelengths (100,000 times shorter than light’s) allow greater magnification (10,000,000x) and higher resolution (50 picometers). 

Acoustic microscopes

The acoustic microscope, uses sound waves as the medium. Similar to sonar, the acoustic microscope uses sound waves to “bounce” from a structure, and a computer to detect the differences in the rate of return of the waves. It allows for a comprehensive surface view of the structure being observed.

The advent of microscopes helped scientists discover a whole new, microscopic world. This has led to a revolution in various fields, from biology, to medicine to forensics. With these tools, the inner working of the smallest unit of life can now be viewed. The different types of microscopy allow us to have the tools necessary for every specific need. And with the continuous technological innovation we have, the field of microscopy remains promising.

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Pros and Cons of DNA Fingerprinting


Variations of VNTR allele lengths in 6 individuals.

DNA fingerprinting uses short fragments of DNA containing STRs or short tandem repeats to identify an individual as well as compare other DNA samples obtained. This is very useful in determining relationships (e.g. paternity, maternity) as well as in comparing DNA samples in the scene of the crime with persons contained within a database. This technology has changed law enforcement, forensics, medicine and modern identification techniques. It thus has the capacity to affect numerous lives, both in a positive and a negative way.

DNA Fingerprinting

DNA fingerprinting uses biological samples, blood, hair or skin, to obtain DNA. The advent of polymerase chain reaction (a DNA amplification technique) allows the extraction of sufficient DNA from even the smallest amount of blood, semen or hair. A portion of this DNA is scanned for trademark base pairs and kept in a database containing DNA fingerprinting results. Deoxyribonucleic acid contains four base pairs: adenine, guanine, cytosine and thymine. These base pairs may occur in repeat patterns called short tandem repeats that can be distinguished with comparative ease. Samples between individuals can then be matched by comparing the presence of these short tandem repeats. The more closely related a person, the closer to 100% the match is. If two samples belong to the same person, then the match is statistically 100% (adjusted for percent error). This is useful when identifying unidentified corpses or when establishing presence in the scene of the crime. Several locations in a person’s genome can also contain trademark sequences that indicate a tendency for a particular disease. DNA fingerprinting helps identify the occurrence of a disease on a particular person by scanning the location where telltale STRs can be found.

DNA fingerprinting, for all its great applications, is simply a tool, albeit a powerful one. There are thus numerous pros and cons when talking about DNA finger printing.

DNA Fingerprinting Pros

DNA Fingerprinting has made identification and establishment of relationships easier. In crime scenes, even a small drop of blood can be stored in a database, and matched with existing entries in that database. This makes solving crime and establishing presence in the crime scene faster and more efficient.

The DNA is a highly resilient molecule. It does not denature easily, except with certain compounds and other specific environmental conditions. Thus a DNA sample can linger for quite a while, making them accessible for analysis in crime scenes discovered after a while.

DNA fingerprinting is also a very flexible, efficient and versatile process. With a few drops of blood, one can establish identity, location in a crime scene, paternity and other relationships.

DNA Fingerprinting Cons

It is the lingering presence of a DNA database that is the source of concern for civil libertarians. The ease with which a DNA sample can be obtained precludes the right of the person to actually consent to have their DNA tested. The DNA database contains not only DNA fingerprints for convicted criminals, but also from those proven innocent, patients in psyche wards and juvenile delinquents. Since DNA fingerprinting does not compare the whole genome, there is a very small probability that a match can occur by sheer chance.

The resilience and prevalence of DNA can also inundate a crime scene with extraneous DNA, especially if it is located in a public place, like a restroom or a bar. Human error can also play a part in confusing and labeling the DNA of one individual with that of another.

Even with these concerns, DNA fingerprinting remains a powerful tool in law enforcement and identification. Further advances in technique and procedure can only augment DNA fingerprinting’s positive points while rendering the negative ones less likely to occur.

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Kingdom Protista Characteristics

Eukaryotes and protists belong to Kingdom Protista. In the 1860s, John Hogg observed that this kingdom was composed of primitive unicellular forms of plants and animals. Back then, it was called Kingdom Protoctista (Sengupta, 2011). In 1886, Ernst Haeckel proposed that a third kingdom, Kingdom Protista, must be established. By the 1960s, R.Y. Stanier, C.B. Van Niel and their colleagues proposed that living things be divided into prokaryotes and eukaryotes. This division is based on whether or not the organisms have a true nucleus, the complexity of their genetic material and the presence or absence of membranes that enclose the cell’s organelles.  Today the Kingdom Protista includes eukaryotic microorganisms as well as bacteria (Encyclopedia Britannica, 2011).




Kingdom Protista can be broken down into several subgroups: plant-like, animal-like and fungus-like. Plant-like protists are further classified into euglenoids, diatoms and dinoflagellates. Euglenoids are unicellular organisms with a nucleus, chloroplasts, flagellum and cell membrane. Diatoms are golden brown in color and can store their food in the form of oil. Dinoflagellates, the last classification of plant-like protists, have two flagella and are phosphorescent. Animal-like protists are sub classified into sarcodina, flagellates, ciliates and sporozoans. Sporozoans are distinct from the other groups with their capability to produce spores. These protists are heterotrophs and are saprophytic. The fungus-like protists are multicellular and tend to live in sites where moisture is high. Some of them are capable of forming two forms during their life cycle (Sengupta, 2011).


Members of the Kingdom Protista have very distinct locomotory organelles. Some move with their flagella and others use hair like structures called cilia that are embedded around the cell. These locomatory organelles also serve as basis for classifying protists. For instance, those with flagella are called flagellates, while those that have cilia are called ciliates. However, some groups of protists are not named based on their organ of locomotion. For example, those that belong to the Phylum Sarcodina move with the help of their pseudopods (Encyclopedia Britannica, 2011).

Cilia and flagella should not be confused with the prokaryotic flagellum found in bacteria. Locomotory organelles in protists contain tubulin, while those in bacteria have flagellin. Also, the prokaryotic flagellum is entirely extracellular and does not have a common ancestral origin with the flagella found in protists (Encyclopedia Britannica, 2011).

Respiration and Nutrition

Most protists are obligate aerobes. However, there are also some which are anaerobic. These anaerobes include parasitic organisms that inhabit sites that are depleted of free oxygen and ciliates that are found in the sulphide zone of some marine and freshwater sediment. These organisms do not have mitochondria but rather they have hydrogenosomes or symbiotic bacteria that act as respiratory organelles (Encyclopedia Britannica, 2011).

Some members of the Kingdom Protista, the algal protists, are autotrophic. This means that they require a small amount of inorganic material and some light energy to make their own food for their survival and growth. Other protists such as ciliates engulf particulate food through phagotrophy. They ingest prey that serve as their source of energy, nitrogen, carbon, vitamins and growth factors. Protists feed in different ways. Some use their pseudopods or rhizopods to capture their prey, others trap particles of food through their buccal organelles and some use simple diffusion to absorb nutrients through their cell membrane (Encyclopedia Britannica, 2011).


Typically, protists reproduce through binary fission. The body is pinched into two halves and a pair of daughter nuclei appears in place of the “parental” body. For unicellular plant-like protists, fragmentation is their mode of reproduction.  Multiple fission, budding, sporogony and schizogony are other ways by which protists reproduce (Encyclopedia Britannica, 2011).

The complexity of the protest cells sets them apart from those in plants and animals. They are not just cells, but are also whole, independent organisms that are capable of adapting to different habitats, much like higher forms of life.


  • Protist. (n.d.). Retrieved November 4, 2011, from Encyclopedia Britannica: http://www.britannica.com/EBchecked/topic/480085/protist/41620/Respiration-and-nutrition
  • Sengupta, S. (2011, September 20). Protists-Characteristics. Retrieved November 4, 2011, from Buzzle.com: http://www.buzzle.com/articles/protista-characteristics.html
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Aerobic Versus Anaerobic Bacteria and their Examples

Anaerobic and aerobic bacteria in liquid culture

Anaerobic and aerobic bacteria in liquid culture (Wikipedia)

There are different ways of classifying bacteria; one of which is according to their ability to use oxygen. Aerobic bacteria use oxygen for cellular respiration while anaerobic bacteria don’t. Aerobic bacteria are those that can survive when oxygen is present, while anaerobic bacteria cannot (Jilani 2010).

Aerobes can detoxify oxygen while anaerobes do not have this ability. Oxygen is toxic to bacteria but aerobes use certain enzymes such as catalase and superoxide to get rid of oxygen and turn it into a substance that is not harmful to them. In environments where oxygen is not available, anaerobic bacteria can still exist, unlike aerobic bacteria. This means that anaerobes can cause infection in parts of the human body where there is a depleted supply of oxygen such as in the area from the stomach up to the rectum. While anaerobic bacteria cannot produce much energy through fermentation, aerobes are capable of producing more energy (Naik, 2010).

Aerobic Bacteria

When a bacterium absolutely requires oxygen for their reproduction, growth and survival, they are considered to be obligate aerobes. However, there are also some species that require only a very low concentration of oxygen. These organisms are called microaerophiles (Sandhyarani, 2011).

It is very easy to isolate aerobes and microaerophiles in the laboratory. Since these bacteria need oxygen, they grow on the top surface of liquid media and do not require special equipment for cultivation. All you need is an incubator that is set to the temperature at which the organisms grow optimally. Examples of aerobes and microaerophiles include Mycobacterium tuberculosis, Lactobacillus and Nocardia(Sandhyarani, 2011).

M. tuberculosis is the causative agent of tuberculosis. It is an obligate aerobe that is rod shaped and has a waxy layer in its cell wall. Since it needs oxygen for survival, it invades the lungs of mammals. Nocardia is also another group of bacteria that belong to obligate aerobes. With more than 80 species, some of them are pathogenic while others are not. They are usually found in the oral cavity as normal flora but are considered as pathogens when they invade the lungs and cause an infection called nocardiosis (Sandhyarani, 2011). An example of a microaerophilicorganism is C. jejuni. It only requires about 3 to 5% oxygen for its growth. When this limit is exceeded, it renders stress to the bacteria. It is one of the leading causes of food-borne illness in the United States (MicrobeWiki).

Anaerobic Bacteria

Anaerobes are bacteria that are able to survive without oxygen. They can be further classified into obligate anaerobes, aerotolerant anaerobes and facultative anaerobes. Obligate anaerobes cannot withstand the presence of oxygen. On the other hand,aerotolerant anaerobes cannot use oxygen for respiration but can survive despite its presence. Facultative anaerobes are bacteria that can grow without oxygen and can use oxygen for respiration. E. coli, Bacteroidesand Clostridium are examples of anaerobic bacteria (Alphonse, 2010).

C. botulinumis a gram positive, obligate anaerobe. It produces the world’s most potent toxin and is usually found in meat products that are not cooked or handled properly. An example of an aerotolerant anaerobe is Bacteroides. It can infect several parts of the body such as the peritoneal cavity and the female urogenital tract. E. coli is one example of a facultative anaerobe. This bacterium is very common and can be found in the gastrointestinal tract of mammals. E. coli can cause infection in the respiratory and urinary tract (Alphonse, 2010).

One important role that oxygen plays for organisms that are able to use it is to help break down food molecules so that energy can be produced for the continued survival of the cell. For organisms that cannot use oxygen, they also have a means by which they produce energy, but they are not as efficient as aerobes (Port, 2009).

  • • Alphonte, M. (2010, February 18). Anaerobic Bacteria. Retrieved November 3, 2011, from Buzzle.com: http://www.buzzle.com/articles/anaerobic-bacteria.html
  • • Jilani. (2010, April 2010). Difference Between.net. Retrieved November 3, 2011, from Difference Between Aerobic and Anaerobic Bacteria: http://www.differencebetween.net/science/difference-between-aerobic-and-anaerobic-bacteria/
  • • MicrobeWiki. (n.d.). Campylobacter jejuni. Retrieved November 3, 2011, from MicrobeWiki: http://microbewiki.kenyon.edu/index.php/Campylobacter_jejuni
  • • Naik, A. (2010, August 16). Aerobic Versus Anaerobic Bacteria. Retrieved November 3, 2011, from Buzzle.com: http://www.buzzle.com/articles/aerobic-vs-anaerobic-bacteria.html
  • • Port, T. (2009, July 15). Difference between Aerobic & Anaerobic Bacteria. Retrieved November 3, 2011, from Microbilogy Suite 101: http://tami-port.suite101.com/difference-between-aerobic–anaerobic-bacteria-a132294
  • • Sandhyarani, N. (2011, September 27). Aerobic Bacteria. Retrieved November 4, 2011, from Buzzle.com: http://www.buzzle.com/articles/aerobic-bacteria.html
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Archaea Versus Eubacteria: Differences Between Archaea and Eubacteria

Eubacteria and archaebacteria (or simply archaea) belong to Kingdom Monera. All members of this kingdom are considered as prokaryotes. There are several differences between eubacteria and archaea which are discussed in this article(Tortora, 2007).

Between eubacteria and archaea, the former is studied more extensively by scientists. Since archaebacteria are usually found in hostile environments such as volcanic vents, it is not practical to study them. Take note that almost all known pathogens on earth are classified under eubacteria (Mukhergee, 2009).



Halobacteria, an archaea

Archaea are organisms that are usually found in extreme conditions. They are categorized into three phyla: methanogens, halophiles and thermoacidophiles. Methanogens got their name from their ability to convert hydrogen and carbon dioxide into methane.  They are very common in swamps and are responsible for marsh gas. Halophiles, the second group of archaea, derived their name from their ability to survive under extreme salty conditions.  Thermophiles, the last group of archaea, can withstand acid environments that are exposed to high temperatures (Mukherjee, 2009).

When we talk about bacteria in the clinical context, we are usually referring to the eubacteria. These microorganisms have a very complex structure and can be found in neutral conditions such as food, the human body and almost everywhere around. Eubacteria are divided into three phyla: cyanobacteria, spirochetes and proteobacteria.  Cyanobacteria are photosynthetic organisms that are usually found in aquatic environments. They can use light energy to produce their own food and produce oxygen as a by-product. Spirochetes are gram negative bacteria that may be parasitic or symbiotic with their hosts. They can survive on their own (not parasitic). Another group is the proteobacteria which consists of a wide variety of species  are free living and are responsible for nitrogen fixation in the soil (Mukeherjee 2009).

Biochemical Characteristics

Biochemically, archaea are more similar with eukaryotes than eubacteria. They have a complex RNA polymerase in terms of subunits like the eukaryote nuclear polymerase. They also have amino acid sequence homology with some eukaryotic subunits. Although both archaea and eubacteria have operons which they transcribe to polycistronic mRNA, the protein initiator amino acid for archaea is methionine while eubacteria have N-formyl methionine. It has also been found out that eubacteria do not synthesize protein in response to diphtheria toxin, while archaea do (Fox, 2010). Eubacteria are susceptible to antibiotics, while archaea are not affected by such substances. In addition, eubacteria contain an rRNA loop, which binds to ribosomal protein  and have a common arm of tRNA, while archaea don’t (Tortora, 2007).

Cell membrane Components

All eubacteria, except the genera Mycoplasma and Chlamydia possess a peptidoglycan layer. This layer in the organism’s cell wall contains a sugar called muramic acid which cannot be found anywhere else in nature. The counterpart of this bacteria  in archaebacteria is pseudomurein. Instead of N-acetylmuramic acid, pseudomurein has N-acetylglucosamine and N-acetyltalosaminuronic acid as its components (Fox, 2010). Membrane lipids of these two major bacterial groups are also different. Those in archaea are composed of branched carbon chains that are attached to glycerol by ether linkage, while the membrane lipids in eubacteria are straight and unbranched (Tortora 2007).

To sum up everything, archaebacteria live under extreme conditions, are simple single celled organisms and lack a peptidoglycan layer, while eubacteria live in neutral environments, are more complex than archaea, have peptidoglycan in their cell membrane and are studied more extensively by human beings.

With today’s advances in technology, we are able to classify organisms according to their various phenotypic and even genetic properties. Continued research in this field is very much essential in understanding what these microorganisms can do to harm or benefit the world.


Works Cited

  • Fox, A. (2010, May 18). The Bacterial Cell. Retrieved November 3, 2011, from Microbiology and Immunology Online: University of South Carolina School of Medicine: http://pathmicro.med.sc.edu/fox/protype.htm
  • Mukherjee, P. (2009, September 18). Difference Between Eubacteria and Archaebacteria. Retrieved November 3, 2011, from Difference Betwee.net: http://www.differencebetween.net/science/health/difference-between-eubacteria-and-archaebacteria/
  • Tortora, G. J., Funke, B. R., & Case, C. L. (2007). Microbiology: An Introduction. Singapore: Pearson Education South Asia Pte Ltd.
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Career Opportunities for Biology Majors

Majoring biology in college is the initial step in pursuing the study of life. After graduation, there are a myriad career opportunities available for biology graduates. Here are some of them:


Getting a degree in biology prepares one for life as a researcher. Researchers delve into the different fields of biology, like botany, zoology and microbiology among others. Researchers lead a methodical, systematic approach with the aim of adding to the human scope of knowledge. Researchers can be employed by the government, academic institutions, consultancies, research organizations and pharmaceutical companies. For those who are diligent, careful, systematic and patient who derives excitement from breakthroughs and discoveries, this career is for you. This is a passion career where monetary benefits take a back seat to discovery and science. There are numerous specific careers in the field of research. Become a botanist and find new species of plants. Delve into zoology and find out more about the animal kingdom. Succor the seas for knowledge as a marine biologist. Save the world and life within as a conservation biologist. Be a lab rat by working on the latest wonder drug. A degree in biology opens up these fields for you. Being a research assistant in the field of your choice is usually the first stepping stone when entering the field of research. The long hours, the paperwork, laboratory experiments and field expeditions all prepare you for taking more responsibility as you gain proficiency in your job.

Teaching/ Academe

Having a biology degree enables you to impart your obtained knowledge to others. As a teacher, the academe is your playground, teaching students just like you several years ago the sum of your accumulated knowledge. You can opt to stay with your alma mater or explore other teaching opportunities at other universities and schools. For those who love interaction, and who are excited with giving knowledge to others, this career is a good choice. Note that in the academe, teaching and publishing goes hand in hand, you may have to do research just to advance your career and improve your pay grade.


Entering the field of medicine becomes so much easier if you have the knowledge a degree in Biology imparts. Do note however that doing so may require further study in veterinary, medical or nursing school. The knowledge in your anatomy, physiology, microbiology and cell biology classes taken during college will be indispensible once you begin a career in medicine. Knowing the functions of life can aid you in your goal to become a vet, a nurse or a doctor. Use that knowledge to cure people, prevent outbreaks and even solve crime as a forensics expert. If you are dedicated, diligent and passionate about saving lives, then this path is for you.

Environmental Management

The anthropogenic changes we have wrought on Earth is now taking its toll on our planet. This has led to a huge concern over protecting the environment. If you are a Biology graduate you can use your knowledge on the fundamental processes and interactions of life as well as our own interaction with the environment to help minimize our impact to the environment. A career in environmental management entails passion and sacrifice. Careers in environmental management can be attained both in the public and private sector though most work for non-profit outfits.

When you take up Biology as your major it opens up a wide range of possibilities. It gives you a stepping stone to a rewarding career in science. Not only that, you can also branch out to statistics, mathematics and even business. In today’s environment, health and science centered world, Biology majors are in a unique position to have a good academic background in almost all aspects of science. This training translates to possible careers not just within the fields mentioned, but in other sectors as well.

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Simple Explanation of Photosynthesis

Photosynthesis is the process by which plants and other organisms convert light energy into chemical energy through several stages (Bassham). It is one process which does not only benefit the organism that synthesizes it, but the environment and other species as well.

Different Stages



Photosynthesis is a two-step process. In the first series of reactions or the Light Dependent Process light hits chlorophyll and excites electrons to a higher state. Along an electron transport process, light energy is transformed into ATP and NADPH. These are used to make covalent carbon to carbon bonds in the next step. Water is also split and oxygen is released as a by-product. This occurs in the grana. The Light Independent Process or Dark Reactions on the other hand, are the second set of reactions. These reactions take place in the stroma of chloroplasts. Atmospheric carbon dioxide is modified by adding hydrogen to form carbohydrates. This process by which carbon is incorporated with other substances to produce organic compounds is called carbon fixation. (Farabee, 2010).

Photosynthetic electron transfers

Charge separation reactions or the initial electron transfer in the photosynthetic reaction center initiates a long series of reduction-oxidation reactions. The electron passes along a number of cofactors and fills up the “electron hole” on the chlorophyll. Organisms that are capable of photosynthesis have two types of reaction centers: photosystem II and photosystem I (PS II and PS I). Both of these photosystems are pigment/protein complexes located in thylakoids. Thylakoids are specialized membranes inside chloroplasts and are found in the grana. Since prokaryotes or single celled organisms do not have chloroplasts, pigment/protein complexes can be found in the cytoplasmic membrane, in its invaginations or in thylakoid membranes that are part of more complex structures within the cell (Vermaas, 2007).

In organisms that produce oxygen, all chlorophyll is in thylakoids and is associated with both photosystems or with antenna proteins that provide energy for the photosystems. PS II is where water is split and oxygen is generated. When the reaction center chlorophyll in PS II is oxidized, an electron is pulled from tyrosine, which also gets an additional electron from the water-splitting complex. After this reaction is completed, electrons go into molecules called plastoquinone in the thylakoid membrane and into the cytochrome b6f complex. Meanwhile, PS I hastens light-induced charge separation in a similar way with PS II. The difference is that PS I electrons are transferred to NADP, which can be converted into NADPH and used for carbon fixation.  The end result of the two photosystems is water oxidation, oxygen evolution and NADPH production, with light providing the energy for the said process (Vermaas, 2007).


Factors affecting photosynthesis

Several factors can affect the rate at which the process is completed. Some of these factors include light, temperature, carbon dioxide and water. At moderate temperatures and low to medium light conditions, the rate of photosynthesis increases as light intensity increases, but is not affected by temperature. However, as the intensity of light increases, the rate tends to be dependent on temperature. An increase in carbon dioxide also results to an increase in the rate of photosynthesis, but the degree varies depending on the species and condition of the plants. For plants that grow on land, the availability of water also contributes as a limiting factor. Not only is it directly required by the photosynthetic process, but is also transpired form the leaves through the stomates. These openings allow the entry of carbon dioxide, but also seves as an exit of water vapour (Bassham).

Basically, photosynthesis is an oxidation-reduction reaction. Light is used to oxidize water to produce oxygen, hydrogen ions and electrons. The hydrogen ions and electrons are then transferred to carbon dioxide, which is converted into other organic products. The unused electrons and hydrogen ions are used to reduce nitrate and sulphate to amino and sulfhydryl groups. Starch and sucrose are some of the major organic products of this process (Bassham).


Works Cited

Bassham, J. A. (n.d.). Photosynthesis. Retrieved November 1, 2011, from Encyclopedia Britannica: http://www.britannica.com/EBchecked/topic/458172/photosynthesis

Farabee, M. (2010, May 18). Photosynthesis. Retrieved November 1, 2011, from http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BiobookPS.html

Vermaas, W. (2007, June 12). An Introduction to Photosynthesis and Its Applications. Retrieved November 1, 2011, from Arizona State University: http://photoscience.la.asu.edu/photosyn/education/photointro.html

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Types of Microscopes and Their Magnifications

To enable scientists to see and observe microorganisms, microscopes were invented. The word microscope comes from the Latin word micro, which means small, and the Greek word skopos which means, to look at (Tortora et al., 2008). With the advances in technology, the microscope has also evolved and more types are added into the list. With the need to study the organelles of cells and microorganisms, more powerful microscopes are invented.

Basically, a microscope consists of two magnifying lenses, the objective and the eyepiece or ocular. The total magnification is computed by multiplying the magnifications of these two lenses. For example, the total magnification of an object as observed using a 10x ocular and a 40x objective is 400 times (Tortora et al., 2008).  To determine what microscope should be used to observe a particular microorganism or cell, understanding the types of microscopes and their magnifications is very important.

Compound Light Microscope

Both stained and unstained specimens can be examined using this microscope. It uses visible light as its source of illumination (Turgeon, 2007). This type of light has a long wavelength and cannot resolve structures smaller than 0.2 um. With this and other considerations, the magnification achieved by even the best compound light microscopes is only until 2000 times. However, most microscopes have three objectives with the following magnification power: 10x (low power), 40x (high power), 100x (oil immersion) (Tortora et al., 2008).

Phase Contrast Microscope

Phase contrast microscopy is useful in examining internal structures of living microorganisms. Its principle is based on the wave nature of light rays. It uses a special condenser containing an annular diaphragm. The diaphragm allows light to pass through the condenser and focuses the light to hit the specimen and the diffraction plate in the objective lens. Direct and reflected or diffracted light rays are brought together to produce an image. It has a total magnification of 100 to 1,000 times (Tortora et al., 2008).

Electron Microscopes

The principle behind electron microscopy is the same as that of brightfield microscopy. However, instead of a beam of light, the specimen is illuminated with a beam of electrons. This beam is concentrated onto the specimen, and the objective provides the primary magnification (Turgeon, 2007). There are two general types of electron microscopes: scanning and transmission. The main difference between the two is that transmission electron microscopes (TEMs) produced a two-dimensional image and can magnify objects from 10,000 to 100,000 times, while scanning electron microscopes (SEMs) produce an image that is magnified 1,000 to 10,000 times and appears three-dimensional.

Scanning Tunnelling Microscope (STM)

This type of microscope uses a tungsten probe that scans the specimen and reveals the elevations and depressions of the atoms on the surface of the specimen. It can magnify objects that are about 1/100 the size of an atom.  STMs are used to provide very detailed images of molecules such as that of deoxyribonucleic acid or DNA. (Tortora et al., 2008).

Atomic Force Microscope (ATM)

ATMs make use of a metal-and-diamond probe that is forced down onto a specimen. As it moves on the surface of the specimen, its movements are recorded and a three-dimensional image is produced. They are used to magnify images of biological substances as well as to document molecular processes such as the formation of fibrin strands during blood coagulation (Tortora et al., 2008). The maximum magnification for an ATM is about 2000 times (Advanced Surface Microscopy Inc.).

Microscopes have been an indispensable tool in different fields of science. To maximize the use of microscopy, knowledge of its different types and magnifications is not the only requirement. Proper care and maintenance is also very important to keep your microscope in its optimum condition.

  • Advanced Surface Microscopy Inc. (n.d.). Atomic Force Microscopy. Retrieved October 29, 2011, from Advanced Surface Microscopy Inc.: http://www.asmicro.com/applications/afmpage.htm
  • Tortora, G. J., Funke, B. R., & Case, C. L. (2008). Microbiology: An introduction (9th ed.). Singapore: Pearson Education South Asia Pte Ltd.
  • Turgeon, M. L. (2007). Linne and Ringsrud’s Clinical Laboratory Scienc: The Basics and Routine Techniques (5th ed.). Singapore: Elsevier Inc.
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MNEMONICS for the 12 Cranial Nerves: A Compilation

Are you having a hard time memorizing the 12 cranial nerves? Here are a number of mnemonics you can use to make your life easier when preparing for a quiz or exams.

I – Olfactory nerve

II – Optic nerve

III – Oculomotor nerve

IV – Trochlear nerve

V – Trigeminal nerve

VI – Abducens nerve

VII – Facial nerve

VIII – Vestibulocochlear nerve/Auditory nerve

IX – Glossopharyngeal nerve

X – Vagus nerve

XI – Accessory nerve/Spinal accessory nerve

XII – Hypoglossal nerve

  1. On Occasion Our Trusty Truck Acts Funny. Very Good Vehicle Any How

  2. On Old Olympus’ Towering Tops A Friendly Viking Grew Vines and Hops

  3. On Old Olympus’ Towering Top A Finn And German Viewed Some Hops

  4. On Old Olympus’ Towering Top A Finely Vested German Viewed A Hawk

  5. On Old Olympus’ Tufted Top A Fat Armed German Viewed An Hop

  6. On Old Olympus’ Towering Top AFinn And German Vault And Hop (Note: the Vestibulocochlear nerve is referred to as Auditory nerve in this mnemonic)

  7. OLympic OPium OCcupies TROubled TRIathletes After Finishing VEgas Gambling VAcations Still High

  8. OLiver the OPTImistic OCtopus TROts TRIumphantly ABout FACIng AUDIences GLOSSily VAGUely SPINning HIPPOs (Note: Accessory nerve is referred as Spinal accessory nerve, and the Vestibulocochlear nerve by its former name, Auditory)
  9. Orange Orangutans Often TRy To Avoid Feeding Angry Gorillas Very Ancient Hotdogs (Note: the Vestibulocochlear nerve is referred to as Auditory nerve in this mnemonic)
  10. Oh Once One Takes The Anatomy Final Very Good Vacations Are Heavenly
  11. OLd OPrah’s OCcupation: TROpical TRIps ABoard FAmous VESsels, GLamorous VAcations, ACCumulating HYPe
  12. OLd OPie Opened The TRunk And Found VEry Green Vestiges And Hemp
  13. OLd OPie OCcasionally TRies TRIGonometry And Feels VEry GLOomy, VAGUe, And HYPOactive
  14. Oh, Oh, Oh, They Traveled And Found Voldermort Guarding Very Secret Hallows
  15. O! O! O! There’s The Abercrombie and Fitch. Very Gorgeous and Very Adorable! Ha! (Note: the Vestibulocochlear nerve is referred to as Auditory nerve in this mnemonic)
  16. Oh, Oh, Oh, To Touch And Feel Very Good Velvet. Such Heaven! (Note: Accessory nerve is referred as Spinal accessory nerve, and cranial nerve VIII is referred to as both Vestibulocochlear and Auditory)
  17. Oh Oh Oh To Touch And Feel Very Green Vegetables AH!! (Note: AH=Accessory & Hypoglossal combined)
  18. Oh, Oh, Oh To Touch And Feel AGirl’s Very Soft Hands
  19. Oh, Oh, Oh, To Touch And Fondle AGorgeous Very Sexy Human
  20. OOOTruly There Are Five Very Gorgeous Vixens Awaiting Him
  21. Oh Oh Oh Topless Tiffany And Fat Valery Got V*ginitis And Hepatitis 


To familiarize yourselves whether a cranial nerve is Sensory, Motor or Both, the following mnemonics apply:

I. Olfactory Sensory
II. Optic Sensory
III. Oculomotor Motor
IV. Trochlear Motor
V. Trigeminal Both
VI. Abducens Motor
VII. Facial Both
VIII. Vestibulocochlear Sensory
IX. Glossopharyngeal Both
X. Vagus Both
XI. Spinal Accessory Motor
XII. Hypoglossal Motor



Some Say Marilyn Monroe But My Brother Says Bridget Bardot Mmm, Mmm!

Some Say Marry Money, But My Brother Says Big Business Makes Money

Some Say Marry Money, But My Brother Says Big Br**sts Matter Most



These mnemonics, which were taken from other web sites are just the most commonly used. You can make your own mnemonics and codes at your ease by associating the names of the cranial nerves to the things you see or to the things that get your attention easily.




  • http://pinoy-md.com/2010/01/cranial-nerves-mnemonics-for-medical-students.html
  • http://www.saintcyr.com/2001/mnemonic.html
  • http://en.wikipedia.org/wiki/List_of_mnemonics_for_the_cranial_nerves
  • http://www.ehow.com/how_5696780_use-memorize-twelve-cranial-nerves.html
  • http://www.gwc.maricopa.edu/class/bio201/cn/cranial.htm
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How to Keep Raccoons Out of Your Yard



Most people don’t like raccoons even though they are cute, cuddly, interesting, and intelligent. It is because raccoons turn people’s yard or garden into chaos. They disarrange the garbage, eat garden plants and vegetables, left smelly feces, and put things upside down. They can also carry the unwanted rabies virus and roundworms. Because they do more bad things than good, people simply wish them out of their yards. There are ways on how to keep raccoons out of your yard. Here are some examples:


  1. Consider making homemade repellents that will drive raccoons away. These repellents are made up of hot chili which raccoons really hate. Click this link to get the recipe for homemade raccoon repellents.
  2. Use motion activated mechanical repellent like the “Scarecrow” of Contech. When the Scarecrow detects motion, it will automatically spray water to repel the raccoons.
  3. Determine the things that motivate raccoons in visiting your hard. The availability of potential meal in your yard entices raccoons to come. These potential meals include pet foods, garbage foods, garden plants, vegetables, etc. When you learned the reason why raccoons keep coming in your yard, do something about it.
  4. Don’t left pet foods in your yard because raccoons can smell them. Seal your garbage bins in such a way that raccoons will have a very hard time opening it. Raccoons are not only intelligent but possess dexterous paws capable of opening lightly sealed containers.
  5. Spray ammonia to rugs and place them in places where you usually spot raccoons. You can also put the rugs in places that you don’t really want raccoons to go to. Ammonia scares raccoons because it is the main compound found in the urine of predators (e.g. coyotes). Online and offline specialty stores are selling predator urine either in liquid or powdered form. You can sprinkle the powdered urine into your house perimeter to drive away raccoons.
  6. Raccoons don’t like water and can be discouraged when soaked with it. You can install a motion sprinkler in your yard which is capable of detecting raccoon’s presence. When raccoons are doused with water, they may go away.
  7. Raccoons are afraid of human beings. They go away when they sense human presence (movements and sounds). Since it is not feasible to guard your yard during the night, consider leaving a radio programmed to a talk station. Just wish that raccoons leave your yard when they hear the DJ speaking.
  8. An extreme way of driving raccoons away (or killing raccoons) is putting an electric fence in your yard. Animal activists and wildlife officials strongly oppose this method. Raccoons will be automatically electrocuted once they touch an electric fence. Take note that there are laws that prohibit killing and inhumane treatment of raccoons. Beware to avoid penalties.
  9. Consider having a dog as pet. Its urine will discourage raccoons to proceed in your yard. Raccoons are also afraid with dogs.
  10. Remove sources of water for raccoons. Raccoons have the behavior of dipping their food in water.
  11. Install motion activated lightning in your yard. Lighting discourages raccoons.
  12. Buy and install humane raccoon traps in your hard. If you catch a masked bandit, call the right authority to get it. Do not kill it.


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