KEY TO IDENTIFY THE RANGE OF ORGANISMS

 SCIENCE_BIOLOGY

KEY TO IDENTIFY THE RANGE OF ORGANISMS

Introduction

As biology is concerned with the study of living organisms, the characteristics of one organism is different from another though they belong to the same group or phylum. Identifying the characteristics of organisms is a challenging task for the biologist. After identifying the characteristics of an organism, they are classified and named. Naming of organisms is done with genus and species is termed as binomial system of  nomenclature. Carolus linnaeus was the first Swedish scientist to classify the organism scientifically.

Charles Darwin was the first biologist to study and explain about the evolution of organisms and published an article Theory of Evolution. Complex organisms evolved from the simple existing organism. Here the complex organism refers to the organism with advanced characteristics. When the biologist explores nature and studies these organisms they use the reference character of the pre-existing organism. It is a completely complicated task for a layman to classify the organism by studying their character even which were already classified. So in order to make these tasks easy and convenient, scientists have developed a tool called dichotomous key, which helps a layman to identify objects and organisms.

The term dichotomous is derived from the two Greek word “Di” which means “two” and “tome” which means “cutting instrument”

A dichotomous key consists of a series of questions, when a question is answered, the key directs the user as to what question to ask next. Consider an example of dichotomous key to classify the vertebrates:

Mammals: We might ask, does it have fur? If the answer is “yes” it leads to mammals.

Birds: if said “no” next maybe next may be “does it have feathers”? If the answer is “yes” we identified birds

Reptiles: if the answer is “no”, we may ask if the organisms have dry or moist skin? If we say dry the organisms will be identified as reptiles.

Pisces: if the answer is “moist”, we might ask if the organism has smooth skin or scales? If the answer is scales we have  identified as pisces.

Amphibians: if the answer is moist skin, it is an amphibian.

A dichotomous key looks like a flow chart a feature a series of images and text with two choices branching off at two each step: we choose the one that fits the organisms you want to identify

At each stage, we are presented with a choice of characteristics and answer ‘yes’ or ‘no’ until, we  make an identification of an organisms

How to make a dichotomous key:

Step 1. Listing down the characteristics: 

List down the character that you can notice. For example if we are trying to classify group of plants, you may notice that some of them have sharp leaves, cones ,whereas other have flat leaves and flowers

Step 2. Organising the characteristics  in order:

While creating a dichotomous key the characters of an organism are identified and then they are assembled. While assembling the characters they are arranged from simple to complicated

Step 3. Divide the specimen:

We can use statements to divide our specimen into two groups. The first differentiation should be made on the first most general characteristics

Step 4. Divide the specimen even further:

Taking reference of more contrasting characters, we need to divide the specimen further. First we may group our organisms as they have sharp leaves or flat leaves, in which the plants with sharp leaves are classified as conifers and while the plants with flat leaves can be classified as angiosperm.

Step 5. Draw a dichotomous key diagram:

We can either create or draw graphical diagrams with images or text based dichotomous diagrams for the organism we are trying to identify.

Step 6. Test it out:

Once the dichotomous key is set up or created we need to test it whether it works or not. The specimens that are going to be classified should be checked with all the diagnostic characters and  should coincide. Necessary adjustment or editing can be done if it is required.

Uses of  dichotomous Key:

A dichotomous key is used for

• Identifying and categorizing organism

• Helping students easily understand complicated nomenclature concepts

• Assembling large amount of information to make identification of an organisms much easier

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ACCURATE MEASUREMENT IS ESSENTIAL

SCIENCE_PHYSICS

ACCURATE MEASUREMENT IS ESSENTIAL

Introduction

The process of comparing unknown quantities with known standard quantities of similar kind is measurement. Simply it is the action of measuring something. If the object or the quantity to be measured is not accessible for direct comparison, it is converted or transduced into analogous measurement signal. The process involves the interaction between object and observer or the observing instrument. During this process there is always an exchange of energy which is  negligible and can be studied under the mathematical process of limit and accuracy.

Quantification, quantifying, calculation, computation, mensuration, estimation, evaluation, weighing and sizing are the various synonyms of measurement.

Measurement Theory

Measurement theory is the study of how numbers are assigned to objects and phenomenon and its concerns include the kinds of things that can be measured, how different measures relate to each other and the problem of error in the measurement process

History of Measurement

The history of measurement began from the fourth century BC. During this time a theory of magnitudes was developed by Greek mathematician Eudoxus of Cnidus. Early Babylonians and Egyptians records and the Hebrew Bible indicate the length was first measured by the forearm hand or finger and the time was measured by the periods of sun moon and other heavenly bodies. In order to measure the capacity/ volume of the clay or metal vessels they were filled with plant seeds and later counted to measure the volume. As the time passed to bring more accuracy in the measurement of mass and weight seeds and stones were used as the standard masses. In 18 th century the measurement process was first incorporated into social science by Jeremy Bentham, a British Utilitarian moralist, by introducing the theory for the measurement of value.

Approximation in Measurement:

Though measurement is a physical activity it is always not concerned with the exact solution to a problem.  Approximation is the quality of the state of being close or near  to the value. In these instances approximate mathematical expressions are good enough for practical purposes. Sometimes approximation is also called guesstimates. Some examples of approximations are shown below.

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Sometimes approximation and estimation seem to be similar in meaning, in fact there are some differences. Estimation refers to roughly calculated data derived from imperfect data, while approximate is to carry out advance near to; cause to approach.

Unit

How do we measure something really, really small or big?

If we are measuring the distance between the Sun then not by meter rod. Units must exist that can describe sizes many times  bigger  than the biggest marking a meter rod.

The units that are used during the measurement process are based on the International System of Units (SI), which is a form of metric system( base of 10). The SI unit is the abbreviated form of French term  Le Système international d'unités.

As the technology of measurement processes progresses, new units are evolved and their definitions are changed through international agreement among many nations. The SI unit is made up of seven base units. These base units are also called fundamental units The seven units are tabulated as below. From these seven fundamental  units several other units are derived which are classified under derived units.

Name	Symbol	Quantity
meter	m	Length
kilogram	kg	Mass
second	s	Time
ampere	A	Current
kalvin	K	Temperature
mole	mol	Amount of substance
candela	Cd	Luminous intensity of light

Use of prefix in SI Unit

Several prefixes are added to the SI Unit to make multiple of the original unit. For example kilo is the prefix that stands for a multiple of thousand while mili stands for the multiple of a thousandth.

tera, giga, mega, kilo, hecto, deca, deci, centi, mili, micro, nano, pico are the prefixes used to add to the SI Unit to make multiple of the original unit. All prefixes are the multiple of 10. 

Practise Section

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