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The mosquito (Culex pipiens) lays its eggs in stagnant water. The eggs stick together in a ‘raft’ and are buoyed up by the air trapped between them. The eggs hatch into larvae which escape into the water from the bottom of the egg cases. The larvae hang from the surface film of the water by means of a breathing tube, through which they take in air. If disturbed, they swim by flicking movements to the bottom, and then return to the surface. They feed on microscopic plants which they collect by whisking movements of their mouthparts which carry a dense fringe of bristles. They shed their ‘skins’ at intervals as they grow.

By the time the last larval ‘skin’ is shed, the larva has turned into a pupa, quite different in appearance from the larva. The pupa does not feed but continues to breath air through two breathing tubes while hanging from the surface film of the water.

By this time, the pupa has developed all the features of the adult: wings, legs, compound eyes etc. but these are all crammed into the pupal skin, giving it a somewhat grotesque comma shape.

The pupal case eventually breaks open at the top and the adult mosquito works its way out and supports itself on the floating pupal case and the surface film while its wings expand and harden before it flies away.

The adult mosquito has 3 pairs of legs and one pair of wings on its thorax. Its head bears a set of mouthparts which are adapted to piercing and sucking. The female mosquito often feeds on blood before she lays her eggs. She lands on a suitable animal and pushes her sharp piercing mouthparts through the skin until they reach a capillary blood vessel. She injects saliva which contains a substance that prevents the blood from clotting, and then sucks up a meal of blood which is digested in her gut. The mouthparts of male mosquitoes cannot penetrate the skin, and males feed on plant juices such as nectar.

When humans are ‘bitten’ by a mosquito, the salivary secretions often lead to an inflamed itchy swelling. In the tropics, however, the bite of a mosquito can transmit the disease malaria.

More information, and illustrations to accompany this article, can be found on biology-resources.com

Marketing research “The systematic gathering, recording and analyzing data about problems relating to the marketing of goods and services”.

Market research on the other hand, is only a part of marketing research that covers a few of aspects of marketing. It is only the sub function of marketing research ‘some companies use “market research” for describing research into markets the size geographical distribution incomes, and so on. However it fails to cover the idea of research into the effects of marketing efforts on markets, for which the term marketing research is the accurate. Elements of marketing research.

1. Market Research. It covers the aspects regarding size and nature of the market including export markets dividing the consumers in terms, of their age, sex, income (market segmentation), economic aspects of marketing etc.

2. Sales Research. This relates to the problem regional variations in sales fixing sales territories, measurement of the effectiveness of salesman, evaluation of sales methods and incentives, etc.

3. Product Research. This relates to the analysis of strengths and or weakness of existing product testing problems relating to diversification, simplification, trading up and trading down (all product line decisions), etc.

4. Packaging Research. In essence, it is a part of product research. But the recent development in packaging and its contribution in the advertising made it to occupy an independent position. This necessitates a separate study concerning the aspects of package to know its impact and response in the market.

5. Advertising Research. It undertakes a study relating to the preparation of advertisement copy (copy research), media to be used (media research) and measurement of advertising effectiveness.

6. Business Economic Research. Problems relating to input output analysis, forecasting, price and profit analysis, and preparation of break -even charts are the main fields of the research.

7. Export Marketing Research. This research is intended to study the export potentials of the product. In such cases any or all kinds of research mentioned above become necessary.

Chemistry is the study of matter and the changes that it undergoes. Since all matter consists of atoms, it is important that you understand the atom and its components especially the electron.

Why the electron? Because the electron configuration determines how an element will behave in chemical bonding and chemical reactions. So if you understand the electron you will better understand chemistry.

However, you must keep in mind that the atom and its components are so small that scientists are unable to work directly with the atom. Therefore, chemists and physicists need to create models to aid in the description of the atom. But, a scientific model is limited to the information available at the time it is created. So, when new experiments lead to new discoveries the model must be changed or discarded.

Despite the fact that scientific models change, models are the only way man has to describe how several natural phenomena work. And knowing how a process functions is often crucial to further scientific discovery. So, models are not truth, models are man’s best estimates at how things work. For that reason, the importance of models is not their truth, but their workability.

Remember that models are created by humans and can have biases, flaws and inaccuracies. Always examine models in the light of the scientific method and be willing to discard that which doesn’t measure up.

Although models are not perfect there are five models of the atom that lead to the understanding of matter. The more you understand these models the better you will be at chemistry. The five models are:

The Solid Sphere model The Plum Pudding Model The Nuclear Model The Bohr Model The Wave Mechanical Model
Solid Sphere Model

The solid sphere model was proposed in 1803 by John Dalton. John Dalton was an English chemistry and math tutor who took the ideas of his day and put them into a model of how matter was arranged. He stated that matter was made of tiny indivisible particles called atoms and atoms of the same element were all alike. Also, he included the law of multiple proportions and the law of definite composition in his model. Although his model was not perfect it was the main main model for over 90 years.

Plum Pudding

In 1897 English physicist, J. J. Thomson, suggested that cathode rays consisted of negatively charged particles even smaller than atoms. As a matter of fact he suggested these particles were subatomic parts of the atom. Thus, Dalton’s theory of an indivisible particle was no longer workable. A new theory that allowed for subatomic particles was needed.

So, Thomson proposed that the atom was a mass of positive charge with negative electrons placed into it like raisins in a pudding, and dubbed it the Plum Pudding model. Thomson’s model, although attractive, nevertheless had many shortcomings.

The Nuclear Model

In 1906 Ernest Rutherford and his assistants, performed the famous Gold Foil experiment that led to the discoveries of the atomic nucleus and that the atom is mostly space.

The Gold Foil experiment demonstrated that the mass of the atom was the same as predicted by Thompson’s model, but the volume of the mass was much smaller and seemed to be located in the center of the atom. Thomson’s Plum Pudding model was no longer workable. So, in 1911, Rutherford proposed the Nuclear model of the atom.

The Bohr Model

In 1913 Danish physicist, Neils Bohr, suggested applying the quantum theory to the Rutherford model. Bohr’s new model proposed that electrons are in fixed energy levels he called orbits. The energy of these orbits is quantized and electrons must absorb or release energy (photons) at certain wavelengths to move between energy levels.

The Wave Mechanical Model

In 1921 Louis de Broglie stated, without any empirical evidence, that if waves have matter properties then matter should have wave properties. Later, Bell Laboratories would prove that De Broglie’s hypothesis was indeed correct. De Broglie’s hypothesis was a revelation that even impressed Einstein and changed the view of the atom forever.

Combining Louis de Broglie’s hypothesis with Bohr’s model, Erwin Schrodinger proposed the electron was a 3-D waveform circling the nucleus in a whole number of wavelengths allowing the waveform to repeat itself as a stable standing wave representing the energy levels of the Bohr model.

In support of his hypothesis, Schr