Month: April 2010

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[Yr13 NCEA Internal] – Biotechnology

Question: DNA profiling is being used as part of an international research project to identify twenty thousand marine fish species by the year 2010. Scientists will identify the sequence of bases in a specific region of mitochondrial DNA which does not show much variation within species, but between species is very different. The DNA is sourced from muscle tissue using standard DNA extraction techniques.

Discuss the human need or demand for DNA profiling technology in relation to identifying marine fish species.

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[‘MERIT’ ANSWER]

This use of DNA profiling enables fish species to be accurately identified. This allows biodiversity / conservation issues to be addressed, Evolutionary links to be identified.

Data on fish species will also enable fish quotas/stocks to be ascertained. DNA profiling is faster and more accurate than any other method of identification so that data on fish species can enable fish quotas/stocks to be ascertained to ensure they are sustainable.


[‘EXCELLENCE’ ANSWER -add these statements to MERIT answer]

This use of DNA profiling is justified as it enables fish species to be identified faster and more accurately than any other method. This allows biodiversity and conservation issues to be addressed more accurately, as data on each fish species is more accurate. Without the use of DNA profiling different species of fish that look similar may have been misidentified and this would have made it appear that there were more of a species present than was actually the case.

When the stocks of a fish species are able to be quickly and accurately determined it helps to ensure that appropriate management strategies are implemented to maintain a sustainable catch.

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Physical change VS. Chemical change

1. Physical change is a reversible change.

Physical changes involve change in position. A physical separation involves moving one substance away from another. Iron can be moved away from sulfur and iron mixture by passing a magnet over a mixture containing the two substances. Water can be moved away from passing mixture of sand and water through a funnel and catching the sand in the funnel. We begin with two separate substances, which happen to be close to each other. We en up with the same two separate substances, but they are no longer close to each other. No new substances are formed and we can easily put the parts of the mixture together again.

Dissolving, melting, boiling, condensing, freezing and evaporating are all reversible changes.

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2. Chemical change is an irreversible change.

Chemical changes involve changes in the connections between substances. A chemical reaction can form a new substance. However, a chemical change involves the formation of a new substance, requires energy and cannot be reversed.

  • Cooking can cause an irreversible change. For example: an egg can be heated and cannot be returned to its previous state.
  • Burning materials, such as wood, paper, natural gas, causes an irreversible change.
  • Irreversible changes can form new materials that can be useful e.g. plaster of Paris and water.
  • Dead plants and animals decay and some metals rust. These chemical changes are permanent.
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Friction

Our life is pull of forces. We cannot see them but we can see how they affect things. Forces can change the shape of something, its speed, or the direction that it is moving in.

This is an example of friction.

Forces are either pushes or pulls. These pictures show some changes caused by forces. Many forces need to touch an object before they can affect it. These are called contact forces.

Friction is the force between two touching objects. It can slow things down or make things stand still. The friction between our clothes and a chair stops us from sliding off it. Walking would be very difficult without the frictions between our feet and the floor – we would slip and slide everywhere.

Friction can also wear things away. The brake pads on a bicycle eventually wear away, and so do car tyres. Parts of your clothes get thinner as friction wears them away.

Friction produces heat and noise. If a car engine runs without any oil in it, the large friction between the moving parts inside the engine causes it to overheat and stop working. Rusty door hinges squeak and make a door difficult to open.

We can increase friction by using certain materials. Rubber produces a lot of riction which is useful to use. The tyres of a Formula One racing car stop the car from sliding off the road as it speeds round a sharp bend. The rubber mat in a bath stops us from slipping.

We can reduce friction by making surfaces smooth. Skiers wax the bottom of their skis to make them very smooth. This reduces friction and allows them to ski faster.

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공부의 비법 1,2,3

케이블 방송같은데 한국에서 유명한 강사들이 매주 나와서 쇼프로 형식으로 강의를 한다.  과목별로 공부를 하는 방법을 알려주기때문에 꼭 한국에서 공부하는 학생이 아니더라도 한번쯤은 꼭 들어야 할 필요성이 있다.

한국의 수능은 미국이나 영국시험제도와 비슷하기때문에 우리가 하고있는 공부와 비슷하다. 꼭 한번 들어보길…

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공부의 비법 3회[사탐&과학]: http://joonmedia.net/videos/play/18631/4

공부의 비법 2회[수학]: http://joonmedia.net/videos/play/18486/4

공부의 비법 1회[국어]: http://joonmedia.net/videos/play/18013/4

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excretory system

The job of the excretory system is to remove various produced by the body. The removal is known as excreation. It is important for the body to remove these various waste, also known as toxic, because toxic build up can lead to servere death.

About sixty percent of your body contains water. A portion of the water is in the tissues and cells. The word excretion means the removal of waste substances from the body. Several organs are involved with the excretory system, including the kidneys, sweat glands, lungs . and rectum, The primary organs of excretions, however, are the kidney. Excretion is vital to the health of the body because the wastes are poisonous. If the wastes build up and are not eliminated, they can cause serious problems. As you know , carbon dioxide and water vapor are removed by the lungs.

Other wastes , namely urea, uric acid, various salts, and assorted nitrogenous wastes , are removed by the kidneys and sweat glands. Urea is produced when protein is broken down to glucose. The nitrogen part is the urea which is toxic to our body.

The water contains salt. the salt needs to be kept at the right concentrations. If there is little salt the body feeds it more, if there is too much salt the body gets rid of the salt not needed. This is the task of the two Kidneys.

The liver acts as a filter for the blood. It cleans out toxic waste and acid in the blood.

The skin plays a major role in excretion. It helps the body get rid of excess water, salts, and waste such as urea.

Urethra leads urine from bladder to outside, therefore it is also part of the excretory system.

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what happens in the small intestine?

The small intestine is the longest portion of the digestive tract – it is more than 6 meters long and is located within the middle of the abdomen. It has three sections, the duodenum, jejunum and ileum.

Small intestine has an important function in digestion of fats, proteins and carbohydrates contained in the foods you consume. The resulting nutrients produced are absorbed through the lining of the small intestine and transferred to the bloodstream.

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nucleus

Nucleus is at the centre of an atom which contains neutron and proton. Neutron has no charge but proton has positive charge. Electrons are outside the nucleus and they have negative charge. Electrons are like cloud outside the nucleus.

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Memorizing Periodic Table?

Hey, don’t hard out your self for learning the whole periodic table. Because you don’t need to. You are only expected to remember the first 30 elements on your periodic table. Your school will never ask you to remember the whole Periodic table and there is a big theory behind the Periodic table. It will be not even until Year11.

You will always get your periodic table during the test – BUT YOU NEED TO REMEMBER THE SYMBOL AND THE NAME of elements.

So, don’t learn their mass numbers of atomic numbers. It will be just a waste of time. When the time is right, you will get used to the properties of elements and understand why they have such placements.

But here is a tip for first 20 elements.

Harry He Like Beer Cold But Not Over Frothy. Nelly the Nanny Might Although Silly Punk She Climbs Around Kinky Cave.

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How to remember the scientific “terms”?

Learning science is like learning another language. If you are learning to speak another language like Chinese or Japanese – WHAT WOULD YOU DO?

It is the same procedure while  you are learning science. My advise is – use the word more often. How would you use the word more often though?

Well, everybody has different ways and methods. You could build your own table of glossary per each topic in science or make a memory card (front page with the definition and back page with the term), or even write the word many times. Some psychologists say that humans learn words by saying it or by forgetting the word few times. This is why teachers make you to do different activities and ask you to get involved into the discussion in the class.

Probably, the best way to learn science language is by ENJOYING IT! :) So, don’t bore yourself. Move on to something else if you can’t really learn the word -because you can alway come back to it.

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Blood

Blood

 

Oxygen is carried by red blood cells. Glucose is dissolved in the liquid part of the blood, called plasma. Plasma leaks out of the capillaries and forms tissue fluid around cells in the body. Some of the oxygen leaves the red blood cells dissolves in the tissue fluid. The red blood cells stay inside the capillary.

If you press two fingers firmly onto your wrist, you can feel your blood being pumped. This is called your pulse. Your pulse rate is the number of beats you can feel in one minute.