Oct 29, 2009
Incomplete combustion of fossil fuels
Combustion sources - motor vehicle exhaust, smoke from fires, engine fumes
Can combine with haemoglobin - carboxyhaemoglobin - reduces the ability of blood to transport oxygen.
Early symptoms - headaches, nausea & fatigue
Prolonged exposure - brain damage & even fatal.
Combustion of fossil fuels.
Contributes to acid rain which damages buildings.
Contribute to greenhouse effect and global warming.
Combustion of fossil fuels.
Motor vehicle exhaust.
Damages lung tissues.
May cause bronchitis.
Irritates the eyes.
Lowers the body's defence against flu.
Contributes to acid rain which reduces the pH of soil, lakes and rivers.
Contributes to acid rain which destroys buildings.
Combustion of fossil fuels which contain sulphur.
Irritates and damages the lining of the eyes, air passages and lungs.
Causes coughing and wheezing.
Combines with rainwater to form acid rain that may cause skin diseases.
reduces the growth of plants.
Damages the leaves and may kill the plants.
Contributes to acid rain which lowers the pH of soil, lakes and rivers.
Contributes to acid rain which corrodes iron, copper, steel, aluminium and stonework, thereby destroying buildings.
Combustion of fossil fuels from motor vehicles, agricultural burning and industries.
Quarries and asbestos factories.
Irritates the eyes and respiratory tract.
Contributes to haze which can cause asthma attack, conjunctivitis, sore throat, bronchitis and reduced visibility.
Deposits on leaves and darkens vegetation.
Blocks stomata, thus lowering the rate of photosynthesis.
The crop yield is reduced.
Soot can darken buildings.
Contributes to formation of haze and smog which can reduce light intensity.
Combustion of fossil fuels.
Reduces the sensitivity of the hands and feet coordination.
Retards mental development in children.
Disrupts body's ability to produce new cells.
Combustion of fossil fuels from motor vehicles.
Posted by rozaini at 9:15 PM
Oct 25, 2009
Oct 21, 2009
Rh incompatibility is a condition that develops when a pregnant woman has Rh-negative blood and the baby in her womb has Rh-positive blood.
During pregnancy, red blood cells from the foetus can get into the mother's bloodstream as she nourishes her child through the placenta. If the mother is Rh-negative, her system cannot tolerate the presence of Rh-positive red blood cells.
In such cases, the mother's immune system treats the Rh-positive foetal cells as if they were a foreign substance and makes antibodies against the foetal blood cells. These anti-Rh antibodies may cross the placenta into the foetus, where they destroy the foetus's circulating red blood cells.
First-born infants are often not affected -- unless the mother has had previous miscarriages or abortions, which could have sensitised her system -- as it takes time for the mother to develop antibodies against the foetal blood. However, second children who are also Rh-positive may be harmed.
Haemoglobin changes into bilirubin, which causes an infant to become yellow (jaundiced). The jaundice of Rh incompatibility, measured by the level of bilirubin in the infant's bloodstream, may range from mild to dangerously high levels of bilirubin.
Rh incompatibility develops only when the mother is Rh-negative and the infant is Rh-positive. Special immune globulins, called RhoGAM, are now used to prevent this sensitisation. In developed countries such as the US, hydrops fetalis and kernicterus have decreased markedly in frequency as a result of these preventive measures.
Rh incompatibility can cause symptoms ranging from very mild to fatal. In its mildest form, Rh incompatibility causes destruction of red blood cells.
Symptoms may include:
Jaundice, Hypotonia, Motormental retardation, Polyhydramnios (before birth)
Since Rh incompatibility is almost completely preventable with the use of RhoGAM, prevention remains the best treatment. Treatment of the already affected infant depends on the severity of the condition.
Rh incompatibility is almost completely preventable. Rh-negative mothers should be followed closely by their obstetricians during pregnancy. If the father of the infant is Rh-positive, the mother is given a mid-term injection of RhoGAM and a second injection within a few days of delivery. These injections prevent the development of antibodies against Rh-positive blood. This effectively prevents the condition.
In February 1997, a research team at the Roslin Institute in Edinburgh, Scotland, headed by Dr. I. Wilmut, reported (in the 27 February 1997 issue of Nature) that they had succeeded in producing a healthy lamb, named Dolly, from the nucleus of a cell taken from an adult sheep.
The cells in an adult are descended from the fertilised egg and have been produced by mitosis.
So each cell in the adult would be expected to carry the complete diploid complement of genes of the organism.
Back in the 20s, the German experimental embryologist Hans Spemann showed that even after 5 divisions of the fertilised egg, the nuclei retained the potential to program the complete development of an adult. Using strands of baby hair, he tied loops around fertilized amphibian (newt) eggs so that they were constricted into two halves with the nucleus confined to one half and a narrow bridge of cytoplasm connecting the two halves.
Spemann found that at first only the half containing the zygote nucleus would divide by mitosis. Eventually a nucleus would cross into the other half and it, too, would begin dividing. So long as both halves contained some of a cytoplasmic region called the gray crescent, the second half would then go on to develop into a second perfectly-formed embryo.
Spemann's results suggest, then, that cloning should be possible. Genetically-identical nuclei should be able to produce genetically-identical individuals. And, of course, that is what occurs in human identical twins, triplets, etc. They are "miniclones".
Since Spemann's time, the development of micromanipulators has made it possible to remove nuclei from cells. To test the developmental potential of these nuclei, they can then be injected into "enucleated" eggs; that is, eggs whose own nucleus has been removed or destroyed. Using this technique (called somatic-cell nuclear transfer or SCNT), it was found that the nucleus of any of the thousands of cells of the frog blastula is able to guide perfectly normal development when transplanted into a frog egg lacking its own nucleus.
Furthermore, when a transplanted nucleus has programmed the formation of a new blastula, the cells of the new blastula can then serve as the source of identical nuclei to use to form a clone of genetically-identical tadpoles.
Up to now, adult cells have not worked. When nuclei from adult frog cells are transplanted into enucleated eggs, the results have not been so successful. Many of the resulting embryos are abnormal and stop developing. Despite years of effort, no adult frogs have been produced by nuclei transplanted from adult frog cells. (However, some other animals have been successfully cloned using nuclei from adult cells.
No one knows for certain. But what is known is that during development, the DNA of differentiated cells does change — not in its sequence — but in its ability to be expressed (transcribed). The DNA becomes chemically altered. As many as 8% of the cytosines (C) in an organism's DNA become methylated. Genes containing methylated DNA are inactive. So it appears that although every cell in the adult organism contains the entire genome, many of the genes can no longer be expressed.
What Dr. Wilmut's group has done is find a way to unlock the full potential of gene expression in the nuclei of cells taken from an adult mammal. They do not know the biochemical basis of their achievement, but this is how they did it.
Enucleate the eggs produced by Scottish Blackface ewes (female sheep). Then treat the ewes with gonadotropin-releasing hormone (GnRH) to cause them to produce oocytes ready to be fertilised. Like all mammals, these are arrested at metaphase of the second meiotic division (meiosis II). After that plunge a micropipette into the egg over the polar body and suck out not only the polar body but the haploid pronucleus within the egg. Then, fuse each enucleated egg with a diploid cell growing in culture.
Cells from the mammary gland of an adult Finn Dorset ewe (they have white faces) are grown in tissue culture. Five days before use, the nutrient level in the culture is reduced so that the cells stop dividing and enter G0 of the cell cycle. Donor cells and enucleated recipient cells are placed together in culture. The cultures are exposed to pulses of electricity to cause their respective plasma membranes to fuse and to stimulate the resulting cell to begin mitosis (by mimicking the stimulus of fertilisation).
Culture the cells until they have grown into a morula (solid mass of cells) or even into a blastocyst (6 days).
Transfer several of these into the uterus of each (of 13, in this case) Scottish Blackface ewes (previously treated with GnRH to prepare them for implantation. Wait (with your fingers crossed).
The result: one ewe gave birth (148 days later) to Dolly.
What made Dolly different?
The Wilmut group also used the same technique to produce healthy lambs using cells from lamb embryos (9 days after fertilisation) and lamb foetuses (26 days after fertilisation). But in these experiments, there was no way to know the phenotype of the nuclear donor because it had not yet been born. So, too, the recent cloning of monkeys from embryo nuclei represents simply an expansion of nature's ability to produce identical twins, etc. whose traits we will not know until they are born and grow up. But the nucleus that made Dolly came from an adult animal whose phenotypic traits were there to be seen.
How do we know that Dolly is not the progeny of an unsuspected mating of the foster mother?
She has a white face and the foster mother is a Scottish Blackface
DNA fingerprinting reveals bands found in Finn Dorset sheep (the breed that supplied the mammary cells), not those of Scottish Blackface sheep. Some scientists have argued that Dolly could have come from a feetal cell that contaminated the mammary gland tissue culture (the cell donor was pregnant at the time). However, two groups have reported (in the 23 July 1998 issue of Nature) that DNA fingerprinting proves that Dolly has a genome identical to the cultured cells and the Finn Dorset ewe that supplied them
Cloning other mammals by somatic-cell nuclear transfer (SCNT)
Since the arrival of Dolly, somatic-cell nuclear transfer (SCNT) has been used to produce seemingly-healthy cows, mice, rats, goats, pigs, rabbits, cats, a mule ("Idaho Gem"), a horse, and a dog.
So what about the prediction (above) that humans will not be cloned from adult cells?
Don't count on it. Great interest is being shown in using somatic-cell nuclear transfer to create embryonic stem cells that could be used to replace missing or defective cells in the body of the nuclear donor.
But the same blastocysts could, in theory, instead be implanted in a uterus to produce a foetus that was a clone of the cell donor.
But keep in mind that humans are not sheep, cows, or mice. In humans, nuclear genes take over earlier in development (at the 4-cell stage) than they do in cattle and sheep (8 cells). Perhaps there will not be enough time for the DNA from an adult human cell to be reprogrammed so that all its genome can once again be expressed.
In monkeys (and presumably in humans), removal of the resident nucleus also removes essential components of the centrosome. Although insertion of the donor nucleus triggers mitosis, the spindles are defective and the resulting cells become aneuploid; that is, fail to receive a correct complement of chromosomes.
Despite these concerns, a group of South Korean scientists have tried to produce cloned human blastocysts by somatic cell nuclear transfer (SCNT) using nuclei from adult human skin cells and placing these in eggs from unrelated women. The blastocysts were to be a source of embryonic stem cells with no attempt made to implant them to create a baby. However, their claims of success appear invalid.
Posted by rozaini at 11:28 PM
Oct 18, 2009
http://www.scribd.com/doc/21252288 (Paper 1)
http://www.scribd.com/doc/21252306 (Answer P1)
http://www.scribd.com/doc/21252342 (Paper 2)
http://www.scribd.com/doc/21252377 (Answer P2)
http://www.scribd.com/doc/21252467 (Paper 3-Edited)
http://www.scribd.com/doc/21252503 (Answer P3)
Posted by rozaini at 10:28 PM
Oct 17, 2009
Michael Jackson's This Is It Production year: 2009 Country: USA Directors: Kenny Ortega Cast: Michael Jackson More on this film This Is It, directed by Jackson's creative partner and tour co-ordinator, Kenny Ortega, will be released for a limited two-week period. Billed as a rare, behind-the-scenes portrait of the singer, the film will chronicle the period from April to June 2009, during which Jackson was rehearsing for his proposed 50-date O2 Arena stint, due to begin in July.
Ortega, who has also directed the High School Musical films, said: It's a very private, exclusive look into a creative genius's world. This Is It may go down as the greatest concert that no one got a chance to see, but with this film, we get a rare portrait of Michael as he prepares for his final curtain call and what I believe was going to be his master work."
Posted by rozaini at 12:52 PM
Let's try to answer Trial P1, P2 and P3 2008 from MRSM.
http://www.scribd.com/doc/21201465 (Paper 1)
http://www.scribd.com/doc/21201543 (Paper 2)
http://www.scribd.com/doc/21201592 (Paper 3)
Posted by rozaini at 12:27 PM
Oct 15, 2009
http://www.scribd.com/doc/21094284 (Paper 1)
http://www.scribd.com/doc/21094346 (Paper 2)
Here's the Kedah Trial Biology STPM.
If any students/teachers who have the Trial Biology STPM from other states, please e-mail me.
Thanks..and Good luck
Posted by rozaini at 10:35 AM
Oct 14, 2009
Posted by rozaini at 10:52 PM
http://www.scribd.com/doc/21055338 (Chapter 1)
http://www.scribd.com/doc/21055421 (Chapter 2)
http://www.scribd.com/doc/21055483 (Chapter 3)
http://www.scribd.com/doc/21055515 (Chapter 4)
http://www.scribd.com/doc/21055556 (Chapter 5)
http://www.scribd.com/doc/21055623 (Chapter 6)
http://www.scribd.com/doc/21055715 (Chapter 7)
Posted by rozaini at 10:23 PM
Oct 13, 2009
Waiting for Soo Choon Jian to share with me...
No news till now..
Many F1 students ask for the Science revision exercise so that they can prepare well for the coming final exam.
Here are all the Science Revision Exercises which I've compiled.
Try this and I'm very sure you'll get flying colours for the Science Final Exam.
http://www.scribd.com/doc/20996879 (Chapter 1)
http://www.scribd.com/doc/20996924 (Chapter 2)
http://www.scribd.com/doc/20996960 (Chapter 3)
http://www.scribd.com/doc/20996991 (Chapter 4)
http://www.scribd.com/doc/20997012 (Chapter 5)
http://www.scribd.com/doc/20997047 (Chapter 6)
http://www.scribd.com/doc/20997077 (Chapter 7)
Posted by rozaini at 10:56 PM
Oct 12, 2009
Let's try to answer the objective questions.
Refer the answer when you have finished.
Try your best.
Posted by rozaini at 12:22 AM
The Form 4 students can try this as a practice for your coming exam.
The Form 5 students can also try this as a preparation for your SPM.
Answers are included for your reference.
Posted by rozaini at 12:18 AM
Oct 11, 2009
Oct 10, 2009
Photosynthesis takes place in the chloroplast. Photosynthesis occurs in 2 stages. The light reaction and the dark reaction. Light reaction occurs in the grana of the chloroplast. Light is absorbed by chlorophyll. Then it excites the electron in the chlorophyll. Electrons go through a transfer system and produce ATP. Light energy also split water molecules into hydrogen ions and hydroxyl ions (photolysis of water). Oxygen is released as by product.
Dark reaction occurs in the stroma of the chloroplast without the presence of sunlight. ATP and hydrogen (from photolysis of water) are used to reduce carbon dioxide into glucose. Glucose produced will be converted to starch and stored or transformed into sucrose and transported or used for synthesis of cellulose or converted to amino acids and fatty acids.
Posted by rozaini at 12:06 AM
Oct 9, 2009
Commensalism - interaction between one organism (commensal) benefits and the other (host) neither benefits nor harmed
Epizoics - animals which live as commensals on the outside of other animals
Epiphytes - plants which grow on the surface of other plants to obtain sunlight and air (do not absorb food)
Parasitism is an interaction between two organisms in which one organism (parasite) benefits and the other (host) is harmed.
Ectoparasites - parasites which live on the outside of the host
Endoparasites - parasites which live inside their hosts
The host suffers from malnutrition.
Mutualism - an interaction between two organisms in which both benefit
Saprophytism - a type of interaction in which a living organism obtains food from the dead and decaying remains of other organisms
Saprophytes - plants which feed on decaying matter
Saprozoic - animals which feed on decaying organic matter
Prey-predator - interaction between a predator which hunts and eats another animals (prey).
Intraspesific - among the same species
Interspecific - among different species
Posted by rozaini at 4:35 PM
Posted by rozaini at 3:53 PM
Students should try to answer the 2008 questions also coz sometimes the questions can also be tested this year.
Posted by rozaini at 3:42 PM
Oct 6, 2009
The pioneer species of a mangrove swamp are the Sonneratia sp. and Avicennia sp.
Posted by rozaini at 10:50 PM
Mangrove swamps are mostly found in the tropical and subtropical region where fresh-water meets salt water.
They have muddy soft soil and are a hostile environment for normal plants. This is because the soil has very low levels of oxygen and a high concentration of salt.
In addition, mangrove swamps are exposed to high intensities of sunlight and strong winds.
Posted by rozaini at 10:30 PM
An ecosystem is a community of living organisms interacting with one another and with non-living organisms
A habitat is the natural environment in which an organism lives.
A species consists of a group of organisms that look alike and have similar characteristics, share the same ecological niche and are capable of interbreeding.
A population consists of organisms living in the same habitat at the same time.
A community is a natural collection of plant and animal species living within a defined area or habitat in an ecosystem.
The function of an organism or the role it plays in an ecosystem is known as the ecological niche.
Posted by rozaini at 10:11 PM
Oct 5, 2009
Here are some questions for the Form 3 students.
Wanna wish you all good luck and try your best.....
Never say give up....
Posted by rozaini at 11:43 PM
There are some errors in the marking scheme. Please consult your teacher.
Posted by rozaini at 11:06 PM
Posted by rozaini at 11:02 PM
Posted by rozaini at 10:54 PM
Oct 3, 2009
Producer Jerry Bruckheimer brings his first 3-D film to the big screen with G-Force, a comedy adventure about the latest evolution of a covert government program to train animals to work in espionage. Armed with the latest high-tech spy equipment, these highly trained guinea pigs discover that the fate of the world is in their paws. Tapped for the G-Force are guinea pigs Darwin, the squad leader determined to succeed at all costs; Blaster, an outrageous weapons expert with tons of attitude and a love for all things extreme; and Juarez , a sexy martial arts pro; plus the literal fly-on-the-wall reconnaissance expert, Mooch, and a star-nosed mole, Speckles, the computer and information specialist
Posted by rozaini at 2:17 PM
Posted by rozaini at 2:05 PM
Earlier top seed Nikolay Davydenko and third seed Robin Soderling won through to the semi finals. Davydenko defeated Gael Monfils 6-3, 6-3 in one hour 13 minutes and Soderling stopped Tomas Berdych 6-2, 6-2 in one hour four minutes.
Gonzalez wasted no time in opening up a 4-1 lead in the first set. His first serve percentage wasn’t great, it was 59% but he won 81% of those points. Youzhny meanwhile was at a first serve percentage of 68% but was winning77%. The Chilean only needed that one break and he served out the set to love in the ninth game.
In the second set Gonzalez lifted his level and that first serve was at 64% and he was still winning 81% of those points. The Russian’s rate had dropped significantly and he was being put under a lot of pressure with his service games. In the vital seventh game he cracked and Gonzalez was able to pounce and break serve and eventually claim victory.
Verdasco and Gasquet played a highly entertaining match that saw quite a few momentum swings. First Gasquet went up 3-0, Verdasco followed with the next three games as the big crowd lapped up the excitement. The eleventh game saw Gasquet go up 30/0 but Verdasco won the next four points to break. He then managed to hold serve after facing six deuces and five break points. That gave him the set.
The second set went with serve till 3-3 but in the seventh game Gasquet had a terrible service game – he didn’t win a point and dropped it with a double fault. That was the opportunity Verdasco needed and he closed out the match to love with his serve.
Posted by rozaini at 1:58 PM
Oct 2, 2009
Reabsorption occurs along the renal tubule (PCT, LOH,DCT) and the collecting duct.
At the PCT, glucose, amino acids, Na+, Cl- are reabsorbed into blood capillaries through active transport. Water is reabsorbed through osmosis.
At the LOH, water is also reabsorbed through osmosis. Na+ and Cl- are reabsorbed through active transport.
At the DCT, more water, Na+ and Cl- are reabsorbed.
When the filtrate reaches the CD, very little salt (Na+ and Cl-) is left and 99% of water has been reabsorbed. Only little water will be reabsorbed here.
Secretion occurs along the renal tubules and the collecting duct (actively at the DCT). It occurs through PT and AT.
The substances secreted include H+, K+, NH3, urea, creatinine, toxins and certain drugs.
Secretion helps eliminate and increase waste removal.
Urine mainly consists of water, nitrogenous wastes (urea, uric acid), salts (H+, K+, HCO3-), drugs or toxins.
Posted by rozaini at 10:40 PM
Posted by rozaini at 10:23 PM