1. 1 Prepared by; Miss Anzal Faiqa Yousuf (M.Sc. Botany I.U. B)
House #10/C officers Colony Bahawalnagar (Contact # 03338810387) BIOLOGY 9Th
Unit -02 Solving a Biological Problem
Q 1: Describe the steps involved in biological method taking malaria
an example?
Ans: Biological Problem:
Malaria: Malaria is a common disease in many countries including Pakistan. Malaria has
killed more people than any other disease. In ancient times more than 2000 years ago,
physicians were familiar with the disease. It was thought that stagnant water of marshes
poisoned the air as result of breathing in this ‘’bad air’’
People got malaria.
Treatment of malaria:
The bark of the tree quina-quina was very suitable for curing fevers. Cinchona was also
used for the treatment of malaria.
In 1878, a French army physician Leveran began to search for the cause of malaria. He
took a small amount of blood from a malarial patient and examined it under the
microscope. He noticed some tiny living creatures. Three year later it was called
plasmodium.
Observations:
At that time there were four major observations about malaria:
1. Malaria and marshy areas have some relation.
2. Quinine is an effective drug for treating malaria.
3. Drinking the water of marshes does not cause malaria.
4. Plasmodium is seen in the blood of malarial patients.
Hypothesis:
A scientist uses whatever information and observation he has and makes one or more
hypothesis. Plasmodium is the cause of Malaria.
Deduction:
If plasmodium is the cause of malaria then all person ill with malaria should have
plasmodium in their blood.
CH-(02) Long QUESTIONS
2. 2 Prepared by; Miss Anzal Faiqa Yousuf (M.Sc. Botany I.U. B)
House #10/C officers Colony Bahawalnagar (Contact # 03338810387) BIOLOGY 9Th
Experiments:
The next step was to test the deduction through experiments which were designed as
Blood of 100 malaria patients was examined under microscope. For the purpose of
having a control group, the blood of 100 healthy persons was also examined under
microscope.
Result: The result of the experiments showed that almost all malaria patients had
Plasmodium in their blood while 7 out of healthy persons also had plasmodium in their
blood.
Conclusion: The results were quite convincing and proved that the hypothesis
‘’Plasmodium is the cause of malaria’’ was true.
Q 2: Problem 2: How plasmodium gets into the blood of man?
Ans: Observation: Biologists were having following important observations
1. Malaria is associated with marshes.
2. Drinking water of marshes does not cause malaria
3. It can be concluded that plasmodium was not in the marsh water.
In 1883 a physician A. F. A King listed 20 observations.
Some important are given bellow:
1. People who slept outdoors were more likely get malaria than those who slept
indoors.
2. People who slept under fine nets were less likely to get malaria than those who
did not use such nets.
3. Individuals who slept near smoky fire usually did not get malaria.
Hypothesis: Mosquitoes transmit plasmodium and so are involved in the spread of
malaria.
Deductions: If mosquitoes are involved in the spread of malaria then;
Plasmodium should be present in mosquitoes
A mosquito can get plasmodium by biting a malarial patient.
Experimentation: In order to test the above deductions. Ronald Ross a British army
physician working in India in 1880”s performed important experiments. He allows a
female Anopheles mosquito to bite a malaria patient. He killed the mosquito some days
later and found plasmodium multiplying mosquito’s stomach.
3. 3 Prepared by; Miss Anzal Faiqa Yousuf (M.Sc. Botany I.U. B)
House #10/C officers Colony Bahawalnagar (Contact # 03338810387) BIOLOGY 9Th
The next logical experiment was to allow an infected mosquito having plasmodium to
bite a healthy person. If the hypothesis was true, the healthy person would have got
malaria. Next step was to allow the infected mosquito to bite a healthy person. But this
was a risky work as that healthy person can be suffered from malaria. So he selected
sparrows for his experiment. He allowed a female Culex mosquito to bite a malarial
sparrow. Then he allowed those mosquitoes to bite a healthy sparrow. The healthy
sparrow also suffered from malaria.
Result: In this way he proves that plasmodium is the real cause of malaria and they are
transmitted by mosquitoes. In 1898, an Italian biologists performed same experiments on
human beings and find the same results. This confirmed that mosquitoes are involved in
the spread of this disease. When a hypothesis has been proved by consistent results it
becomes a theory.
