Different stages of biological method are:
1-Observation:
After determination of any problem observations are made to collect information.
Malaria was a dreadful disease in past. Many peoples die with this. There was no
treatment of malaria. Scientist made following observations in this regard:
i) Malaria and marshy places were some how associated.
ii) Quinine from cinchona bark was an effective remedy for malaria.
iii) Malarial patients always have parasite in their blood.
iv) Drinking marshy water did not cause malaria.
Observations of A.F.A King:
A.F.A King made his observations in 1883. His observations were:
i) People who slept outdoors in open spaces suffered more from malaria than
those who slept indoors.
ii) People who slept under mosquito nets did not suffer from malaria.
iii) Person who slept near smoky fire also did not suffer form malaria.
2-Hypothesis:
Some propositions are made in the light of observations which is called hypothesis.
The characteristics of a good hypothesis are:
i) It is close to observed facts.
ii) The deductions can be drawn from it.
iii) The deductions could be tested experimentally.
iv) Results should be produced. Either positive or negative.
Regarding malaria the hypothesis made was:
“Plasmodium is the cause of malaria”
3-Deduction:
Logical conclusion drawn from hypothesis are called deductions.
Regarding malaria deduction was made:
“If plasmodium is the cause of malaria, then all person ill with malaria should
have plasmodium in their blood.”
4-Experiments:
Experiments are designed to test the deduction.
Regarding malaria scientists examined the blood of 100 healthy persons and 100
affected person.
Experiment of Ronald Ross:
Ronald Ross performed experiments in 1880.
i) He observed that plasmodium was growing and multiplying in the stomach of
female Anopheles mosquito.
ii) Malaria was the disease which has no treatment in those days therefore he
selected sparrows for experiment.
iii) He allowed some mosquitoes to bite a malarial sparrow.
iv) Then he allowed those mosquitoes to bite a healthy sparrow.
v) The healthy sparrow also suffered from malaria.
vi) In this way he proves that plasmodium is the real cause of malaria and
they are transmitted by mosquitoes.
5-Results:
Most the malarial patients had plasmodium in their blood. This experiment verified
the above deduction for malaria.
6-Theory:
When a hypothesis has been proved by consistent results it becomes a theory.
7-Scientific Principal:
When a theory can explain many natural phenomena and consistently supported by
experiments, and also universally accepted by scientists it becomes a scientific
principal.