Class 9 Biology Notes Chapter 2 – Solving a Biological Problem



Question#1) Define science and Scientific method?


Answer; Science: word science is derived from scientia means knowledge.

Science is the systemized knowledge derived from observations and experiments.


The knowledge that gives understanding about this world and how it works is called science.


The systemized knowledge obtained by observations and experiments is called science.

Scientific method: A way to gather information and answer questions in science is called scientific method.   “OR”   A method used by scientists to solve scientific problems is called scientific method.    “OR”   The scientific method is a process for experimentation that is use to explore observations and answer questions.


Question#2) Define biological method? What is the importance of biological method?

Answer: Biological method: The scientific method in which biological problems are solved is called biological method.  OR  “A method used by biologists to solve biological problems is called biological method.


Importance of Biological method: Biological method is the best to obtain reliable knowledge about biology. It comprises all the steps a biologist adopt in order to solve a biological problem. Biological method contribute to advancements in all biology related fields like medicine, ecology, biotechnology, etc. Biological method also ensures the quality of data for public use.


Question#3) Define biological problem?

Answer: Biological problem: A biological problem is a question related to living organisms that is either asked by some one or comes in biologist’s mind by himself. The problem faced by a biologist during biological experiments , study or research is called biological problem.


Question#4) What are the basic steps to solve a biological problem? OR what are the basic steps of a biological method?

Answer: Steps of a biological method  “OR”  Steps to solve a biological problem: Following are the basic steps a biologist can adopt during his research work or during a biological method.


1• Recognition of biological problem

2• Observations

3• Hypothesis formulation

4• Deductions

5• Experimentation

6• Summarization of results (create tables, graphics etc)

7• Reporting the results


Man has always been a biologist. He had to be a biologist in order to live. Early in history, he was a hunter of animals and a gatherer of fruits, seeds, roots etc. The more he knew about animals and their habitat, the more successful hunter he was. The more he knew about plants, the better he distinguished between edible and non-edible plants.


Darwin not only observed and took notes during his voyage, but he also read the works of other naturalists to form his theory of Evolution.


1• Recognition of biological problem: Biologists go for adopting biological method when they encounter some biological problem. A biological problem is a question related to living organisms that is either asked by some one or comes in biologist’s mind by himself.


2• Observations: The act of noticing something is called observation. As the first step in solving a biological problem, biologist recalls his/her previous observations or makes new ones. Observations are made with five senses of vision, hearing, smell, taste and touch. Observations may be both qualitative and quantitative.


  • Quantitative observations:Observations that are measureable are called Quantitative observations. E.g: size of the plants, number of petals, etc.


  • Qualitative observations: Observations that are descriptive and non measureable are called qualitative observations. E.g, color of flower, taste , etc.


Qualitative observations Quantitative observations

• The freezing point of water is colder than the boiling point.

• A liter of water is heavier than a liter of ethanol.


• The freezing point of water 0 oC and the boiling point is 100 0C0.

• A liter of water weighs 1000 grams and a liter of ethanol weighs 789 grams.


  1. Formulation of Hypotheses: Tentative explanation of observations is called a hypothesis. A hypothesis may be a prepositions that might be true. A scientist is seeking. His hypothesis may be true or false. But he accepts it to be true. A hypothesis is a possible answer to a biological(scientific) problem(question). A hypothesis is an educated guess or statement made by biologist about a certain process on the basis of available information.


  • Characteristics of a good hypothesis:A hypothesis should have the following characteristics:
  • It should be a general statement.
  • It should be a tentative idea.
  • It should agree with available observations.
  • It should be kept as simple as possible.
  • It should be testable and potentially falsifiable. In other words, there should be a way to show the hypothesis is false; a way to disprove the hypothesis.

A great deal of careful and creative thinking is necessary for the formulation of a hypothesis. Biologists use reasoning to formulate a hypothesis.



Logical conclusion drawn from hypothesis are called deductions. At this step hypothesis is taken as true and expected results (deductions) are drawn from it. Deductions involves the use of “if-then” logic.

Regarding malaria deduction was made:

“If plasmodium is the cause of malaria, then all person ill with malaria should

have plasmodium in their blood.”


Biologists can’t usually check every situation where a hypothesis might apply. Let’s consider a hypothesis:

“All plant cells have a nucleus”. Biologist cannot examine every living plant and every plant that has ever lived to see if this hypothesis is false. Instead, biologists generate deduction using reasoning. From the above hypothesis, a biologist can make the following deduction: “If examine cells from a blade of grass, then each one will have a nucleus”.

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