Which of the following statements is not true ?

Options

A. Life span is the period from birth to the natural death of an organism
B. All small organisms have very short life span
C. Life expectancy is the characteristic of populations
D. Maximum life span is the characteristic of species

Answer

To determine which statement is not true among the given options, we will analyze each statement one by one.

### Step-by-Step Solution:

1. **Understanding Life Span**:
- The first statement claims that "life span is the period from birth to the natural death of an organism."
- This statement is true. Life span indeed refers to the duration of life of an organism from the moment it is born until it dies naturally.

2. **Evaluating Small Organisms**:
- The second statement asserts that "small organisms have a very short life span."
- This statement is not true. While many small organisms may have short life spans, there are exceptions. For example, some small organisms like certain species of tortoises or fish can live for many years. Therefore, life span is not solely determined by size.

3. **Life Expectancy**:
- The third statement mentions that "life expectancy is the characteristic of the population."
- This statement is true. Life expectancy refers to the average number of years a member of a population can expect to live based on statistical averages.

4. **Maximum Life Span**:
- The fourth statement states that "maximum life span is the characteristic of the species."
- This statement is also true. Maximum life span refers to the longest period an individual of a species can live under ideal conditions.

### Conclusion:
- After analyzing all the statements, the second statement, which claims that small organisms have a very short life span, is the only incorrect one.

### Final Answer:
The statement that is not true is: **"Small organisms have very short life span."**

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