Which one is right for logistic model for population growth
I. population growth rate increases as the size of population approaches the carrying capacity
II. All individual have same effect on population growth
III. There are unlimited natural resources
IV. As population increases the competition goes on increasing
select the correct combination.

Options

A. I and II
B. only IV
C. IV and III
D. I and III

Answer

To determine the correct statements regarding the logistic model for population growth, let's analyze each of the four statements provided:

### Step-by-Step Solution:

1. **Understanding the Logistic Growth Model**:
- The logistic growth model is characterized by an S-shaped curve, where population growth starts slowly, accelerates, and then slows down as it approaches the carrying capacity of the environment.

2. **Evaluating Statement I**:
- "Population growth rate increases as the size of population approaches the carrying capacity."
- This statement is **incorrect**. As the population approaches the carrying capacity, the growth rate actually decreases due to limited resources.

3. **Evaluating Statement II**:
- "All individuals have the same effect on population growth."
- This statement is also **incorrect**. Different individuals have varying effects on population growth based on their adaptability and reproductive success.

4. **Evaluating Statement III**:
- "There are unlimited natural resources."
- This statement is **incorrect**. The logistic model assumes that resources are limited, which is why the population growth slows down as it approaches the carrying capacity.

5. **Evaluating Statement IV**:
- "As population increases, the competition goes on increasing."
- This statement is **correct**. As the population grows, competition for limited resources such as food and space intensifies.

### Conclusion:
Based on the evaluations:
- The only correct statement is **IV**. Therefore, the correct combination is **IV**.