Which one of the following statements about variations is not true ?

Variation is the difference in DNA among individuals or populations. Statement 1 is true because asexual reproduction produces offspring that are genetically identical or very similar to the parent, resulting in minimal variation [1]. Statement 3 is true as changes in genetic constitution, such as mutations and recombination, are the primary sources of variation [5]. Statement 4 is true because environmental factors act as a selective pressure, favoring variants that are better adapted to their surroundings [5]. However, Statement 2 is false. Not all variations have equal chances of survival; some variations may be lethal or disadvantageous, leading to the death of the individual, while others provide a survival advantage in specific environments [5]. Natural selection specifically filters these variations based on their fitness and the survival benefits they provide [5].

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 8: Heredity > p. 128
2. [2] Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 2: PLANT AND ANIMAL KINGDOMS > the contribution of charles Darwin > p. 3
3. [3] Science , class X (NCERT 2025 ed.) > Chapter 8: Heredity > What you have learnt > p. 133
4. [5] https://www.sciencedirect.com/science/article/pii/B9780443219801000097