With the help of two suitable examples, explain why certain experiences and traits earned by people during their lifetime are not passed on to their next generations. When can such traits be passed on ?

Certain experiences and traits earned by people during their lifetime (known as acquired traits) are not passed on to their next generations because they do not cause any change in the DNA of the germ cells (reproductive cells).

Why they are not inherited:

According to the rules of heredity, only the genetic material (DNA) present in the germ cells is transmitted to the progeny during sexual reproduction. Any change or experience acquired during a lifetime only affects the somatic (non-reproductive) cells of the body. Since somatic cells do not contribute genetic material to the next generation, these changes cannot be inherited.

Two Examples:

1. Learning a skill: If a parent learns to play the violin or speak a foreign language, this knowledge is an acquired experience that does not alter the DNA of their gametes. Consequently, their children will not inherit this skill automatically.
2. Physical injury or modification: If a person loses a finger in an accident, or gets a body piercing, their offspring will still be born with normal limbs and unpierced ears because the DNA in their germ cells remains unaffected.

When can such traits be passed on?

These traits can only be passed on if the change or mutation occurs directly in the DNA of the germ cells (sperm or egg), or if an environmental factor directly alters the genetic makeup of the reproductive cells.