Biology · Rung 1 of 4

Heritable variation

Individuals in a population differ. Some differences come from heritable variants; others depend on the environment. Mutations introduce sequence changes and recombination rearranges variants. Their occurrence is not directed at meeting an organism's future need.

Where this sits

Comes after
Inheritance
Opens up
Natural selection

Exercises from this rung

Generated by the app, from easiest to hardest

  1. Is a mutation in a skin cell passed on to the children?

    • No: it belongs to the body, and the gametes do not carry it
    • Only if it is repeated for many generations
    • Yes: it is in the gametes
    • No: it is learned, it is not in the DNA

    Why No: it belongs to the body, and the gametes do not carry it. Children come from an egg and a sperm cell, and whatever happens to the rest of the body, a scar, a muscle, a mutation in the skin, is not copied into them. Weismann docked the tails of mice for twenty generations and every pup was born with a tail.

    easier

  2. Which change can be passed genetically to offspring in sexual reproduction?

    • A skill learned through practice
    • A scar acquired on a leaf
    • A DNA variant in a gamete

    Why To pass through gametes, a variant must be in the genetic material that reaches the new organism. A bodily injury or a learned skill does not thereby become a heritable DNA change.

    in between

  3. Two cuttings from the same plant grow to different heights under different light. What can this observation show?

    • The environment can influence phenotype
    • One cutting must belong to another species
    • Height never has genetic components

    Why Phenotype is the set of observable characteristics, resulting from genotype and its relationship with the environment. This comparison shows environmental influence but does not rule out genetic influence. A visible difference alone does not demonstrate a mutation.

    harder