Question

Where do variation in traits within a species come from?


species evolve & develop traits as their surroundings change


there is no variation if it's the same species


the variations are in their DNA

Answer 1

Short answer: Mostly from differences in DNA, plus environmental effects.

More detail:
- Genetic variation (the main source) comes from mutations, sexual reproduction (independent assortment and recombination), gene flow between populations, and chromosomal changes. These create new alleles and different combinations of alleles that cause trait differences between individuals.
- Environmental effects and developmental “noise” can change how genes are expressed, so the same genotype can produce different phenotypes (phenotypic plasticity).
- Evolution (change in trait frequencies over generations) happens when natural selection, drift, migration, or mating patterns act on that variation — organisms do not “decide” new inherited traits in response to the environment.

About your options:
- “The variations are in their DNA” — basically correct, but remember environment also affects traits.
- “Species evolve & develop traits as their surroundings change” — partially true as a population-level outcome (selection changes frequencies), but misleading if taken to mean individuals develop inherited changes at will.
- “There is no variation if it's the same species” — false; most species show lots of within-species variation.