Only Heritable Traits Drive Evolution
- For evolution to occur, traits must be heritable, passed from parents to offspring through DNA.
- Traits that are acquired during an organism’s lifetime, such as muscle growth or injuries, are not inherited and do not contribute to evolution.
A spider that loses a leg does not pass this trait to its offspring because the injury does not affect its reproductive cells.
Exam technique- Don't confuse heritable traits with acquired traits.
- Heritable traits are encoded in DNA and passed to offspring, while acquired traits, like muscle growth from exercise, are not.
Genes, Not Experience, Determine Traits
Definition
Heritability
Heritability refers to the ability of a trait to be passed from parents to offspring through genetic information.
- Heritability refers to a trait's ability to be passed to offspring via genetic material.
- Traits are encoded by genes, which are segments of DNA that determine characteristics.
- Offspring inherit a combination of alleles, forming their genetic blueprint.
Only Genetic Changes in Germ Cells Matter
- Genetic information is passed through germ cells (sperm and egg), not somatic (body) cells.
- Somatic cell changes (e.g., muscle growth, injuries) do not affect DNA in germ cells and are not inherited.
- Only mutations in germ cells can be passed to offspring and influence evolution.
Epigenetics Can Influence Traits, But It Doesn’t Change DNA
- While acquired traits do not alter DNA, environmental factors can sometimes affect gene expression through epigenetic changes.
- Epigenetic tags are chemical markers that influence how genes are expressed.
- A small fraction of these tags can be inherited, but they do not change DNA sequences.
- Epigenetic changes are reversible and not a major driver of evolutionary change.
More on this covered in D2.2.
TipEvolution occurs through changes in DNA sequences, not temporary shifts in gene expression.
Theory of Knowledge- How does the distinction between heritable and acquired traits influence our understanding of human evolution?
- Consider the role of culture and technology in shaping modern humans.
