7.8 Continuing Evolution
- Syllabus
- 2025
- Topic
- 7.8
- Level
- —
Learning objectives
Why Evolution Is Still Happening
All species have evolved and continue to evolve. Heritable variation persists or arises, environments keep changing, and variants differ in reproductive success, so the genetic makeup of populations can keep changing across generations.
| Ongoing-evolution evidence | What the change shows |
|---|---|
| Genomic changes over time | Population DNA changes can be tracked across generations |
| Continuous change in the fossil record | Organismal forms have continued to change through Earth history |
| Resistance to antibiotics, pesticides, herbicides, or chemotherapy drugs | Treatment creates selection pressure that changes the representation of resistant variants |
| Pathogens causing emergent diseases | Pathogen populations evolve traits that can alter transmission, host interaction, or disease patterns |
A population contains variation → a drug or pesticide removes more susceptible individuals → resistant variants survive and reproduce more successfully → resistance-associated variation becomes more common in later generations.
These examples occur at different time scales, but each records the same defining feature: inherited population characteristics are not fixed. Past fossil transitions and present genomic or resistance changes are parts of one continuing evolutionary process.
Antibiotics or pesticides do not cause organisms to make a useful mutation because they need it. The treatment is a selective pressure; it increases the relative success of variants that can already survive under that condition.