What Is Unity and Diversity in Biology?
Definition
Unity
Shared biological features found across all living organisms.
Definition
Diversity
Differences in traits between organisms or species.
- Life shows unity because all organisms descend from ancient common ancestors.
- Life shows diversity because species adapt to different environments over millions of years.
Why Do Living Things Share So Many Similarities?
- Core biological processes evolved early and were so successful that evolution conserved them.
- Even very different organisms rely on the same basic chemistry and cellular structures.
Example
- Deeply conserved features:
- DNA is used as the universal genetic material.
- ATP is the main energy-carrying molecule in all cells.
- Cell membranes are built from phospholipids across all domains of life.
- Enzymes control chemical reactions using similar mechanisms.
- Cell division follows shared patterns that ensure accurate genetic transfer.
Common Mistake
- Conserved does not mean “unchanged.”
- It means only a narrow range of changes remain functional.
How Does Evolution Create Diversity While Keeping Core Features the Same?
- Evolution modifies existing structures rather than creating new ones from scratch.
- This produces new adaptations but keeps fundamental frameworks intact.
Example
- Vertebrate limbs
- Unity: All vertebrates share the same basic limb pattern (one upper bone, two forearm bones, wrist, digits).
- Diversity:
- Fish → fins
- Birds → wings
- Humans → arms
- The underlying structure stays the same, but its form and function change.
What Processes Generate Biological Diversity?
- Diversity arises because populations experience different pressures and random changes over time.
- Mutation introduces new genetic variation.
- Natural selection favours traits that improve survival or reproduction.
- Genetic drift spreads traits by chance, especially in small populations.
- Environmental differences create different challenges that select for different adaptations.
Example
- Polar bears, grizzly bears, and sun bears share a common ancestor.
- Each species adapted to its environment, developing differences in fur, behaviour, and diet.
How Do Classification Systems Show Unity and Diversity?
- Classification groups organisms based on shared characteristics.
- Broad groups show unity as organisms share fundamental traits.
- Narrow groups show diversity as species differ in adaptations and behaviour.
Hierarchy of Classification
- Recall the hierarchy runs from: Domain → Kingdom → Phylum → Class → Order → Family → Genus → Species
- Unity example: All animals are multicellular and obtain food by feeding.
- Diversity example: Lions and tigers share many features but differ in habitat, behaviour, and adaptations.
Self review
- Why does common ancestry lead to shared biological features?
- What makes some traits highly conserved across evolution?
- How does natural selection create diversity while keeping core structures the same?
- How can the same basic limb structure produce different adaptations in different species?
