Higher Speciation and Evidence for Evolution

Higher Speciation and Evidence for Evolution

Speciation is the process by which one species splits into two or more new species. It typically requires:

1. Geographic isolation: A physical barrier (mountain range, sea, river) separates a population into two groups. Gene flow between the groups stops.
2. Different selection pressures: The two separated populations face different environmental conditions, so different mutations are favoured in each group.
3. Accumulation of genetic differences: Over many generations, allele frequencies diverge as different mutations become common in each population.
4. Reproductive isolation: Eventually the populations become so genetically different that if they meet again, they cannot interbreed to produce fertile offspring — they are now separate species.

Key evidence for evolution:

• Fossil record: Shows gradual changes in organism structure over geological time. Gaps in the fossil record exist because soft-bodied organisms rarely fossilise and not all fossils have been discovered.
• Antibiotic resistance in bacteria: Observed evolution happening in real time over days to weeks — the strongest direct evidence because we can measure allele frequency changes.
• Comparative DNA analysis: Species with more similar DNA sequences share a more recent common ancestor. DNA comparisons have refined and corrected classification systems.
• Homologous structures: Similar underlying bone arrangements in the arms of humans, wings of bats, and flippers of whales suggest all descended from a common ancestor with that limb structure.