Seahorses are fish that have an unusual appearance and many specialised adaptations. Fig. 8.1 shows a seahorse. Two species of seahorse, Hippocampus erectus and H. zosterae, are present in the coastal waters of the Gulf of Mexico and the Caribbean Sea. It is believed that these two species of seahorse share a common ancestor. The ranges of the two species overlap in many places. Male and female seahorses stay together for the entire breeding season. H. erectus is much larger than H. zosterae. Very few seahorses are found that are intermediate in size between the two species. Use this information to name and explain the type of speciation that may have happened in the evolution of these two species.
For many years, farmers have used selective breeding to improve the milk yield of dairy cattle and the yield of crops. Explain why selective breeding for higher milk yield in cattle can be harder than selective breeding for higher crop yields.
State two examples of crop characteristics that can be improved by selective breeding to raise crop yield.