The morphological species concept defines a species as a group of organisms that share the same observable physical features: their morphology. These features include body shape, size, structure, colour and patterns such as the arrangement of veins in a leaf or the number of segments in an insect's leg.When a new species is described, a preserved reference specimen, the type specimen, is kept in a museum. Other specimens are identified by comparing their features with the type specimen and its written description.This was the concept used by Linnaeus, and it is still very widely used, because it has clear advantages:
• it is quick and needs no special equipment
• it can be applied to fossils and to preserved or dead specimens, which cannot breed
• it can be applied to organisms that reproduce asexually.However, appearance does not always match species:
• males and females of one species can look very different, called sexual dimorphism. A male mallard duck has a green head, while the female is mottled brown.
• different life cycle stages look nothing alike. A caterpillar (a larval stage) and an adult butterfly are the same species.
• some organisms that look identical cannot interbreed. These are called cryptic species. For example, two species of pipistrelle bat in Britain look almost the same and were only separated when their echolocation calls and DNA were studied.
• it is quick and needs no special equipment
• it can be applied to fossils and to preserved or dead specimens, which cannot breed
• it can be applied to organisms that reproduce asexually.However, appearance does not always match species:
• males and females of one species can look very different, called sexual dimorphism. A male mallard duck has a green head, while the female is mottled brown.
• different life cycle stages look nothing alike. A caterpillar (a larval stage) and an adult butterfly are the same species.
• some organisms that look identical cannot interbreed. These are called cryptic species. For example, two species of pipistrelle bat in Britain look almost the same and were only separated when their echolocation calls and DNA were studied.