Migratory species show clearly how different approaches to the study of biology can be necessary for a full understanding of biological phenomena. Four themes are touched upon, with links to articles that explore them more fully and give concrete examples.
Migration
Many vertebrate and invertebrate species migrate. They need to do this in order to maximise their breeding efficiency. Evolution works by the ‘survival of the fittest’, so individuals who move to the best feeding areas as the seasons change might be expected to be the most successful. Their increased reproductive success will mean that they pass on their genes to the next generation, and over time the whole species might become ‘migratory’. (See ‘Migration’).
Habitat Destruction and Introduced Species
There are thousands of distinct habitats on the planet, and they are all home to many species of animal, plant and micro-organism. Damaging a habitat will sometimes make it useless for migrating species, and if it is in a critical geographical location this can be very serious. If an important feeding or resting place is damaged then an entire migration route can become useless. In extreme cases the loss of just one critical ‘staging-post’ could spell disaster for a whole species. (See ‘Habitat Destruction’).
Genetics
Species change over time by the gradual shifting of gene-frequency within the population. Genes which increase the chances of survival to reproduce successfully will become more common. If these successful genes affect the shape or colour of an animal then the change will be seen in dead ‘museum’ specimens, but if they alter behaviour in some way then change will only be apparent if the animals are carefully studied in the wild. Migratory species require a great deal of time to alter their behaviour, so they cannot respond to the sudden changes that mankind can bring about. (See also ‘Sex and Genetics’).
Animal Senses
Navigation along migratory routes requires sophisticated interpretation of fixed ‘clues’. Vision is obviously useful, and it is something we can easily understand, but what about the ability to detect magnetic fields or the polarisation of light? We are only beginning to appreciate the wide range of ‘environmental clues’ that different animals can use (see ‘Animal Senses’).
There are many other approaches to the study of Biology (see ‘Big Ideas’ for a few more examples). Most issues of ecological concern require an appreciation of their complexity, and a lot of ‘Fish and Insects’ articles attempt to provide the appropriate information.
Other articles by John Blatchford
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