Exercise 3
The songs of the humpback whale are beautiful collections (collect) of moans and sighs and it is possible to make recordings (record) of these with a microphone. With enough practice (practise), you can listen to a song and tell which year it was sung in and where it came from.
The whales do most of their singing (sing) in the winter season, after their annual migration (migrate) south from the Arctic. It is always the young males who set off first to the tropical breeding areas, and most of the performances (perform) are given by solitary males who are looking for a mate.
The songs all have a definite sequence of parts. This arrangement (arrange) is never changed, and there are clear rules of composition (compose) which must not be broken. There is very little difference (differ) between the songs at the start of a season and those from the previous year. However, over the next few months, the different parts of each song may be swapped, shortened, and alterations (alter)may be made to the notes. During a breeding season, the whales all try to sing the most up-to-date version of the song. This development (develop) is similar to the way human language evolves, with contributions from many members of the population.