Recent research has found that on one island of the Galapagos two finch species interbred. This interbreeding may have resulted in a hybrid species that ultimately led to the extinction of one of the species Darwin discovered. They call this speciation in reverse, or despeciation. Based on what you know about speciation, why are these terms appropriate?

Speciation is the method by which unique species evolve from a common ancestor. In this case, two of these species that split from a common ancestor interbred and created a hybrid. This hybrid was apparently stronger and possibly better adapted to the environment, which led to extinction of a species formed by the initial speciation event.

the diploid number of chromosomes is sometimes represented by the symbol 2n. for the fruit fly, the diploid number is 8, which can be written as 2n = 8, where n represents twice the number of chromosomes in a sperm or egg cell.