Speciation and extinctionIB MYP Biology: Flashcards

Exam questions on Speciation and extinction

1. About five million years ago, a mountain range slowly rose through the middle of a forest in South America. A single population of tree frogs lived there. The mountains were too high and cold for the frogs to cross, so the frogs were divided into two groups, one on each side. The climate and the insects available as food were slightly different on the two sides.
   Explain why the two groups of frogs may eventually become different species.2 marks
2. The dodo was a large, flightless bird that nested on the ground on the island of Mauritius. Before humans arrived it had no natural predators. After sailors arrived in the 1500s, dodos were hunted for food. The ships also brought pigs, rats and monkeys, which ate the dodos' eggs, and settlers cleared forest for farming. The last confirmed sighting of a dodo was in the 1660s, and the species became extinct.
   Explain why the dodo was especially vulnerable to the new predators.2 marks
3. Scientists surveyed birds in fragments of rainforest in Borneo that were left when the surrounding forest was cleared. They used the same method for one morning in each fragment. A 1 hectare fragment held 8 bird species, a 10 hectare fragment 21 species, a 100 hectare fragment 45 species and a 1000 hectare fragment 70 species. Each fragment was surveyed only once, and the fragments were different distances from the large forest.
   Describe the trend in the number of bird species and suggest one reason for it.3 marks