Speciation and extinctionIB MYP Biology: Subtopic test

1. 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.

   (a)

   What term describes the separation of the frog population by the mountain range?

   [1 mark]

   • AGeographical isolation
   • BMutation
   • CExtinction
   • DInterbreeding

   (b)

   Which definition of a species is correct?

   [1 mark]

   • AA group of organisms that live in the same place
   • BA group of organisms that look identical
   • CA group of organisms that can interbreed to produce fertile offspring
   • DA group of organisms that eat the same food

   (c)

   Explain why the two groups of frogs may eventually become different species.

   [2 marks]

   Total for question 1: 4 marks

2. 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.

   (a)

   What does the word extinct mean?

   [1 mark]

   • AThere are fewer than a thousand individuals of the species
   • BNo individuals of the species remain alive anywhere
   • CThe species has moved to a different habitat
   • DThe species only survives in zoos

   (b)

   The pigs and rats ate the dodos' eggs. Which cause of extinction does this show?

   [1 mark]

   • AClimate change
   • BHabitat loss from forest clearance
   • CDisease
   • DNew predators

   (c)

   Explain why the dodo was especially vulnerable to the new predators.

   [2 marks]

   Total for question 2: 4 marks

3. 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.

   (a)

   Describe the trend in the number of bird species and suggest one reason for it.

   [3 marks]

   (b)

   A student concludes that clearing forest causes extinction of birds. Evaluate how well the data support this conclusion and suggest one improvement to the method.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   Fossils show that there have been five mass extinctions in the last 500 million years, each wiping out more than half of all species. Many scientists now warn that human activities are causing a sixth. A government in South-East Asia is deciding whether to ban the clearing of a large area of rainforest for palm oil plantations. The forest is home to many species found nowhere else, but the plantations would employ thousands of local workers.

   (a)

   Explain how an asteroid impact about 66 million years ago caused a mass extinction, and how life recovered afterwards.

   [6 marks]

   (b)

   Discuss and evaluate whether the government should ban the clearing of the rainforest for palm oil. Give a justified conclusion.

   [6 marks]

   Total for question 4: 12 marks

End of questions