3.1 Biodiversity and evolutionIB Environmental Systems and Societies HL: Subtopic test

1. 1
   The cheetah (Acinonyx jubatus) has very low genetic diversity compared with most other large mammals. Genetic evidence indicates that cheetah populations passed through a severe reduction in numbers in the past, so that today individuals are genetically very similar to one another. Captive cheetah populations have suffered high juvenile mortality and have been badly affected by disease outbreaks. Conservationists are now managing small, separated populations in Africa.

   (a)

   The lack of variation between individual cheetahs is an example of low diversity at which level?

   [1 mark]

   • AGenetic diversity
   • BSpecies diversity
   • CEcosystem diversity
   • DHabitat diversity

   (b)

   [HL] Which process is the original source of new alleles in a population?

   [1 mark]

   • ASexual reproduction
   • BNatural selection
   • CMutation
   • DReproductive isolation

   (c)

   [HL] Explain how sexual reproduction would increase genetic diversity in a recovering cheetah population.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   In Gorongosa National Park, Mozambique, a civil war (1977 to 1992) was accompanied by heavy poaching of elephants for ivory, and the park's elephant population fell by about 90%. Before the war roughly one in five female African elephants (Loxodonta africana) in the park lacked tusks. Among the females that survived the war, roughly half lacked tusks, and tuskless mothers were more likely to have tuskless daughters. The trait is inherited.

   (a)

   Which of the following must be present in a population for natural selection to occur?

   [1 mark]

   • AIdentical alleles in all individuals
   • BInherited variation in characteristics that affect survival and reproduction
   • CUnlimited food and other resources
   • DTransmission of characteristics acquired during life

   (b)

   [HL] Which was the main selective force acting on the female elephants in Gorongosa?

   [1 mark]

   • ACompetition between elephants for water
   • BDisease outbreaks
   • CMutation
   • DHuman poaching for ivory, which favoured survival of tuskless females

   (c)

   [HL] Explain how poaching led to an increase in the proportion of tuskless females in Gorongosa.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A class sampled gastropods in quadrats of equal total area on two rocky shores. Both shores have four species (common periwinkle, flat periwinkle, dog whelk and limpet) and 30 individuals were counted on each. Shore X: 12, 8, 6 and 4 individuals of the four species. Shore Y, next to a harbour: 27, 1, 1 and 1 individuals. The class wants to compare the diversity of the two shores and to monitor them over several years.

   (a)

   Calculate Simpson's reciprocal index for Shore X. Show your working.

   [3 marks]

   (b)

   The index for Shore Y is 1.2. Explain what the two indices show about the shores and outline how the class could use the index to monitor Shore Y.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   About 66 million years ago an asteroid impact and associated volcanic activity caused a mass extinction in which roughly three-quarters of plant and animal species, including all non-avian dinosaurs, disappeared. Fossils in rock layers above this boundary show that mammals, which had been small and mostly nocturnal, diversified rapidly into many new forms over the following several million years. Earth is about 4.5 billion years old. Some scientists now argue that human activity is changing Earth so rapidly that a new geological epoch, the Anthropocene, should be recognised, and that evidence of it, such as plastics, radioactive isotopes from nuclear weapons testing and a high rate of species extinction, will be detectable in future rock layers.

   (a)

   [HL] Explain how processes acting over Earth's history have led to the evolution of life and how mass extinctions affect later biodiversity.

   [6 marks]

   (b)

   [HL] Evaluate the case for recognising the Anthropocene as a new geological epoch.

   [6 marks]

   Total for question 4: 12 marks

End of questions