Examination Candidate Number: Desk Number: UNIVERSITY OF YORK BSc Stage 1 Degree Examinations 2017-18 Department: BIOLOGY Title of Exam: Animal and Plant Biology Part II Time allowed: 2 hours Total marks available for this paper: 56 Answer all questions in the spaces provided on the examination paper The marks available for each question are indicated on the paper A calculator will be provided For marker use only: 1 2 3 4 5 6 7 8 9 10 For office use only: Total as % DO NOT WRITE ON THIS BOOKLET BEFORE THE EXAM BEGINS DO NOT TURN OVER THIS PAGE UNTIL INSTRUCTED TO DO SO BY AN INVIGILATOR page 1 of 9
Answer all questions in the spaces provided 1. Describe the structure of an arthropod skeleton (4 marks) 2. a) What are the main problems faced by aquatic animals when obtaining oxygen from water? (3 mark) b) In freshwater fish, how do the kidneys contribute to osmoregulation? (1 mark) 3. a) Why is bile required for the digestion of dietary lipids? (4 mark) page 2 of 9
b) Where is leptin produced, and how does it affect feeding behaviour? (2 marks) c) During feeding, how does the gut stimulate the anorexigenic pathway? (2 marks) 4. Describe the hormonal control of spermatogenesis in humans. (6 marks) page 3 of 9
5. A researcher tests the ideal free distribution on a group of doves in an aviary. She sets up two feeding stations and food drops automatically onto two feeding tables for twenty minutes after a bell rings each day. One feeding station (A) drops four millet seeds per second and a second (B) drops twelve. a) If there are 20 birds in the aviary, what is the expected distribution of birds under an ideal free distribution? (1 mark) A: B: b) Towards the end of the feeding period the observed distribution of birds was in fact as shown below. Use the formula below to test if this is different from the expected distribution. (2 marks) A: 10 B: 10 Chi-squared = (O E) 2 E The critical value of chi-squared for 1df is 3.84 page 4 of 9
c) Suggest two reasons for the discrepancy between the observed and expected values (2 marks) 6. a) The bower of a male bower-bird is an impressive animal display. Explain how such a display might be selected for. (2 marks) b) Tinbergen would have categorized the above explanation as functional. Give two other broad categories of explanation for why bower-birds make bowers (2 marks) c) Outline a potential explanation using one of the broad categories in b) above. (2 marks) page 5 of 9
7. Bromus rubens is an annual grass species invasive to the Mohave desert where it has drastically altered the native plant community since its introduction there in the 1970s as a forage plant. Ecologists have collected data from a number of sites in the Mohave desert to determine the biotic and abiotic effects of B. rubens invasion. This data is summarised in the table below. Average plant species richness (species/100 cm 2 ) Inter-fire period (years) Average total aboveground plant biomass (g/m 2 ) Sites with B. rubens Sites without B. rubens 2.5 7 250 6.5 39 52 a) What term is given to species that actively shape their physical environment? (1 mark) b) Using data given in the table above, discuss the impact of B. rubens invasion on the native plant community and suggest the mechanism involved. (3 marks) page 6 of 9
c) Ecologists found that when B. rubens plants are manually removed from plots, native plant species richness increases considerably. Discuss how the removal of this invasive species impacts upon the realised niches of these native species? (2 marks) 8. A team of ecologists study the growth of a willow tree population on a newly colonised area of land. Over the 10 years that they study the site the willow population increases exponentially. Draw a graph in the space below to demonstrate the predicted growth of the population over the next 10 years as it approaches the carrying capacity of the environment (K). Explain why this is an oversimplification of population growth. (3 marks) page 7 of 9
9. Our understanding of the species richness of oceanic islands has been informed by MacArthur and Wilson s theory of Island Biogeography. Describe and explain how island area and isolation are related to species richness. (4 marks) the space above this line should be sufficient for your answer page 8 of 9
10. The pitcher plant Sarracenia alata is a carnivorous plant that appears to benefit from consuming insects in nutrient poor soils. S. alata grows in habitats that are prone to fires. Burning releases nutrients into the soil. After long periods without a fire the amount of nutrients in the soil is greatly reduced. S. alata produces seeds that are resistant to fire. a) Suggest a simple experiment that would test whether carnivory is a successful adaptation for S. alata in its natural habitat. (3 marks) b) Suggest one way that non-carnivorous plants might be adapted to nutrient poor soils. (2 marks) c) In a period where there are no fires, explain which plants are more likely to benefit? (2 marks) d) Briefly explain how S. alata and non-carnivorous plants avoid competition in this habitat. (3 marks) page 9 of 9