The Student Room Group

Biology Central Concepts - contains official questions

Rite here goes, im looking at the paper we jus done for Central Concepts Jan 24th 07, if u dont wanna no dont look!

1a)
i) Describe the process of coppicing and explain how it is used in the sustainable management of woodland. (3 marks)

ii) State 2 ways in which managing woodland as a mix of standard and coppiced trees can be of economic benefit to the owner. (2 marks)

b) i) List 3 features of organisms belonging to the Kingodm Fungi. (3 marks)

ii) State 2 features that fungi have in common with plants. (2 marks)

iii) Explain how the fungal decomposition of deadwood is of benefit to the living trees within the woodland. (4 marks)


2a)
i) Name the type of speciation that occurs when there is no geographical barrier to gene flow. (1 mark)

ii) Explain how the fig. supports the hypothesis that the type of speciation named in i) has occured in seahorses. (2 marks)

b) Explain how disruptive selection occurs in seahorse populations. (3 marks)

c) In terms of reproductive potential, explain why it is beneficial for large females to mare with large, rather than small, mates. (2 marks)


3a) Fig. Shows the absorption spectra for 3 different photosynthetic pigments.

i) Explain what is meant by the term photosynthetic pigment. (3 marks)

ii) Using the Fig. Describe the pattern shown by chlorophyll a. (2 marks)

b) Explain the diff between primary and accessory pigments. (2 marks)

c) Describe how light energy absorbed by these photosystems is converted into chemical energy in the light dependent stage of photosynthesis. (8 marks + 1 for Comm)


4a)
i) State the name given to the exchange of segments of chromatids by breaking and rejoining. (1 mark)

ii) Name the stage of the 1st divison of meiosis when the exchange of segements occurs. (1 mark)

iii) Describe the genetic diff between sister and non-sister chromatids. (1 mark)

b) complete the diagram to show four possible gametes formed at the end of meiosis. Using letters Q, q, r, R. (2 marks)

c)
i) Complete the genetic diagram to explain the cross. Use following symbols to represent alleles: A- grey body colour, a - black body colour, B - normal wing shape, b - bent wing shape. (5 marks)

In cross -parental phenotypes: grey body/normal wing x black body/bent wing.

ii) Complete table by calculating expected numbers. (1 mark)

iii) Calculate x2 value for data. (2 marks)

iv) The student concluded the results showed independent assortment had take place.
The critical value of x2 for this investigation with 3 degrees if freedom is 7.82.
Explain whether your answer to c) (iii) supports the students conclusion. (1 mark)


5a)
i) Explain the following terms:
decarboxylation and dehydrogenation. (2 marks)

ii) State the letters of steps in cycle where decarboylation occurs. (1 mark)

b) State the number of ATP molecules made directly per turn of the cycle. (1 mark)

c)
i) State the number of follwing formed in krebs cyle from one molecule of acetyl CoA. Reduced NAD: and reduced FAD: (2 marks)

ii) State where reduced NAD and reduced FAD molecules are reoxidised and describe what happens to the hydrogen atoms. (4 marks)

d) Explain why the build up of fats occurs in the liver of an individual who consumes large amounts of alcohol. (3 marks)


6a)
Diagrams show:
1- Resting potential - there is a +ve charge outside the membrane and -ve inside.
2- Potassium efflux - charge is polarised as -ve charge is now on outside.
3- Sodium influx - now -ve charge is again on the inside. +ve outside.
i) State which of the 3 diagrams of the axon membrane in the Fig. match up to the phases labelled in the diagram. (1 mark)
phase number
A
B
C

ii) With reference to diagram showing action potential explain changes in membrane potential in Fig (explained above). (5 marks)

b) Explain how action potentials are transmitted along a nonmyelinated neurone and describe which parts are diff in myelinated neurones. No credit is given to events at synapse.(7 marks + 1 mark form comm)


7a)
i) Suggest how the dwarf variety may have arisen. (2 marks)

ii) State 2 environmental factors that would need to be controlled during this experiment. (2 marks)

b) With reference to the table describe the effect of the gibbrellin solution on stem elongation in bothe the wild type and dwarf varieties. (5 marks)

c) Explain the diff effects of the gibbrellin soln on stem elongation in these 2 varieties. ( 2 marks)



Does ne1 think this paper was easy and do u think there is a real chance in the exam board lowering the grade boundaries this year becasue i think judging from the majority of peoples responses this was one of the hardest papers people have sat. I no im jus day dreamin but wot do u honestly think will be the boundary for an A.
Reply 1
hm
Reply 2
65/90