AS & A Level Biology - 9700 Paper 2 2009 Summer Zone 1

Fig. 1.1 shows the outline of a ciliated cell from the human gas exchange system.


(a) (i) Inside the ciliated cell in Fig. 1.1, draw the nuclear envelope and a mitochondrion as they would be seen with an electron microscope.
Label these structures. [3]

(ii) Calculate the magnification of the ciliated cell in Fig. 1.1.
Show your working and express your answer to the nearest whole number.
magnification = ................................. [2]

Fig. 1.2 is a drawing of Mycobacterium tuberculosis.


(b) State three structural features that are found in both M. tuberculosis and animal cells, such as the ciliated cell in Fig. 1.1.

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3. .................................................................................................................................................................. [3]

(c) Describe how M. tuberculosis is transmitted from an infected person to an uninfected person.
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Table 1.1 shows the numbers of new cases of tuberculosis (TB) and the death rates from TB in selected countries in 2005. The fatality ratio is the number of deaths as a proportion of the number of new cases.

[Table_1]

(d) (i) Complete Table 1.1 by calculating the fatality ratio for Uganda.
Enter your result in Table 1.1. [1]

(ii) Suggest why fatality ratios are higher in some of the countries shown in Table 1.1 than in others.
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(a) The table below gives some terms that are used in ecology and their definitions. Complete the table.

term	definition
ecosystem	all the organisms and the physical factors that influence them in an area, such as a forest
	a place where an organism lives
community
	role of organism in an ecosystem
	all the organisms of the same species in an ecosystem at the same time

[4]

Fig. 2.1 shows a three-toed sloth, Bradypus variegatus, that lives in forest ecosystems in Central America. The sloths living in these forests form part of the community. Sloths feed mainly on the leaves of many different tree species that grow in the under canopy in the forest. These leaves are rich in cellulose, which is digested by bacteria and other microorganisms in the stomachs of sloths. The main predators of sloths are jaguars, harpy eagles, snakes and humans.

[Image_1: Fig. 2.1 shows a three-toed sloth.]

(b) With reference to the information above,

(i) state the trophic level occupied by the sloth in the food chain;
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(ii) suggest one advantage to the sloth of having bacteria and other microorganisms in its stomach;
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(iii) suggest why there are few predators, such as jaguars and harpy eagles, in the forest ecosystem even though there are many producers, such as trees.
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(a) With reference to Fig. 3.1 and the information above, explain how flatworms survive without a transport system for respiratory gases.
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(b) This flatworm lives in freshwater that has a low concentration of sodium ions. The flatworm's body fluids have a higher concentration of sodium ions than the surrounding water.

(i) Suggest how the flatworm retains sodium ions in its body fluids.
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(ii) State one role of sodium ions in organisms.
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(a) With reference to Fig. 4.1,
(i) name
process A ..............................................................
molecule B ..............................................................
structure C ..............................................................
sequence of bases D .................................. [4]
(ii) state two ways in which the structure of catalase is similar to the structure of haemoglobin and one way in which it differs
structural similarities
1. ............................................................................
2. ............................................................................[2]
structural difference
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(iii) State why it is possible for a catalase molecule to bind to four substrate molecules at the same time.
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(b) The enzyme amylase catalyses the following reaction:
starch + water → maltose
The progress of this reaction may be followed by measuring either the starch concentration or the maltose concentration at intervals of time.
State which chemicals you would use to detect the disappearance of the substrate and the appearance of the product, in order to follow the progress of the reaction.
disappearance of substrate
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appearance of product
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Fig. 5.1 shows part of a transverse section of a leaf.

(a) Explain, in terms of water potential, how water moves from Q to R.
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(b) State and explain three ways in which the structure of xylem vessels is adapted to transport water.
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explanation ....................................................................................................................
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explanation ....................................................................................................................
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3. ....................................................................................................................
explanation ....................................................................................................................
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(a) Fig. 6.1 is an electron micrograph of a cancer cell in the process of dividing by mitosis.

The stage of mitosis visible in Fig. 6.1 is metaphase.

State which features of the cell shown in Fig. 6.1 indicate that it is at metaphase and not at anaphase.
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(b) People who have smoked cigarettes for many years are at risk of developing lung cancer.

Describe how cigarette smoke is responsible for the development of lung cancer.
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(c) Fig. 6.2 shows the change in the percentage of smokers in the male population of the UK between 1950 and 2005. Fig. 6.3 shows the change in mortality rate in the UK in men aged 75 to 84 between 1950 and 2005.


Fig. 6.2 and Fig. 6.3 appear to show that there is no link between the percentage of the population that smoke and the death rate from lung cancer.

Explain why the mortality rate from lung cancer among men increased and then decreased over the period shown in Fig. 6.3, even though the percentage of smokers decreased over the same period of time.
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