end of topic test

1 a Identify the organelle with each of the roles or functions listed below.i site where amino acids are assembled into proteins

_________________________________________________________________________

ii structure regulating exit and entry to a large permanent vacuole

_________________________________________________________________________

iii small spherical sac containing hydrolytic enzyme

_________________________________________________________________________

iv site of carbon dioxide fixation and oxygen gas formation

_________________________________________________________________________

v site of mRNA formation

_________________________________________________________________________

b List any of the organelles you have identified in part a above that are formed or containedby a double membrane.

(7)

2 The following is an account of plant cell walls. Read the text and then fill in the blanks,using the most appropriate term from this list:

impervious plasmodesmata meshwork fibresmicrofibres lignin secondary middle lamellaprimary water cytokinesis cellulose

When a growing plant cell divides on completion of mitosis, a cell wall is laid down across

the old cell, dividing the contents, as part of __________.

In the first step, a gel-like layer of calcium pectate, known as the __________, is delivered

and deposited by vesicles cut-off from the Golgi apparatus and endoplasmic reticulum. These

vesicles coalesce along the midline of the dividing cell. Some of the endoplasmic reticulum of

the parent cell becomes trapped across this layer at various points. These persist and form the

cytoplasmic connections between the new cells, called __________.

Onto this early wall material is added several layers of cellulose microfibres, typically

deposited transversely. They form the __________ cell wall. Then, as the cell enlarges,

microfibres begin to slide past each other as they re-orientate in response to the strains

imposed by the lengthening cell. A __________ of microfibres results.

Subsequently, more layers of __________ are normally added to the inner surface of the wall,

forming __________ cell wall. These additional layers are mostly added after growth in

overall size of the cell nears completion. The combined effect of layers of __________, lying

at different angles, is to increase the strength of the wall. In cells clearly specialised for

Edexcel Biology for AS Dynamic Learning CD-ROM © Hodder Education 2008

4 Biodiversity and natural resourcesEnd-of-topic test


support, the secondary layers become very thick indeed – much of the interior of the cell may

be taken up by wall material. This is the case in the plant cells called __________.

In addition, certain cells’ walls may become impregnated with a complex hydrophobic

material called __________ which further strengthens them. It is the xylem vessels and fibres

that have this addition. Their walls are now more-or-less __________. Consequently, the pits

that form in xylem vessel walls (and are found in many other plant cell walls, too) are the

main channels by which __________ moves from xylem to the living cells of root, stem and

leaves.(12)

3 In an investigation of ion uptake, bean and maize plants were maintained with their roots inculture solutions under aerobic conditions, for a period of four days. The initial concentrationof ions in the culture solution is recorded below, together with the concentrations of the sameions in the root tissue at the end of the period of ion accumulation.

Ion Initial concentration in the medium/mM Concentration in root tissue after 4 days/mM

maize bean

K� 2.0 160 84

Ca2� 1.0 3 10

Na� 0.32 0.6 6

Pi* 0.25 6 12

NO3� 2.0 38 35

SO42� 0.67 14 6

*Pi � inorganic phosphate, which has several ionic forms

data from The Physiology of Flowering Plants by H. Opik and S. Rolfe (2005) CUP, page 119

a The culture solution was kept vigorously aerated throughout the experiment. What was thesignificance of this condition for plant root cells?

b Comment on the concentrations of potassium and nitrate ions recorded above, comparedwith those of the other ions listed.

c Taken as a whole, what does this data suggest to you about the mechanism of ion uptake inplant roots generally?

2 BIODIVERSITY AND NATURAL RESOURCES – END-OF-TOPIC TEST


d At the same time, uptake of water will have occurred from the culture solution into theplants. Contrast the mechanisms of water uptake and ion uptake.

Water uptake:

Ion uptake:

(12)

4 Imagine that a new drug proposed for the treatment of prostate cancer had successfullycompleted the pre-clinical stage of drug testing at the laboratory of the pharmaceutical firmthat discovered it, and that the outcome was promising at this stage.a Outline the procedures of the subsequent three phases of clinical trials that would be

required under UK legislation.

b Identify the main ethical issue that a thoroughly conducted clinical trial raises for themedical profession and society.

(10)



5 By means of succinct definitions and appropriate examples, explain what you understand bythe following terms: a biodiversity

b endemism

c species richness

d genetic diversity.

(12)

6 By reference to examples, explain the concepts of ‘habitat’ and ‘niche’.Habitat:

Niche:

(8)



7 a Explain how the force that carries water up the stem of a plant in the xylem is generated.

b Identify the structural features by which a xylem vessel is adapted for its role as conduit forwater transport.

c What properties of water make possible its movement through the plant in this way?

d Describe the ways in which the structures of fibres and xylem vessels differ.

(12)

8 a What structures are common to animal and plant cells, when viewed by electronmicroscopy?



b Complete the table by listing further differences in structure between plant and animalcells.

(12)

Plant cells Animals cells

cellulose cell wall present no cell wall present

9 a By means of fully annotated diagrams, describe the structure of cellulose.



b Starch is also a polysaccharide made from glucose monomers. List three ways in which thestructure of starch differs from that of cellulose.1.

2.

3.

(12)

10 Read the following report on biological sources of plastics, and then answer the questions byreference to the report and in the light of your own understanding and opinions.

For some time now, alternative sources of oil-based products, particularly plastics, have beensought. The reasons given include the realisation that fossil fuels will eventually run out. Areplant-based products the answer? For example, there is an almost unlimited supply of cheapstarch available from existing crop plants. Can this carbohydrate be used to manufactureplastics?

A bacterium, Alcaligenes eutrophus, has the ability to produce granules of a plastic calledpolyhydroxybutyrate (PHB) and store them in the cytoplasm. The bacterium produces mostPHB when supplied with excess carbohydrate nutrients, but is kept deficient in nitrate andphosphate ions. This natural plastic is held as a food reserve in the cytoplasm, but can beextracted under industrial conditions, and forms a plastic similar to polypropylene. Theaddition of varying amounts of proprionic acid to the medium when Alcaligenes is grown in anindustrial fermenter allows the strength and flexibility of the product to be adjusted.

Unfortunately, production of this plastic is still quite an expensive process, compared withtraditional plastic made from fossil fuels. However, it has been used to manufacture bottles,films and fibres. PHB and its derivatives are strong materials, and they have the addedadvantage of quite speedy biodegradability when discarded in contact with soil micro-organisms.

An alternative source of PHB, from species of flowering plants like oil seed rape that store oilsas food reserves, is under investigation. The ‘weed’ plant thale cress (Arabidopsis thaliana), hasbeen successfully genetically engineered to produce and store granules of plastic in itschloroplasts, in the light. In this case, the genes for PHB synthesis were obtained from thebacterium, Alcaligenes. However, plastics from fossil fuels are still cheaper to produce.

adapted from Microbes in Action by C.J. Clegg (2002) Hodder Murray



5

10

15

20

a The bacterium Alcaligenes eutrophus has the ability to produce PHB whereas thale cress hasto be genetically engineered to do so. What does ‘ability’ imply in this context (lines 6 and20)?

b What role does the PHB molecule fulfil in the metabolism of Alcaligenes eutrophus (line 9)?

c Suggest two advantages of engineering thale cress to produce plastic as an alternative sourceto fossil fuel.

d What economic conditions are most likely to trigger the commercial exploitation of thesenew sources of plastic?

e What is meant by ‘biodegradability’ and why is this an advantage in a plastic product (line16)?

f Suggest a reason why starch from existing plant crops is not readily exploited as analternative source of plastic (line 4).

(12)





11 Below is a tissue map of the stem of the nettle plant (Urtica dioica) seen in transverse section(TS), in which the position of the band of fibres is labelled.

fibres

a Draw and label a representative two of these adjacent fibres as seen in TS.

b Complete the table below to identify three ways in which the structure of parenchyma cells(of pith or cortex) differ from the structure of fibres.

Parenchyma cells Fibres

c Nettle plants may be a source of fibres for making into cloth. Outline three steps in theprocess of obtaining nettle fibres, commenting on the purpose of each step.

1.

2.

3.

(11)

12 Outline an experimental method you are familiar with by which the strength of fibresextracted from the nettle, and from one other plant source, can be reliably compared.

(6)



13 Individual barley seedlings were grown in full light and with roots submerged in aeratedculture solution of variable composition, for a period of six weeks. The condition of the plantsat the end of this period is summarised in the table below.

Culture medium Height of aerial system/cm Comment on growth

complete 50 normal – healthy, green plant

deficient in phosphate ions 32 leaves abnormally dark

deficient in magnesium ions 21 leaves yellowing (chlorotic)

deficient in iron ions 18 leaves yellowing (chlorotic)

deficient in nitrate ions 14 leaves yellowing (chlorotic)

deficient in potassium ions 11 leaves yellow-edged, with dead spots

deficient in calcium ions 4 stunted root and leaf growth

a Describe appropriate laboratory apparatus you might use for the growing of the barleyplants, as outlined in this experiment.

b What changes would you propose to this experiment in order to convince a scepticalobserver that the results where significant and representative?

c Outline the role of calcium ions in plant wall growth that may account for the observedeffects of calcium ion deficiency.

d Nitrates are used by plants to manufacture amino acids. Suggest a hypothesis for theobserved effects of nitrate deficiency on the growth of barley plants.



e Magnesium and iron ions are used by plants to manufacture chlorophyll. Suggest ahypothesis for the observed effects of their deficiency on the growth of barley plants.

f At the six-week stage and when grown in complete culture solution, this variety of barleyhad its full complement of leaves. If maintained under favourable conditions, what wouldyou expect the next stage in the plant’s development to be?

(16)

14 a Indicate by means of a tick or cross which of the followings statements concerningevolution by natural selection are true (✓) and which are false (✘).

It offers an explanation of how new species may arise.

It points out that changes in the environment may favour some individuals but not others.

It observes that improvements in the characteristics of an organism in its life-time are likely to be inherited by at least some of its offspring.

It takes into account overcrowding and competition pressures between individuals.

It claims that natural selection causes variations to occur in a group of individuals.

It takes into account the fact that characteristics can be inherited.

b DDT is an insecticide that was once widely used. In an experiment, an isolated populationof flies was sprayed with DDT, and the survivors were allowed to breed and produce a newgeneration. These offspring were then sprayed and again the survivors allowed to breed.This process was repeated for many generations. At each generation the numbers ofsurvivors was recorded, as shown here.

Generation 5 10 15 20

Survivors 5 34 50 70

Indicate by means of a tick or cross which of the followings statements concerning thesurvival of flies are true (✓) and which are false (✘).

With each generation, the number of DDT-resistant flies increases.

The efficiency of DDT as an insecticide decreases with time.

DDT-resistance is genetically controlled.

The proportion of DDT-resistant flies increased with time.

Individual flies became more resistant to DDT with time.

(11)



15 a Outline the biochemical evidence on which the existence of three major forms of lifecalled ‘domains’ was based.

b Complete the blank spaces in the table of characteristics of the three domains. (8)

Archaeabacteria Eubacteria Eukaryote

ribosomes – size 70S 80S

histones with the nucleic acid absent presentof chromosomes

introns within chromosomes absent absent

plasmids in cytoplasm many present



16 a Outline three reasons in support of our striving to maintain species diversity in the face ofincreasing extinctions, today.1.

2.

3.

b Explain by means of examples the difference between in-situ and ex-situ conservation.In-situ conservation:

Ex-situ conservation:

(12)



end of topic test

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