2008 Bio Prelim P2 Ans

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Methodist Girls’ School Biology (5094) Paper 2 Preliminary Exam 2008

Section A [50 marks] Answer all questions in the spaces provided.

1. The photographs below show cells from an onion root tip undergoing cell division.

(a) Name the phase that is seen in [1]

(i) Fig 1.1 metaphase (ii) Fig 1.2 anaphase

(b) What is the function of the spindle microtubules in cell division? [1]

• Attach to chromosome/centromere • Shorten to move chromosome/chromatid to poles of cell

(c) What is a difference between cell division in plant cells and animal cells? [1]

• No centrioles formed OR

• Cells do not separate during cytokinesis/ vesicles fuse to form cell wall between daughter cells.

[Total :3 marks]

2. (a) What are the major differences between anaerobic respiration occurring in yeast and muscle cells? [2]

Yeast – produce ethanol and co2 Muscle – produce only lactic acid

Fig 1.1 Fig 1.2

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(b) Construct a table below to compare and contrast a similarity and two differences between photosynthesis and respiration. [3+1]

photosynthesis Respiration enzymes Both processes require/are catalyzed by enzymes where In plant cells ½ energy Absorbs light energy Produces energy Products Glucose and oxygen Carbon dioxide and water Reactants Carbon dioxide and water Glucose and oxygen Location/organelle chloropasts Mitochondria conditions Requires light and

chlorophyll Does not require light and chlorophyll

Table with suitable headings, merged cell for similarity [1] [Total: 6 marks]

3. Gluten, a protein found in wheat, rye and barley can cause an allergic reaction

to the bodies of some who eat it. This reaction causes celiac disease where the body’s immune system destroys and damages the inner wall of the small intestine.

(a) Predict a physical symptom that will occur in patients with this disease and explain why it occurs.

[3]

• Excessive loss of weight (1m) • Walls of small intestines are lined with villi (1/2); • that aids absorption of digested materials like glucose and aa (1/2); • when the small intestine gets damaged, rate of absorption of nutrients will

drop drastically (1/2); • glycogen and fat stored will be utilized for energy production thus leading to

excessive loss of weight (1/2);

OR

• diarrhea with oily stools (1m) • When walls of intestines get damaged, it will affect the secretion of intestinal

juice (1/2); • Lipase, which digests fats into fatty acids and glycerol will not be secreted

(1/2); • and hence will not digest fats. Undigested fats (1/2); • passes through the small intestines to the large intestines and finally out of

the body as oily stools (1/2);

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(b) Describe what will happen to proteins that have been digested and absorbed into the small intestines of a healthy individual.

[2]

• Proteins get digested to form amino acids;

• Amino acids are used to produce proteins needed for cell division, growth and repair;

• Excess amino acids are deaminated in the liver and;

• Converted to urea to be excreted by the kidneys;

[Total: 5 marks]

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4. The diagram below shows the appearance of the abdominal cavity. The abdominal organs have been removed.

(a) Suggest what structure may be found in the X [1] Oesophagus, Blood Vessels (dorsal aorta and posterior vena cava)

(b) Using the appearance shown in the diagram and the knowledge of materials

that make up the diaphragm, describe how the diaphragm is suited to perform its function. [2]

Thin, flexible, stretchable, fibrous-muscles allowing it to change shape accordingly.

(c) A hiatus hernia is the protrusion of the upper part of the stomach into the thorax

through a tear or weakness in the diaphragm.

Suggest one possible symptom associated with this condition. [1]

• The symptoms include acid reflux, and pain, similar to heartburn, in the chest and upper stomach. Sometimes patients experience heartburn and regurgitation, when stomach acid refluxes back into the esophagus. OR

• Patient has difficulty drawing breath; • Tear in diaphragm pressure in thorax cannot be lowered

OR • Chronic indigestion; • Stomach is compressed by diaphragm, cannot contract properly

[Total: 4 marks]

diaphragm

backbone wall of

abdomen

X

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5. The diagram below shows how the branch of a small apple tree varied in diameter

over a 24-hour period.

(a) Using the date given in the table below, draw a curve on the graph above to show how rate of transpiration of the apple tree varied over the same 24-hour period.

[1]

Time/ h Rate of transpiration/ arbitrary units (AU)

0 24

6 5

12 30

18 40

24 25

Time/ h

Dia

met

erof

bran

ch

0

10

2

0

30

40

Rat

e of

tran

spira

tion

(AU

)

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(b) (c)

Account for the changes in the rate of transpiration over the 24-hour period. [1]

Greater temperature during the day, greater evaporation of water from leaf therefore greater rate of transpiration

Water molecules are attracted to one another by a force called cohesion. They may also be attracted to other molecules (the walls of the xylem vessels) by adhesion. From your answer in (a), state how rate of transpiration affects the diameter of the apple tree and suggest an explanation for this relationship.

[1]

• Diameter of apple tree branch becomes narrower when transpiration rate

increases (1/2);

• When rate of transpiration is high, the water molecules will pull in on the

sides of the xylem more and so the branch will become narrower (1/2).

(d) (e)

Briefly describe how water from the soil is absorbed and enters the xylem tissue in roots of plants. • Water potential higher in soil, than in root hair cell, (1/2);

• Water enters root hair cell across the partially permeable member by osmosis. (1/2);

• Cause cell sap to be diluted / increase water potential in vacuole. (1/2);

• Causes root hair cell to be lower in water potential in neighboring cells. (1/2);

• Process of osmosis is thus repeated as water is moved deeper into the root until it reaches the xylem. (1/2);

Using your knowledge of how mineral ions enter a root hair cell against the concentration gradient from normal garden soil, explain why uptake of mineral ions in a waterlogged soil may be inhibited.

[2]

• If the soil is waterlogged, the roots will be short of oxygen (1/2);

• This reduces the rate of respiration (1/2);

• And therefore energy release (1/2);

• For active transport of mineral salts to occur (1/2)

[Total : 7 marks]

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6. A student drank a large amount of ice-cold water. His mouth temperature, skin temperature and rate of sweating were recorded and the results are shown in the graphs below.

(a)(i) State the effect of ice-cold water on the student’s mouth

temperature. Explain why this change occurs. [2]

It lowers the mouth temperature (1/2)

Ice-cold water enters the blood and cools it (1/2) thus reducing blood temperature (1/2) mouth is lined with blood vessels hence mouth temperature drops too (1/2)

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(ii) Deduce from the graphs, the relationship between mouth

temperature and the rate of sweating. What is the significance of this relationship to the body?

[2]

Rate of sweating decreases with drop in mouth temperature/ directly proportional (1m) Helps to reduce heat loss/ conserve heat (1/2); To prevent further drop in body temperature (1/2);

(iii) Explain why skin temperature rose between 18 and 25 minutes. [1]

Because when rate of sweating decreases, less heat is lost (1/2); by evaporation (1/2);

(b)(i) What will happen to the quantity and concentration of urine

when the rate of sweating is high? Outline how this change is brought about in the kidneys.

[2]

Quantity of urine decreases (1/2);

And concentration increases (1/2);

Increased secretion of ADH (1/2);

Causes more reabsorption of water by kidney tubules (1/2);

(ii) When the urine of a man is boiled with Benedict’s solution, a brick-red precipitate appears. What can you deduce from this observation? Suggest an organ other than the kidney that may be diseased.

[1]

Reducing sugar is present in his urine/ he is suffering from diabetes (1/2); His pancreas/ liver may be diseased (1/2);

[Total : 6 marks]

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7. The diagram below shows a fetus developing in the uterus and other associated organs of the human female reproductive system.

(a) Name the structures and state their function. [3]

Structure Name Function A Placenta Site where nutrients and

oxygen from mother’s blood diffuses into fetal blood/ produces progesterone to support pregnancy/ actively produces antibodies to protect fetus

B Umbilical cord Contains blood vessels that carry nutrients and wastes to and from fetus

C cervix Muscular ring that supports fetus

(b) Cells in structures D and E undergo cell division. What are two significant

differences between the daughter cells produced in structures D and E? [2]

(mitosis) Cells in structure E

(meiosis) Cell in structure D

Number of chromosomes Diploid number Haploid number genes of daughter cells Identical to parent cell Different from parent cells

A

B

C

D

E

F

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(c) During a pregnancy, liquid from F containing cells may be removed and tests carried out on the chromosomes of the cells found in the liquid.

The karyogram below shows the results of one such test.

(i) What is the gender of the fetus? Explain. [1]

Female. Sex chromosomes are of equal size, implies both are X chromosomes.

(ii) What possible condition might the fetus suffer from? [1]

Down’s Syndrome (iii) Based on your knowledge of cell division resulting in the formation of an egg

cell, suggest how the condition in might have come about. [2]

• Meiosis • During anaphase II • sister chromatids do not separate • both go into the same cell, resulting in egg with two copies of

chromosome 21

[Total: 9 marks]

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8. Roses come in various colours. An amateur gardener crossed a red rose plant with a white rose plant and the all resultant plants produced pink flowers.

(a) Describe the relationship between the two alleles that control flower colour in

roses. [1] Incomplete dominance

(b) The gardener was so pleased with his new rose colour that he decided to self-

cross the pink rose plants to produce a pure breeding line of pink rose plants. Would he succeed? Explain your answer with the help of a clearly labeled genetic diagram. [4]

Not possible. • Pink plants are always heterozygous [½] • Crossing 2 pink plant will only produce 50 % pink plants in the next

generation. [½]

Let R represent the allele for red flower Let r represent the allele for white flower R=r

P phenotype Pink pink P genotype

Rr Rr

Gametes

(c)

F 1 genotype RR Rr Rr rr F1 phenotype Red pink pink white Ratio 1 red: 2 pink:1 white

• Key • Headings • Correct parent genotype • Crosses are correctly liked • Correct F1 genotype • Correct F1 phenotype

[½] each point

R r R r

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(c) The photo on the right shows a red rose. Give 2 visible features that indicate roses are insect pollinated. [1]

• Brightly coloured • Large conspicuous flower • Anther and stigma enclosed by flower/do not

protrude Any two reasons

(d) In recent research, scientists found that pollution has affected how far the scent

of a flower will travel. Previously, scents of flowers would travel for about 1 km. Recently, this distance has dropped to about 200 m. Suggest what the impact this ‘loss of scent’ might have on the population of rose plants. [2] • Drop in population • Pollinators/bees/butterflies cannot smell flowers from afar, • fewer flower will be pollinated, Less fertilization; • fewer viable seeds; fewer plants will develop

[Total: 8 marks]

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Section B [30 marks] Answer three questions in this section on the writing paper provided.

9. Kangaroo rats generally live in an arid (dry) environment while laboratory rats live in a controlled environment.

In an experiment carried out in a laboratory, water loss and water gain in a kangaroo rat and a laboratory rat were observed on a daily basis. The readings were as shown in the table below.

Water loss ml of water/kg body weight/day Description Kangaroo Rat Laboratory Rat Gain in water from metabolism of food

+ 54.0

Loss due to evaporation - 44.0 -77.0 Loss in faeces - 2.5 - 13.6 Loss in urine - 13.5 - 22.0

Reference: Hainworth Animal Physiology: adaptations in function, Addison-Wesley Publishing Company, Reading, Massachusettes,1981.

(a) What are 2 variables that must be controlled in this experiment? [1] • Type of diet • Amount of food given to each animal per kg weight per day • Humidity of environment • Temperature of environment • Level of activity

(b) How can the reliability of the experimental results be increased? [1]

Repeat experiment/ have more animals per test, use average.

(c) Draw a bar graph using the data in the table to compare the components of water loss in kangaroo rats and laboratory rats on the graph paper provided. [3]

• Axes correctly labeled; scale is appropriate • Correct headings, suitable presentation ( diff type of rat compared at

each component) • Correct plot based on data.

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(d) One source of water in the body is through metabolism of proteins, carbohydrates and fats.

The kangaroo rat was observed to gain an average of 3.5 ml of water a day through the metabolism of food. The weight of the kangaroo rat was 65 g.

Calculate the amount of metabolic water gained in ml of water/kg/day for the kangaroo rat. [1] Gain in metabolic water = (3.5 ÷ 0.065) ml/kg/day

= 53.8 ml/kg/day

(e) Calculate the minimum amount of water the kangaroo rat and laboratory rat must drink each day. [2] Kangaroo rat 53.8 – (44.0 + 2.5+ 13.5) = 6.2 ml/kg /day Laboratory rat 54 – (77.0+ 13.6 + 22.0) = 58.6 ml/kg/day [- ½m] no units/incorrect units

(f) Compare water loss in the kangaroo rat and the laboratory mouse. [2]

• Overall more water loss in lab mouse ( water balance ) 6 ml cf 58 ml • Water loss is also greater for each component for lab mouse compared

to kangaroo rat. • Water loss through evaporation main component for both animals.

Any 2 comparisons made. [-1m] no values quoted throughout answer

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10. Bacillus thuringiensis (or Bt, for short) is a naturally occurring soil bacterium. It is

able to produce a protein endotoxin that kills butterfly larvae, in particular, the European corn borer.

(a) Bt-Corn is a genetically modified form of corn where the Bt endotoxin gene has been inserted into the DNA of corn. This type of corn has been grown in USA for about 10 years and renders the corn toxic to butterfly larvae. At present, the endotoxin does not seem to have adverse effect on humans, other mammals, birds or fish.

(b) Outline the process of creating genetically engineering Bt-Corn. [4]

• Identify/isolate Bt endotoxin gene on bacterium.

• Cut endotoxin gene with suitable restriction enzyme; cut corn DNA with the same restriction enzyme.

• Create complementary sticky ends on corn DNA and Bt endoxin gene [½]

• Using a ligase, insert Bt endotoxin gene onto cut segment of corn DNA, recombinant DNA formed.

• Reintroduce recombinant DNA into corn cell (retrovirus [½] ), when cell undergoes cell division, copies of the Bt endotoxin gene also duplicated.

(c) Suggest two possible harmful effects of growing Bt-Corn may have on an ecosystem over a period of time. Explain clearly, using Biological concepts, the reasons for your suggestions. [6]

NATURAL SELECTION

• Diversity Decreases,

o Because Bt-corn is resistant of insect attack, selected for, survive and reproduce, over many generations fewer wild/other varieties of corn.

• Toxin resistant larvae, Unable to kill insects with insecticides

o If there are mutations that allows insect to be resistant to toxin, toxin resistant insects selected, survive and reproduce, over many generations most insects will be resistant. Unable to kill insects with insecticides?

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FOOD WEB/CHAIN INTERACTIONS

• Plants will not have pollinators, fewer seeds, fewer plants in succeeding generations

o If the larvae are killed by the toxins, fewer butterflies in the ecosystem – other plants may lack pollinators, plants not pollinated, fewer fruit for other organisms, fewer seeds to develop into next generation of plants.

• Lack of food source, drop in population of other organisms in

ecosystem/food web o Butterfly larvae may be a food source of birds or other

insectivorous organisms. Population of these organisms will also drop a their food source is lost or reduced.

• Bioaccumulation and amplification of toxins

o Insect larvae consume toxin which may not be biodegradable, accumulates/stored in their body

o When bird/ predator eats larvae, bioamplification of toxin occurs o Eventually toxin reaches level in tertiary consumer

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BEGIN QUESTION 12 ON A FRESH SHEET OF PAPER.

EITHER 12.E A bare-foot boy steps on a sharp object and a series of reactions as shown

below occur. Reaction 1: Leg muscles contract to draw back foot upon stepping on the sharp object. Reaction 2: Pain is felt on the foot with blood flowing out Reaction 3: Boy starts to cry.

(a) Describe the route taken by the nerve impulse starting from the eye that leads to reaction 3. [6] • Image of blood gets pick up by receptor, the eye • initiates an electrical impulse that travels through the sensory neuron(SN)

from the eye • to the brain • via the optic nerve • The electrical impulse is transmitted from the dendrite of the SN to • the intermediate/ relay neuron across • a synapse by • chemical means/ neurotransmitter • Impulse enters the conscious part of the brain • Decision made by the brain to activate tear glands • Electrical impulse travels along the axon of the RN until it reaches the

nerve ending • The electrical impulse is transmitted across a synapse to the motor neuron • which leaves the brain and transmits to the tear gland • electrical impulse gets converted to chemical means at end of axon of MN

that activates tear gland. • Tears are released as a result.

(b) Explain the action of the body’s clotting mechanism on the large wound formed in reaction 2. [4]

• Wound is too large so platelet plug is not large enough to block blood loss

(1/2); • Platelets disintegrate (1/2); • Thrombokinase/ thromboplastin is released by damaged tissues (1/2); • Reacts with calcium (1/2); • And prothrombin (1/2); • Converts prothrombin into thrombin (1/2); • Thrombin converts soluble (1/2) fibrinogen; (1/2) • Into insoluble (1/2) fibrin; (1/2) • That acts as a clot; (1/2) • To prevent further loss of blood (1/2)

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OR 14. O A small fruit free was planted in a British meadow in 1988. Today it has grown

into a big tree weighing more than 500 kg.

(a) Explain how this gain in weight is brought about. [4] • Photosynthesis • Carbon dioxide and water combine to form glucose and oxygen • ½ light energy converted to chemical energy • Glucose used by plant to produce energy for growth during respiration

(Use of products of photosynthesis (max 2)) • Amino acids proteins ; cell structure • Cellulose cell wall • Sucrose transport/storage in fruits and flowers • Starch storage in organs (e.g. stem, roots) • ½ formation of new xylem and phloem

(b) State and explain 3 factors that affect the rate of growth of the fruit tree in the

meadow. [6] Factors that affect photosynthesis • light intensity,

increase in light intensity, greater photosynthesis photolysis

• CO2 conc, Greater CO2conc, greater photosynthesis Raw material

• temperature(seasonal variation)

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increase in temperature, greater photosynthesis enzymes required for photosynthesis ; increase temp will increase

rate of enzyme activity.

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2008 Bio Prelim P2 Ans