Microsoft Word - Trial Stpm Kedah Bio (answer)

JABATAN PELAJARAN NEGERI KEDAH STPM TRIAL EXAMINATION 2009

BIOLOGY MARKING SCHEME PAPER 1 & PAPER 2

1

OBJECTIVE MARKING SCHEME 2009 1. D

26.D

2. B

27.C

3. A

28.C

4. C

29.C

5. D

30.B

6. A

31.C

7. B

32.C

8. A

33.C

9. C

34.D

10. C

35.D

11.A

36.C

12.A

37.C

13.C

38.B

14.D

39.D

15.B

40.B

16.A

41.A

17.B

42.D

18.C

43.C

19.D

44.D

20.C

45.D

21.B

46.C

22.A

47.B

23.D

48.B

24.C

49.C

25.C

50.C

2

Answer Paper 2 Section A 1(a) R= carbon dioxide T= ATP

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(b)

The light-dependent reaction/light stage/photosystem I

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(c)

Carbon dioxide combines with a 5C compound (RuBP) to form an unstable 6C compound, catalysed by enzyme RUBISCO

1m

The 6C compound breaks down to form 2 molecules of glycerate 3phosphate (GP/PGA) which is a 3C compound.

1m

GP is converted to triose phosphate (PGAL) using ATP and reduced NADP from the light dependent stage.

1m

PGAL molecules combine to form a 6C hexose sugar that polymerizes to produce starch.

1m

Some of PGAL are also used to regenerate RuBP.

(d)

1m Max=4m

Light- dependent reaction occurs in thylakoid whereas light independent reaction occurs in stroma of chloroplast.

1m

Light-dependent reaction produces ATP and NADPH, whereas lightindependent use ATP and NADPH for the formation of starch.

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Light-dependent reaction requires light, whereas light-independent reaction does not require light.

1m

2(a) Assume that the population is in equilibrium Let p be frequency of R allele and q be the frequency of r allele Therefore, frequency of agouti (rr)= q2 = 64%=0.64 Allelic frequency of yellow (r) = q=√0.64=0.8 Allelic frequency of yellow (R) = p=1-q=1-0.8=0.2

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(b)

1m 1m 1m Max=3m

No, If the population is in equilibrium The population is very large, mating is random, there is no selection, no mutation and no migration. OR

3

(c)

3(a)

Yes, If the population is not in equilibrium The population is small, no random mating, there is selection, mutation and migration.

1m 1m 1m Max=3m

Homozygous yellow coat (RR) is p2 = 0.2 x 0.2= 0.04 Therefore, 4% from 20% = 4/20 x 100%= 20%

1m 1m Max=2m

Parasite is a heterotrophic organism which is dependent on a host organism from which it obtains its organic nutrition.

1m 2m

(b)

Obligate parasites cannot survive independently of their hosts. Facultative parasites can survive on their own away from their hosts.

1m 1m

(c)

A is the sucker.

1m

For secure attachment to intestine wall. Maintain its position in the body of the host Absorb food in the form of simple soluble digested in the intestine of the host.

1m 1m

(d)(i) Saprophytic

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(ii) Mucor produces digestive enzymes, none produced in the tapeworm Mucor is a decomposer//saprophyte//saprobiont//lives on dead organic products, tapeworm is a parasite//lives on a living host. Tapeworms obtain their food with special mouthparts, none present in Mucor.

4

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4 (a) (b)

(anterior) pituitary gland

1m

FSH : Stimulates development of Graafian follicles in the ovary Stimulates ovary to secrete oestrogen LH: Induces ovulation Stimulates corpus luteum to secrete progesterone

1m 1m Max=1m 1m 1m Max=1m

(c)

X – oestrogen Y – progesterone

1m 1m

(d)

Day 16 Oestrogen reaches a peak (followed by a decline) on day 14 LH peaks on day 16. This induces ovulation

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(e)

Either As the level of oestrogen builds up This inhibit the production of FSH by the pituitary

1m 1m

OR: As the level of progesterone builds up This depresses the production of LH by the pituitary gland

5

1m 1m

Paper 2 Section B QUESTION 5 (a) • Transport water and ions from the roots to the leaves • Transport water soluble organic product such as hormones • Maintain water potential gradient that enables water and dissolve mineral to move up to the leaves from the roots • Provides cooling effect to the plant • Provides water for production of turgor pressure in cells, which functions as a support for the plants • Provides water to cells to function in the metabolic pathways such as in hydrolysis and photosynthesis (b) • Transpiration is a process of water loss by evaporation in plants • Transpiration is facilitated by root pressure, capillary action and transpiration pull (i) Root Pressure • Root pressure is caused by water that is actively forced out from the living cells into the xylem vessels • Endodermis cells actively loads salt into xylem vessels to lower the water potential of the xylem vessel • More water enters the xylem vessel through osmosis, creating root pressure that forces water up through the xylem vessel of stems (ii) Cohesion-tension theory • Cohesion-tension theory explains the ascent of water in tiny xylem vessels of plants • Cohesion force is the force of attraction between water molecules in the xylem vessels • Adhesion force is the force of attraction between water molecule and the xylem vessel walls. (iii) Transpiration pull • Transpiration pull is the combined suction force exerted by all the leaves in a plant when it transpires • During transpiration, the loss of water from the mesophyll cells through the stoma ultimately sucks the water from the xylem vessels of leaves • Since the xylems of leaves are continuous from the xylem of roots, the continuous stream of water from the soil to the leaves is produced QUESTION 6 (a) (i) • antigens are foreign substances that stimulate the production of cells or antibodies in the body to specifically destroy them. • Antigens are macromolecules found on the surface of microorganisms, plasma membrane or as free molecules. • Protein produced in the same body cannot act as antigens, but 6

1m 1m 1m 1m 1m 1m [Max 5m] 1m 1m [Max 1m] 1m 1m 1m

1m 1m 1m

1m 1m

1m

[Total 10m] 1m 1m 1m

when it is transferred into another organism’s body, they can act as antigen. (ii) • Epitopes are small specific parts of a larger antigen that can bind with a specific antibody • Epitopes are antigenic determinants that have a specific configuration. • Pathogens phagocytosised by the macrophage are broken down into epitopes and then presented on the plasma membrane as antigen-MHC complex for recognition by lymphocytes.

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1m 1m

[Total 6m] (b) • B cells are formed and mature in the bone marrow. • The mature B cells form antibodies, which are then attached to their plasma membrane with their two tips acting as receptors. • The B cells with complimentary antibody phagocytosise the free complimentary antigens encountered. • The antigen is cut into smaller pieces and presented as the antigen-MHC complex on its plasma membrane. • T helper cell (TH) with complimentary TCR recognises and binds to the antigen-MHC complex on B cells. • Then, TH secretes interleukin 2. • Interleukin 2 stimulates the B cells to divide and form a large clone of effector B cells (plasma cell) and memory cells. • The effector B cells (plasma cells) produce a large quantity of free antibodies with same specific configuration. • The antibodies released then destroys antigen including pathogen and parasitic worms by various methods such as agglutination, precipitation and antitoxins.

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[Total 9m]

QUESTION 7 (a) Parameters that can be used to measure growth are dry mass, wet mass, volume or size and length or height. (i) Dry mass • It is obtained by repeated drying in the oven at 1100C and 7

[Max 3m]

measurement is done until no changes in mass are observed. 1m Advantage: • Gives a more accurate measurement of growth as it measures the growth of organic material in the organism.

1m 1m

Disadvantage: • • •

•

Organism has to be killed to obtain its dry weight. Repeat measurement on the same specimen cannot be done as it is killed in the first measurement. A large population is needed and the selection of specimens from population must be random. All individuals in the population must be of the same age and grow in the same condition. Problem in measuring big sized organisms such as big tree and elephants.

(ii) Wet mass

1m

1m 1m 1m 1m 1m

Advantage : • • • •

1m

Can be easily and quickly measured. Organism is not killed Repeat measurement on the same organism can be done. Small population or only one organism is needed for measurement.

1m

1m

Disadvantage: • •

Measurement that includes water contents of an organism is in accurate as the water content in organisms varies. Measurement does not show the different rates of growth of organs in the organism such as the allometric growth of organs in humans.

(iii) Size or volume Advantage: • Suitable for constant sized or spherical shape organisms. Disadvantages: • Involves complex mathematical calculations. • Shape of organism can change during growth. (iv) Length or height Advantage: • Suitable for the measurement of the height of animals or plants, or the length of animals and leaves of the plants. • Easy and quick measurement. 8

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1m 1m

1m 1m [Max 1m]

1m

Disadvantages: • Growth in other dimensions such as the weight of animals is not taken into account. For example, when human increase in dry weight but they do not increase in height. (b) •

•

1m

1m

Seed dormancy occurs when a viable seed is prevented from germinating.

1m

It functions to delay the germination of the seed until a favourable condition is met to increase the plant’s chance of survival.

1m

The factors affecting seed dormancy are as shown below: • • • •

•

Immature embryo in the seed Physiologically immature seed. For example, the embryo cannot synthesise gibberellic acid. High level of abscisic acid prevents seed germination. Seed coat (testa) is impermeable to water and oxygen, scarification of testa must occur to allow imbibition of water and diffusion of oxygen into the seed. Some seed require a cold period to germinate (stratification). This is to ensure that the seed remain dormant in winter and germinate in spring.

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1m

QUESTION 8 (a) Concept •

Taxonomy involves classification, identification and nomenclature

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•

Classification is a process by which organisms in the world are classified based on certain observed features studied by the taxonomist

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9

•

Identification is a process by which organisms are recognized and identified based on the Linnaeus hierarchy

•

Nomenclature is a way of naming organisms scientifically based on Linnaeus binomial system

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Importance 1m

•

Classification allows taxonomists to store and provide information of an organism systematically because materials and the information are filed and catalogued

•

Nomenclature allows taxonomist to give scientific names to organisms scattered all over the world

•

Scientific name of organisms enables the communication and exchange of data and information to be carried out effectively within the scientific community

•

Natural classification system provides information evolutionary relationship between organisms

the

1m

•

Taxonomy provides evidence to support organic evolution as taxonomists can discover the natural relationship among organisms in different categories in the Linnaeus hierarchy

1m

•

Taxonomy allows biologists to continuously discover unknown species and to update information on biodiversity and evolution

1m

•

Taxonomy enables ecologists to discover ecological relationship between organisms and the environment

on

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1m

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b) Artificial classification •

Only one or two features are used to divide the organism into two groups at a time

Natural classification •

Three main methods are used: Phenetic - uses features Phylogenetic - only 10

many

1m

homologous features are used Cladistic – only secondary homologous features are used •

Objective economic purpose

•

•

based on or practical

•

Objective is to show evolutionary relationship between organisms

Simple to classify

•

Difficult to classify. A lot of information on the organisms are needed

Used in constructing biological dichotomous keys

•

Used as an evidence to support organic evolution

1m

1m

1m

c) •

Observable features which may be qualitative or quantitative.

1m

•

Features must be constant for that species and not affected by environmental influences.

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•

Made up of pairs of statements or leads which are numbered

1m

•

Statements are expressed in contrasting mutually exclusive forms.

1m

•

Process of elimination, the unknown organism is identified until the lowest taxonomic group possible.

1m

•

Features such as sex or habitat are avoided.

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•

Features found on immature stages are also avoided.

1m

•

Dichotomous keys commonly used in identifications of plants, insects, aquatic flora and fauna

QUESTION 9 (a ) • Genetic drift is a process by which allele frequency in the population changes over time, due to some random events. • The effects of genetic drift are more severe in a small population and is insignificant in very large populations. •

Two types of commonly observed genetic drift:

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1m 1m

( i) Founder effect • Occurs when a small population is separated from the original population and migrates to an isolated area • By chance, the genes composition (allele frequency) of the founding population is not the same with original population. • Reproduction in the founding population over several generations produces new allele frequency that is different from the original population. • The pioneer population becomes a new species and loses its ability to reproduce with the original population. • Example: Galapagos tortoise population in Galapagos Island.

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1m

1m

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(ii) Bottleneck effect • Occurs when a population undergoes the dramatic decrease in size, which is cause by ecological or natural disasters. • The disaster randomly eliminates a major proportion of the population. • A small and random population that survives has a different allele frequency compared to the original population. • Reproduction in the new and small population over several generations produces new allele frequency that is different from the original population, thus speciation occurs. • Example: population of cheetah in the wild.

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(b) •

• • • • • •

Adaptive radiation is the gradual change of an ancestral species to a number of diverse species in which each species occupies a new habitat or ecological niche. Example: Darwin’s finches in Galapagos Islands. The original population of Darwin’s finches are mainland finches that has short and straight beak to crush seeds. The original population occupied and ecological niche with little competition. As the population increased, intraspecies competition increased. Due to the changes in the gene pool and natural selection, the finches become more adapted to the environment. New ecological niches were found and occupied by 14 species of finches to reduce the competition and to take advantage of the various food sources available in the island:
Ground finches food sources are seeds and cactus
Three finches food source is insects 12

1m

1m 1m 1m 1m 1m 1m

•


Warblers food sources are insects, fruits and nectar. Adaptive radiation of Darwin’s finches show divergent evolution.

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QUESTION 10 (a) •

•

•

• • •

Management and conservation programmes are aimed at sustaining the biodiversity of ecosystems and at the same time, maintaining or improving the quality of life. Conservation of the ecosystem is important because: The ecosystem may contain biological resources that may be useful or of the economic value; for example, in the production of medicine. Biogeochemical cycles in the ecosystem may be disrupted by the extinction of some species resulting in the destruction of an ecosystem. Destruction of the earth’s ecosystem may lead to global climatic changes. Ecosystem in their natural state provides aesthetic values for humans. Human have a moral obligation to protect the environment for future generations.

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1m

1m

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(b) • • •

•

• •

(i) Conservation of the forest is important because forests: Contain large biodiversity, which in turn contain many undiscovered species that may have economical or medicinal values. Play an important role in producing rain as the transpiration of plants in forest releases water into environment. Play an important role in the carbon cycle. Plants use carbon dioxide for photosynthesis and the destruction of forest will increase the carbon dioxide level in the atmosphere causing the green house effect. Play an important role in maintaining soil fertility and in preventing floods. (ii) in forestry, the following sustainable development are used: Replanting programmes : replanting the trees in the area that have been logged. Selective logging: only selected trees with certain diameters or 13

1m 1m 1m 1m

1m

1m 1m

•

• • •

species can be felled. Creating forest reserves to avoid the complete destruction of forests and to maintain the diversity of the forest. Preferably one third (1/3) of the nation should be covered with forests. Restoration programmes of damaged forests. Enforcement of laws and surveillance to prevent illegal logging. Recycling of paper to reduce the demand for new raw materials

14

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