MARKING SCHEME - University of Malta · MARKING SCHEME: SEC BIOLOGY ... d 12 e 0 Accept 1 f 0 g 4 h 16 i 1 j 4 ... ii Lipase digests fats into (3)

MARKING SCHEME

SEC BIOLOGY

MAY 2017

MARKING SCHEME: SEC BIOLOGY (MAY 2017)

Page 2 of 26

TABLE OF CONTENTS

PAPER 1 ............................................................................................................................................................................................................................................ 2

PAPER 2 A ......................................................................................................................................................................................................................................... 9

PAPER 2 B ....................................................................................................................................................................................................................................... 17

PAPER 1 Question Answer Mark Additional comments

1 b 2

1 mark each

c 3

d 12

e 0 Accept 1

f 0

g 4

h 16

i 1

j 4 Allow 8

k 1

Total 10 marks

2 a i plasma (cell) membrane 1 mark

ii nucleus 1 mark

iii vacuole 1 mark

iv cytoplasm 1 mark

b

i

cytoplasm

cell wall

vacuole

nucleus

3 marks

1 mark for correct drawing,

2 marks for correct labels

(0.5 marks for each label)

ii Large surface area / hair-like projection / projection 1 mark

iv Chloroplast 1 mark

c i Releases mucus 0.5 marks Expect specific reference to


Page 3 of 26

Foreign particles stick to it 0.5 marks mucus

ii Cilia sweep dirty mucus

up the trachea towards the throat (where they are swallowed) / away from

lungs

0.5 marks

0.5 marks

Allow cilia trap particles

Total 11 marks

3 a Pancreas

Correct labelling

1 mark

1 mark

b i

ii

iii

Bile

Liver

Gall bladder

1 mark

1 mark

1 mark

c i

Emulsification

Increases surface area of fat droplets (over which lipase acts)

1 mark

1 mark

ii Lipase digests fats into (3) fatty acids and glycerol 2 marks

d By the wave like contraction created by (circular muscles and longitudinal)

muscles in the intestinal wall – known as peristalsis

2 marks Deduct 1 mark if the term

peristalsis is not included

Total 11 marks

4 a i)

1 mark

ii Provides support to the plant. 1 mark Do not accept transport of

mineral ions.

b

Hollow lumen / Cells contain no cytoplasm /Cells are empty (as cell is dead)

No end walls between cells

Vessel elements link together to form a continuous tube.

Tubular

Wide

1 mark

Any ONE

c i Phloem 1 mark

Xylem


Page 4 of 26

ii Leaves

Photosynthesis

1 mark

1 mark

iii No sugar arrives to roots;

Metabolic activity / Respiration in roots stops

Roots die therefore plant dies

OR

There is no water uptake, so tree dies.

1 mark

1 mark

1 mark

Total 9 marks

5 a Seed A: there was a lack of oxygen / low concentration of oxygen

Seed C: lacked water

1 mark

1 mark

Accept: No oxygen present.

Do not accept: No air

b i X - Y: Dry mass decreases

as the stored food in the cotyledons is used in respiration to produce energy

needed for growth

1 mark

1 mark

(If answer includes

explanation only without the

description award 2 marks)

ii Y - Z: Dry mass increases

First leaves grow and photosynthesis starts taking place at a faster rate than

respiration.

1 mark

1 mark

c i Starch 1 mark

ii Add iodine solution

Blue black colour when starch is present.

1 mark

1 mark

Allow: Add iodine

Total 9 marks

6 a Have jointed appendages

Have a hard exoskeleton

Have a segmented body

1 mark Any ONE

(Allow: Has an external

skeleton)

b W: Otiorhynchus sulcatus

Z: Lilioceris cheni

1 mark

1 mark

(Ignore rules in writing

scientific name)

Award marks if Genus name

only is written.

Do not accept if species name

only is written.

c septempunctata 1 mark Award mark only if name

starts in lower case and is


Page 5 of 26

underlined.

d Class: Insects / Insecta

Characteristics: Have 1 pair of antennae

Have 3 pairs of legs

Body divided into head, thorax and abdomen / into three

parts

1 mark

1 mark for

each

characteristi

c

(Any TWO characteristics)

Do not accept have

antennae.

Do not accept have wings.

e i Translocation 1 mark

ii Covering the leaf reduces the surface area to absorb light, thus less

photosynthesis takes place. OR

Black fungus physically blocks stomata, preventing uptake of CO2 for

photosynthesis.

1 mark

1 mark

iii Biological control

No air pollution due to chemical use

Harmless organisms are not affected.

Pesticides do not end up in the food chain.

(Any ONE)

1 mark

1 mark

Do not accept pest control

iv Incomplete (metamorphosis) 1 mark

Total 13 marks

7 a

a

a

Group Can

photosynthesi

se

Have cell

walls

Produce

seeds

Are

decomposers

Plants yes yes some

Animals no no no

Fungi yes no some

Bacteria yes no some

Viruses no no no

1 mark for

each correct

line -

Max 5 marks

Do not award half marks.

b i

Correct statement:

Deforestation degrades the fertility of the soil in the deforested area

Reason:

Minerals leached away from soil

1 mark

Do not accept – Deforestation

does not improve / cannot

improve fertility.


Page 6 of 26

Microorganisms washed away disturbing soil recycling

Less vegetation on soil surface, less decaying vegetation to recycle nutrients

(Any ONE)

1 mark Do not accept reference to

soil erosion.

ii Correct statement:

Live shellfish, such as mussels, living in close proximity to the fish farm

contain high concentrations of pesticide / contain pesticide.

Reason:

Pesticides enter food chain in plankton which is eaten by shellfish,

accumulating in them OR

Pesticides enter food chain in plankton and travel up the food chain in upper

trophic levels.

1mark

1 mark

Total 9 marks

8 a i 367.5/7 = 52.5 cm2 2 marks Deduct 0.5 marks if units are

not included.

ii Thermometer Temperature change

Thermometer placed in the outer test tube in

the setup with a group of 7 test tubes

Medium decrease in T

Thermometer placed in the inner test tube in

the setup with a group of 7 test tubes

Small decrease in T

Thermometer in setup with a single test tube Large decrease in T

1 mark

1 mark

1 mark

iii Thermometer Temperature change

Thermometer placed in the

outer test tube in the setup

with a group of 7 test tubes

Part of the test tube is exposed to

ambient temp while the other part to

hot water therefore less steep thermal

gradient / difference in temp

Thermometer placed in the

inner test tube in the setup

with a group of 7 test tubes

Test tube totally surrounded by other

test tubes: thermal gradient very low

Thermometer in setup with a

single test tube

Test tube is totally surrounded by

ambient temperature therefore there is

a steep thermal gradient.

1 mark

1 mark

1 mark

b As blood passes through the horns heat is dissipated to the surrounding

environment

The horns provide a large surface area and a region away from the body

1 mark

1 mark

Total 10 marks


Page 7 of 26

9 a Electric cars generate less / no greenhouse gases.

Less / no exhaust – thus less respiratory problems

1 mark each

point

Or equivalent

Award 0.5 marks for

unqualified reference to

reduction in air pollution

Accept reference to charging

only if linked to a renewable

resource eg solar energy.

b Carton boxes are biodegradable /(Most) plastics are non-biodegradable

Production of plastic involves use of fossil fuels

Paper is made / derived from a renewable source

1 mark each

– max 2

marks

Any TWO – or equivalent

(Do not accept: plastics harm

the environment.)

c More plants – removal of CO2 and addition of oxygen.

Way how to cool the building underneath

Trapping of rain water

Increase habitats for insects

Increase food supply for birds / predators of insects

1 mark each

– max 2

marks


d Reduce production of greenhouse gases

Use a source of biogas / increase efficiency of biogas production

Easier to recycle

Reduction of waste in landfills

Used as compost / fertilizer

1 mark each

– max 2

marks


e Protection of biodiversity at all trophic levels

Protection of endangered species

Save genetic diversity

Identifying the conservation area creates awareness thus greater chance of

people protecting / saving it

Allows degraded areas / exploited species to return back to sustainable

levels.

1 mark each

– max 2

marks


Total 10 marks

10 a i 2 4 5 1 3 1 mark Award mark if all parts are in

correct sequence.

b i Albumin is a large molecule

It will not pass through the wall of the capillaries and Bowman’s capsule

(Allow converse for mineral salts and glucose)

1 mark

1 mark


Page 8 of 26

ii All glucose

is reabsorbed (in the proximal / 1st convoluted tubule)

1 mark

1 mark

iii As a lot of water / all other substances has / have been reabsorbed

A solution with a higher concentration of urea and salt is left in the nephron

1 mark

1 mark

(Accept reference to

secretion of mineral salts and

urea from blood / plasma into

urine (in the distal / 2nd

convoluted tubules)

c Collecting duct 1 mark

Total 8 marks


Page 9 of 26

PAPER 2 A Question Answer Mark Additional comments

1 a Cell extracted from Sparus:

has a membrane-bound nucleus,

Has membrane-bound organelles

Lacks a cell-wall

Does not have a slime capsule

Does not have plasmids

Vibrio cell:

lacks membrane-bound nucleus,

Lacks membrane-bound organelles,

Has a cell-wall

Has a slime capsule

Has plasmids

(Any TWO differences)

1 mark each

difference –

max 2 marks

Accept correct reference to

ribosomes

Do not accept: Cell from fish

is eukaryotic, cell from

bacterium is prokaryotic

Do not accept reference to

flagellum.

b Cell from Sparus:

Lacks a cell wall

Lacks a permanent vacuole

Lack chloroplasts

Store glycogen

Cell from Opuntia

Has a (cellulose) cell wall

Has a permanent vacuole

Has chloroplasts

Store starch


1 mark each

difference –

max 2 marks

c Cell membrane

DNA

Ribosomes

1 mark Accept cytoplasm

d Chordata / Vertebrata

Presence of a spinal cord OR vertebral column OR backbone

1 mark

1 mark

Do not accept spine

e Expect reference to TWO characteristics e.g.

Shape of fins / tail

Size of fins / tail

Shape of body / Patterns on skin surface

Type of teeth

1 mark each –

max 2 marks

Acknowledge reference to

comparison of DNA, & cross

breeding to check if offspring

are fertile.

Do not accept colour

f Increase in salinity: higher loss of water due to osmosis

OR

Uptake of ions / salts by diffusion

2 marks

g 37oC

Optimum temperature for enzymes to work / for bacteria to grow

1 mark

1 mark

Accept any temperature

(as text does not hint to

any temp value)

Do not accept ideal


Page 10 of 26

Total 13 marks

2 a Title included

Axes are labelled

Correct plotting of graph

Key / legend included

Adequate scales chosen

1 mark

2 marks

1 mark

1 mark

1 mark

Do not award any marks if

graph is drawn on squared

paper / or graphs are

drawn separately or only

one set of data is drawn.

Deduct 3 marks if axes are

swapped.

If first plot is joined to the

0,0 (origin) deduct 1 mark

b A 400 nm the highest % of light is absorbed

So most energy available for photosynthesis

1 mark

1 mark

c Amount of carbon dioxide / intensity of light/ water availability/ presence

of chlorophyll, temperature (heat). (Any TWO)

2 marks

d The higher the SA, the higher the rate of photosynthesis.

More light trapped over surface (due to more chlorophyll / more

chloroplasts.)

1 mark

1 mark

Total 12 marks

3 a Fainting and breathless may be symptoms of anaemia, lack of iron in the

diet. Iron is required for the formation of haemoglobin and the healthy

functioning of red blood cells that carry oxygen around the body.

1 mark

1 mark

1 mark

Award 3 marks if explanation

includes any 3 of the bold

phrases.

b i Autosomal: does not occur on the sex chromosomes (pair no.23)

but occurs on any other chromosome (pair 12).

1 mark

1 mark

Award 1 mark for – Not

sex linked

ii Unlike males, females have their monthly menstrual cycle / period,

making the problem more evident.

1 mark

c Phenotype: Normal / Carrier: Normal / carrier

Parents : Rr Rr

Gametes: ® (r) ® (r)

Offspring: RR Rr Rr rr

(suffers from Von Willebrand)

1 mark

1 mark

1 mark

1 mark

Award marks if presented

in Punnet squares

Do not award marks if

disease is represented

using X and Y

chromosomes.

(Do not deduct marks if

gametes are not

encircled)


Page 11 of 26

d i Prevents loss of blood

Prevents the entrance of pathogens in the body

1 mark

1 mark

ii Platelets OR

Any TWO of Fibrinogen, Thrombin, Prothrombin, Fibrin, Calcium

1 mark If platelets only – award 1

mark

If platelets with one or

two incorrect components

– award 0.5 marks

(NOTE: Question asks for

COMPONENTS – so it is

open to interpretation.

Marker’s discretion is

applicable)

e i Red blood cells: transport of oxygen

Lymphocytes: Produce antibodies

1 mark

1 mark

ii Red blood cells

Biconcave shape

No nucleus

Haemoglobin present

Smaller

Lymphocytes

Spherical / Circular

Nucleus (large nucleus) present

Lack haemoglobin

Larger

1 mark each

- - max 2 marks

Any TWO

f i Blood flows through two circuits / pathways:

from the heart to the lungs and back

from the heart to the body tissues / systems and back

1 mark

1 mark

1 mark

ii

Arteries Veins

No valves present Have valves

Thick wall Thin wall

Elastic wall Non-elastic wall

Narrow lumen Wide lumen

1 mark each –

max 3 marks

Do not accept functions of

arteries and veins

Any THREE

g Less oxygenated blood is pumped to the body

Resulting in fatigue, breathlessness, chest pain, light-headedness

1 mark

1 mark


Page 12 of 26

(or equivalent)

Total 25 marks

4 a i May have same genus name but a different species name.

May have a different genus name.

1 mark

1 mark

ii When reaching high numbers on a tree therefore high (intraspecific)

competition

The aphids can fly off to feed on nearby trees (new feeding territory)

therefore increases survival rate.

1 mark

1 mark

Do not deduct marks if

intraspecific is not

mentioned.

iii Broad range insecticides kill all insects the pesticide comes in contact

with, including beneficial insects and upsetting the natural food web.

Allow: Oil and detergent stops the insects from attaching to leaves and

feeding on trees. No other organism is affected by this mixture.

1 mark

1 mark

Do not accept; has no

impact on the

environment.

b i An organism that lives in or on another organism /host

and benefits by deriving nutrients at the host's expense / harming the host

in the process.

1 mark

ii The virus harms the citrus tree eventually leading to its death (as tree is

its host)

Virus does not harm or cause aphid to die.

1 mark

1 mark

iii A tissue is a group of cells having the same structure and function. 1 mark Do not accept: A group of

cells.

iv

2 marks for

correct

diagram

2 marks for

correct labels:

protein coat/

capsid/

capsomeres

nucleic acid/

genetic

material.

(Max 4 marks)

Accept diagram of any form

of virus to include


Page 13 of 26

v

1 mark for

each stage:

(Max 4 marks)

Accept written description of

viral replication.

vi If the phloem tissue is infected by the virus then these cells cannot

transport sucrose to all parts of plant needed for reactions for synthesis

and growth.

1 mark

1 mark

c

1 mark for

each tropic

level

1 mark for

correct arrow

signs

(Max 5 marks)

Do not award marks if:

Food web is drawn upside

down

Lines do not show arrow

heads

Citrus tree is drawn in

middle of food web i.e. not

in 1st trophic level.

Deduct 1 mark if mice are

written twice

Total 25 marks

5 a i

The rate of diffusion increases with an increase in temperature.

An increase in temperature increases the (kinetic) energy of the

molecules making up the cell membrane.

The cell membrane is damaged

Therefore allowing diffusion of pigment molecules out of the beetroot

cells.

2 marks

1 mark

1 mark

1 mark

Accept:

An increase in temperature

increases the (kinetic)

energy of the pigment

molecules.

Making the pigment

molecules move faster.

Therefore they diffuse out of

the beetroot cells more

quickly

ii Water volume;

Surface area of beetroot core;

Time left in water bath

1 mark each –

max 2 marks

Accept size of beetroot.

Any TWO

iii The cell/vacuolar membrane is selectively permeable and therefore stops

the passage of the pigment molecule.

1 mark Accept: semi-permeable


Page 14 of 26

iv Containing water in plant cells and therefore turgor within the cell.

Maintaining an acidic internal pH

Isolating materials that might be harmful or a threat to the cell and

containing waste products such as calcium oxalate and tannins.

Storage of unwanted substances from the cell

Store cell sap

(Any ONE)

1 mark

b i Dicots have tap root systems

(Monocots have fibrous root systems)

2 marks

ii Leaves: broad

OR

network of veins

Flowers: floral parts multiples of

4 or 5

1 mark

0.5 marks

0.5 marks

iii Beetroot plant has vascular tissue which gives it support to grow larger

than the

moss plant.

2 marks

iv Ferns need water for male gametes to reach the female gametes

This is not so for beetroot

2 marks Accept reference to

pollination by insects / wind.

v Beetroot plant seeds are enclosed within a fruit whilst those in

gymnosperms are not. The latter are formed in cones.

1 mark

1 mark

c i Vaseline:

Decrease in transpiration rate

Stomata are covered / blocked by petroleum jelly, so no transpiration

occurs from lower epidermis.

1 mark

2 marks

ii Leaf in bag:

Decrease in transpiration rate until transpiration stops

Air in bag becomes slowly saturated with water vapour reducing

transpiration until the air becomes fully saturated.

1 mark

2 marks

Total 25 marks

6 a

i Mitosis

Are diploid

Genetically identical to the parent cell / to each other

1 mark

1 mark

1 mark

ii Growth

Repair of damaged tissues

Formation of gametes needed to carry out sexual reproduction

1 mark each –

max 2 marks


Page 15 of 26

(Any TWO)

iii Anaesthetic prevents electrical messages created by pain receptors

From reaching the brain / CNS

2 marks

iv Bones/skull/cranium

Cerebro-spinal fluid

Blood-brain barrier

1 mark

1 mark

Accept meninges.

Do not accept fluid

v Unconscious actions are controlled by the medulla oblongata in the

brain. Thus if a person is unconscious, breathing and heart beat still

function.

1 mark

1 mark

Award mark for the term

medulla only if brain is

mentioned.

vi An organ is a structure in the body made up of different types of tissues

and part of a system, responsible to carry out a particular function.

2 marks

vii Sensory: receives information from the body

Motor: sends information to the body

Association: links sensory information to an appropriate response.

1 mark

1 mark

1 mark

b i Reflex action 1 mark

ii

2 marks for

correct

diagram

1 mark:

sensory

1 mark: relay

1 mark: motor

neurones.

1 mark:

synapse

2 marks:

correct arrows.

Total 25 marks

7 a i Bacterial population increase rapidly on entry of sewage up to approx. 4.5

km downstream.

The population decrease less rapidly to 8km downstream and remains

constant up to 12 km.

1 mark

1 mark


Page 16 of 26

while the oxygen concentration decreases rapidly with increasing bacterial

population up to 4.5 km

It increases again as the bacterial population decreases up to 8km and

remain constantly high

1 mark

1 mark

ii On sewage efflux, an increase in bacterial activity will increase uptake of

dissolved oxygen in water decreasing the oxygen concentration in the

stream,

The death of algae and sewage will provide enough nutrients for bacterial

exponential growth.

1 mark

1 mark

b i The number of animals will decrease substantially.

Due to a decrease in oxygen levels that will not substantiate life.

1 mark

1 mark

ii The number of plants will decrease but not substantially as these plants

are autotrophic.

In daylight, they produce oxygen as a by-product of photosynthesis,

The oxygen is used by respiring cells for energy storage.

1 mark

1 mark

1 mark

c As the bacterial population dies; decomposition of these bacteria releases

nitrites and nitrates into the water as well as carbon compounds

Algae along with the products of photosynthesis uses these for growth

2 marks

1 mark

d Denitrifying bacteria break down

nitrates (and nitrites)

To release nitrogen in the air,

1 mark

1 mark

1 mark

e i Fermentation process uses anaerobic bacteria

To break down soluble organic molecules and convert the products into

methane

1 mark

1 mark

ii The chemical energy stored in methane is converted to electrical energy.

Reducing the combustion of fossil fuels for electrical use.

Thus fewer pollutants from fossil fuels are released in air.

1 mark

1 mark

1 mark

f i Carbon dioxide 1 mark Accept water vapour, ozone,

nitrous oxide

ii Absorbs and emits infrared radiation

Prevents excessively cold temperatures, allowing temperatures on planet

to be mild and suitable for living organisms.

Increase in greenhouse gases results in global warning and climate

change.

(Any ONE or equivalent)

1 mark each -

max 2 marks

Total 25 marks


Page 17 of 26

PAPER 2 B Question Answer Mark Additional comments

1 a Vibrio =Bacteria

Sparus = Animal / Animalia

1 mark

1 mark

b Cell extracted from fish:

has a membrane-bound nucleus,

Has membrane-bound

organelles

Lacks a cell-wall

Does not have a slime capsule

Does not have plasmids

Cell extracted from Vibrio:

lacks membrane-bound nucleus,

Lacks membrane-bound

organelles,

Has a cell-wall

Has a slime capsule

Has plasmids


1 mark each

difference –

max 2 marks

Accept reference to ribosomes.

Do not accept: Cell from fish is

eukaryotic, cell from bacterium is

prokaryotic

Do not accept reference to flagellum.

c i Phylum: Chordata / Vertebrata

Class: Fish / Pisces

Have a vertebral column (extending to form a tail) OR a spinal cord

Have an internal skeleton

1 mark

1 mark

1 mark

1 mark

Max: 4 marks

Accept: Have a tail

ii Has a streamlined body

Has fins

Has gills

Body covered with scales

(Any TWO)

1 mark each:

Max 2 marks

iii Shape of fins / tail

Size of fins / tail

Shape of body / Patterns on skin surface

Type of teeth

(Any ONE or equivalent)

2 marks Acknowledge reference to comparison

of DNA, & cross breeding to check if

offspring are fertile.

Do not accept colour

d Kingdom: Plant

Phylum: Angiosperm / Magnoliophyta

1 mark

1 mark

Allow: Phylum Flowering Plant

e Similarities:

Both

1 mark

Allow reference to named

membrane-bound organelles e.g.


Page 18 of 26

Have a (membrane-bound) nucleus, *

Has membrane-bound organelles

Have a cell membrane

Have cytoplasm

1 mark

1 mark each

difference –

max 2 marks

both have mitochondria.

* As question asks only for

similarities – there is no need to

mention a membrane bound

nucleus. Award full marks for

nucleus.

Sparus

No cell wall

No chloroplasts

Lacks permanent vacuole

Does not store starch

Opuntia

Cell wall present

Chloroplast present

Permanent vacuole present

Stores starch

(Any TWO)

f Cell membrane

1 mark Accept DNA, ribosomes

and / or cytoplasm

g High temperature: may denature enzymes / alter shape of proteins /

decrease amount of oxygen in water

2 marks Expect ONE reason

h 37oC

Optimum temperature.

Enzymes work at their fastest rate / highest rate of cell division / for

bacteria to grow.

1 mark

1 mark

1 mark

Accept any temperature (as text

does not hint to any temp value)

Do not accept ideal

Total 25 marks

2 a i) Anaemia 1 mark

ii) Iron 1 mark

b i) Autosomal: does not occur on the sex chromosomes (pair no.23)

but occurs on any other chromosome (pair 12).

1 mark

1 mark

Award 1 mark for – Not sex linked

ii) Unlike males, females have their monthly menstrual cycle/ period,

making the problem more evident.

1 mark

c Phenotype: Normal / Carrier: Normal / carrier

Parents : Rr Rr

Gametes: ® (r) ® (r)

Offspring: RR Rr Rr rr

1 mark

1 mark

1 mark

Do not award marks if given letter R is

not used.

Award marks if presented in

Punnet squares

Do not award marks if disease is


Page 19 of 26

(suffers from Von Willebrand)

Probability = 25%

1 mark

1mark

represented using X and Y

chromosomes.

(Do not deduct marks if gametes

are not encircled)

d i Prevents loss of blood

Prevents the entrance of pathogens in the body

1 mark

1 mark

ii Platelets OR

Any TWO of Fibrinogen, Thrombin, Prothrombin, Fibrin,

Calcium

1 mark If platelets only – award 1 mark

If platelets with one or two

incorrect components – award 0.5

marks

(NOTE: Question asks for

COMPONENTS – so it is open to

interpretation. Marker’s discretion

is applicable)

e i Red blood cells: transport of oxygen

Lymphocytes: Produce antibodies

1 mark

1 mark

ii Red blood cells

Biconcave shape

No nucleus

Haemoglobin present

Smaller

Lymphocytes

Spherical / Circular

Nucleus (large nucleus) present

Lack haemoglobin

Larger

1 mark each

- - max 2 marks

Any TWO

iii Prevent disease

by engulfing / killing bacteria in blood (by phagocytosis)

2 marks

f Arteries Veins

No valves present Have valves

Thick wall Thin wall

Elastic wall Non-elastic wall

2 marks each

difference –

max 6 mks

Any THREE

Do not accept functions of arteries and

veins


Page 20 of 26

Narrow lumen Wide lumen

Total 25 marks

3 a

Graph marks as follows:

Title

Labelling of axes

Plotting of graph

Adequate scales chosen

1 mark

2 marks

2 marks

1 mark

Deduct 1 mark for inverted axis

b Chlorophyll 1 mark

c 490nm, 600 nm, 670nm

(Any TWO)

1 mark each

– max 2

marks

Award marks if wavelengths

correspond to graph drawn.

Deduct 0.5 marks if units are

omitted.

d Amount of carbon dioxide / intensity of light/ water availability/

presence of chlorophyll, Temperature / heat. (Any TWO)

1 mark each –

max 2 marks

e Palisade cells, spongy cells, guard cells

(Any TWO)

1 mark each –

max 2 marks

f i) Oxygen 1 mark

ii) A large number of glucose molecules are joined / linked together. 1 mark

g i) Region Enzyme Structure Product 0.5 marks each Accept small intestine i/o duodenum


Page 21 of 26

Mouth (Salivary) amylase Salivary gland Maltose – max 6 marks

Duodenum (Pancreatic) amylase Pancreas Maltose

Duodenum Maltase Wall of duodenum Glucose

ii) Starch is too large

to be absorbed. 2 marks

iii It provides energy

As it is the starting point of respiration 2 marks

Total 25 marks

4 a

i Mitosis

Are diploid

Genetically identical to the parent cell

2 marks

1 mark

1 mark

ii For growth

repair of damaged tissues

formation of gametes needed to carry out sexual reproduction (Any

ONE)

2 marks

iii Bones/skull/cranium

Cerebro-spinal fluid

Blood-brain barrier

(Any ONE)

2 marks

Accept meninges.

Do not accept fluid

iv Cerebellum: balance / posture / co-ordinated movements

Pituitary: formation of hormones (e.g. ADH)

1 mark

1 mark

v Unconscious / Involuntary actions are controlled by the medulla

oblongata in the brain. Thus if a person is unconscious, breathing

and heart beat still function.

1 mark

1 mark

Award mark for the term medulla

only if brain is mentioned.

vi Small Intestine, large intestine, liver, stomach, kidneys, ovaries,

testes, penis (any TWO or equivalent)

1 mark each:

Max 2 marks

b i Reflex action 1 mark Award 0.5 marks for reflex.

Do not accept reflex arc.


Page 22 of 26

ii

2 marks

5 marks

3 marks

2 marks for correct diagram

1 mark – sensory

1 mark – relay

1 mark – motor

1- Stimulus

1 mark-effector

3 marks– correct arrows.

Total 25 marks

5 a i large petals

nectary

Stamen and carpel protected within petals

1 mark each -

max 2 marks

Any TWO

ii anther

ovary

1 mark

1 mark

iii Anthers shed pollen when the stigma is not ripe(open) yet to receive it

OR

Anthers have finished shedding pollen when the stigma is open to

receive the pollen.

2 marks

iv (Meiosis occurs in stamens and ovary)

i) anthers split open releasing pollen

ii) pollen transferred to stigma

iii) pollen tube grows down the style into the ovary

iv) the male nucleus fuses with the female nucleus

1 mark each

point –

max 4 marks

Award 0.5 marks for ‘Fertilisation

occurs’.

b i

The seeds are distributed (dispersed) far from parent / OR

Removes germination inhibitors from the seed coat / OR

Faeces acts as a fertilizer

2 marks

ii Geotropism = response of plants to gravity

Stems move away from gravity / stems grow upwards against gravity

Roots move towards gravity / Roots grow downwards towards gravity

1 mark

1 mark

1 mark

c i Fruit wall develops from Ovary

Seed develops from Ovule

X –develops from Stigma

1 mark

1 mark

1 mark

Accept carpel

Expect candidates to specify the

links clearly


Page 23 of 26

ii Seeds shaken out by the wind/splitting of the pericarp / explosive

mechanism 2 marks

d i

A – sperm duct / vas deferens

B – testis

1 mark

1 mark

Accept testes

ii Penis 1 mark

iii Deepening of the voice

Enlargement of testis / penis

Rapid rate of growth

Muscular development

(Any TWO or equivalent)

1 mark each:

Max 2 marks

Total 25 marks

6 a i Brown citrus aphid and black citrus aphid

Both aphids belong to the same genus (Taxoptera)

1 mark

2 marks

ii Scientific naming is standardised / universal

Overcomes language barriers

Avoids confusion – only one name for each species

2 marks Any ONE or equivalent

iii When reaching high numbers on a tree therefore high (intraspecific)

competition

The aphids can fly off to feed on nearby trees (new feeding territory)

therefore increases survival rate

1 mark

1 mark

Do not deduct marks if

intraspecific is not mentioned.

iv Broad range insecticides kill all insects the pesticide comes in contact

with including beneficial insects and upsetting the natural food web.

2 marks Allow: Oil and detergent prevent

insect from attaching to plant and

feeding

b i A parasite is lives on another organism (host) and derives food or

nutrients from it

Harming the host in the process.

1 mark

1 mark

ii A tissue is a group of cells having the same structure and function. 2 marks Do not accept: A group of cells.


Page 24 of 26

iii

2 marks for

correct

diagram

2 marks for

correct labels:

protein coat/

capsid/

capsomeres

nucleic acid.

(Max 4 marks)

Accept diagram of any form of virus to

include

iv If the phloem tissue is infected by the virus then these cells cannot

transport sucrose to all parts of plant needed for reactions for

synthesis and growth

1 mark

1 mark

1 mark

c

1 mark for

each tropic

level

2 marks for

correct arrow

signs

(Max 5 marks)

Total 25 marks

7 a i Bacterial population increase rapidly on entry of sewage up to approx.

4.5 km downstream.

The population decrease less rapidly to 8km downstream and

Remains constant up to 12 km.

1 mark

1 mark

1 mark

If no values are quoted in answer

deduct 0.5 marks

ii The oxygen concentration decrease rapidly with increasing bacterial

population up to 4.5 km

It increases again as the bacterial population decreases up to 8km and

remains constantly high

1 mark

1 mark


Page 25 of 26

b The number of animals will decrease substantially.

Due to a decrease in oxygen levels that will not support life.

1 mark

2 marks

c i As the algae decrease the oxygen concentration decreases as well. 2 marks

ii (Intra specific) Competition

for resources such as light and space and trace elements

2 marks

1 mark

d i Aerobic process –use of oxygen

Anaerobic process- without use of oxygen

1 mark

1 mark

Deduct 1 mark for (Contains O2)

ii Denitrifying bacteria break down nitrates and nitrites

To release nitrogen in the air.

2 marks

1 mark

iii The chemical energy stored in methane is converted to electrical

energy.

Reducing the combustion of fossil fuels for electrical use.

Thus fewer pollutants from fossil fuels are released in air.

1 mark

1 mark

1 mark

e i Carbon dioxide 1 mark Accept water vapour, ozone, nitrous

oxide

ii Absorbs and emits infrared radiation

Prevents excessively cold temperatures, allowing temperatures on

planet to be mild and suitable for living organisms.

Increase in greenhouse gases results in global warning and climate

change

1 mark

1 mark

1 mark

Total 25 marks

8 a i In both cases there is an increase in water loss.

Fan- air currents move the water vapour particles away from the leaf,

Increasing the water concentration / diffusion gradient

Warm air- causes particles to collide quicker to each other and

therefore expanding

Increasing water concentration / diffusion gradient

2 marks

1 mark

1 mark

1 mark

1 mark

ii Rate of water loss would decrease

As surrounding air becomes saturated with water and

Water concentration gradient becomes less steep

1 mark

1 mark

1 mark

iii Gaseous exchange occurs through the open stomata

Due to a concentration gradient between the inside of the leaf and air

outside.

1 mark

2 marks


Page 26 of 26

b i Diffusion is the movement of molecules from a concentrated (highly

concentration) solution to a dilute (low concentration) solution

2 marks

ii B 1 mark

iii Containing water in plant cells and therefore turgor within the cell.

Maintaining an acidic internal pH

Isolating materials that might be harmful or a threat to the cell and

containing waste products such as calcium oxalate and tannins.

Storing unwanted substances from the cell

Contain cell sap.

(Any ONE)

2 marks

iv Sucrose is a disaccharide

made up of glucose

and fructose

1 mark

0.5 marks

0.5 marks

c i Leaves: broad

OR

network of veins

Flowers: floral parts multiples of

4 or 5

1 mark

0.5 marks

0.5 marks

ii Beetroot plant has vascular tissue which gives it support to grow

larger than the moss plant.

2 marks

iii Ferns need water for male gametes to reach the female gametes

This is not so for beetroot

2 marks Accept reference to pollination by

insects / wind.

Total 25 marks

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