Answers to Workbook

Cambridge ® IGCSE Biology Practice Book

A N S W E R S

Answers 1 Characteristics of living things 1 Characteristic

3

Exam focus

Definition the breakdown of food in cells to release energy

1 2

respiration

an increase in size, mass and complexity of an organism

3

excretion

producing offspring, which prevents extinction of the species

sensitivity

this involves feeding – obtaining nutrients for growth, energy and maintaining health

nutrition

2

reproduction

in response to changes, e.g. presence of a predator, to find food or a mate

growth

the ability to detect changes in the surroundings

movement

getting rid of the waste products made by chemical reactions in cells

Any suitable sentence with seven words linked to the characteristics of life, e.g. Most Rats Start Gathering Rice Every Night. Across 5 excretion 6 nutrition 7 respiration Down 1 sensitivity 2 reproduction 3 movement 4 growth

4 Organism plant

animal

5

6

Product 1 carbon dioxide/ water 2 o ox xygen 1 carbon dioxide/ water 2 urea

(Breathing) is the process of getting oxygen into the lungs and the removal of carbon dioxide. Ref. to faeces being undigested food, which has not been formed through metabolic processes.

Process respiration photosynthesis respiration deamination

(Respiration) is the release of energy from food substances in cells.

4

B Any three three from: from: movement, excretion, nutrition (feeding), sensitivity (irritability). (a) Any two (a) Any two from: from: movement, excretion, sensitivity. sensitivity. (b) Any (b) Any two two from: from: growth, reproduction, respiration. Any three three from: from: sensitivity sensitivity,, nutrition, growth, excretion.

2 Classification of living organisms 1 protoctists, fungi, plants, bacteria 2 A (a) (dragonfly) (a) (dragonfly) insect (b) Key features – any two two from: from: three pairs of legs, two pairs of wings, one pair of antennae, body divided into three parts, one pair of compound eyes. B (a) (earthworm) annelid annelid (b) Key features – any two two from: from: elongated, cylindrical body, segmented body, clitellum present. C (a) (a) (snail) (snail) mollusc (b) Key features – any two any two from: from: has a shell, muscular foot, eyes on tentacles. D (a) (a) (spider) (spider) arachnid (b) Key features – any two two from: from: four pairs of legs, body divided into abdomen and cephalothorax, several pairs of simple eyes, chelicerae for biting prey. 3 Any two two from: from: no backbone, have exoskeleton, segmented bodies, jointed limbs. 4 (fish and amphibians) Common features – any two two from: from: cold blooded, have eyes, produce jelly-covered eggs (in water). Differences: ref. to gills/lungs, fins/legs, scales/moist skin. (amphibians and reptiles) Common features – any two two from: from: four legs, eyes and ears, cold blooded, lungs.

Cambridge IGCSE Biology Practice Book © Hodder & Stoughton Ltd 2013

1

S R E W S N A

Differences: ref. to moist skin/scales, eggs jelly covered/waterproof covered/waterp roof shell (birds and mammals) Common features – any two two from: from: eyes and ears, warm blooded, lungs. Differences: ref. to feathers/fur, two legs/four legs, eggs with hard shell/live young, beak/no beak (or ref. to teeth), ears/ears with pinna, no mammary glands/mammary glands. 5 (a) (i) (i) Any three three features features from: multicellular, multicellular, have roots, stems, leaves, ref. to seed production. (ii) Any three (ii) Any three features features from: (cellulose) cell wall, sap vacuole, nucleus, cytoplasm, membrane. (b) (leaf (b) (leaf shape) broad (leaf veins) parallel (cotyledons) two (grouping of flower parts) in threes 6 (a) (fungi) (a) (fungi) Any two two from: from: presence of hyphae, ref. to mycelium, chitin in cell walls, no chlorophyll present, ref. to spores, enzymes secreted for food digestion. (bacteria) Any two two from: from: small, cell wall – not cellulose or chitin, membrane/cytoplas membrane/cytoplasm m present, glycogen granules present, DNA in form of one coiled chromosome, no nucleus. (viruses) Any two two from: from: very small, no special cell structure, have a strand of DNA/RNA, surrounded by protein coat/ref. to capsid, only show reproduction. (b) virus, (b) virus, bacteria, fungi (c) only show reproduction reproduction as a characteristic of life

4 Cell structure and organisation 1

2

3

cell wa wall

chloroplast

cytoplasm

Exam focus 1 2

B (a) (i) (i) Any two two from: from: exoskeleton, segmented body, segmented limbs. (ii) Any two (ii) Any two from: from: five pairs of legs, two pairs of antennae, exoskeleton in the form of a carapace, compound eyes. (b) Ref. (b) Ref. to maintaining constant body temperature/ warm blooded, moves around more to find food or to find a mate.

4

3 Using simple keys 1

A insect, B arachnid, C myriapod, D crustacean, E mollusc, F annelid, G nematode

2 Plant A B

1a 1b –   –

2a – –

C

–



–

D



–



2b 3a 3b Name of plant – –  Primula vulgaris  – – Narcissus pseudonarcissus –  – Ranunculus ficaria – – – Hyacinthoides non-scripta

Exam focus 1

2

A B C D E

Nucellus lapillus Calliostoma ziziphinum Patella vulgata Littorina obtusata Cerastoderma edule

(a) F (b) F (c) T (d) T (e) F (f) T (g) T (h) F (i) T (j) T (a) A membrane, B cytoplasm, C cell wall, D chloroplast, E (sap) vacuole, F nucleus (b) chloroplast, (b) chloroplast, cell wall, (sap) vacuole Cell part Description a flu fluid-filled space surrounded by a membrane a round or oval structure containing DNA in the form of chromosomes a tough, non-living layer made of cellulose, which surrounds the membrane

membrane

jelly-like, with particles particles and organelles in it

nucleus

an organelle containing chlorophyll

sap vacuole

a partially permeable layer that forms a boundary around the cytoplasm

(a) contains cell organelles, site of chemical reactions (b) prevents (b) prevents cell contents from escaping, controls the passage of substances into and out of cell (c) controls cell activities, activities, controls cell division/ development

Exam focus 1 2

(a) cell membrane, cytoplasm, nucleus nucleus (b) (i) (i) chloroplast (ii) chlorophyll, traps light energy for photosynthesis (a) Any two (a) Any two from: from: cell wall, chloroplast, sap vacuole. (b) Function Cell part controls cell activities and development contains cell organelles and is the site of chemical reactions waft mucus and bacteria away from the lungs controls what substances enter and leave the cell

Cambridge IGCSE Biology Practice Book © © Hodder & Stoughton Ltd 2013

B D A C

3

(a) Any five parts compared from: Cell part cell wall membrane cytoplasm nucleus chloroplast sap vacuole

Liver cell Palisade mesophyll cell 























(b) Functions of six parts, such as: cell wall – prevents the cell from bursting membrane – controls what substances enter and leave the cell cytoplasm – contains cell organelles nucleus – controls cell activities sap vacuole – contains sugars and salts chloroplast – traps light energy for photosynthesis.

5 Levels of organisation 1 2

6 Any five named leaf cells (max. 3 marks for each), with features described and functions stated, such as: Epidermal cell: thin, transparent, no chloroplasts present, allows light through/acts as a barrier to disease organisms. Palisade mesophyll cell: columnar, packed with chloroplasts, for photosynthesis/to trap light energy. Spongy mesophyll cell: mostly spherical shaped, chloroplasts present, for photosynthesis/allows gaseous exchange within the leaf due to air spaces between cells. Guard cell: found in pairs, mainly in lower epidermis, contains chloroplasts, controls opening of stomata. Xylem cell: long and thin, with lignified cell wall, lacks end wall/cell contents, transports water and mineral salts. Phloem cell: sieve plate present in end wall, transports sugars and amino acids/ref. to translocation. 7

chromosome, nucleus, cell, tissue, organ, organ system, organism Example Term leaf

heart

Name

Location

Function

plant cell

root hair cell

on surface of young roots

animal cell 1

sperm cell

produced in testes

animal cell 2

ciliated cell

bronchus/ oviduct

animal cell 3

villus cell

small intestine

absorption of water/ absorption of mineral salts/ anchorage of plant into the soil fertilisation of egg/ reproduction waft bacteria or mucus away from the lungs/ move egg from ovary to uterus absorbs digested food molecules/ water

cell

organ

skeleton tissue root hair organ system spongy mesophyll

worm 3

4 5

organism

(a) magnification = observed size actual size 12 (b) = × 4.3 2.8 15 15 100 = = 0.15 mm ; actual size = 100 actual size (a) a group of cells with similar structure, performing a special function (b) Any two animal tissues and any two plant tissues and their functions: e.g. ciliated cells – waft mucus with dust or bacteria away from the lungs muscle cells – can contract to cause movement red blood cells – transport oxygen around the body root hair cells – absorb water and mineral salts/ anchor the plant into the soil xylem cells – transport water and mineral ions from roots to leaves/provide strength for the stem.

A N S W E R S

Exam focus 1

Organ – several tissues grouped together to make a structure with a special function, e.g. heart, leaf. Organ system – a group of organs with closely related functions, e.g. circulatory system, flower. Tissue – a group of cells of similar structure that work together to perform a special function, e.g. muscle, xylem.

2 Cell

Organelle(s)

muscle cell

mitochondria

red blood cell

nucleus

More/ less/ none more

none

Explanation

need a lot of energy from respiration for contracting provides more space for haemoglobin (Continues overleaf)


3

S R E W S N A

2

(Continued)

upper epidermis

Cell

Organelle(s)

upper epidermal cell

chloroplasts

liver cell

mitochondria

more

xylem

nucleus

none

3

More/ less/ none none

Explanation

makes the cell transparent so light can pass through carry out many chemical reactions, requiring energy from respiration allows water to flow freely through the vessel

C D E

F

Name

Function

(waxy) cuticle waterproofs the leaf upper epidermis allows light to pass through/acts a barrier to microbes palisade main site of photosynthesis (mesophyll) xylem transports water and mineral salts phloem transports products of photosynthesis/carries out translocation guard cell controls exit of water vapour from the leaf

6 Diffusion and active transport 2

3

4

air space

(a) The leaf contains a number of different tissues, which work together to carry out photosynthesis/ transpiration. (b) Leaf part A B

1

palisade mesophyll cell

movement of a substance from a region of high concentration to a region of lower concentration down a concentration gradient (a) (i) oxygen (ii) Any three points from: short distance, big concentration gradient, small molecules, large surface area, higher temperature. (b) (i) Rate of diffusion would drop, because the molecules have a lower kinetic (movement) energy/molecules move more slowly. (ii) Rate of diffusion would increase, because the concentration gradient would increase or be maintained. (a) (i) labels to parts as shown in the following diagram (ii) arrows as those shown in the following diagram (through a stoma, through air space in spongy mesophyll, into palisade mesophyll cell)

stoma

4

5

6

(b) (i) Upper epidermis has an impermeable layer of waxy cuticle. (ii) The guard cells close the stomata to reduce transpiration, preventing gas exchange. (a) F (b) T (c) F (d) F (e) T (f) T the movement of a substance across a membrane from a region of lower concentration to a region of higher concentration, against a concentration gradient, using energy (a)

Process(es) plant A

Reason roots have absorbed nitrate until there is no concentration diffusion only gradient plant B the roots have absorbed nitrate against a concentration diffusion and active gradient, building up a higher transport concentration than that present in the soil (b) Plants need energy from respiration to carry out active transport. Cyanide prevents respiration.

Exam focus 1 2

D

Type of cell

Substance Process(es) absorbed used

Gradient: Energy high to low/ used? low to high?

root water osmosis hair cell phosphate 1. diffusion

villus glucose cell in small intestine

high to low 1. high to low 2. active 2. low to transport high 1. diffusion 1. high to low 2. active 2. low to transport high


no 1. no 2. yes 1. no 2. yes

3

4

(a) A alveolus/air sac B capillary C red blood cell (b) (i) arrow from inside the alveolus to a red blood cell (ii) arrow from blood plasma to inside the alveolus (iii)arrow along capillary from pulmonary artery to pulmonary vein (c) (i) diffusion (ii) Ref. to breathing to keep oxygen levels in the alveoli high; ref. to blood constantly moving through capillaries, bringing blood low in oxygen. (a) A capillary – absorbs digested food molecules, e.g. glucose, amino acids B lacteal – absorbs fatty acids, glycerol C epithelial lining – one cell thick for efficient absorption/has microvilli to increase surface area for absorption (b) to increase surface area for efficient absorption/ to increase rate of diffusion (c) (i) diffusion (ii) Any two from: walls are one cell thick, form a network to provide a large surface area, close to the surface of the villus. (d) (i) When the concentration of glucose in the intestine is the same as/lower than the concentration in the capillary. (ii) Energy is required.

1 2

roots, osmosis, higher, lower, membrane, turgid, flaccid, wilting, small, partially (a) Level in the hollow goes down, level in the dish goes up. (b) There is a higher concentration of salt in the dish, so water moves from the hollow to the dish, through the potato cells by osmosis. (c) Water moves out of the root hair cells by osmosis, so the cells become flaccid and die. The plant then dies because it has lost its ability to absorb water. Diffusion

Osmosis

  oxygen water  (accept )   phosphates    carbon dioxide

6

A N S W E R S

Exam focus 1

2

(a) (i) The concentration of water is higher outside the cell, so water enters the cell, by osmosis, the cell becomes turgid. (ii) The concentration of water is higher inside the cell, so water leaves the cell, by osmosis, the cell becomes plasmolysed, then flaccid. (b) (i) The concentration of water is lower inside the cells than in the plasma, so water enters the cells, by osmosis, the cells become turgid, then burst because they have no cell wall. (ii) Red blood cells are no longer able to transport oxygen, so cells are unable to respire, resulting in an energy shortage. (a) (b) Start length/ cm

Length after 1 hour/ cm

Change in length/ cm

0.0

5.0

5.3

0.3

6.0

0.2

5.0

5.1

0.1

2.0



0.4

5.0

4.7

–0.3

–6.0



0.6

5.0

4.4

–0.6

–12.0



0.8

5.0

4.3

–0.7

–14.0

1.0

5.0

4.3

–0.7

–14.0

-

Active transport 

There is a higher water potential in the soil than in the root hair cells, so water passes into the root hair by osmosis. The sap in the root hair cell develops a higher water potential than the cell next to it (cortex cell), so water moves across from cell to cell until it reaches the xylem. Water moves up the xylem vessels, so a water potential gradient is maintained. 5 Zone A – as the sugar solution becomes less concentrated, more water enters the potato cells by osmosis, so the tissue gains mass. The more dilute the sugar solution, the more mass is gained. Zone B – as the sugar solution becomes more concentrated, more water leaves the potato cells by osmosis, so the core loses mass. The more 4

-

Sugar concentration /mol dm 3

3 Substance

-

7 Osmosis

concentrated the sugar solution, the more mass is lost. Between 0.6 mol dm 3 and 1.0 mol dm 3, there is no additional mass lost as the potato cells have become fully flaccid in each case. Zone C – at this point there is no net gain or loss of mass by the potato core as the water potential inside the cells is the same as the water potential of the surrounding sugar solution. (a) Ref. to transport medium/moves mineral salts or sucrose or amino acids around the plant maintains the turgidity of cells/to keep cells firm/ to prevent wilting. Ref. to raw material for photosynthesis. (b) (i) Ref. to root hair cells, absorb water by osmosis, from a high concentration in the soil, to a lower concentration in the cell. (ii) Ref. to cortex cells, have a lower concentration of water than epidermal cells, so water moves by osmosis, until water reaches xylem, ref. to transpiration pull. (iii)Water in leaf cells evaporates, into air spaces, higher concentration of water vapour in air space than in atmosphere, so molecules move out of leaf by diffusion, through stomata.

(c)

% change in length

10.0

5.0

h t g 0.0 n 0.0 e l n i e –5.0 g n a h c –10.0 %

0.2

0.4

0.6

0.8

1.0

1.2

sugar concentration/mol dm–3

–15.0

–20.0


5

S R E W S N A

(d) (i) 0.26 mol dm 3 (ii) The concentration of sugar in the potato cells is the same as the concentration in the surrounding solution, so there is no net movement of water molecules. (e) Any two from: leave all the cores in the solutions for the same amount of time, use the same volume of solution in each test tube, cut all the cores to the same diameter. (f) Any one from: set up two or more cores for each concentration, measure the length of the cores in millimetres, weigh the cores instead of measuring length. -

8 Enzymes 1

2

6

(a) a chemical that speeds up the rate of a reaction without being changed itself (b) a biological catalyst, protein in nature, which speeds up the rate of a reaction (a)

Exam focus 1

enzyme

amylase starch

maltose

substrate

end product

(b) Any two from: starch is a larger molecule, starch is insoluble while glucose is soluble, starch is a polysaccharide/polymer while glucose is a monosaccharide/monomer. (c) Protease only digests proteins, amylase only digests starch. The active site in protease will have a different shape to the active site in amylase, so the substrate (starch) will not fit. 3 (a)

optimum reaction rate

s t i n u y r a r t i

b r a / e t a r

5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0

the reaction is speeding up fastest here

makes the bread dough rise. The ethanol evaporates as the bread is baked. Brewing, e.g. beer or wine. Enzymes in yeast convert sugar to ethanol and carbon dioxide. The ethanol makes the drink alcoholic; carbon dioxide gives the drink its ‘fizz’. Cheese-making. The enzyme rennin, extracted from cows’ stomachs, is used to clot milk. Making baby foods. Trypsin (a protease) is used to pre-digest baby foods. (a) (i) Stir the mixture of feedstock and microorganisms/distribute the heat through the liquid. (ii) Extracts the microorganisms from the filtrate. (iii)Provides nutrients for the microorganisms to grow, respire and produce enzymes. (b) fungi, bacteria (c) Microorganisms are filtered from the feedstock, then crushed and washed with water.

2

(a) (i) lipase (ii) protease/pepsin (b) Enzymes digest molecules causing the stains, the small molecules produced are soluble. (c) The enzymes in the powder would be denatured, so they would not digest the stains. (d) Amino acids are small, soluble molecules while proteins in blood are large, insoluble molecules. (a) (i) amylase (ii) maltose (iii) Any two from: energy source, to convert to cellulose, convert to materials for growth. (iv)Starch is a large, insoluble molecule; maltose is smaller, soluble. (b) (i) Ref. to water passes through the micropyle. (ii) Enzymes are only active in water; cells become turgid – leading to expansion.

9 Nutrition and nutrients 1

(a) (i) starch (iii)

denaturing is taking place here

(ii) obtaining energy

chemical bond glucose unit

(b) (i) fat/lipid

the reaction is slow here

0

20

40

(ii) energy/insulation/formation of cell membranes/hormone formation

(iii)

60

temperature/°C

4 5

6

(b) (i) The reaction would speed up because the substrate and enzyme molecules would move faster/gain more kinetic energy, so there would be more collisions. (ii) There would still be no reaction because all the enzyme molecules have been denatured by the high temperature. temperature, pH, concentration of substrate Any two from: Baking, e.g. bread. Enzymes in yeast convert sugar to ethanol and carbon dioxide. The carbon dioxide

glycerol

(c) (i) protein

chemical bond

fatty acid

(ii) growth/tissue repair/enzymes/ cell membranes/hormone formation

(iii) amino acid chemical bond


2 Food tested

Chemical reagent used

Colour for a positive result

reducing sugar

iodine solution

blue-black

fat

Benedict’s solution

violet (halo)

Exam focus 1 2 3

protein

starch 3

4

5

ethanol

brick red

Biuret solution (sodium hydroxide + copper sulfate solution)

white emulsion

(a) iron (b) water (c) calcium (d) fibre (e) vitamin C (a) Yeast is mixed with flour, some sugar and water to make dough. The dough is kept warm to allow the yeast to respire the sugar, producing pockets of carbon dioxide. These make the dough rise. Baking kills the yeast. (b) Bacteria (e.g. Streptococcus thermophilus and Lactobacillus bulgaricus) are used to ferment milk at 46 oC. As a result, lactic acid is produced (as fermentation progresses the pH drops). The lactic acid makes the milk coagulate. The temperature is then reduced to 5 oC to prevent further bacterial action. Any three from: Name of group

Function of additive

Advantage

Disadvantage

antioxidants

stop food reacting with oxygen

stop the taste of the food being spoiled/ stop colour changing food becomes more attractive

may have side effects for some consumers, e.g. stomach problems, kidney stones may be hazardous to health/trigger allergic reactions/cause hyperactivity in children

e.g. sugar increases calorific value, risking obesity, artificial sweeteners can have side effects some additives, e.g. sodium nitrite, may be carcinogens

colourings

improve the appearance of the food

flavourings

enhance the taste of the food

improve the flavour

increase the shelf life of the food

food can be kept for longer

preservatives

A vitamin C B amino acids (a) Any two from: less saturated fat, more fibre, more calcium. (b) (i) Any one from: other red meat, liver, kidney, eggs, green vegetables, chocolate, etc. (ii) needed for the formation of haemoglobin in red blood cells (iii)Ref. to anaemia, constant tiredness, lack of energy. (c) (i) filamentous fungus (ii) better flavour, cheaper to produce (d) Any two from: the food is cheaper to produce, farmers have no vets’ bills, less energy lost/more energy available.

A N S W E R S

10 Plant nutrition 1

(a) light

carbon dioxide + water

2

3

chlorophyll

glucose + oxygen

(b) (i) Sucrose (ii) Starch (c) Chlorophyll traps light energy. (d) Any three from: shortage of oxygen, shortage of food, shortage of nesting sites, shortage of hiding places. (a) palisade (mesophyll) cells (b) guard cells (c) (upper) epidermis cells (d) xylem cells (e) phloem cells (a) Nitrate ions are needed to form amino acids, to build proteins. Proteins are needed for growth. (b) Magnesium ions are needed to make chlorophyll. Chlorophyll is needed to trap light energy for photosynthesis.

4 leaching

5

6

rapid algal growth

death of algae

decay by bacteria

death of aquatic animals

Boil the leaf in water: to kill the leaf – this makes it permeable. Boil the leaf in ethanol: to decolorise the leaf, since chlorophyll dissolves in ethanol. Rinse the leaf in water: boiling the leaf in ethanol makes it brittle, so the water softens it. Spread the leaf out on a white tile: so the results will be easy to see. Add iodine solution to the leaf: to test for the presence of starch. (a) (i) violet and orange/red (ii) green (b) Use a bright light to shine on the Elodea in a beaker of water. Measure the light intensity using a light meter, or measure the distance between the lamp and the plant. Allow the plant to adjust to the light intensity. Count the number of bubbles produced by the plant over a fixed time period (e.g. 1 minute). Move the lamp further away from the plant. Measure the new light intensity or the new distance between the lamp and the plant. Allow the plant to adjust to the light intensity.


7

S R E W S N A

Count the number of bubbles produced by the plant over the same time period. Repeat the process for at least five different light intensities or distances. Keep the temperature of the water the same, use the same plant, use the same beaker, the same time period for counting bubbles. Alternatively, the oxygen could be trapped in a graduated container such as an inverted gas cylinder, so the volume of gas could be measured.

Exam focus B palisade mesophyII (a) (i) (Description): Any two from: plants would show poor growth, stems weak, lower leaves yellow/dead, upper leaves turn pale yellow. (Explanation): nitrates needed to produce proteins, which are needed for growth. (ii) Any two from: apply animal manure, crop rotation involving leguminous plants, apply artificial fertilisers. (b) Leaves turn yellow/ref. to chlorosis, from the bottom of the stem upwards, poor plant growth, ref. to inability to form chlorophyll. 3 (a) an external factor, which restricts the effects of others (b) Any two from: Carbon dioxide – needed as a raw material for photosynthesis, converted into carbohydrate. Temperature – increased temperature speeds up photosynthesis, as enzymes work faster at higher temperatures. Light intensity – light energy needed for photosynthesis, more light speeds up the process, so more carbohydrate produced. 4 Destarch two similar potted plants. Place them in sealed bell jars/large transparent containers. To one container add a CO2 absorber. Expose both plants to same, optimum conditions, e.g. light, warmth. Leave for 2 days. Test a leaf from each plant for the presence of starch. Only the control plant leaf (without CO2 absorber) will turn blue-black, indicating the presence of starch. 5 (a) (i) A guard cells B upper epidermal cell C spongy mesophyll cell D palisade mesophyll cell (ii) B D C A (b) Xylem – transports water, mineral salts from roots around the plant. Phloem – transports sucrose, amino acids from leaves to storage or growth regions of the plant. 1 2

11 Human diet 1

8

(a) Any two advantages from: high carbohydrate level – for energy good source of calcium – for strong bones and teeth/to prevent rickets protein present – for growth/repair. Any two disadvantages from: high in animal fat – can cause heart disease/ atherosclerosis/obesity lack of fresh fruit/vegetables/fibre – to prevent constipation low in vitamin C – to prevent scurvy low in iron – to prevent anaemia.

(b) Any two from: constipation, risk of obesity/ scurvy/anaemia, risk of heart disease/ atherosclerosis. (c) (i) a diet that contains all the main nutrients in the correct amounts and proportions (ii) fibre 2 Any three from: too much food/too little food, too much carbohydrate/fat/protein, too little fibre, too few vitamins or minerals, the wrong balance of food. 3 (a) Any two from: addiction (alcoholism), cirrhosis of the liver, stomach ulcers, cancer of the digestive system, heart disease. (b) Increases risk of miscarriage, results in a decrease in average birth weight. 4 (a) Any three points and descriptions from: climate change and natural disasters, e.g. flooding or drought pollution – can lead to breaks in the food chain, poisoning of food sources, chronic diseases could adversely affect workforce responsible for producing food shortage of water, due to diversion of rivers, building dams for hydroelectricity eating future seed stock due to food shortage poor soil, or lack of fertiliser or inorganic ions, so crops are poor desertification due to soil erosion, as a result of deforestation destruction of forests, reducing numbers of animals to hunt or food to collect shortage of money for agriculture war, making it too dangerous to farm the land use of land for building houses or roads pest damage or disease increase in population. (b) Any two from: transport in chilled containers, picking fruit before it is ripe, preserving the food, e.g. canning, storage in salt or vinegar, freezing food.

Exam focus 1 Component

Function

1

carbohydrate source of energy

2

fat/oil

source of energy

3

protein

4

fibre/ roughage

5

water

growth, tissue repair, formation of enzymes, etc. adds bulk to the diet to maintain peristalsis formation of blood, medium in which enzymes work, transport of nutrients, etc.


Good food source e.g. rice, potato, yam, cassava, bread, cakes, etc. butter, milk, cheese, egg yolk, fatty meat, nuts, etc. meat, fish, eggs, soya, nuts, milk, Quorn, etc. vegetables, fruit, wholemeal bread, etc. drinks, fruit, vegetables

2

Deficiency Constituent disease scurvy vitamin C

rickets

vitamin D/ calcium

Symptoms

Food

bleeding under the skin, bleeding gums soft bones, which become deformed, bowleggedness

citrus fruits, blackcurrants, cabbage, etc.

2

A B C D E F G H (a)

mouth

oeso stomach phagus

duodenum

lleum

anus

rectum

canine slightly more pointed than incisors

premolar two points/ cusps

molar four/five cusps

one/two roots tearing and grinding food

two/three roots chewing and grinding food

A N S W E R S

colon

3 Name incisor Description chiselshaped

(for vitamin D) milk, cheese, egg yolk, fish liver oil (for calcium) milk, cheese, fish

12 Digestion and absorption 1

(b)

Function

4

mouth gullet/oesophagus stomach large intestine/colon rectum anus small intestine/ileum duodenum

anus

food is ingested here.

colon

a tube, carrying boluses of food between mouth and stomach

duodenum

has an acid pH and proteins are digested here

ileum

first part of the small intestine

mouth

absorption of the products of digestion takes place here

oesophagus (gullet)

muscular, to control the egestion of faeces

rectum

absorption of water

stomach

stores faeces

5

biting off pieces of food

biting off pieces of food

(a) Physical digestion involves breaking large pieces of food into smaller pieces. This increases the surface area of the food, achieved by chewing food in the mouth and churning food in the stomach and intestine. Chemical digestion involves the use of enzymes to break down large insoluble molecules into small, soluble ones. (b) Starch is digested in the mouth and duodenum by amylase in slightly alkaline conditions. It is broken down to maltose. Maltase then breaks down the maltose to form glucose. Protein is digested in the stomach and duodenum by protease. Conditions required are acid in the stomach and alkaline in the duodenum. The end products are amino acids. Arguments for: Tooth decay among children using the water supply decreases. There is no need to buy fluoridated toothpaste. Arguments against – any two from: It is a form of mass medication, so people have no choice about whether or not they want the treatment. Fluoride can cause mottling of the teeth/white patches/fluorosis. Fluoride is only a benefit to growing children – adults do not benefit. If people take proper care of their teeth, fluoridation is unnecessary.

Exam focus 1 2

C (a) (i) molar (accept premolar), 2 cusps visible/ 2 roots visible (ii) A root B crown C enamel D dentine E pulp cavity F gum G cement H jaw bone I nerve (b) (i) enamel (ii) (vitamin) D, (mineral) calcium (iii)fluoride (reject fluorine)


9

S R E W S N A

3

4

(c) Any six from: ref. to bacteria present on the surface of teeth, food collects on teeth, combines with bacteria to form plaque, bacteria feed on sugars, producing acids, acid reacts with enamel, forming hole, dentine is softer so dissolves faster, cavity forms. (a) Ref. to too large and insoluble to be absorbed through the gut wall. (b) diffusion, active transport (c) Any two from: ref. to large surface area, presence of microvilli, one cell thick (explanation) speeds up diffusion. (d) 1 (blood capillaries) absorb glucose, amino acids, transport them away to maintain diffusion gradient 2 (lacteal) absorbs fatty acids, glycerol (a) Part

Name

Function

A

oesophagus/ gullet

moves food from mouth to stomach

B

ileum/ small intestine

digestion of maltose, peptides/ absorption of products of digestion (accept absorption of water)

Structural feature presence of circular and longitudinal muscles for peristalsis presence of villi to increase surface area for absorption

2

3

4

10

Exam focus 1 2 3

C D

Process diffusion

(b) (i) protein (ii) Ref. to secretion of protease, hydrochloric acid, muscular churning to mix food with enzyme. (iii)Ref. to deamination, excess amino acids broken down, urea formed, energy source produced.

13 Transport in plants 1

(b) Named plant: e.g. cactus. Leaves reduced to spines – this reduces the surface area for transpiration. Reduced number of stomata. Stomata are closed during the day – when conditions for transpiration are greatest. Fleshy stem – to store water. e.g. marram grass. Very long roots to search for water deep down in sand dunes. Leaves have the ability to roll up in dry weather to increase humidity around stomata, reducing transpiration. Sunken stomata create high humidity and reduce transpiration. Fine hairs surround stomata, reducing air movement, so humidity builds up and transpiration is reduced. e.g. pine tree. Leaves are needle-shaped to reduce surface area for transpiration. Sunken stomata to create high humidity and reduce transpiration. Thick waxy cuticle on the epidermis to prevent evaporation from the surface of the leaf. (c) Any three from: ref. to spraying onto the leaves of the plants, absorbed into the leaf, transported by translocation; pest feeds on plant sap and takes in the pesticide; which kills the pest.

Transpiration – the loss of water vapour from the leaves through the stomata by diffusion. Translocation – the movement of sucrose and amino acids from regions of production/storage to regions of use for respiration or growth. (a) Any three from: anchoring the plant in the soil, absorption of water, absorption of mineral salts, food storage organ. (b) Root hair cells have a cell extension, increasing the cell’s surface area to make it more efficient for absorbing water and minerals. (c) root hair cell, cortex, endodermis, xylem (a) Any three from: increase in temperature, increase in air movement, decrease in humidity, increase in light intensity. (b) Wilting happens when the amount of water lost from the leaves of a plant is greater than the amount taken into the roots. This results in the plant having a water shortage. Cells become flaccid and no longer press against each other. Stems and leaves then lose their rigidity and wilt. (a) Xerophyte

osmosis

active transport

transpiration

4

Definition the movement of a substance from a higher concentration to a lower concentration down a concentration gradient the movement of water from a higher concentration to a lower concentration through a partially permeable membrane the movement of a substance from a lower concentration to a higher concentration against a concentration gradient, using energy the loss of water vapour from the leaves through the stomata, by diffusion

Explanation oxygen diffuses from the air into a leaf, carbon dioxide diffuses out of a leaf, mineral salts diffuse from soil into root hairs osmosis is used to absorb water by roots, cells absorb water by osmosis to become turgid, which keeps young stems rigid plants obtain mineral salts by active transport when the concentration of salts in the soil is lower than in the root cells

transpiration results in more water being drawn through the plant, carrying mineral salts from the roots

(a) Water enters the leaf in the xylem vessels (A), then passes into the surrounding spongy mesophyll cells (B). A thin layer (C) forms on


the surface of the cells, which evaporates and saturates the air in the air spaces (D), then the water molecules diffuse into the atmosphere through the stomata (E). (b) Transpiration from the leaves loses more water than is being taken in by the roots, cells in young stems lack water, become flaccid and stop pressing against each other, so stems and leaves lose their rigidity and wilt.

(cause) Smoking Obesity Stress Inherited factors 5

14 Transport in humans 1 2

3

4

(a) left atrium, left ventricle (b) aorta, pulmonary vein, coronary artery (a) a group of cells of similar structure, carrying out the same function (b) (cardiac) muscle (c) Cardiac muscle can contract. (d) It needs to build up enough pressure, to move blood to all organs, while the right ventricle only moves blood to the lungs. Ref. to vena cava, with valves, to prevent backflow of blood, into right atrium, which contracts, to increase blood pressure, to move blood through tricuspid valve, into right ventricle, which contracts, to increase blood pressure, tricuspid valve closes, to prevent backflow of blood, ref. to pulmonary artery, semilunar valve closes, to prevent backflow of blood. (a) x -axis drawn and labelled ‘time/min’, y -axis drawn and labelled ‘pulse rate/beats per min’, points plotted accurately, line drawn between points

(preventative measure) stop smoking go on a controlled diet/take regular exercise find ways of relaxing/identify causes of stress and reduce them make sure other factors are reduced/monitor health

A N S W E R S

outer layer, made of tough fibrous tissue to hold contents together lumen, much narrower than in a vein. This helps to maintain high blood pressure thick wall, made of muscles, elastic fibres and fibrous tissue, which prevents bursting and maintains pressure wave

6

1 mark for correct shape, 1 mark each for labels of up to two features, 2 marks for annotations (a) lungs labelled in upper box, body labelled in lower box (b) arrows in blood vessels and heart correct (see diagram below) (c) right atrium, right ventricle, vena cava, pulmonary artery shaded lungs

140 120

n i m r 100 e p s t a 80 e b / e 60 t a r e 40 s l u p

rest of body

7

Stretch and challenge

20 0

0.0

2.0

4.0

6.0

8.0

10.0

time/min

Across 3 plasma 4 lymphocyte 5 platelet Down 1 haemoglobin 2 nucleus

(b) (i) 60 beats per minute (ii) at 1 minute (iii)at 8 minutes (iv)Heart must beat faster to circulate more oxygen, exercising muscles need more oxygen, more glucose, and produce carbon dioxide (or lactic acid) which needs to be removed. (v) Rate starts higher than 60 bpm, reaches a higher peak, takes longer to return to normal. (vi)Keeps heart muscle in good tone, results in the heart being more efficient in maintaining blood pressure. (c) Any three of the following answers (you must give the cause and the preventive measure for each mark):

8 Any three of the following: Permeable wall – to allow diffusion of materials between the capillary and surrounding tissues. Wall is one cell thick – allows fast diffusion/allows white blood cells to squeeze between cells of the wall. Lumen is one blood cell wide – slows down blood flow to allow diffusion of materials and transfer of tissue fluid. Valves are absent – blood pressure is high enough to keep blood flowing. 9 (a) Produced by lymphocytes, formed in lymph nodes, antibodies make bacteria clump together, so that phagocytes can digest them. They also neutralise toxins produced by bacteria, and remain in blood to provide long-term protection. (b) Phagocytes can move out of capillaries, to the site of an infection; they engulf pathogens, and kill them by digestion. 10 Donor organ used is of similar tissue type to that of the patient, ref. to use of immunosuppressive drugs, keep patient in isolation during recovery.


11

S R E W S N A

11 Returns tissue fluid (in the form of lymph) to blood/ prevents build-up of fluid in the tissues, produces lymphocytes, absorbs fatty acids and glycerol from the small intestine.

4

Exam focus 1 2 3

4

5

C B (a) A C E G J L

5 aorta left atrium bicuspid valve left ventricle tricuspid value vena cava

B D F H K M

pulmonary vein semilunar valve tendon right ventricle right atrium pulmonary artery

(b) (i) right atrium (ii) pulmonary vein (iii) semilunar valve (iv) left ventricle (v) tendons (vi) vena cava (vii) aorta (viii) tricuspid valve (a) Blood passes through the heart twice, for each complete circulation of the body. (b) (artery) Any two from: thick and tough wall, narrow lumen, valves absent. (vein) Any two from: thin wall, large lumen, valves present. (capillary) Any two from: permeable wall, wall one cell thick, lumen one red blood cell wide, valves absent. (a) (i) transport of dissolved substances to cells/ removal of wastes from cells (ii) transport of oxygen (iii)produces antibodies to fight disease (iv)engulfs bacteria to fight disease (v) forms blood clots (b) (i) biconcave disc shape/no nucleus/contains haemoglobin (pink colour) (ii) large nucleus (iii)lobed nucleus/cell can change shape

6

Exam focus 1 2

3

15 Respiration 1

(a) glucose + oxygen water + carbon dioxide + energy (b) ATP (adenosine triphosphate) (c) (i) lactate/lactic acid (ii) Lactic acid causes muscle cramp (muscle fatigue), which will stop the athlete running. An oxygen debt builds up, which needs to be repaid.

2 Product 1 carbon dioxide 2 ethanol/alcohol 3

(a) mouth

12

Food manufacturing process breadmaking/brewing brewing

trachea

bronchus

bronchiole

red blood

alveolus/

cell

air sac

(b) (i) diffusion (ii) thin, moist, large surface area, has a concentration gradient (a) the volume of air breathed in/out during normal, relaxed breathing (b) the maximum amount of air that can be inhaled/ exhaled in one breath cancer, emphysema, lungs, carcinogen, carbon monoxide, tar, bronchitis, nicotine, tobacco, filter intercostal muscles contract ribcage moves up and out diaphragm muscle contracts diaphragm moves down volume in the lungs increases air pressure in the lungs decreases air moves in to fill the lungs

4

D (a) A spinal cord B left lung C heart (b) (i) lung (ii) Any four from: contains many alveoli, contains many blood capillaries, for gas exchange, ref. to oxygen and carbon dioxide, ref. to diffusion. (c) Any six from: intercostal muscles contract, ribs move upwards and outwards, diaphragm muscle contracts, diaphragm moves down, volume of thorax increases, air pressure in thoracic cavity decreases, to become lower than atmospheric pressure, so air moves into the lungs. (a) Volume of air per breath increases, from normal tidal volume, e.g. from 0.5 litres, rate of breathing increases, from 12 to over 20 breaths per minute. (b) Any three named chemicals and their effects from: Carbon monoxide – any two from: poisonous gas, combines with haemoglobin to produce carboxyhaemoglobin, preventing red blood cells from carrying oxygen, smoker gets out of breath easily, increases risk of atherosclerosis, thrombosis, coronary heart disease. Nicotine – any two points from: addictive, resulting in prolonged exposure of lungs to other harmful chemicals, raises blood pressure, risk of stroke, stimulates brain, can reduce birth weight of baby if mother smokes during pregnancy. Smoke particles – any two points from: irritates air passages in lungs, causes inflammation, increased mucus production, causes chronic bronchitis, emphysema. Tar – any two points from: ref. to carcinogen, increases risk of lung cancer, paralyses cilia in air passages, can cause bronchitis. (a) (i) respiration (ii) carbon dioxide (iii)turns from colourless to milky (iv) ethanol/alcohol (b) Any five from: Respiration of yeast is very slow at low temperatures, as molecules have little kinetic energy so few collisions. 30 ºC is optimum temperature for yeast respiration, as molecules have lots of kinetic energy to collide.


Enzymes in yeast begin to denature at 45 ºC, so respiration slows down. All yeast enzymes denatured at 100 ºC, so no respiration.

16 Excretion in humans 1 2

(b)

blood, water, glucose, reabsorbed, ADH, more, concentrated, osmosis, diffusion, active transport (a) The removal of toxic materials, the waste products of metabolism and substances in excess of requirements from organisms. aorta

renal artery

capillary

nephron

urethra

bladder

ureter

(c) Any two from: expensive to buy/maintain, very tiring for the user, may require frequent hospital visits.

17 Reactions to stimuli by plants and invertebrates 1

2 (a) Surplus amino acids are removed from the blood by the liver and broken down into urea by the process of deamination. (b) Any three from: breakdown of poisons/alcohol, breakdown/removal of drugs, breakdown of hormones, storage of vitamins, storage of iron, controlling levels of glucose in the blood, making bile. 4 Any two advantages from: The patient can return to a normal lifestyle – dialysis may require a lengthy session in hospital, three times a week, leaving the patient very tired after each session. A dialysis machine is available for other patients to use. Dialysis machines are expensive to buy and maintain. Any two disadvantages from: Transplants require a suitable donor – with a good tissue match. The operation is very expensive. There is a risk of rejection of the donated kidney/ immunosuppressive drugs have to be used. Transplants are not accepted by some religions. 3

2

(a) (i) A renal vein B left kidney C ureter D bladder E urethra (ii) (in part A) amino acids present, glucose present, more salts (iii) Any three from: smaller volume, more concentrated, urea more concentrated, salts more concentrated. (b) Vena cava (X) has a thinner wall, larger lumen, contains valves. (a) (i) a method of removing one or more components from a solution using the process of diffusion (ii) (pump) keeps blood flowing through the machine (dialysis fluid) receives wastes/toxins from the blood by diffusion (bubble trap) removes any air bubbles before the blood is returned to the patient’s vein (partially permeable membrane) allows small molecules in higher concentrations to pass out of the blood, but prevents loss of blood cells, large molecules from blood (b) (i) Visking tubing/cellulose (ii) provides a large surface area, for efficient diffusion (iii) Any two from: to maintain a concentration gradient, concentrations of removed substances build up, so diffusion slows down.

(a) a plant response to gravity (b) (i) Root. Advantage: access to water/access to minerals/better anchorage. (ii) Shoot. Advantage: access to light. (a) taxic responses/taxes (b) (i) avoid predators/protection from UV light (ii) prevents dehydration/source of food (c) They move faster in unfavourable conditions, so will tend to move out of them, but move slower in favourable conditions, so tend to stay there. (a) auxin (b) (i) The shoot bends/grows towards the light. (ii) When a shoot is exposed to one-sided light, auxins produced by the tip move towards the shaded side of the shoot/auxins are destroyed on the light side, causing an unequal distribution. Cells on the shaded side are stimulated to absorb more water than those on the light side, making them bigger. The unequal growth causes the stem to bend towards the light. (c) (i) weedkiller/chemical which kills weeds (ii) They are sprayed onto plants, causing rapid, uncontrolled growth and respiration that results in the death of the plant.

Exam focus 1

Exam focus 1

3

A N S W E R S

(a) (i) mean numbers: A 3.2 B 0.8 C 5.4 D 20.6 (ii) A dark and dry B light and dry C light and damp D dark and damp (iii)1 dark and damp 2 dry and light (iv) taxic response/taxis (v) Any two from: less risk of dehydration, less likely to be found by predators, could be a good food source (due to presence of decaying materials/bacteria). (b) (i) increases reliability of results/helps to identify anomalous results (ii) to give them more time to acclimatise to the conditions/more time to explore the options available (iii)to prevent contact with the drying agent/ drying agent could be toxic/prevent drowning

18 Coordination and response 1

(a) Central nervous system: made up of brain and spinal cord, which have the role of coordination. Peripheral nervous system: made up of nerves, which connect all parts of the body to the central nervous system.


13

S R E W S N A

(b) (i) a group of receptor cells responding to a specific stimulus, e.g. light, sound, touch, temperature, chemicals (ii)

Sense organ 1 ear 2 eye 3 nose 4 tongue 5 skin

Stimulus detected sound/body movement light chemicals/smell chemicals (taste) temperature, pressure, touch, pain

(a) Any three from: sensory neurone has dendron present/very long, sensory neurone has no axon / very short axon, cell body is near the end of the sensory neurone, dendrites are present at the end of the sensory neurone. (b) 1 acts as electrical insulation/stops impulse leaking out/makes transmission of impulse more efficient 2 makes connections with other neurones 3 transmits the impulse along the neurone 4 coordinates the cell/contains DNA 3 (a) A chemical secreted by an endocrine gland. It is transported in the bloodstream and usually has a long-term effect on a target organ. (b) Any three from: causes heart rate to increase, blood supplies muscles with oxygen and glucose more quickly, blood supply to skin reduced, blood supply to digestive organs is reduced, blood is diverted to vital organs, liver is stimulated to convert glycogen to glucose. (c) 2

Feature

Nervous

form of transmission transmission pathway speed of transmission duration of effect

electrical impulses nerves

Hormonal (endocrine) chemical/ hormones blood vessels

fast

slow

short term

long term

4

5

6

7

(a) A ciliary muscles – contract B suspensory ligaments – slacken C lens – thickens (b) (i),(ii) D circular muscles – contracted E radial muscles – relaxed F pupil – constricted (a) the maintenance of a constant internal environment (b) (i) 37 ºC (ii) Increase in sweating – sweat is secreted onto the skin surface. Water from sweat evaporates, taking heat from the skin surface. Vasodilation – arterioles dilate to allow more blood to flow near the skin surface, so more heat is lost through radiation. (a) (i) Automatic action, generally a reflex, which cannot be overridden. (ii) faster (iii) Any two examples from: heart beat, peristalsis, uterine contractions during birth. (b) The drop in glucose is detected by the pancreas. It secretes glucagon. This is transported to the liver in the blood. In the liver, glucagon converts glycogen to glucose.

Exam focus 1 2

C (a) Any three from: used to treat disease, reduce sensation of pain, help to calm the patient down, used as anaesthetic, to cause unconsciousness. (b) (i) Drug

Effects on the body

alcohol

small amounts – relaxes the body, large amounts – acts as a depressant, slows down reactions, coordination impaired, creates mood swings, can trigger violence has narcotic effect, increases relaxation, reduces pain

(a) (i), (ii), (iii) relay neurone B

ganglion pain receptors

spinal cord

heroin

A

sensory neurone

D

biceps muscle

motor neurone C

14

(b) it contracts (c) (i) synapse (ii) acetylcholine

nicotine (in tobacco)

raises blood pressure, heart rate

Dangers to the person using the drug increases reaction times, so driving and handling machinery is impaired, can lead to criminal activity, promiscuity, alcoholism, financial problems, liver disease, etc. addictive, tolerance to drug increases, so risk of overdosing, risk of infection from using unsterilised needles can lead to criminal activity, promiscuity, alcoholism, financial problems, etc. addictive, other chemicals in the cigarette can lead to cancer, risk of atherosclerosis, thrombosis, coronary heart disease, etc.

(ii) Any three from: ref. to criminal activity, sexual promiscuity, financial problems for family, dangers for unborn children. Cambridge IGCSE Biology Practice Book © Hodder & Stoughton Ltd 2013

3

4

Any eight from: Homeostasis means maintaining a constant internal environment. Pancreas acts as a sensor in negative feedback and acts as an effector by secreting hormones. If glucose levels rise above normal, change is sensed by the pancreas. Insulin is secreted by the pancreas and passed into bloodstream. Insulin instructs the liver to remove excess glucose from the blood. Glucose is converted to glycogen and stored. Rate of respiration in the liver is increased to use up glucose. Glucose levels return to normal. If glucose levels fall below normal the pancreas stops secreting insulin and starts to secrete glucagon. Glucagon instructs the liver to convert glycogen to glucose. Glucose is passed into the blood, returning glucose levels to normal. (a) (i) A scapula B humerus C biceps D radius E ulna F triceps (ii) tendon (b) (i) (effector) a muscle or gland which responds when it receives an impulse from a motor neurone. (antagonistic muscle) pairs of muscles which oppose each other when they contract. (ii) Triceps muscle contracts, pulling on the ulna. (iii) Biceps relaxes.

19 Reproduction, growth and development in plants 1

(a) the formation of a new organism, without the involvement of gametes or fertilisation (b) (i) Ref. to binary fission. Inside each bacterium the DNA replicates, then the cell divides into two, with each daughter cell containing identical DNA. The daughter cells grow before dividing again. (ii) Ref. to spore production. Spores may be produced in a sporangium, which bursts when ripe, allowing spore dispersal. The spores germinate and grow into new individuals. (iii)Ref. to stem tubers. The parent plant photosynthesises and the food produced is stored in underground stems. These swell with starch, forming tubers. Connections with the parent plant die. The tuber has buds that can produce new stems and roots, forming a new plant.

2

3

4

anther

protects the flower while in bud

ovary

often large and coloured to attract insects

petal

produces pollen grains containing male sex cells

sepal

sticky, to receive pollen grains during pollination

stigma

contains ovules, the female sex cells

A N S W E R S

stigma style ovary ovule (accept seed) filament anther carpel stamen Ref. to feathery/with a larger surface area/ hanging outside the flower – to increase the chance of trapping pollen grains. 2 Ref. to larger numbers of pollen grains/ pollen grains lighter – to increase chances of pollination/to be more easily carried by the wind. (a) Growth – an increase in dry mass of an organism, as a result of cell growth and division. Development – an increase in complexity through the differentiation of cells. (b) (i) Named seed – any one from the following or any other suitable example: e.g. dandelion – has a group of fine hairs called a pappus, which catches the wind and acts like a parachute. e.g. sycamore – has a wing with a large surface area. It spins and falls slowly. (ii) Named seed – any one from the following or any other suitable example: Blackberry – is a succulent fruit that attracts animals because it is brightly coloured/ juicy/nutritious. When eaten, the seeds pass through the animal’s gut without being digested and are deposited with the animal’s faeces. Bur – has hooked seeds, which catch onto an animal’s fur as it brushes past the parent plant. Eventually, the seeds drop off or are removed as the animal grooms itself. (c) (i) Oxygen is needed for respiration to provide energy for the growing seedling. (ii) Warm temperatures activate/speed up enzymes to release soluble nutrients for the germinating seed.

(i) A B C D E F (ii) 1 2 (iii)1


15

S R E W S N A

5

(iii)Water activates enzymes and allows stored foods to be broken down/digested/dissolved for transport. (d) (i) Stored food in the cotyledon is used for respiration. (ii) Photosynthesis starts, producing food that can be stored or built up into new tissues. (a) Any two advantages from: Variation in offspring is produced. New varieties of plant can be created. Seeds are formed, which allow dispersal away from the parent plant. Two disadvantages: Two parents are usually needed. Growth of a new plant tends to be slow. (b) Definition

Advantage Disadvantage Reduces the selfThe Smaller pollination transfer numbers of variation of pollen pollen in the offspring/ from the grains anther need to be less likely to to the produced/ cope with adapting stigma of there is a the same greater to environflower, or chance of mental change. to another successful flower of pollination. the same plant. crossThe Increases Reduces the pollination transfer variation/ chance of the ability fertilisation. of pollen from the to adapt anther of to environa flower to mental the stigma change. of a flower on a different plant of the same species.

Exam focus 1

16

(a) (i) arrows from pollen grain down through the stigma (A), style (B) around either side of the ovary wall (C), into micropyle (D) to the ovule (ii) Any six from: pollen grain germinates, pollen tube grows, pollen tube contains the male nucleus, grows down through the stigma (A), through the style (B), through the ovary wall (C), into micropyle (D) to the ovule, male nucleus fuses with nucleus of ovule. (b) (i) Any one from: pollen grain would be lighter/ have a larger surface area/no spikes on surface/smooth surface. (ii) Stigma would be feathery, hangs outside the flower.

2

(a) (type of pollination) wind (explanation) any six from: A = stigma, which is feathery, hangs outside the flower, has large surface area. B = filament, which is long to expose the anther to the wind. C = anther, which hangs outside the flower, exposed to the wind, contains large amounts of light, smooth pollen grains. (b) Any six from: mature anthers burst, releasing pollen grains into air, wind carries pollen grains, some are trapped by feathery stigmas, hanging outside flowers, or other flowers of the same species.

20 Reproduction, growth and development in animals 1 Across 2 prostate gland 5 seminal vesicle 6 testis 7 sperm duct 8 penis Down 1 urethra 3 epididymis 4 scrotum 2 (a) Sperm released from the testes pass through the sperm duct, into the urethra through the penis. They are ejaculated into the vagina, swim through the cervix and uterus and into the oviduct. (b) An ovum passes down the oviduct. A single sperm penetrates the membrane of the ovum by secreting a protease enzyme. The sperm nucleus fuses with the ovum nucleus to form a zygote. 3 A The lining of the uterus is starting to build up, under the influence of oestrogen. B Ovulation occurs – the wall of an ovary ruptures, releasing an egg. This is due to secretion of LH (luteinizing hormone). C The lining of the uterus is maintained, due to high levels of progesterone, produced by the corpus luteum. D Menstruation occurs – the lining of the uterus breaks down, due to a drop in progesterone. 4 (a) placenta (b) 1 cervix 2 vagina (c) zygote (d) Any two from: oxygen, glucose, amino acids. (e) carbon dioxide, urea (f) amniotic fluid (g) menstruation (h) ejaculation (i) oviduct (Fallopian tube) (j) mitosis 5 (a) 1 A rubber sheath placed over the penis to stop sperm entering the vagina. 2 The sperm ducts are tied or cut, so no sperm can leave the testes.


6

3 Contains progesterone and oestrogen, which prevent ovulation, or progesterone only – which prevents implantation of a blastula. 4 A plastic-coated copper coil surgically inserted into the wall of the uterus – which prevents implantation of a blastula. (b) condom (c) Any two from: abstinence from sexual intercourse, screening of blood used for blood transfusions, use of sterilised needles for drug injections, feeding a baby with bottled milk when the mother has HIV, use of sterilised surgical instruments. (a) progesterone, oestrogen (b) (i) FSH and LH treatment causes multiple release of ova (eggs). The ova are collected. Some of them are fertilised in a Petri dish using the male partner’s sperm. The early embryos produced are then inserted into the uterus to achieve pregnancy. (ii) (advantage) Any one from: increases the chance of pregnancy, can result in pregnancy of a woman with blocked oviducts, fertilised eggs can be screened for genetic diseases, (disadvantage) Any one from: expensive, quite a low success rate.

21 Inheritance 1 allele

a section of DNA, coding for a specific protein

chromosome

having a pair of identical alleles

dominant

a thread of DNA, made up of genes

gene

a gene that always shows in the phenotype

genotype the characteristics visible in an organism

Exam focus 1 2 3

4

5

A N S W E R S

D A (a) Testis is the male gonad, producing sperm; testa is the seed coat, which is waterproof/protects seed from microbes. (b) Urethra is the tube carrying urine from the bladder, passes through the penis in males; ureter is the tube carrying urine from the kidneys, to the bladder. (c) Ovary is the female gonad, producing ova in animals, ovules in plants; ovule contains the female sex cell. (d) Fertilisation is the fusion of the male and female sex cells, to form a diploid zygote; implantation is the embedding of an embryo, into the uterus lining. (a) (AIDS) virus, (Gonorrhoea) bacterium (b) AIDS (c) Ref. to may not use condom during sex when under the influence of the drug. Drug may be injected using an infected needle/ ref. to sharing needles. (a) A ovary B oviduct (Fallopian tube) C uterus (wall) D cervix E vagina (b) Ref. to oviducts closed/blocked, so eggs cannot pass down/sperm cannot reach egg. (c) (i) in vitro fertilisation (ii) X placed on lining of uterus (iii) Ref. to being expensive, ref. to low success rate. (d) Any three from: ref. to maintaining healthy diet, ref. to eating more protein/iron/calcium/ vitamin C/energy-containing foods than normal, avoid alcohol, avoid drugs, avoid contact with rubella.

homozygous

an alternative form of a gene

the genetic make-up of an organism

phenotype 2 Parent phenotype

male

Parent genotype

XY X

Gametes (sex cells)

First filial generation (F1) Phenotype The ratio is

3

female XX

x Y

X

x

X

XX

XX

XY

XY

female

female

male

male

1

female:

1

male.

(a) Any two differences from: Mitosis produces cells with the same number of chromosomes as the parent cell/the diploid number of chromosomes is maintained. Meiosis produces cells with half the number of chromosomes/haploid cells produced. Mitosis produces identical cells. Meiosis results in variation. Mitosis involves body cells/somatic cells. Meiosis happens in the gonads/ovaries and testes.


17

S R E W S N A

Mitosis results in growth or replacement of old or damaged cells. Meiosis makes sex cells. (b) leg muscle cell 8 sperm cell 4 zygote 8 skin cell 8 (c) (i) Parent phenotype

grey

Parent genotype

GG

2

black x

gg

G

Gametes (sex cells)

F1 generation

Gg

Phenotype

G

Gg

grey

g

x

g

Gg

grey

rat B X

rat C X

X

Y

(ii) 50% (iii)sperm cell, the Y chromosome determines male, absence of Y in the zygote results in female (b) (i) an alternative form of a gene, pairs of alleles occupy the same relative positions on chromosome pairs (ii) 1 C 2B (c) Rat E has genotype Gg, where G = grey fur, g = white fur. (rat B)

(rat E)

Parent phenotype

grey

grey

Parent genotype

Gg

Gg

grey

grey

x

Gg

(ii) (a Punnett square is acceptable) Parent phenotype

grey

Parent genotype

Gg

grey x

g

G

Gametes (sex cells)

x

g

G

GG

Gg

Gg

gg

Phenotype

grey

grey

grey

black

3

(a) The term describes a pair of alleles, neither of which is dominant over the other. Both can have an effect on the phenotype when they are present together in the genotype. The result is that there can be three different phenotypes. (b) (i) red

Parent genotype

CRCR CR

Gametes (sex cells)

white CWCW

x CR

g

x

g

G

Gg

F2 generation

Parent phenotype

G

Gametes (sex cells)

Ratio 3 grey: 1 black

4

(a) (i)

CW

CW

x

First filial generation (F1)

GG

Gg

Gg

gg

Phenotype

grey

grey

grey

white

(a) A gene is a section of DNA that codes for a protein, an allele is an alternative form of a gene. (b) A diploid nucleus contains pairs of chromosomes, e.g. in body cells. A haploid nucleus contains a single set of unpaired chromosomes, e.g. sex cells. (c) Phenotype describes the characteristics visible in an organism, genotype describes the genetic make-up of an organism. (d) Homozygous refers to chromosomes that have a pair of matching alleles controlling the same characteristic, heterozygous refers to chromosomes that have a pair of dissimilar alleles for a characteristic. (e) A dominant gene is a one that always shows in the phenotype, a recessive only has an effect on the phenotype if the genotype is homozygous.

22 Variation F2 generation Phenotype

CRCW

CRCW

CRCW

CRCW

pink

pink

pink

pink

1

(ii) 1 red : 2 pink : 1 white

Exam focus 1

(a) (i) Blood clotting can occur, due to reaction between antibodies and antigens, leading to death of the patient. (ii) Ref. to possible transmission of HIV. (b) Parent phenotype blood group A IAIo

Parent genotype Gametes (sex cells)

IA

blood group B IBIo

x Io

IB

x

Io

2

18

F2 generation

IAIB

IAIo

IBIo

IoIo

Phenotype

AB

A

B

O

(a) (i) a spontaneous change in a gene or a chromosome (ii) Any two from: faulty copying of DNA, faulty separation of chromosomes during cell division, exposure to radiation, exposure to some chemicals. (b) (i) During ova formation in the ovaries in the division process (meiosis), one of the chromosomes (number 21) sticks to its partner. This results in one ovum with 24 chromosomes and one with only 22. The ovum with 24 chromosomes is still viable. If it is fertilised, the fetus formed has 47 chromosomes instead of 46. (ii) Any three from: lowered life expectancy, mental retardation, early puberty, a distinctive round face/short neck. (a) Continuous variation shows a complete range of a characteristic within a population. It is caused by both genes (often a number of


different genes) and the environment. When the frequency is plotted on a graph, a smooth curve is produced, with the majority of the population sample grouped together and only small numbers at the extremes of the graph. e.g. height, body mass, intelligence, hand span, shoe size. Discontinuous variation is where there are obvious, distinct categories for a feature. There are no intermediates between categories. It is caused by a single gene or a small number of genes, with no environmental influence. When the frequencies are plotted on a graph, bars are produced that cannot be linked with a smooth curve, e.g. blood group, ability to tongue-roll, ear lobe shape. (b) Continuous variation graph, e.g.

Parents

man

Parent genotype

HNHn

Gametes (sex cells)

height in a class

12

5

More of the next generation carry the advantageous genes, resulting in a stronger population, better adapted to a changing environment. Gradually, over a long period of time, the whole species becomes stronger. (a) Any three symptoms from: episodes of pain, younger children may develop painful swelling in their hands or feet, older children can be affected in their ribs/long bones/spine, increase in vulnerability to other diseases, jaundice, increased risk of leg ulcers, delayed growth in children, progressive organ damage. (b) (i) (ii)

s 10 t n e d 8 u t s f 6 o r e b 4 m u n 2

genotype of first filial generation (F1) Phenotype

HN

HNHN

A N S W E R S

woman HNHn

x Hn

HNHn

normal some haemoglobin, abnormal no anaemia haemoglobin, sickle cell trait

x

HN

HNHn some abnormal haemoglobin, sickle cell trait

Hn

HnHn abnormal haemoglobin, sickle cell anaemia

0 120 – 130 – 140 –

150 – 160 –

170 –

129

159

179

139

149

169

height / cm

1

Discontinuous variation graph, e.g. y c n e u q e r f e g a t n e c r e p

45 40 35 30 25 20 15

10 5 0 A

B

AB

O

blood group

3

4

Exam focus

One named example of an animal, e.g. cow: Select one variety of cattle with a higher than average milk yield. Select another variety that has a very high meat yield. Cross-breed the two varieties to form a new breed with the benefits of both parental varieties, e.g. high milk production in females, high meat yield in males. (a) the passing on of genes by the best adapted organisms (b) Named example, e.g. lion: Variation within a lion population gives some individuals an advantage over others, e.g. bigger muscles in the legs of some lions enable them to run faster/get food more successfully. If there is a food shortage, the lions with the biggest leg muscles are most likely to survive to being an adult and pass on the advantageous genes to their offspring. The weaker individuals die before having the chance to breed.

2

3

(a) (i) discontinuous variation (ii) (example) any example of continuous variation, e.g. height, body weight, hand span, intelligence (explanation) ref. to influence of genes, and environment (b) (i) The malarial parasite is unable to invade and reproduce in the sickle cells. (ii) Any two from: they have sickle cell anaemia so red blood cells deform and become sickleshaped, when blood oxygen levels get low, so cells become stuck in capillaries, e.g. in lungs. (a) Involves transfer of pollen from the anther of a flower to the stigma of a flower on a different plant of the same species, so there is mixing of genetic material leading to variation. (b) Tubers form at the tips of underground stems of the parent plant, so the tuber cells will have the same DNA as the parent. (a) (i) bacterium (ii) Any three from: presence of cell wall, presence of slime capsule, presence of single strand of DNA, presence of flagellae, ref. to small size. (b) binary fission (accept asexual reproduction) (c) Any two from: ref. to mutation, during cell division, variation has provided resistance to the antibiotic. (d) Any three from: some of the bacteria will have survived but have been exposed to the antibiotic so mutations are possible, which can result in a resistant strain forming so future use of antibiotic will be ineffective, bacteria in the patient will breed again causing disease symptoms to return.


19

S R E W S N A

23 Energy flow, food chains and food webs (a) A list of organisms that shows the feeding relationship between them. Arrows link the organisms to represent the direction of flow of energy. (b) (i) (ii) snail thrush sparrow hawk clover tertiary ➞ primary ➞ secondary ➞ producer consumer consumer consumer (c) (i) The thrush population would decrease/thrushes die because they have fewer snails to eat. (ii) The sparrow hawk population would decrease/sparrow hawks die because they have fewer thrushes to eat. (d) Snails use less energy because they move less/ more slowly/don’t hunt. Snails are cold blooded, so less energy used maintaining a constant body temperature. 2 (a) (i) photosynthesis (ii) sunlight (iii) Any three from: light is reflected off shiny leaves, light is the wrong wavelength for chlorophyll to trap, light passes through the leaves without passing through any chloroplasts, light does not fall on the leaves. (b) (i) Energy is lost at each level in a food chain. So, very little of the energy entering the chain through the producer is available to the top carnivores. (ii) Fewer levels to lose energy from. 90% of the energy is lost at each level/a smaller percentage of the energy trapped by the producers is lost in a short food chain. 3 (a)

4

1

leopard

tertiary consumer

baboon

secondary consumer

scorpion

primary consumer/ herbivore

Exam focus 1

lizard locust maize

2

primary consumer/ herbivore

producer

(b) When feeding on impala it is a secondary consumer, but when feeding on baboons it is a quaternary/fourth consumer. (c) Any three from: over-predation or hunting, disease, pollution, use of pesticides, lack of food (or other resources). (d) They represent the direction of flow of energy/ point towards the consumer of the previous organism.

20

(b) (i) 35% (ii) (waxy) cuticle (iii) Any two from: ref. to presence of large numbers of chloroplasts, ref. to closely packed nature of palisade cells, ref. to position near upper surface of leaf, ref. to ability of chloroplasts to migrate to top of cells. (c) (i) 90% (ii) Any two from: movement, e.g. to find food or a mate, maintaining constant body temperature, some heat lost in urine or faeces, not all of the food organism is eaten by the consumer/some parts are indigestible. (a) (i) (grass) (cow) (humans) producer primary secondary consumer consumer (ii) Ref. to leaves, capture light energy, and convert it into carbohydrates/stored food. (iii) Any three from: movement, e.g. to find food or a mate, maintaining constant body temperature, building up proteins/muscles, some heat lost in urine or faeces. 200 × 100 = 0.2% 100 000 (ii) Ref. to fewer trophic levels, so less energy lost/more energy conserved for top consumer. (c) (i) Ref. to greater range of vitamins and minerals available in a mixed diet, meat contains a greater range of amino acids. (ii) (b) (i)

locust grass

(a) (i) an organism’s position in a food chain, food web or food pyramid (ii) e.g. maize ➞ locust ➞ lizard ➞ snake (iii)e.g. snake

impala

(a) The producer may be a single large plant, e.g. a tree. The top consumers may be parasites, which are small but many feed on the previous level. (b) There is a reduced amount of energy at each successive level. (c) The organisms have to be killed and burned to measure their energy content.

humans

cows

grass

maize


24 Nutrient cycles 1 2

3

4

25 Population size

photosynthesis, respiration, combustion, decomposition A evaporation B condensation C transpiration D precipitation (rain) E osmosis (a) (i) Present in soil/(leguminous plant) root nodules. Convert nitrogen into compounds of ammonia. (ii) Convert compounds of ammonia into nitrates. (iii)Present in waterlogged soil. Break down nitrites into nitrogen. (iv)Energy from the lightning converts gaseous nitrogen into nitrogen oxides, which dissolve in rain to form nitrates. (b) adding artificial fertilisers adding manure/compost growing leguminous plants, then ploughing the roots (with their nodules) into the soil (a) photosynthesis, respiration (b) Any two from: cutting down forests/ deforestation, combustion of fossil fuels, increasing numbers of animals/increasing the human population. (c) Any three from: ref. to melting of polar ice caps, causing flooding of low lying land ref. to a change in weather conditions in some countries, increasing flooding ref. to reducing rainfall – changing arable (farm) land to desert ref. to causing the extinction of some species that cannot survive in increased temperatures.

1

2

Maize long and narrow parallel one in threes

Bean broad branching two in fives

log phase

death phase

time

2

(b) Any three factors from: food supply, predation/ hunting, disease, use of contraceptives (for human growth). (c) (i) Ref. to no stationary or death phase, the log phase will continue upwards instead of the line levelling off. (ii) Any four from: greater pressures on the environment, more land needed for housing, more land needed for growing crops, more land needed for road building, deforestation due to increased demand for wood for fuel/ housing, more pollution due to increased industry/vehicle use, greater demands on education, greater demands on health care. Lag phase – the new population takes time to settle and mature, before breeding begins. When this happens, a doubling of small numbers does not have a big impact on the total population size, so the line of the graph only rises slowly with time. Log (exponential) phase – there are no limiting factors. Rapid breeding in an increasing population causes a significant increase in numbers. A steady doubling in numbers per unit of time produces a straight line. Stationary phase –– limiting factors such as shortage of food causes the rate of reproduction to slow down and there are more deaths in the population. When the birth rate and death rate are equal, the line of the graph becomes horizontal. Death phase – there are more deaths than births, due to factors, e.g. famine/disease/war/mass use of contraceptives.

Exam focus 1

Any eight from: ref. to osmosis, water passes through xylem, into leaves, evaporates into air spaces, in spongy mesophyll, present in higher concentration than in atmosphere, so diffuses, through stomata, ref. to transpiration, forms clouds, ref. to precipitation/rain, returns to soil, drains into river, runs down to sea

stationary phase

lag phase

(a) (i) (root) nodule (ii) bacteria (iii) Any four from: ref. to nitrogen fixing bacteria, in the root nodules, take in gaseous nitrogen from air spaces in the soil, convert it to compounds of ammonia, which are changed to nitrates, then used to make protein, for plant growth. (iv) Any two from: add manure/compost, add artificial fertilisers, use crop rotation, with leguminous plants in the cycle. (b) Any two from: Feature leaf shape leaf veins cotyledons groupings of flower parts

(a) (i) (ii)

s m s i n a g r o f o r e b m u n

Exam focus 1

A N S W E R S

(a) (i) 1 lag phase label at start of graph 2 log phase label as the line rises steeply (ii) (lag phase) any one from: the yeast population takes time to settle/acclimatise to new conditions/takes time to mature, doubling of small numbers does not have big impact on total population size. (log phase) any one from: there are no limiting factors, e.g. food or predators or disease/ref. to rapid breeding in an increasing population causes significant increase in numbers.


21

S R E W S N A

(b) (i) line flattens off, then falls (ii) flattened line labelled as stationary phase, dropping line labelled as death phase (iii)lack of food, presence of predators, presence of disease (c) alcohol/ethanol

26 Human influences on the ecosystem 1

2

Any four points from the following (note: this list is not exhaustive): The development/use of chemical fertilisers on farm land – boosting levels of nutrients in the soil, increasing crop yields. The development/use of pesticides – these kill pests that feed on or damage crops, so crop yields are increased. The development/use of herbicides – these kill weeds that compete with crops for nutrients/light/ water/space, so crop yields are increased. The development of biological control methods for pest control as an alternative to pesticides – some pesticides are non-selective. The use of tractors/combine harvesters to enable land and crops to be managed more efficiently. Artificial selection to produce plant varieties that are suited to particular climates/soil types, or breeds of animals for specific purposes, e.g. optimum meat/ milk/wool production. (a) deforestation (b) Any three from: provide land for farming, provide land for roads, provide timber for building/furniture, ref. to fuel source. (c) Any four from: Reduction of habitats/food sources for animals, which can result in their extinction. Animal and plant diversity is reduced, so food chains are disrupted. The loss of plant species and their genes – may be important for medical use/genetic engineering in the future. The removal of trees, so no roots to hold soil, resulting in soil erosion and leaching of minerals. Desertification can eventually occur. Lack of roots, leading to flooding/mudslides/lakes can become silted up. Leaching of nutrients into lakes and rivers – leading to eutrophication. Less carbon dioxide is absorbed from the atmosphere, increasing the greenhouse effect. Less oxygen produced, so atmospheric oxygen levels can drop. Less transpiration – can lead to reduced rainfall.

3 C

4

22

G

A

E

B

F

D

(a) Any four from: Ref. to bioaccumulation. Occurs if the chemicals enter a food chain. Plankton absorb the chemical but cannot excrete it. Animals, e.g. small fish, feed on large numbers of plankton.

Ref. to a build-up of the chemical because they cannot excrete it. Animals at the top of the food chain eat many fish – accumulating high concentrations of the chemical, which is toxic at these levels. (b) (i) combustion of coal/oil, volcanoes (ii) Any three from: damage to plant leaves, eventually killing the plants, acidification of lakes, destroying fish stocks, increasing the risk of asthma attacks/bronchitis in humans, corrosion of stonework on buildings, release of soluble aluminium ions in soil – toxic to fish when washed into lakes. 5 Any five from: Large objects, e.g. sticks, are screened out of the raw sewage. Suspended grit is allowed to settle out by gravity in a grit settling tank. Organic matter is allowed to settle out by gravity in a sludge settling tank. The sludge is digested in a sludge digester. Digested sludge can be used as fertiliser on farmland. Methane gas can be generated, for use a fuel. The remaining liquid is sprinkled onto the top of an aeration tank containing stones. Microorganisms on the surface of the stones digest any remaining organic matter. Ref. to chlorination of water to kill any bacteria, so it is safe to drink.

Exam focus 1

2

(a) Any four from: named species, e.g. tiger, extinction would result in genes being lost, which may be important for genetic engineering, to produce chemicals such as medicines, species may be important in food chain, so its loss could endanger other species. (b) (i) description of habitat of organism named in (a), e.g. forest, in mountains (ii) Any three from: use laws to protect habitat, use wardens to protect habitat, control public access, maintain species features of habitat, e.g. by controlling water drainage or number of prey animals or top carnivores. (a) (farming) any four from: Pesticides applied to land may leach into river, and kill aquatic animals. Ref. to bioaccumulation of chemicals, e.g. DDT, in food chain, killing top carnivores. Herbicides applied to plant crops may leach into river, and kill aquatic plants. Fertilisers leach into river, cause rapid growth of river plants, plants die, bacteria feed on dead plants, use up oxygen in respiration, so fish die. Water extracted from river for agriculture, so organisms in river die. (b) (power station) any four from: Waste water from power station is at high temperature, so river organisms die/population species change. Radiation from power station leaks into river, causes mutations, ref. to bioaccumulation in food chains, makes fish unsafe to eat, causes cancer in top carnivores.


(c) (town) any four from: Sewage enters the river, causes rapid growth of river plants, plants die, bacteria feed on dead plants, use up oxygen in respiration, so fish die, chemicals from factories enter river, killing river organisms, water becomes unfit to drink.

4

Past exam questions 1

[4] Feature

Fish

mammary glands fur/hair scales/ scaly skin

2

Amphibia Rep- Birds tiles

Mammals



























(except feet and legs)





5

Tube

external ears











feathers











1 mark for each row (ticks and name)

A B C D

[5]

1 1 2 2 3 3 4 4 5 5 Name of (a) (b) (a) (b) (a) (b) (a) (b) (a) (b) arthropod A    Pediculus Anopheles   B  Ornithodorus C   Pulex    D Musca  E  Periplaneta   F  3

(a) Any three from: growth, movement, reproduction, respiration. (b) 1 mark for each horizontal line Feature

Animal cell

or: ref. to finding shade or darkness to avoid predators/very bright light may damage chlorophyll or enzymes or cytoplasm. [2] (a) Ciliated tissue – moves dust and bacteria up from bronchi. Root hair tissue – absorbs water and minerals from soil. Xylem tissue – transports water and minerals through the stem. Muscle tissue – contracts to cause movement. [4] (b) A leaf contains different types of cells or tissues/a tissue contains one type. At least two named examples of tissues or cells in a leaf, e.g. xylem, phloem, palisade mesophyll, spongy mesophyll, etc. A leaf/organ carries out a number of functions. [3] (a) (i) [4]

[3] [4]

Plant cell

Bacterial cell

chloroplast







cytoplasm







membrane







nucleus







(c) Any three from: ref. to gradient/gradient described for water, so water will move in (to the cell), by osmosis/diffusion, cell will become turgid/swell up/increase in size, resulting in bursting/contractile vacuole prevents bursting. [3] (d) Any two from: (i) ref. to movement towards light/away from light using flagellum/reference to eye spot detects bright light or a change in light intensity/ eye spot contracts in response to light ref. to taxis. [2] (ii) Depending on response to (d)(i): either: light (energy) needed for photosynthesis to make food/glucose/sugar/starch/ carbohydrate

6

Colour of indicator at start pinky red pinky red pinky red pinky red

A N S W E R S

Colour of indicator after 6 hours yellow yellow yellow purple

(ii) Tube A 1 respiration occurs 2 carbon dioxide produced/added to water 3 becomes acidic/more acidic/pH falls Tube D 4 photosynthesis occurs 5 carbon dioxide removed from water 6 becomes alkaline/less acidic/pH rises [4] (b) Tube E 1 colour stays pinky red/does not change 2 respiration and photosynthesis balance out 3 carbon dioxide amount in water/pH does not change OR 1 colour goes purple 2 photosynthesis more than respiration 3 carbon dioxide amount in water drops/pH rises OR 1 colour goes yellow 2 respiration more than photosynthesis 3 carbon dioxide amount in water rises/pH falls Any one prediction – 3 marks. [3] (a) (i) heat [1] (ii) condensation/cooling of water vapour [1] (b) (i) transpiration/evapo-transpiration [1] (ii) humidity temperature wind/air movement light/sunlight Any three – 1 mark each. [3] (c) (i) reduced transpiration (in forest area) leading to less water vapour (moving inland)/less clouds form thus less/no rainfall/less humid (inland) Any two – 1 mark each. [2] (ii) more surface runoff of rain water/flooding increased surface wind speed can result in greater erosion of soil/silting up of streams/rivers/landslides


23

S R E W S N A

7

8

24

desertification destruction of habitats/disrupt food chains possible extinction of animal/plant species more carbon dioxide/less oxygen in atmosphere Any two – 1 mark each. [2] (a) osmosis water diffuses/moves down water potential gradient through partially permeable membrane/sugars/ solutes in root hair cell (to lower water potential) [3] (b) 20.0 [1] (c) (rate of water) uptake increases positive correlation/exponential/not linear e.g. 0.4 mm min–1 at 0 m s–1 /no wind, 20 mm min–1 at 8 m s–1 [2] (d) Any two from: temperature, humidity, light intensity. [2] (e) (raw material for) photosynthesis/forming glucose or carbohydrate turgidity/support transport of: solutes/named solute/food substances forming vacuoles/growth/(cell) expansion taking part in chemical reaction(s); e.g. hydrolysis/breaking down food substance medium for chemical reactions Any two – 1 mark each. [2] (f) loss of water (vapour) through stomata (in leaves) evaporation from surfaces of (mesophyll) cells/ into air spaces (in leaf) loss of water from leaf (cells) lowers water potential water moves into leaf (from xylem) (this) pulls on/creates tension (in water column in xylem) cohesion of water molecules [4] (g) (Note question says structural adaptations.) leaves, small/reduced to spines/are needles no leaves curled/rolled leaves hairs on the leaves/stems thick (waxy) cuticle sunken stomata few stomata fleshy/succulent leaves/stems small surface area: volume ratio deep roots long/extensive shallow roots ignore stomata close during the day Any three – 1 mark each [3] (a) (i) Any two from: oxygen, glucose, accept other valid substances such as water, amino acids, etc. [2] (ii) carbon dioxide/lactic acid [1] (b) (i) (cardiac) muscle [1] (ii) Ref. to contraction/shortening. [1] (iii)Any three from: pressure will increase, the blood will be forced out from the heart, into the aorta, the volume of blood decreases. [2] (c) (i) Any two from: high fat diet/cholesterol, smoking, stress, lack of exercise, obesity, genetic influence. [2] (ii) all parts of the artery below point B shaded [1]

(d) (feature) (explanation)

presence of valves prevents backflow of blood/ blood flows in one direction (feature) ref. to wide lumen (explanation) allows blood to flow with minimum resistance/flows more easily (feature) ref. to tough wall/collagen present (explanation) to prevent bursting (feature) thin/elastic walls (explanation) makes it easier for body muscle contractions to cause blood to move forward [4] 9 (a) (i) oxygen/dust/particles [1] (ii) carbon dioxide; water (vapour) [2] (iii) lower [1] (b) mix air with/bubble through lime water; which goes cloudy/white/milky [2] (c) (diffusion is) random movement of particles/ molecules/ions from their high concentration to their lower concentration/down concentration gradient Any two – 1 mark each [2] 10 (a) because they are toxic/poisonous [1] (b) (i) ureter [1] (ii) (urinary) bladder [1] (iii)renal vein [1] (c) filter (from the blood)/ultrafiltration plasma /soluble/dissolved substances/named examples reabsorption of useful substances/named example remainder becomes/forms urine Any three points – 1 mark each. [3] (d) (i) liver [1] (ii) urea [1] 11 (a) (i) 184 [1] (ii) liver [1] (iii)line meets/cuts horizontal axis at 4 pm [1] (iv) 9 am (approx.) [1] (b) (i) slows down nerve impulses/crossing synapses responses/reactions take longer interferes with judgements Any two points – 1 mark each. [2] (ii) liver – causes cirrhosis/cancer/kills/destroys cells brain – damages/kills/destroys cells stomach – irritates/damages wall/lining of/ cause ulcers kidney – can cause damage to cells heart – increased risk of coronary disease Any two points – 1 mark each. [2] (iii) aggressive behaviour/fighting family break up/loss of friends inability to concentrate/poor time keeping – loss of job financial problems/money spent on alcohol lack of personal care/hygiene problems with law/theft drunk driving/higher risk of accidents/lose licence homelessness Any two points – 1 mark each. [2]


12 (a) (i) label G clearly indicating testis [1] (ii) label S clearly indicating sperm duct [1] (iii)label T clearly indicating testis [1] (iv)label U clearly indicating urethra [1] (b) (stimulate) production of sperm growth/development of pubic/axillary hair growth/development of facial/body hair breaking of the voice widening of shoulder (girdle) development of more muscle/more muscular increased aggressive behaviour growth of penis/testes Any two points – 1 mark each. [2] (c) meiosis; four; haploid; half [4] 13 (a) blue – because no white flowers in offspring/in presence of inherited blue allele [1] (b) (i) blue – BB; white – bb [2] (ii) offspring – Bb [1] (iii)parents Bb bb gametes B b b b offspring genotypes Bb Bb bb bb phenotypes blue, blue, white, white ratio 2 : 2 or 1 : 1 Any four – 1 mark each. [4] (c) (i) shows extremes and all intermediates (of cob length) [1] (ii) (amount of) light (amount of) minerals (amount of) water temperature Any three – 1 mark each. [3] (iii)flower colour only blue or white/no intermediate colours (thus is discontinuous variation) [1] 14 (a) (i) high temperatures denature enzymes kill bacteria to give optimum temperature (for, enzymes/ bacteria) [2] (ii) respiration is anaerobic; lactic acid produced [2] (iii)named example of a food additive: colouring; preservative/stabiliser/emulsifier/ antioxidant; flavouring/(artificial) sweetener; thickening agent [1] (b) (description) sigmoid (growth curve) or lag phase + exponential/log + stationary phase little/no growth, rapid growth, no growth/‘levelling off’ (explanation) lag phase: small number of bacteria produce proteins/enzymes/DNA exponential phase: binary fission/asexual reproduction no limiting factors/no competition/plenty of food/plenty of resources stationary phase: death rate = ‘birth’ rate resources/food used up pH not favourable/optimum [5]

(c) conditions not favourable: cannot compete with S. thermophilus (or reverse argument) cannot increase until pH falls/changes (or reverse argument) cannot increase until oxygen concentration decreases (or reverse argument) grows slower than S. thermophilus takes longer to adapt/feed fewer L. bulgaricus to start with idea that substance/condition provided by S. thermophilus [2] 15 (a) (i) Any one from: NOx/oxides of nitrogen, vehicle/car, exhausts/fumes/emissions/gases, burning fossil fuels in houses/burning forests, volcanic eruptions/snow melt. [1] (ii) Any two from: Leaves/trees/producers/vegetation/plants harmed/damaged/killed. Trees more likely to get diseased. Bark is damaged. Roots killed. (Sensitive species of) lichens killed. (Named) microorganisms killed e.g. bacteria/ fungi. Soil pH decreases/soil becomes more acidic. Aluminium ions become mobile. Nutrients/named example(s) leached. Food chains/food webs disrupted. Loss of habitat/less biodiversity/extinction of species. [2] (b) Any two from: Use alternative/renewable/green energy sources (e.g. nuclear power/wind power/wave power/ solar power/hydrogen power). Use low-sulfur fuels. Reduce use of coal. Flue gas desulfurisation/‘use scrubbers’/chimney electrostatic precipitators/neutralise waste gases with lime. Catalytic converters. Provide/use more public transport. Car sharing/car pools/reduce use of cars/hybrid cars/electric cars/use biofuels. Walking/cycling. Reduce food miles. [2] (c) (look for positive features, not absent ones apart from unsegmented) unsegmented/not segmented/shell/(muscular) foot [1] (d) (i) frogs/black-fly larvae [1] (ii) clams/snails/molluscs [1] (iii) Any two from: enzymes do not function (well) acid damages shells/scales/skin calcium ions not available for shells/difficult to make shells aluminium in solution is toxic to fish/fish die acid/low pH kills fish fish produce (lots of) mucus blocks gills [2]


A N S W E R S

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Answers to Workbook

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