exam qs + past paper

Question 1

Describe two ways that monocultures can negatively impact ecosystems. [2]

Answer 1

pest/disease, pesticides, reduced biodiversity

if there’s a pest or disease that affects the species, it could kill all of the crop being grown.
Monocultures can require lots of pesticides which can pollute water.

Monocultures can reduce biodiversity, as they contain fewer plant species than a natural ecosystem, so they don’t provide habitats for as many organisms.

Question 2

Describe two ways that intensive livestock production can negatively impact ecosystems. [2]

Answer 2

waste, chemicals, ethics

waste from livestock can build up, causing the spread of disease and pollution of water sources.
The chemicals used to treat disease can pollute the environment.

Question 3

Certain gases in the atmosphere can cause air pollution. Explain the relationship between greenhouse gases and climate change. [3]

Answer 3

Increasing levels of greenhouse gases in the atmosphere [1 mark] have enhanced the greenhouse effect [1 mark] causing global warming — this is climate change [1 mark]

Question 4

The Siberian Tiger is an endangered species. Explain how captive breeding programmes could help to increase the number of Siberian tigers in the wild. [2]

Answer 4

E.g. more offspring will survive to reproduce if the Siberian tigers are bred in captivity as there is less infant mortality [1 mark]. Some of these individuals can then be released into the wild [1 mark]

Question 5

To make a protein, mRNA carries a copy of the gene from the DNA in the nucleus to the cytoplasm.
(a) Name the part of the cell that assembles amino acids into protein molecules. [1]
(b) State what determines the order of amino acids in a protein. [1]
(c) Briefly explain how genes affect cell function.

Answer 5

ribosome
base sequences in DNA / mRNA

cell function is controlled by production of proteins which is controlled by genes in DNA

Question 6

Explain how meiosis leads to variation in the mosquito’s offspring.

Answer 6

Meiosis produces cell that are genetically different to each other [1]
by forming new combinations of paternal and maternal chromosomes. [1]

Question 7

Describe how information about light entering the eye is passed to the brain. [2]

Answer 7

information is sent using impulses [1] via optic nerve [1]

Question 8

explain what goes wrong with the regulation of blood glucose level in people with Type 1 diabetes. [

Answer 8

pancreas produces little / no insulin. Liver is unable to remove glucose, so the blood glucose can rise to dangerously high level.

Question 9

A gardener frequently uses products containing synthetic plant hormones in her garden.
(a) The gardener has a problem with weeds in her lawn. She uses a selective weedkiller that targets the weeds without affecting the growth of the lawn.
Explain how selective weedkillers work. [1]

(b) Name the synthetic plant hormone likely to be present in the weedkiller. [1]

Answer 9

selective weedkillers disrupt normal growth patterns which kills the weeds

2,4-D

Question 10

state the name of the ball of cells that implants into uterus after fertilisation. [1]

Answer 10

embryo

Question 11

Describe the functions of amniotic fluid and the amniotic sac. [4]

Answer 11

maintains temperature
mechanical protection
allows movement (of the fetus)
sterile environment and prevents infection
lubrication
provides support (of the fetus)

Question 12

How can HIV be transmitted [2]

Answer 12

saliva
sexual fluids
breast feeding

Question 13

Describe how species like cheetah can be conserved. [3]

Answer 13

captive breeding programmes
eduction of farmers and land users
conservation areas
monitor numbers

Question 14

Herbicide A is a synthetic plant hormone called 2,4-D that selectively kills dicotyledonous
plants only.
(i) State two features that distinguish leaves of dicotyledonous plants from leaves of
monocotyledonous plants [2]

Answer 14

broad leaves
central vein with branches
petiole

Question 15

Herbicide B is a chemical that prevents the uptake of magnesium ions.
Suggest how herbicide B kills plants. [3]

Answer 15

no chlorophyll synthesis ;
cannot trap sunlight ;
cannot photosynthesise ;

Question 16

Galapagos fiches share a common ancestor. Suggest how Galápagos finches have evolved different shaped beaks.[5]

Answer 16

due to random mutations there is variation in population
natural selection

birds with, selective advantage / unique beak shape, more likely to find food and survive ;
the birds that survive reproduce ;
pass on their alleles ;
continues over many generations ;

Question 17

State the name of the process that describes the transport of sucrose in a plant. 1

Answer 17

translocation

Question 18

In addition to sucrose, amino acids are also transported in plants.
State the name of a mineral ion that becomes part of an amino acid. 1

Answer 18

nitrate ions

Question 19

a temp 20 degrees
b temp 25 degrees

(b) Explain why the plants in Group B lost a greater percentage of their mass than the plants in Group A. [3] (c) Explain how humidity can affect the rate of transpiration. [2]

Answer 19

b) higher temp in group b [1]
at higher temps, water particles have higher KE to evaporate and diffuse out of stomata, [1] so the plant loses more mass [1]

c) high humidity = slow transpiration [1]
humid air contains a lot of water, so there’s not much of a conc grandient between inside and outside of the leaf [1]

Question 20

explain why wilting occurs

Answer 20

if no H2O in soil
the cells lose water and become flaccid, no turgor pressure to support the plant tissues

Question 21

Explain how tooth decay occurs. [4]

Answer 21

food remains on teeth
bacteria use sugar and carbohydrates to respire
acid prduced
acid dissolves enamel
dentine is left open and decays more rapidly than enamel

Question 22

describe what changes occur in the eye when the light becomes bright. [3]

Answer 22

circular muscles contract
radial muscled relax
pupils become smaller

Question 23

Why food chains usually have have fewer than five tropic levels. [4]

Answer 23

energy is lost between trophic levels so only 10% energy is transferred [2],
very small total percentage reaches fourth trophic level
not enough energy to support another level

energy is lost in respiration
not all parts of the organisms are eaten
not all nutrients in the organisms are absorbed
lost in excretion
transferred to decomposers

Question 24

Describe negative impact on an ecosystem of the intensive production of livestock, such as chickens. [3]

Answer 24

effect of waste on waterways / crops
release of carbon emissions, so contributes highly to climate change
disease spreading to, wild populations / humans
use of antibiotics and (spread of) antibiotic resistance ;
4 use of pesticides ;
5 loss of biodiversity

Question 25

Forests are cleared for farmland. Deforestation can lead to a loss of soil (soil erosion).
Explain the effects of soil erosion on ecosystems. [3]

Answer 25

landslides
increased risk of flooding
increased rate of evaporation / land is exposed to drying (drought)
silting of rivers

disruption to food chain(s)
loss of habitat
plants cannot grow (well)

Question 26

Suggest advantages of using biofuels instead of fossil fuels. [3]

Answer 26

conserves fossil fuels as fossil fuels are not renewable

plants use carbon dioxide from the atmosphere for photosynthesis so less climate change

uses waste from crops for energy
reduces dependency on fossil fuels from other countries

Question 27

Explain why carbon dioxide is used in greenhouses. [4]

Answer 27

carbon dioxide is required for photosynthesis,
so more carbon dioxide = faster rate of photosynthesis,
more growth / yield

more, glucose is produced ;
carbon dioxide (concentration) is a limiting factor

Question 28

outline the roles of DNA in a cell. [2]

Answer 28

contains genetic information
sequence of bases in DNA codes for proteins and sequence of amino acids

Question 29

state the structures that will form between the nuclei so that the cell divides into two cells. [2]

Answer 29

cell membrane and cell wall

Question 30

A runner went for a 10 mile run on a warm day. When she got home she noticed that her urine was darker in colour than normal. Explain why the runner produced darker coloured urine. [4]

Answer 30

hot day and runner was exercising, so lost lots of water through sweating; didn’t take in enough water to replace water she’d lost, so became dehydrated.
= causing kidneys to reabsorb more water into blood, so small volume of more concentrated urine

Question 31

A hospital patient has kidney failure. She has dialysis three times a week.

(a) Explain how the dialysis machine removes urea from the patient’s blood. [2]
(b) Explain why the patient does not lose glucose from her blood during dialysis. [2]

Answer 31

urea diffuses out through dialysis membrane, as urea concentration in blood is higher than in dialysis fluid

dialysis fluid contains same concentration of glucose as healthy blood, so no concentration gradient and no net movement of glucose

Question 32

some bacteria and viruses cause disease but many are useful to biotechnology industry. Explain why bacteria are useful to biotechnology industry. [3]

Answer 32

no ethical concerns
reproduce quickly
take up very little space
same genetic material to other organisms

Question 33

Why viral infections cannot be treated with antibiotics. [1]

Answer 33

viruses do not have cell wall

Question 34

Describe pathway of water from outside the root to the xylem vessels at the centre of the root.

Answer 34

water enters root hair cells by osmosis
water in soil has much higher water potential than water potential in root hair cells
water moves from an area of high water potential to low water potential
now root hair cells have higher water potential than cortex cells, so process repeats untill xylem

active transport of ions to create a water potential gradient
across partially permeable membrane

Question 35

state the type of microorganism that produces penicilin [1]

Answer 35

fungus

Question 36

state the process that allows eye to view objects at different distances. [1]

Answer 36

accomodation

Question 37

explain why the eye cannot easily identify different colour in low levels of light. [2]

Answer 37

cones are less sensitive in low light
only cones can detect colour
rods work in low light but can’tt detect colour

Question 38

describe how liver responds to increase of insulin concentration

Answer 38

insulin stimulates enzymes production and conversion glucose to glycogen
stores glycogen

increased respiration of glucose by liver cells

Question 39

liver is also involved in processing of amino acids. Describe how excess amino acids are broken down. [2]
State the name of the process that assembles amino acids to form proteins [1]

Answer 39

by deamination
excess amino acids are converted by deamination into ammonia and then converted into urea

protein synthesis

form = synthesis