B4 - Ppq

Front 1

What is meant by codominant alleles? [1]

Back 1

-both alleles expressed in the phenotype

Front 2

In cats, males are XY and females are XX. A gene on the X chromosome controls fur colour in cats. The allele G codes for ginger fur and the allele B codes for black fur. These alleles are codominant. Heterozygous females have ginger and black patches of fur and their phenotype is described as tortoiseshell. Male cats with the tortoiseshell phenotype do not usually occur. Explain why [1]

Back 2

-The Y chromosome doesn’t carry the gene and male cats don’t have an X chromosome

Front 3

A tortoiseshell female (XGXB) was crossed with a black male (XBY). Use a genetic diagram to show all the possible genotypes and the ratio of phenotypes expected in the offspring of this cross.Use XG to indicate the allele G on an X chromosome.Use XB to indicate the allele B on an X chromosome [3]

Back 3

-XGXB, XBXB, XGY,XBY

-Tortoiseshell female, black female, ginger male, black female

-Ratio = 1:1:1:1

Front 4

The allele for polydactyly is dominant. Some cat breeders select FOR polydactyly. Explain how this would affect the frequencies for the homozygous genotypes for this gene in their breeding populations over time [1]

Back 4

-Homozygous dominant increases and homozygous recessive decreases

Front 5

On islands in the Caribbean, there are almost 150 species of lizards belonging to the genus Anolis. Scientists believe that these species evolved from two species found on mainland USA. Explain how the Caribbean species could have evolved [6]

Back 5

-Geographical isolation

-Separate gene pools

-Variation due to mutation

-Different selection pressures

-Differential reproductive success

-Leads to divergent increases in allele frequencies

-Creating new species

Front 6

Anolis sagrei is a species of lizard that is found on some of the smallest Caribbean islands. Describe how you could use the mark-release-recapture method to estimate the number of Anolis sagrei on one of these islands [4]

Back 6

-Collect sample, mark and release

-Method of marking should not cause harm or make more visible to predators

-Leave sufficient time for lizards to randomly distribute before collecting second sample

-Population = (number in first sample * number in second sample) / number marked in second sample

Front 7

In birds, males are XX and females are XY. Use this information to explain why recessive, sex-linked characteristics are more common in female birds than male birds [2

Back 7

-Recessive allele is always expressed in females

-Because they only have one allele

Front 8

In chickens, a gene on the X chromosome controls the rate of feather production. The allele for slow feather production, F, is dominant to the allele for rapid feather production, f. The figure below shows the results produced from crosses carried out by a farmer. Explain one piece of evidence from the figure above which shows that the allele for rapid feather production is recessive [2]

Back 8

-1, 2, and 5

-1 must carry the recessive allele

-If slow feather production was recessive, all offspring from 1 and 2 would have rapid

Front 9

Explain why the results of frequency of an allele are in the form of a ratio [2]

Back 9

-Allows easier comparison

-Sample size may vary

Front 10

Explain what is meant by the term phenotype [2]

Back 10

-Expression of a characteristic due to alleles

-Which alter a characteristic

Front 11

Explain one piece of evidence which shows that the allele for this disease is recessive [2]

Back 11

-3 and 4 and 9 and 11 are affected offspring

-Therefore both 3 and 4 are heterozygous

Front 12

Explain once piece of evidence from the diagram above which proves that the allele for this disease is NOT on the X chromosome [2]

Back 12

-11 is affected, 3 is not

-Therefore father of 11 does not have a recessive allele on his X chromosome

Front 13

The fruit fly is a useful organism for studying genetic crosses. Female fruit flies are approximately 2.5 mm long. Males are smaller and possess a distinct black patch on their bodies. Females lay up to 400 eggs which develop into adults in 7 to 14 days. Fruit flies will survive and breed in small flasks containing a simple nutrient medium consisting mainly of sugars. Use this information to explain TWO reasons why the fruit fly is a useful organism for studying genetic crosses [2]

Back 13

-Large numbers of offspring so large sample size

-Small size so can be easily stored

-Size and markings make females easy to identify

-Short generation time so can make many generations fast

Front 14

Suggest one reason why observed ratios are often not the same as expected ratios when performing genetic crosses [1]

Back 14

-Fertilisation is a random process

Front 15

When a recessive allele is carried on the X chromosome, XY males are more likely to show the phenotype for the allele than XX females. Explain why [2]

Back 15

-Males only have one allele

-Females need two recessive alleles to express phenotype

Front 16

Explain why scientists use a control group [2]

Back 16

-To observe the effects of taking no action

-To use it as a benchmark to test the results of various actions

Front 17

Explain why drying aquatic helps to gain an accurate reading of its biomass [2]

Back 17

-Removes water

-Water can increase weight

Front 18

Explain why collecting samples from a large number of sites is important [1]

Back 18

-To make test more representative

Front 19

Describe a method which scientists could use to ensure that sample sites are chosen without bias [2]

Back 19

-Assign coords to area in grid

-Use random number generator to choose sites

Front 20

Suggest why using percentage cover rather than frequency to record the abundance of a species is better [1]

Back 20

-There could be too many organisms to count

Front 21

Explain why an experiment relating to a factor other than Carbon dioxide concentration and plant growth would take place in a high CO2 concentration environment [1]

Back 21

-So CO2 conc not limiting factor

Front 22

Explain why it is better to use the percentage of {species} affected rather than the number of {species} affected [2]

Back 22

-Number in samples can vary

-Allows a valid comparison between samples

Front 23

When a statistical test is carried out which yields a result of P<0.01, what does this mean? [2]

Back 23

-The probability is less than 1%

-That the results are down to chance

Front 24

Rather than use chemical pesticides or biological agents, farmers often use an integrated system of chemical pesticides and biological agents to control agricultural pests. Explain the advantages of using an integrated system to control agricultural pests [6]

Back 24

--Biological agents

Only need one application

Specific

Maintains low population

Pests don’t develop resistance

Can use less chemicals

--Chemical pesticides

Act quickly

Can apply to specific area

Kills almost all pests

Front 25

Nitrate from fertiliser applied to crops may enter ponds and lakes. Explain how nitrate may cause the death of fish in fresh water [5]

Back 25

-Eutrophication

-Growth of algae blocks light from penetrating water

-So no photosynthesis of submerged plants

-Saprophytes

-Aerobically respire to break down dead plants

-So less oxygen left for fish so fish die

Front 26

Adult toads spend most of their time on land but lay their eggs in water. These eggs hatch into tadpoles, which live in water and develop into adults. The tadpoles are much smaller than adult toads. Use this information to explain why the tadpoles are affected more rapidly by pesticides in water than adult toads. [2]

Back 26

-Larger SA:VOL

-So faster diffusion because of short diffusion pathway

Front 27

Use your knowledge of succession to explain the increase in biomass of an area in the first 20 years of succession [3]

Back 27

-Pioneer species

-Changes abiotic conditions

-increasing diversity of species

Front 28

Suggest three reasons for woodland conservation [3]

Back 28

-To protect habitats and niches

-To protect endangered species

-To reduce the effect of global warming

Front 29

Name the process which results in woodland developing from farmland [1]

Back 29

-Succession

Front 30

Explain the increase in the diversity of birds as a woodland area develops [3]

Back 30

-Greater variety of insect species

-more sources of food

-greater variety of niches

Front 31

Suggest two reasons why a species could rapidly become dominant after being introduced to a new environment [2]

Back 31

-few consumers

-outcompetes competitors

Front 32

Suggest two economic consequences of a species becoming dominant in a new environment [2]

Back 32

-Cost of removal

-Cost of restoring ecosystem

Front 33

Name the pioneer species in this diagram [1]

Back 33

-Ulva lactula

Front 34

Use this diagram to explain the process of succession [4]

Back 34

-Pioneer species Ulva increases then decreases

-Changes conditions to make them less hostile

-Gigartina canacliculata is better adapted to compete so Ulva outcompeted

-Process repeats until G. coulteri becomes climax species and increases in abundance

Front 35

The Amazonian forest today contains a very high diversity of bird species. Over the last 2,000,000 years, long periods of dry climate caused this forest to separate into a number of smaller forests. Different plant communities developed in each of these smaller forests. Each time the climate became wetter again, the smaller forests grew in size and merged to reform the Amazonian forest. Use this information to explain how a very high diversity of bird species has developed in the Amazonian forest. [5]

Back 35

-No interbreeding because of geographical isolation

-Mutation

-Because of different selection pressures

-So adapted organisms survive and reproduce

-which changes allele frequencies

Front 36

Speciation is less frequent in a stable environment. Explain why [1]

Back 36

-Similar environmental factors so less selection pressure

Front 37

The populations of lizard species vary at different times throughout the year. Suggest two reasons why [2]

Back 37

-Breeding seasons

-Temperature varies with season

Front 38

Changes in ecosystems can lead to speciation. A high concentration of copper in soil is toxic to most plants. In some areas where the soil is polluted with copper, populations of grasses are found to be growing. These populations of grass belong to a species also found growing on unpolluted soils. It has been suggested that a new species of grass may evolve on soil that has been polluted with copper. Explain how this new species might evolve. [5]

Back 38

-variation

-through mutation

-Some plants have allele to survive high copper concentration

-adapted organisms survive and reproduce

-increase in frequency of allele

-no interbreeding with other groups

Front 39

This graph shows part of the nutrient cycle. Which one of the processes involved nitrification? [1]

Back 39

-R

Front 40

This figure includes one process by which microorganisms add ammonium ions to soil. Describe another process carried out by microorganisms which adds ammonium ions to soil [2]

Back 40

-Proteins broken down

-by saprophytes

Front 41

Denitrification requires anaerobic conditions. Ploughing aerates the soil. Explain how ploughing would affect the fertility of the soil [2]

Back 41

-Fertility increased as more nitrated accumulates

-No denitrification because soil not anaerobic

Front 42

One farming practice used to maintain high crop yields is called crop rotation. This involves growing a different crop each year in the same field. Suggest two ways in which crop rotation may lead to high crop yields [2]

Back 42

-Growing plants with nitrogen fixing bacteria

-different crops use different minerals from the soil so soil can regenerate

Front 43

Climate change has resulted in an increase in the concentration of salt in the soil water of some parts of the world. Suggest how climate change could result in an increase in soil salinity [2]

Back 43

-Higher global temperature

-Increase in evaporation from soil, leaving salt behind

Front 44

Explain why crops don't grow when soil salinity is above 2% [2]

Back 44

-Soil has reduced water potential

-so water leaves roots by osmosis

Front 45

Use your knowledge of photosynthesis and respiration to describe and explain how the concentration of carbon dioxide in the air changes over a period of 24 hours, and at different heights above ground [5]

Back 45

-High concentration of CO2 caused by more respiration than photosynthesis at night

-No photosynthesis at night because no light

-In light, net uptake of CO2 reduced CO2 concentration

-Decrease in concentration of CO2 with height

-Because less photosynthesis at ground level

Front 46

Give a biological molecule that contains nitrogen [1]

Back 46

Amino acid, protein, enzyme, urea, nucleic acid, chlorophyll, DNA, RNA, ATP

Front 47

Give a biological molecule that contains Phosphorus [1]

Back 47

DNA, RNA, nucleic acid, ATP, ADP, etc

Front 48

Describe the role of microorganisms in producing nitrates from the remains of dead organisms [3]

Back 48

-Saprophytes break down remains and DNA into ammonia

-Ammonia ions converted into nitrite and nitrate

-By nitrifying bacteria

Front 49

Upwelling is a process where water moves from deeper parts of the sea to the surface. This water contains a lot of nutrients from the remains of dead organisms. Nitrates and phosphates are two of these nutrients. They provide a source of nitrogen and phosphate for cells. Upwelling often results in high primary productivity in coastal waters. Explain why some of the most productive fishing area are found in coastal waters [2]

Back 49

-Nitrates absorbed by producers

-More producers mean more consumers so fish thrive

Front 50

Explain how human activities have contributed to global warming [4]

Back 50

-CO2 is a greenhouse gas

-Deforestation removes trees so less CO2 removed by photosynthesis

-Combustion releases CO2

-Methane is a greenhouse gas

-Cattle produce methane

Front 51

Explain how the intensive rearing of domestic livestock increases net productivity [4]

Back 51

-slaughtered when young so more energy transferred to biomass

-Fed on concentrated food source so more food assimilated for biomass

-Movement restricted so less respiratory loss

-Kept warm so less energy used to maintain temperature

-Genetically selected for high productivity

Front 52

Name processes P and Q [2]

Back 52

-P = Nitrification

-Q = Denitrification

Front 53

Leguminous crop plants have nitrogen-fixing bacteria in nodules on their roots. On soils with a low concentration of nitrate ions, leguminous crops often grow better than other types of crop. Explain why [2]

Back 53

-Nitrogen fixing bacteria convert nitrogen to ammonia

-so plants can produce more protein

Front 54

Applying very high concentrations of fertiliser to the soil can reduce plant growth. Use your knowledge of water potential to explain why. [2]

Back 54

-Reduces water potential of soil

-so water leaves roots by osmosis

Front 55

Describe the reasons for the low efficiency of energy transfer through ecosystems [5]

Back 55

-Some light not correct wavelength so reflected off leaves

-Some light misses leaves

-Heat loss-Respiratory loss

-Energy loss through faeces

Front 56

Suggest the appropriate unit for gross productivity [1]

Back 56

Kj/M/Year

Front 57

Explain the decrease in gross productivity as woodland area matures [2]

Back 57

-More competition for light because of shading

-So less photosynthesis

Front 58

What measurements could you take in an investigation to measure the rate of photosynthesis? [1]

Back 58

-oxygen production

Front 59

Other than temperature and pH, give two factors which should be kept the same during an investigation into the rate of photosynthesis of a plant using different wavelengths of light [2]

Back 59

-Light intensity

-Time

Front 60

This graph shows shows the rate of photosynthesis of a plant at different wavelengths of light. Suggest and explain why the rate of PS is low between 525 and 575 nm wavelengths of light [2]

Back 60

-This range represents green light

-And green light is reflected, not absorbed

Front 61

Describe how AcetylCoa is formed during the link reaction [2]

Back 61

-Oxidation of pyruvate to release Co2

-Addition of CoA

Front 62

In the Krebs cycle, AcetylCoA combines with four-carbon oxaloacetate to form six-carbon citrate. This reaction is catalysed by the enzyme citrate synthase. Oxaloacetate is the first substrate to bind with the enzyme citrate synthase. This induces a change in the enzyme, which enables the AcetylCoA to bind. Explain how oxaloacetate enables the AcetylCoA to then bind to the enzyme [2]

Back 62

-Change in active site shape

-So substrate and active site now complementary

Front 63

In muscles, pyruvate is converted to lactate during anaerobic respiration. Explain why converting pyruvate to lactate allows the continued production of ATP during anaerobic respiration [2]

Back 63

-Regenerates NAD

-For use in glycolysis

Front 64

In muscles, some of the lactate is converted back to pyruvate when they are well supplied with oxygen. Suggest one advantage of this [1]

Back 64

-Lactic acid harmful to muscles and can induce cramp

Front 65

Give two factors which could limit the rate of photosynthesis in a plant [2]

Back 65

-Temperature

-Light intensity

-CO2 concentration

Front 66

Explain why CO2 uptake is a measure of net productivity [1]

Back 66

-Shows gross photosynthetic productivity minus respiratory productivity

Front 67

Respiration produces more ATP per molecule of glucose in the presence of oxygen than it does when oxygen is absent. Explain why [2]

Back 67

-Oxygen is the final electron acceptor

-The electron transport chain produces ATP

-only glycolysis occurs without oxygen

Front 68

During the LIdR in photosynthesis, carbon dioxide is converted into organic substances. Explain how [6]

Back 68

-CO2 combines with ribulose bis-phosphate

-produces 2 G3P

-G3P reduced to TP

-Using NADP

-Using energy from ATP

-TP converted to glucose

Front 69

Complete this table:

Back 69

Front 70

Where in the cell is the enzyme RuBisCo found? [1]

Back 70

-Stroma of chloroplasts

Front 71

Describe what happens during the light-dependent reaction of photosynthesis [5]

Back 71

-Chlorophyll absorbs light energy

-Excited electrons

-move down electron transport chain releasing energy

-Energy used to join ADP and Pi to form ATP

-photolysis of water produces electrons, protons, and oxygen

-NADP reduced by electrons and protons

Front 72

There are changes in the birth rate, death rate and size of the population during demographic transition. Describe the changes that occur in the birth and death rates during demographic transition [1]

Back 72

-Birth rate and death rate level out

Front 73

Describe the changes that occur in the size of the population during demographic transition [1]

Back 73

-Population increases then levels out

Front 74

Suggest one reason for the difference in the average life expectancy for males and females in the USA [1]

Back 74

-Males more likely to die from heart disease

Front 75

What information is required to calculate the growth of a population? [2]

Back 75

-Birth rate-Death rate

Front 76

What evidence does this graph show that indicates this country is in an early stage of demographic transition? [2]

Back 76

-High birth rate

-High death rate

Front 77

What is meant by the term population? [1]

Back 77

-Organisms of one species in a habitat

Front 78

Give two factors which could lead to a decrease in the death rate of a human population [2]

Back 78

-Improving medical care

-Improving nutrition

-More food

-Improving sanitation

-Less diseasae

Front 79

The changes in the survival curves between 1751 and 1960 show that a demographic transition has taken place in this country. Explain how the changes show this [2]

Back 79

-Increase in life expectancy

-Decrease in death rate

Front 80

A student collected 17 lizards and marked them before releasing them. Later she collected 20 lizards, 10 of which were marked. Calculate the number of lizards in this area. Show your working [2]

Back 80

(17x20)/10

=34

Front 81

Give TWO conditions for the results of the mark-release-recapture technique to be valid [2]

Back 81

-Marking is not removed and does not change survival rates

-Limited immigration and emigration

-Sufficient time for marked individuals to integrate

-Little births and deaths

-Sampling method is the same