GCSE BITESIZE Examinations

GCSE BITESIZE Examinations General Certificate of Secondary Education AQA SCIENCE A BLY1B Unit Biology B1b (Evolution and Environment) AQA BIOLOGY Unit Biology B1b (Evolution and Environment) HIGHER TIER Specimen Paper Time allowed: 30 minutes Maximum marks: 36 Instructions Answer all of the questions for the Tier you are attempting. Record your answers on a separate answer sheet only. Do all rough work in this book - not on your answer sheet. Advice Do not choose more responses than you are asked to. You will lose marks if you do. 1

HIGHER TIER SECTION ONE Questions ONE and TWO In these questions, match the letters A, B, C and D with the numbers 1-4. Use each answer only once. Mark your choice on the answer sheet. QUESTION ONE Scientists have studied the variety of life on Earth, looking for clues to its origin. Match words A, B, C and D with the numbers 1-4 in the sentences. A B C D natural selection fossilisation mutation evolution Scientists believe that all life on Earth developed from simpler organisms 3.5 billion years ago. This theory is known as the theory of 1. Occasionally, the genes of some organisms changed by a process known as 2. This made these organisms better adapted than the others, so they survived to pass on their genes, while others died out. This is called 3., and has resulted in new species developing over millions of years. However, the remains of some of the ancient species were preserved by a process known as 4., which provides evidence for this theory. 2

QUESTION TWO Scientists monitor the levels of greenhouse gases and pollution in the environment. Match chemicals A, B, C and D to statements 1, 2, 3 and 4. A B C D Sulfur dioxide Nitrates Carbon dioxide Methane Statements 1 Gas which is released from combustion of fossil fuels, respiration and decay 2 Used by farmers in fertiliser. Often washes out of soil into rivers, causing water pollution 3 Greenhouse gas which is increasing in the atmosphere, mainly due to increasing cow farming and rice growing 4 Produced when coal burns. Causes air pollution which leads to acid rain 3

SECTION TWO Questions THREE to NINE Each of these questions has four parts. In each part, choose only one answer. Mark your choices on the answer sheet. QUESTION THREE A group of students carried out an investigation to determine whether the number of dandelions increased as the distance from trees increased. To do this, they set up a series of quadrats at regular one-metre intervals along a tape measure, beginning immediately next to the tree. They used a plastic grid with 25 squares on it to estimate the percentage of the quadrat that was covered by dandelions. They repeated their observations along another tape measure two metres to the right of the first. 4

The table shows their results: Distance from tree (m) Percentage of quadrat covered by dandelions along tape measure 1 0 0 0 1 0 0 2 0 0 3 2 3 4 4 5 5 6 9 6 9 10 7 10 8 8 13 11 Percentage of quadrat covered by dandelions along tape measure 2 3A Why did the students design their experiment to sample along two tape measures which were close together, instead of repeating the samples in different fields? 1 So that there results would be less likely to contain systematic errors. 2 So that they could easily identify a relationship between the distance and the percentage covered by dandelions. 3 So that variables which they were unable to control had the same effect on both sets of readings. 4 So that data could be collected with the same degree of precision. 3B What was the range of values observed in the dependent variable? 1 0 to 11 %. 2 0 to 13 % 3 0 to 8 m. 4 0 to 1 m. 5

3C One of the students suggested that the trend could be explained in terms of competition, with there being greater competition nearer to the trees than further away from them. Which of these would the dandelions compete with the tree for? 1 Food 2 Territory 3 Mates 4 Nutrients 3D Which of these would improve the accuracy of the percentage cover measurements? 1 Using a plastic grid containing 100 smaller squares within the quadrat. 2 Taking readings every half a metre, instead of every metre. 3 Getting another group to repeat the same experiment, and comparing results. 4 Extending the measurements further from the tree. 6

QUESTION FOUR Read the passage below: G.M. mosquito could fight malaria Malaria is a disease which is caused by a parasite. It is spread between humans by bites from mosquitoes, and kills more than 1 million people a year worldwide. A genetically modified (G.M.) strain of mosquito that is resistant to malaria has been created, and it is able to survive better than mosquitoes which carry the disease. The G.M. mosquito carries a gene that prevents infection by the malaria parasite. In experiments, equal numbers of G.M. and ordinary mosquitoes were allowed to feed on malaria-infected mice. As they reproduced, more of the G.M. mosquitoes survived. Adapted from a BBC News Online article, March 2007 4A The results of the investigation were that, after nine generations, 70 per cent of the insects that survived belonged to the malaria-resistant strain. Scientists think that this is because the malaria parasite reduces the health of infected mosquitoes, making them less able to compete against the malaria-resistant mosquitoes. This idea is 1 a hypothesis. 2 an experiment. 3 a theory. 4 a conclusion. 7

4B When scientists began this experiment, they chose large numbers of genetically modified (G.M.) and ordinary mosquitoes for the trial. This was important because 1 it improved the reliability of the experiment. 2 it improved the precision of the experiment. 3 it improved the accuracy of the experiment. 4 it improved the sensitivity of the experiment. 4C In the experiment, scientists also inserted a gene which made the eyes of the genetically modified (G.M.) mosquitoes glow green. The reason for this was 1 It allowed the G.M. mosquitoes to compete better than the wild type mosquitoes. 2 It gave scientists an easily way of counting which mosquitoes were genetically modified, and which were not. 3 It warned the parasite against infecting the G.M. mosquito. 4 It made it harder for the G.M. mosquitoes to survive. 4D Scientists hope that this research will eventually lead to G.M. mosquitoes being released into the environment on a large scale. The aim of doing this will be 1 to prove that genetically modified organisms are safe. 2 to eliminate the spread of the malaria parasite between humans. 3 to eliminate all mosquitoes in warm areas. 4 to protect crops from insect pests. 8

QUESTION FIVE The diagram below shows the stages involved in genetically modifying bacteria to produce human insulin. 5A The human insulin gene is one of 30,000 genes that humans have. To carry out this procedure, the human insulin gene had to be cut out from a 1 chromosome. 2 nucleus. 3 bacterial cell. 4 empty egg cell. 5B The human insulin gene was cut out using 1 a sharp pipette. 2 chemicals which mutate DNA. 3 an electric shock. 4 an enzyme. 9

5C In the final step of this procedure, the bacteria multiply to give large numbers, each containing the human insulin gene. This multiplication is an example of 1 asexual reproduction. 2 sexual reproduction. 3 fusion cell cloning. 4 tissue culture. 5D Scientists have also genetically engineered plants. One reason for this is to make them resistant to herbicides (weed killer). However, growing G.M. crops instead of traditional crops concerns many people. The UK government has limited the growing of G.M. crops in order to carry out extensive trials. Which of these is a legitimate concern about growing G.M. crops on a wide scale in the natural environment? 1 G.M. crops might prove unpopular, leading to protests. 2 Farmers might stop planting traditional, non-g.m. crops, resulting in traditional crop species being lost. 3 G.M. crops might pollinate other plants, allowing the resistance gene to escape and the creation of herbicide-resistant super weeds. 4 G.M. crops might grow more slowly, so farmers will not be able to supply food to meet demand. 10

QUESTION SIX Comparative anatomy involves comparing the bone structure of different species. Diagram 1 shows the bones in a human forelimb (arm). Diagram 2 shows the bones in the forelimbs of other modern-day vertebrates (animals with backbones). Read the three statements in the box below: i) The bone structure indicates that humans share a common ancestor with other vertebrates. ii) iii) The bone structure indicates that humans have evolved from one of the vertebrates in Diagram 2. The bone structure of these limbs has adapted to different ways of moving as the organism has evolved. 11

6A Which of the statements in the box are correct? 1 Statement i) and iii) 2 Statement ii) and iii) 3 Statement i), ii) and iii) 4 None of the statements are correct. 6B Fossil records also allow us to work out evolutionary trees. Using these, scientists have been able to piece together an evolutionary tree for the past 550 million years. However, there is a lack of valid evidence to show how life evolved on Earth before this. This is because 1 scientists have been unable to dig down far enough to reach the evidence. 2 early organisms had soft bodies which left very little trace in the rocks. 3 early organisms were too small for us to now see fossils of them in the rocks. 4 there were fewer organisms alive at that time, so it is more difficult to find fossils of them. 6C The fossil evidence indicates that new species have evolved from ancient ancestral species. New species survived, while ancestral species became extinct. Which of these is most likely to have caused the extinction of these species? 1 An increase in existing predator numbers 2 An increase in prey numbers 3 A change in the environment 4 An increase in the rate of fossilisation 12

6D Darwin s theory of natural selection was published in 1859, but was not widely accepted at the time. All of these are reasons for this, except 1 It contradicted widely held religious beliefs that God created all life on Earth. 2 There was no knowledge of what caused genetic variation or how characteristics were passed onto the next generation. 3 Lamark s theory was widely believed, and people were unwilling to believe an alternative theory. 4 There was insufficient fossil evidence at the time to convince many scientists. 13

QUESTION SEVEN The graph below shows human population numbers over the past 2,000 years. The human population has increased dramatically over the past 500 years, and is predicted to reach 9 billion by the year 2050. 7A Which of these have not contributed significantly to the large increase in the past 500 years? 1 Better agricultural methods 2 Medical improvements 3 Improved fertility techniques 4 Improvements to public hygiene 7B As a result of increasing human population levels, there has been a greater need for land, resulting in more deforestation. Deforestation directly causes 1 an increase in acid rain. 2 a reduction in biodiversity. 3 a reduction in flooding levels. 4 an increase in the release of methane gas. 14

The table below shows the rate of deforestation in Brazil: Year Area of Brazilian rainforest chopped down (km 2 ) 1990 13,813 1991 11,130 1992 13,786 1993 15,410 1994 14,896 1995 29,059 1996 18,160 1997 13,040 1998 16,840 1999 17,259 2000 19,836 2001 18,130 2002 25,500 2003 24,130 2004 26,129 2005 18,900 7C Which of these is a valid conclusion to draw from this data? 1 Deforestation between 2001 and 2005 was the highest seen during any five-year period since 1990. 2 The total area of rainforest cut down has begun to decrease. 3 The amount of deforestation per year since 2000 has generally been lower than it was in the 1990s. 4 Deforestation has increased each year since 1990. 7D Deforestation occurred at a very high rate during the late-1970s and 1980s. The total area of Brazilian rainforest cut down during the period 1978 to 1987 was 211,300 km 2. How much did this decrease by during the period 1996 to 2005? 1 10,762 km 2 2 13,376 km 2 3 15,467 km 2 4 18,160 km 2 15

QUESTION EIGHT This question is about cloning. 8A Which of these statements about clones is true? 1 They all look identical to the original animal/plant from which they were cloned. 2 They contain genes from other species, enabling them to make useful products. 3 They will show no genetic variation from the original animal/plant from which they were cloned. 4 Half of their genes will be from two separate parents. In 1996, researchers at the Roslin Institute in Edinburgh successfully produced the first cloned mammal from an adult cell, using a technique called adult cell cloning. They called the clone Dolly. The diagram below shows the stages by which Dolly was created: 16

8B An empty egg cell was joined with the nucleus from the udder cell, because 1. it would make the surrogate mother pregnant. 2. it is the only type of cell with which the nucleus could fuse. 3. it ensured that Dolly would be born a female. 4. it had the potential to divide to produce any type of cell in the clone. 8C Dolly was a clone of which sheep in the diagram? 1. The Finn Dorset (white-faced) sheep. 2. The Scottish Blackface sheep from which an egg was taken. 3. The Scottish Blackface sheep that was used as a surrogate mother for the embryo to develop in. 4. A combination of all three sheep used in the process. 8D Another method of producing cloned animals involves embryo transplantation. Which of the following sentences describes this process? 1 The nucleus from an adult cell is fused with an empty egg cell, which then divides to produce an embryo. The embryo is then implanted into a surrogate mother to grow into fully developed clones. 2 A sperm fertilises an egg, and this then divides to produce an embryo. The embryo then splits into two smaller embryos, both of which implant in the womb and develop as separate organisms. 3 A small group of cells is grown in a Petri dish containing nutrients and hormones, which causes cell division and produces identical individuals. 4 A fertilised cell is allowed to divide to produce an embryo. The embryo is then split, and each of the smaller embryos is then implanted into a surrogate mother. 17

QUESTION NINE Carbon dioxide is a greenhouse gas. Scientists believe that increasing carbon dioxide emissions in our atmosphere are contributing to global warming. 9A Which of these statements explains why an increase in greenhouse gases can result in an increase in global warming? 1 Greenhouse gases absorb the heat energy radiated by the Sun, and radiate heat towards Earth. 2 Greenhouse gases absorb the heat energy radiated by the Earth, and radiate it back towards Earth. 3 Greenhouse gases reflect less of the heat energy radiated by the Sun back into space. 4 Greenhouse gases generate heat energy, which is radiated towards Earth. The graph below shows the carbon dioxide emissions of different countries in 1990 and 2004. 18

9B In 2004, the nine countries featured in the graph emitted a combined total of 14,600 million tonnes of carbon dioxide. Of these, the biggest polluter was the US. Using information from the graph, calculate the proportion of the total emissions that were produced by the US in 2004. 1 0.904 2 0.411 3 0.455 4 0.486 Total emissions of carbon dioxide in the UK have fallen slightly since 1990. However, some sources of these emissions have increased. The graph below shows the main sources of carbon dioxide emissions in the UK from 1970 to 2004: 9C What was the average rate of decrease in carbon dioxide emissions per year from domestic sources in the UK between 1970 and 2000? 1 13 million tonnes per year. 2 0.43 million tonnes per year. 3 0.38 million tonnes per year. 4 0.36 million tonnes per year. 19

9D Which of these could have contributed to this decrease in carbon dioxide emissions from domestic sources? 1 Reductions in domestic gas and electricity prices. 2 Improvements in the availability and reliability of public transport. 3 The development of energy-efficient appliances. 4 Increases in the amount of city centre accommodation. END OF QUESTIONS 20