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Question 1
Herdwick sheep are hardy hill-sheep that live in the Lake District, where they graze the Cumbrian fells. They can live at heights of more than 900 metres and withstand extremely cold temperatures and relentless rain. Herdwick sheep are able to survive extremely harsh winters because they have a very thick coat that does not part when the wind blows and sheds water quickly. |
a) | Use Charles Darwin’s theory of natural selection to explain why the Cumbrian Herdwick sheep have two thick coats, unlike sheep in the south of England.
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b) | What do you predict will happen to the coats of Herdwick sheep over many generations if the winter temperatures start increasing? Explain your answer.
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Question 2
The theory of natural selection was proposed by Charles Darwin in 1859. His theory was not widely accepted until much later. |
a) | A different scientist suggested that physical changes in organisms during their lifetime can be inherited by their offspring. What was the name of this scientist?
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b) | Give two reasons why Darwin’s theory was only very slowly accepted.
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c) | What is meant by natural selection?
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Question 3
Moles dig tunnels in search for food. Moles have:
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a) | Use Darwin’s theory of natural selection to explain how the mole's front paws evolved.
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b) | The tyrrhenian mole is an extinct species of mole. What does extinct mean?
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c) | The tyrrhenian mole lived in the Mediterranean islands of Corsica and Sardinia during the Pleistocene epoch. Scientists have found a few tyrrhenian mole fossils. What is a fossil?
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d) | Information about extinct animals is often unclear because the fossil record is incomplete. Give three reasons why the fossil record can be unclear for older species.
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Question 4
Gregor Mendel is often referred to as the "father of genetics". Mendel investigated the genetics of peas. The characteristics Mendel investigated included:
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a) | Which term is used to describe the group of alleles that determines an organism's characteristics? A phenotype B allele C genotype D codominance
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b) | Explain how Mendel showed that the tall allele is dominant to the short allele by crossing homozygous tall and homozygous short pea plants.
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c) | The allele for yellow peas (A) is dominant to the allele for green peas (a). Two heterozygous parent plants were used in a genetic cross. |
c) | Draw a Punnett square and use it to calculate the percentage probability that this cross will have offspring that produce green peas.
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d) | Mendel crossed plants that produced round seeds with plants that produced wrinkled seeds. He found that all offspring in the first generation produced round seeds. He then crossed these offspring with each other. In the second generation, some plants produced round seeds and others produced wrinkled seeds. |
Explain how the presence of both types of seed in the second generation showed that inherited traits are not always expressed in an organism.
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Question 5
Organisms can be classified by the five kingdom or three domain system. |
a) | What is the name of the domain that animals belong to? A Archaea B Monera C Eukarya D Protista
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b) | Give one reason why the three domain classification system was proposed.
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c) | Why are the cells from animals described as eukaryotic? A they do not have nuclei B they have a cell wall C they have a nucleus that contains DNA D they have a cell membrane
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d) | Dogs belong to the Kingdom Animalia. Identify the genus of the domestic dog, Canis familiaris.
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Question 6
Antibiotic-resistant bacteria can cause infection outbreaks in hospitals. In the UK, the number of deaths from infections picked up in hospital is estimated to be around 20,000 every year. Half of those 20,000 deaths are thought to be from methicillin resistant Staphylococcus aureus bacteria (MRSA). |
a) | Explain how antibiotic resistant bacteria develop, and why they are such a problem in hospitals.
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b) | Describe some steps that can be taken to prevent the development of antibiotic resistant strains.
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Question 7
The diagram shows a family tree in which some individuals have an inherited disorder called polydactyly. Polydactyly is a condition in which someone is born with extra fingers or toes. |
a) | What proportion of the children of A and B have polydactyly?
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b) | Using parents A and B, and their offspring, explain the evidence which shows that the allele for the disorder is dominant. Use the appropriate letters to identify individuals in your answer.
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Question 8
Cystic fibrosis is a condition that causes sticky mucus to build up in the lungs and digestive system. It is caused by a recessive allele. |
a) | What is an allele?
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b) | What is meant by recessive?
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c) | Explain how someone can be a carrier of cystic fibrosis.
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d) | Draw a Punnet Square between a mother and father who are both carriers. Use it to calculate the probability of having a child with cystic fibrosis. Use the following symbols in your explanation: c = cystic fibrosis allele C = normal allele
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Question 9
Human sex chromosomes are represented by the letters X and Y. |
a) | Doctors take a blood sample from a pregnant woman and extract the baby's DNA from the mother's blood. The baby's DNA is tested to see which chromosomes are present. Which conclusion is correct? A it must be a boy if an X chromosome is present. B it must be a boy if a Y chromosome is present. C it must be a girl if an X chromosome is present. D it must be a girl if a Y chromosome is present.
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b) | The Punnett square below shows the inheritance of sex in humans. |
b) | Give the genotype of:
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c) | A man and a woman have three daughters. The woman is pregnant with a fourth child. What is the chance that this child will also be a girl? A 0% B 25% C 50% D 100%
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d) | Explain how sperm determine the sex of offspring at fertilisation.
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