8. Transport in mammals
A section of Biology, 9700
Listing 10 of 589 questions
Mammoths are extinct mammals related to elephants. About three million years ago, the ancestors of mammoths migrated from Africa into Europe and Asia. There, about 1.7 million years ago, the steppe mammoth evolved and became adapted to the cooler conditions. Then, about 700 000 years ago, as the climate changed and the Arctic became much colder, the woolly mammoth evolved. Woolly mammoths showed a number of obvious adaptations to reduce heat loss, including thick fur, small ears and small tails. Explain how variation and natural selection may have brought about the evolution of the woolly mammoth from the steppe mammoth. A frozen, 43 000 year old woolly mammoth was found in Siberia. Its DNA was extracted and sequenced. The sequences of the genes coding for the α and β chains of haemoglobin were compared with those of modern Asian elephants. The results suggested that, when compared with Asian elephants: • there was only one different amino acid in the woolly mammoth’s α chains • there were three different amino acids in the woolly mammoth’s β chains. Explain the likely effect of these differences on a molecule of mammoth haemoglobin. Scientists synthesised woolly mammoth haemoglobin in order to investigate whether or not the different haemoglobin was part of the mammoth’s adaptation to a cold climate. The affinity of haemoglobin for oxygen is affected by the changes in temperature that can occur in mammals, for example in active muscle tissue or close to the skin surface. It is advantageous for Arctic mammals to have haemoglobin whose affinity for oxygen is only slightly affected by changes in temperature. This is often achieved by using substances called ‘red cell effectors’, which bind to haemoglobin. compares the effect of temperature on the affinity for oxygen of woolly mammoth and Asian elephant haemoglobin, with and without red cell effectors. haemoglobin effect of temperature on the affinity of haemoglobin for oxygen Key woolly mammoth Asian elephant haemoglobin plus red cell effectors Suggest why it is advantageous for Arctic mammals to have haemoglobin whose affinity for oxygen is only slightly affected by changes in temperature. Explain whether or not provides evidence that woolly mammoth haemoglobin is better adapted for a cold climate than Asian elephant haemoglobin.
9700_w13_qp_41
THEORY
2013
Paper 4, Variant 1
View
Mammoths are extinct mammals related to elephants. About three million years ago, the ancestors of mammoths migrated from Africa into Europe and Asia. There, about 1.7 million years ago, the steppe mammoth evolved and became adapted to the cooler conditions. Then, about 700 000 years ago, as the climate changed and the Arctic became much colder, the woolly mammoth evolved. Woolly mammoths showed a number of obvious adaptations to reduce heat loss, including thick fur, small ears and small tails. Explain how variation and natural selection may have brought about the evolution of the woolly mammoth from the steppe mammoth. A frozen, 43 000 year old woolly mammoth was found in Siberia. Its DNA was extracted and sequenced. The sequences of the genes coding for the α and β chains of haemoglobin were compared with those of modern Asian elephants. The results suggested that, when compared with Asian elephants: • there was only one different amino acid in the woolly mammoth’s α chains • there were three different amino acids in the woolly mammoth’s β chains. Explain the likely effect of these differences on a molecule of mammoth haemoglobin. Scientists synthesised woolly mammoth haemoglobin in order to investigate whether or not the different haemoglobin was part of the mammoth’s adaptation to a cold climate. The affinity of haemoglobin for oxygen is affected by the changes in temperature that can occur in mammals, for example in active muscle tissue or close to the skin surface. It is advantageous for Arctic mammals to have haemoglobin whose affinity for oxygen is only slightly affected by changes in temperature. This is often achieved by using substances called ‘red cell effectors’, which bind to haemoglobin. compares the effect of temperature on the affinity for oxygen of woolly mammoth and Asian elephant haemoglobin, with and without red cell effectors. haemoglobin effect of temperature on the affinity of haemoglobin for oxygen Key woolly mammoth Asian elephant haemoglobin plus red cell effectors Suggest why it is advantageous for Arctic mammals to have haemoglobin whose affinity for oxygen is only slightly affected by changes in temperature. Explain whether or not provides evidence that woolly mammoth haemoglobin is better adapted for a cold climate than Asian elephant haemoglobin.
9700_w13_qp_42
THEORY
2013
Paper 4, Variant 2
View
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