18.2. Biodiversity
A subsection of Biology, 9700, through 18. Classification, biodiversity and conservation
Listing 10 of 94 questions
shows a male red deer, Cervus elaphus. Red deer are herbivores, browsing on low vegetation in forests and on waste land. A history of wild red deer on the western European island of Ireland includes these facts: • Red deer have lived in Ireland for at least 12 000 years. • Originally red deer could cross from the neighbouring island of Great Britain to Ireland over a land connection. • A rise in sea levels at the end of the last Ice Age removed this land connection, separating the red deer on the two islands. • In the 1800s the number of red deer in Ireland decreased sharply after the main food crop for the human population failed for several consecutive years. • In the 1900s this decrease in the number of red deer continued as large areas of waste land were drained for agriculture. • By 1960 red deer were nearly extinct in Ireland, restricted to one population, A, of 60 individuals. • Since then protection has allowed population A to increase to over 600 red deer. • Several new red deer populations, B, C and D, have also been established in different parts of Ireland from individuals brought from Great Britain. Use the information given to identify two causes of extinction that may have threatened the survival of red deer in Ireland. Describe how the level of molecular similarity between the red deer in population A and population B can be investigated. Explain why some red deer in population A show unique molecular features that are not found in any of the red deer of populations B, C and D.
9700_w17_qp_42
THEORY
2017
Paper 4, Variant 2
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Describe a method that could be used to estimate the population size of a mobile animal, such as a brown rat. The soft rush plant, Juncus effusus, grows in many habitats in Northern Europe. An investigation was carried out to assess whether there was a relationship between the height of soft rush plants and the altitude at which they grow on exposed hillsides. The mean height of 10 soft rush plants was calculated at each of eight different altitudes. The results are shown in Table 8.1. Table 8.1 altitude / m mean height of soft rush plants / cm The statistical test, Spearman’s rank correlation , was applied to find out if there was a relationship between the altitude and the mean height of the soft rush plants. The formula for calculating Spearman’s rank correlation is: rs = 1 – (6 × ΣD2 n3 – n ) • ΣD2 is the sum of the differences between the ranks of the two samples • n is the number of samples. In this investigation the value of ΣD2 is 164. Calculate the value of rs. Show your working and write your answer to two decimal places. rs = Use your value for rs to evaluate the relationship between the altitude and the mean height of the soft rush plants.
9700_w20_qp_42
THEORY
2020
Paper 4, Variant 2
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Biodiversity can be considered at three different levels. , and are images that show these three different levels of biodiversity. Describe the level of biodiversity most clearly visible in each image. Prairie strips are restored habitat areas planted with native grasses and wildflowers. Prairie strips are usually located between or around the edges of fields of maize or soy bean. Students in North America wanted to investigate biodiversity along a prairie strip. Outline how the students could measure the biodiversity of plants and insects along a prairie strip. plants insects Mathematical methods and statistical tests help to summarise and compare biodiversity data. Name the mathematical method or statistical test that the students can use: to estimate the total biodiversity of a prairie strip to test whether plant biodiversity is associated with insect biodiversity. Prairie strips have environmental and economic effects. Scientists have made long-term measurements of the environmental effects of prairie strips. The scientists found that when prairie strips formed 10% of a crop-field: • soil erosion decreased by 95% • mineral loss from the field decreased by 90% for phosphorus compounds • mineral loss from the field decreased by 85% for nitrogen compounds. Crop plants need phosphorus (P) and nitrogen (N) to grow. Evaluate the economic effects of prairie strips on farming.
9700_w21_qp_42
THEORY
2021
Paper 4, Variant 2
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A large number of alpine plant species grow in the mountains of New Zealand’s South Island. Alpine plants are defined as plants that live above the treeline, which is the height above which trees cannot grow. The current treeline for most of South Island is 1200 m. The alpine areas nearest to South Island are 1500–2000 km away across the sea. Many of South Island’s alpine species live nowhere else in the world. Explain how a large number of alpine plant species developed on South Island. shows two aspects of the history of South Island over the last 3.9 million years. • The dashed line shows how the mean height of mountains in the Clyde region of South Island increased over time. The mountains in this range have a mean height of 2400 m at the present time. • The solid line models the height of the treeline over time based on geological climate data. The treeline was higher when the climate was warmer, and the treeline was lower when the climate was colder, during ice ages. 3.0 2.0 time before present / million years present time height / m 1.0 3.9 With reference to , identify with reasons the time period when South Island’s alpine plant species developed. Suggest how DNA sequence data could be used to confirm the time period you identified in .
9700_w22_qp_41
THEORY
2022
Paper 4, Variant 1
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A large number of alpine plant species grow in the mountains of New Zealand’s South Island. Alpine plants are defined as plants that live above the treeline, which is the height above which trees cannot grow. The current treeline for most of South Island is 1200 m. The alpine areas nearest to South Island are 1500–2000 km away across the sea. Many of South Island’s alpine species live nowhere else in the world. Explain how a large number of alpine plant species developed on South Island. shows two aspects of the history of South Island over the last 3.9 million years. • The dashed line shows how the mean height of mountains in the Clyde region of South Island increased over time. The mountains in this range have a mean height of 2400 m at the present time. • The solid line models the height of the treeline over time based on geological climate data. The treeline was higher when the climate was warmer, and the treeline was lower when the climate was colder, during ice ages. 3.0 2.0 time before present / million years present time height / m 1.0 3.9 With reference to , identify with reasons the time period when South Island’s alpine plant species developed. Suggest how DNA sequence data could be used to confirm the time period you identified in .
9700_w22_qp_43
THEORY
2022
Paper 4, Variant 3
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Biodiversity can be assessed at three different levels. One of these is the genetic variation within each species. Outline two other levels at which biodiversity can be measured. To calculate the genetic variation that exists within a species, scientists: • obtain DNA sequences from many individuals of one species • count the number of nucleotides that differ when the sequences of two individuals are compared • repeat this with different pairs of individuals. This allows scientists to calculate the mean number of differences at every nucleotide position along the sequence (mean number of nucleotide differences per site). Explain why scientists use databases and computers to calculate the mean number of nucleotide differences per site. Table 2.1 shows the mean number of nucleotide differences per site of some species. Table 2.1 species mean number of nucleotide differences per site Drosophila melanogaster, fruit fly 0.0087 Anopheles gambiae, mosquito vector of malaria 0.0301 Plasmodium falciparum, malarial pathogen 0.0015 Zea mays, wild maize 0.0139 State the genus name of the species that shows the most genetic variation. State how many kingdoms of organisms are represented in Table 2.1. Genetic variation is considered important in the conservation of species. Low genetic variation is assumed to decrease the chance of the long-term survival of a species. Give reasons why low genetic variation may decrease the long-term survival of a species. shows how the International Union for the Conservation of Nature (IUCN) categorises species according to their conservation status. Common species with the lowest conservation status (least risk of extinction) are categorised as Least Concern (LC). conservation status Extinct (Eincreasing risk of extinction Extinct in the Wild (EW) Critically Endangered (CR) Endangered (EN) Vulnerable (VU) Near Threatened (NT) Least Concern (LC) Question 2states that ‘low genetic variation is assumed to decrease the chance of the long-term survival of a species’. Predict the relationship between genetic variation and conservation status if this assumption is true. shows the mean number of nucleotide differences per site of some species and sub-species of mammal and their conservation status. 0.0 0.1 0.2 mean number of nucleotide differences per site ×10–2 lion wolf giant panda brown rat chimpanzee gorilla common minke whale LC Key VU EN CR Assess whether the data in provide support for the prediction you made in 2.
9700_w23_qp_41
THEORY
2023
Paper 4, Variant 1
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Biodiversity can be assessed at three different levels. One of these is the genetic variation within each species. Outline two other levels at which biodiversity can be measured. To calculate the genetic variation that exists within a species, scientists: • obtain DNA sequences from many individuals of one species • count the number of nucleotides that differ when the sequences of two individuals are compared • repeat this with different pairs of individuals. This allows scientists to calculate the mean number of differences at every nucleotide position along the sequence (mean number of nucleotide differences per site). Explain why scientists use databases and computers to calculate the mean number of nucleotide differences per site. Table 2.1 shows the mean number of nucleotide differences per site of some species. Table 2.1 species mean number of nucleotide differences per site Drosophila melanogaster, fruit fly 0.0087 Anopheles gambiae, mosquito vector of malaria 0.0301 Plasmodium falciparum, malarial pathogen 0.0015 Zea mays, wild maize 0.0139 State the genus name of the species that shows the most genetic variation. State how many kingdoms of organisms are represented in Table 2.1. Genetic variation is considered important in the conservation of species. Low genetic variation is assumed to decrease the chance of the long-term survival of a species. Give reasons why low genetic variation may decrease the long-term survival of a species. shows how the International Union for the Conservation of Nature (IUCN) categorises species according to their conservation status. Common species with the lowest conservation status (least risk of extinction) are categorised as Least Concern (LC). conservation status Extinct (Eincreasing risk of extinction Extinct in the Wild (EW) Critically Endangered (CR) Endangered (EN) Vulnerable (VU) Near Threatened (NT) Least Concern (LC) Question 2states that ‘low genetic variation is assumed to decrease the chance of the long-term survival of a species’. Predict the relationship between genetic variation and conservation status if this assumption is true. shows the mean number of nucleotide differences per site of some species and sub-species of mammal and their conservation status. 0.0 0.1 0.2 mean number of nucleotide differences per site ×10–2 lion wolf giant panda brown rat chimpanzee gorilla common minke whale LC Key VU EN CR Assess whether the data in provide support for the prediction you made in 2.
9700_w23_qp_43
THEORY
2023
Paper 4, Variant 3
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Questions Discovered
94