The diagram below illustrates the development of antibiotic resistance in bacteria.
Annotate the bacteria labelled A and B.
State the selection pressure that is applied at C.
The mutation for antibiotic resistance is passed on to other bacteria at point D.
List one of the processes by which this could occur.
State one strategy that could be used to reduce the rate at which resistance evolves in bacteria.
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The blackworm (Lumbriculus variegatus) is a species of worm native to North America and Europe. Blackworm habitat includes marshes, swamps and ponds, and they are a popular food source for fish kept in aquariums.
Each body segment is able to regenerate into a complete individual, and sexual reproduction in blackworms is very rare.
Dvortygirl, CC BY-SA 3.0, via Wikimedia Commons (opens in a new tab)
(i) State the main source of genetic variation in a blackworm population.
[1]
(ii) List two other sources of genetic variation in other species.
[2]
The blackworm in the image in part (a) has grown a second tail. Its ability to regenerate body parts can be considered a useful adaptation.
Suggest one role of the regeneration abilities of the blackworm.
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A population of guppies has two alleles of a specific gene in its gene pool. The frequencies of the alleles are shown in the table below.
Month | Frequency of allele 1 | Frequency of allele 2 | Frequency of new allele |
January | 0.81 | 0.19 | 0 |
February | 0.78 | 0.22 | 0 |
March | 0.77 | 0.21 |
|
April | 0.65 | 0.27 |
|
May | 0.51 | 0.34 |
|
June | 0.43 | 0.33 |
|
July | 0.40 | 0.24 |
|
A mutation occurs in the population that leads to the formation of a new allele for the gene.
Calculate the allele frequencies and complete the table to show the frequencies of the new allele between March and July.
The new allele was a dominant allele that provided the guppies with a survival advantage within their population.
Predict what will happen to the frequencies of all three alleles over time.
A few individuals with the mutated allele from the original population travelled to a new area and merged with a different population of guppies.
In the new population the frequency of the new allele remained low over many generations and then decreased.
Suggest a reason for the difference in the frequency of the new allele between the population in part (a) and this new population.
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Natural selection is thought to act less strongly in many modern human populations than it did in the past.
Suggest two reasons why natural selection may be weaker in these populations.
Suggest why scientists often focus on isolated groups, such as the Amish, for studies on inheritance and genetics.
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Define the term population.
A population of beetles lives in leaf litter on a forest floor. The beetles are predated on by various species of small birds and rodents.
The beetles have outer wing cases, known as elytra, that protects their wings. Elytra occur in different colours.
Explain how the beetle population could have evolved from having a diverse range of elytra colours to having mostly brown and green.
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Explain how natural selection could enable a population of bacteria to become resistant to an antibiotic.
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A group of biologists investigated a species of mouse living on a remote archipelago (a group of islands) in the Pacific Ocean. The mice originally had no natural predators. As part of the study, the biologists measured the claw length of a large number of mice on several of the islands.
A species of snake that preys on the mice, but cannot climb trees, was accidentally introduced on half of the islands. Several years after the introduction, the biologists returned and found that, on islands with snakes, the pattern of claw lengths in the mouse populations had changed. Some had shorter claws, enabling them to run faster, while others had longer claws, enabling them to climb trees.
Suggest the benefit to the scientists’ investigation of there being islands without any snakes present.
The evolution of long claws in the mice in part (a) was made possible by a mutation in the gene controlling claw length.
Explain how a mutation could lead to a change in claw length.
When the biologists conducted the investigation in part (a), flooding of the islands was very rare. Now, due to climate change, flooding of the islands occurs more regularly. This flooding can regularly wipe out large numbers of ground-living species.
Using this information and the information from part (a), explain how the claw length of the mice on the islands is likely to change.
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Explain how natural selection can result in antibiotic resistant bacterial strains.
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Mining for gold produces waste rocks and mine tailings, which contain sulfur-bearing minerals. When surface water and shallow groundwater come into contact with these minerals, a chemical reaction occurs which produces sulfuric acid. This process is known as acid mine drainage and it can lower the soil pH to a level where very few plants can survive.
Environmentalists studied the area around an abandoned gold mine and discovered a few specimens of earleaf acacia (Acacia auriculiformis) surviving in the acidic soil. This species typically occurs in more neutral or alkaline soils.
Explain how natural selection could produce a population of Acacia auriculiformis that would be tolerant of the acidic soil found around the mine shaft.
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Describe the process of evolution by natural selection.
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Natural selection would not be possible without the presence of variation within a species.
Explain how variation allows natural selection to occur.
Mutation, meiosis and sexual reproduction are all sources of genetic variation.
Outline the way in which each of these factors contributes to variation within a species.
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3 marksThe turtle-headed sea snake, Emydocephalus annulatus, can be found in waters off the coast of Australia, New Zealand and New Caledonia. These snakes usually have banded patterns of white with dark rings, although some individuals exhibit a single dark colour with no banded patterns.
The dark parts of the skin contain a high concentration of the pigment melanin, which binds to toxic trace elements present in some bodies of water. These trace elements are removed from the body when the snake sloughs off the skin. Melanic sea snakes have been found to slough off their skin more frequently than those with banded colouration.
Scientists studied the frequency of melanic sea snakes in several aquatic sites in urban-industrial areas and non urban-industrial areas. The results are shown in the table below.
Site | Melanic sea snakes / % | |
Urban-industrial waters | 1 | 78 |
2 | 95 | |
3 | 64 | |
4 | 92 | |
5 | 98 | |
Non urban-industrial waters | 6 | 23 |
7 | 0 | |
8 | 14 | |
9 | 2 | |
10 | 7 | |
Calculate the percentage difference in the mean frequency of melanic snakes found in urban-industrial waters and those that were present in non urban-industrial waters.
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The graph below shows the sizes of a rabbit and a wolf population over many generations.
Explain the data in the graph for rabbit and wolf populations over the first 300 generations.
At generation 350 in the graph shown in part (b) the frequency of allele A is high, but never 100 %.
State one reason why it is not beneficial for this population to have one allele at 100 % frequency.
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The evolution of Black bear body mass happened on Earth thousands of years ago.
Suggest how scientists know about their evolutionary past.
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The evolution of some species can be driven by female mating preferences. An example of this can be found in a species of bird called the long-tailed widowbird, in which females have a preference for males with long tails. The long tails of male widowbirds have evolved from short-tailed ancestors despite being heavy and limiting male flying ability.
Describe the selection process that has resulted in long tails in male widowbirds.
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