IB Biology HL (HIGHER level)- 2024 – Practice Questions- All Topics
Topic 5.2 Natural selection
Topic 5 Weightage : 5%
All Questions for Topic 5.2 – Natural Selection, Variation, Competition, Adaptations, Allele Frequency, Adaptive Radiation, Antibiotic Resistance, Theories of Evolution, Selection Pressures, Species Diversification, Artificial Gene Transfer
Question
What would restrict evolution by natural selection, if a species only reproduced by cloning?
A Too few offspring would be produced.
B Mutations could not occur.
C The offspring would show a lack of variation.
D The offspring would be the same sex as the parent.
▶️Answer/Explanation
Ans: C
If a species only reproduced by cloning, then the offspring would show a lack of variation because they would be genetically identical to their parent. This would restrict evolution by natural selection because there would be no genetic variation for natural selection to act upon. In a sexually reproducing species, genetic variation arises from the recombination of genes during meiosis and fertilization. This genetic variation allows natural selection to act upon individuals with traits that are better suited to their environment, leading to the evolution of the species over time. However, in a clonal species, there is no recombination of genes, so there is no genetic variation for natural selection to act upon. As a result, the species is less able to adapt to changing environmental conditions, which makes it more vulnerable to extinction.
How can species of bacteria evolve to be resistant to antibiotics?
I. A variation within one bacterium’s genome confers resistance.
II. Antibiotics enable genes to become adapted through transcription and translation.
III. An incomplete dose of antibiotics allows bacteria with a high resistance to survive and reproduce.
A. I only
B. I and II only
C. I and III only
D. III only
▶️Answer/Explanation
Markscheme
C
A variation within one bacterium’s genome conferring resistance and an incomplete dose of antibiotics allowing bacteria with high resistance to survive and reproduce are main reasons for species of bacteria to evolve to be resistant to antibiotics. When a bacterium acquires a variation in its genome that confers resistance to an antibiotic, it can survive and reproduce in the presence of the antibiotic. If the antibiotic is not completely effective or is not taken for the full prescribed course, bacteria with high resistance to the antibiotic can survive and reproduce. Over time, the population of bacteria will become more resistant to the antibiotic, making it less effective. This is because the bacteria that are susceptible to the antibiotic will be killed off, leaving only the resistant bacteria to reproduce. This can lead to the evolution of antibiotic-resistant strains of bacteria. It is important to use antibiotics judiciously, taking the full prescribed course and only when necessary, to reduce the likelihood of antibiotic resistance evolving.
What promotes natural selection?
I. Overpopulation
II. Competition
III. Variation
A. I and II only
B. I and III only
C. II and III only
D. I, II and II
▶️Answer/Explanation
Markscheme
D
Overpopulation, competition, and variation promote natural selection because they create selective pressures that can lead to the evolution of new traits in a population. When a population is overpopulated, there is increased competition for resources such as food, water, and shelter. This competition creates selective pressures that favor individuals with traits that allow them to better compete for these resources. Over time, these traits become more prevalent in the population, leading to the evolution of the species. Variation is also important for natural selection because it provides the raw material for evolution to act upon. When there is genetic variation within a population, individuals with traits that are better suited to their environment are more likely to survive and reproduce. These traits can be passed on to their offspring, leading to the evolution of the species. Overall, natural selection is driven by the selective pressures that arise from overpopulation, competition, and variation. These pressures create a dynamic environment in which individuals with advantageous traits are more likely to survive and reproduce, leading to the evolution of the species over time.
What type of process causes antibiotic resistance to develop in bacteria?
A. Competition with viruses
B. Overproduction of offspring
C. Evolution due to environmental change
D. Response by bacteria to an epidemic
▶️Answer/Explanation
Markscheme
C
Evolution due to environmental change is said to be the type of process that causes antibiotic resistance to develop in bacteria because it is the process by which bacteria evolve in response to environmental pressures, such as exposure to antibiotics. When bacteria are exposed to antibiotics, those that are not resistant to the antibiotic will be killed off, leaving only the resistant bacteria to reproduce. Over time, the population of bacteria will become more resistant to the antibiotic, making it less effective. This process of natural selection is driven by the selective pressures that arise from environmental change. In this case, the selective pressure is the presence of the antibiotic. Bacteria with genetic changes that provide resistance to the antibiotic are more likely to survive and reproduce in the presence of the antibiotic. These resistant traits can be passed on to their offspring, leading to the evolution of antibiotic-resistant strains of bacteria. Overall, the evolution of antibiotic resistance in bacteria is an example of natural selection acting on populations of bacteria in response to the selective pressures created by exposure to antibiotics. Evolution due to environmental change is the type of process that drives this evolution.
What is the mechanism of natural selection?
A. Any individuals in a population can be selected entirely by chance.
B. After a change in the environment a species will evolve adaptations to the new conditions.
C. If an adaptation to the environment is useful, an individual will develop it and pass it on to its offspring.
D. Variations amongst individuals of a population are selected by a changing environment
▶️Answer/Explanation
Markscheme
Ans: D
The variations amongst individuals of a population are selected by a changing environment because certain variations may provide an advantage to individuals in a given environment. This advantage can allow individuals with these traits to survive and reproduce more successfully than others, leading to the evolution of the population over time. This process is known as natural selection, which is a mechanism of evolution. Natural selection occurs when certain traits become more or less common in a population due to the selective pressures of the environment. Individuals with traits that are better suited to their environment are more likely to survive and reproduce, passing on their advantageous traits to their offspring. Over time, this can lead to the evolution of the population as a whole. Variation is important for natural selection because it provides the raw material for evolution to act upon. When there is genetic variation within a population, individuals with traits that are better suited to their environment are more likely to survive and reproduce. These traits can be passed on to their offspring, leading to the evolution of the species. Overall, natural selection is the mechanism by which the variations amongst individuals of a population are selected by a changing environment. The process of natural selection allows populations to adapt to changing environments over time, leading to the evolution of new traits and species.
The photograph shows vegetation in a rocky area.
Which characteristic of the plants indicates that the area in which they are growing is probably dry?
A. Relatively small size
B. Small flowers
C. Narrow leaf surface
D. Small root system
▶️Answer/Explanation
Markscheme
Ans:C
The narrow leaf surface of plants in a rocky area indicates that the area is probably dry because this is an adaptation that helps the plants to conserve water. In dry environments, water is often a limiting resource, so plants have evolved a variety of adaptations to help them survive in these conditions. One of these adaptations is having a narrow leaf surface area. This reduces the amount of surface area that is exposed to the sun and wind, which can cause water to evaporate from the leaves. By reducing the surface area of their leaves, plants can reduce the amount of water lost to the environment. In addition, plants in dry environments may have other adaptations to help them conserve water, such as deep root systems that can access water deep in the soil, or the ability to store water in their leaves or stems. Overall, the narrow leaf surface of plants in a rocky area is an adaptation that helps them to survive in a dry environment by reducing water loss from their leaves. This is an example of how plants can adapt to their environment in order to survive and reproduce successfully.
Question
By the end of the 19th century in England, the dark form of the moth Biston betularia formed up to $98 \%$ of the total population in industrial areas. From 1970, the percentage of dark forms decreased significantly. What is an explanation for the decrease?
A. An increase in environmental pollution killed the dark forms more than the light forms.
B. Reduction of pollution resulted in greater camouflage for light forms of the moth.
C. Dark forms could no longer find mates.
D. Light forms had superior feeding mechanisms.
▶️Answer/Explanation
Ans:B
Yes, the reduction of pollution resulted in greater camouflage for light forms of the moth, is an explanation for the decrease in the percentage of dark forms of the moth Biston betularia in industrial areas of England. Prior to the 1970s, industrial pollution caused trees to darken, which made the dark form of the moth more visible to predators. As a result, the population of light-colored moths decreased, while the population of dark-colored moths increased. However, since the 1970s, pollution levels have decreased due to environmental regulations, which has allowed lichens to grow on trees and made the trees lighter in color. This has made the light form of the moth more visible to predators, which has led to a decrease in the population of dark-colored moths and an increase in the population of light-colored moths. The lighter color of the trees provides better camouflage for the light-colored moths and makes them less visible to predators, which has allowed their population to increase.