3.4.4 Genetic Diversity and Adaptation Flashcards
Q: What is genetic diversity?
A: Genetic diversity refers to the number of different alleles of genes present in a population. High genetic diversity means a population has a wide range of different alleles, contributing to the overall variability in the gene pool.
Q: Why is genetic diversity important for natural selection?
A: Genetic diversity provides a pool of different alleles, some of which may be advantageous in changing environments. This variation allows natural selection to act upon those individuals with beneficial traits, enhancing survival and reproductive success.
Q: Describe the role of random mutation in genetic variation.
A: Random mutations can create new alleles of a gene. While many mutations are harmful or neutral, some can be beneficial, giving individuals with the new allele a potential advantage in their environment.
Q: How does natural selection lead to increased frequency of advantageous alleles?
A: Advantageous alleles improve an individual’s chances of survival and reproduction. These alleles are more likely to be passed on to the next generation. Over time, the frequency of these advantageous alleles increases in the population.
Q: What is directional selection? Provide an example.
A: Directional selection occurs when natural selection favors one extreme phenotype over the mean, causing a shift in the population’s trait distribution. An example is antibiotic resistance in bacteria, where bacteria with mutations allowing resistance have higher survival rates.
Q: What is stabilising selection? Provide an example.
A: Stabilising selection favors intermediate phenotypes and reduces variation by selecting against extreme traits. An example is human birth weight, where babies of average weight have higher survival rates compared to very small or very large babies.
Q: How do anatomical, physiological, and behavioral adaptations contribute to survival?
A: Adaptations are traits that enhance an organism’s ability to survive and reproduce in its environment:
Anatomical adaptations involve structural features (e.g., camouflage).
Physiological adaptations involve internal processes (e.g., temperature regulation).
Behavioral adaptations involve actions or responses (e.g., migration).
Q: Explain how selection can produce changes within a population.
A: Selection acts on phenotypic variations within a population. Individuals with advantageous traits are more likely to survive and reproduce, passing these traits to their offspring. Over generations, these traits become more common, leading to evolutionary change.
Q: How can data on bacterial growth be analyzed using a logarithmic scale?
A: A logarithmic scale is used to handle large ranges of data, such as bacterial counts, more easily. By converting the number of bacteria to a logarithmic scale, trends and changes in growth rates become more apparent and manageable.
Q: What are the aseptic techniques used in investigating antimicrobial substances?
A: Aseptic techniques prevent contamination and ensure accurate results. These include sterilizing equipment, using sterile media, and handling cultures with care. Techniques such as the streak plate method can be used to assess the effectiveness of antimicrobial substances.
Q: A population of beetles contains two different color morphs: green and brown. The green morph has a higher survival rate in a habitat with green vegetation. Explain how natural selection could lead to an increase in the frequency of the green morph in this population over time. [4 marks]
Marking Points:
Variation in phenotypes – The population has different color morphs (green and brown).
Differential survival – Green beetles have higher survival rates in green vegetation.
Inheritance – The trait for green color is heritable and passed on to offspring.
Increased frequency – Over generations, the green morph becomes more common due to higher survival and reproductive success.
Q: Explain the concept of stabilising selection and provide an example of a trait in a population that might be subject to stabilising selection. [5 marks]
Marking Points:
Definition of stabilising selection – Stabilising selection favors intermediate phenotypes and reduces the extremes.
Mechanism – Individuals with intermediate traits have higher fitness and are more likely to survive and reproduce.
Example trait – Human birth weight.
Explanation of the example – Babies with average birth weights have higher survival rates compared to very light or very heavy babies.
Result – Over time, the trait (birth weight) shows reduced variation as extreme values are selected against.
Q: The frequency of an antibiotic-resistant allele in a bacterial population increased dramatically after the introduction of a new antibiotic. Explain this observation using the principles of natural selection. [6 marks]
Marking Points:
Genetic variation – Bacteria in the population have genetic variation, including some with an antibiotic-resistant allele.
Selective pressure – The introduction of the antibiotic creates a selective pressure where only resistant bacteria survive.
Survival and reproduction – Resistant bacteria survive and reproduce more successfully than non-resistant ones.
Inheritance – The resistance allele is passed to offspring of resistant bacteria.
Increase in frequency – Over time, the frequency of the resistant allele increases in the population.
Adaptation – The population becomes better adapted to the presence of the antibiotic due to increased frequency of the resistant allele.
Q: Describe how random mutations contribute to genetic diversity in a population. [4 marks]
Marking Points:
Random mutations – Mutations occur randomly in DNA sequences.
New alleles – Mutations can create new alleles or variations of a gene.
Genetic diversity – The introduction of new alleles adds to the genetic diversity of the population.
Potential effects – Some new alleles may be beneficial, harmful, or neutral, affecting the population’s genetic composition.
Q: A researcher investigates the effect of a new antimicrobial substance on bacterial growth. They use aseptic techniques to ensure that the results are not affected by contamination. Describe the aseptic techniques the researcher should use. [5 marks]
Marking Points:
Sterilization – Sterilize all equipment and culture media before use.
Clean environment – Work in a clean environment, such as a laminar flow hood, to minimize contamination.
Use of sterile tools – Use sterile tools (e.g., pipettes, loops) and avoid touching non-sterile surfaces.
Proper handling – Flame the neck of culture bottles and avoid opening them unnecessarily.
Disposal – Dispose of contaminated materials properly and clean the work area after the experiment.
