3.4.7 Investigating Diversity Flashcards
Q: Scientists are studying the genetic diversity of two species of fish, Species A and Species B. They analyze the base sequences of DNA and the amino acid sequences of proteins encoded by DNA for both species.
(a) Explain how comparing the base sequences of DNA can help determine the genetic diversity within or between species. [3 marks]
(b) How can comparing the amino acid sequences of proteins provide information about the genetic relationships between different organisms? [3 marks]
Marking Points:
(a) Comparing Base Sequences of DNA
Explanation of DNA Comparison: Comparing base sequences involves looking at the order of nucleotides in DNA. Similarities in base sequences indicate closer genetic relationships, while differences suggest divergence. [1 mark]
Assessment of Genetic Diversity: High similarity in DNA sequences usually indicates low genetic diversity, whereas significant differences suggest high genetic diversity. [1 mark]
Inferring Evolutionary Relationships: Differences and similarities in DNA sequences can help trace evolutionary paths and determine how closely related different species or individuals are. [1 mark]
(b) Comparing Amino Acid Sequences
Protein Synthesis Basis: The amino acid sequence is determined by the DNA sequence through transcription and translation. Thus, similar amino acid sequences indicate similar DNA sequences. [1 mark]
Identifying Relationships: By comparing amino acid sequences, scientists can infer how closely related different organisms are, as closely related species will have more similar protein sequences. [1 mark]
Determining Evolutionary Links: Differences in protein sequences can indicate evolutionary divergence, while similarities may suggest common ancestry. [1 mark]
Q: A researcher investigates the variation in leaf size within a population of oak trees. The researcher takes random samples of leaves from different trees and measures their length.
(a) Describe a method the researcher could use to ensure that their sampling is random. [2 marks]
(b) Once the data is collected, the researcher calculates the mean leaf length and its standard deviation. Explain how these statistical measures can help in understanding the variation within the population. [3 marks]
Marking Points:
(a) Ensuring Random Sampling
Random Sampling Method: To ensure randomness, the researcher could use a random number generator to select which trees to sample from within a given area, or use a systematic method such as random coordinates to choose leaf positions. [1 mark]
Avoiding Bias: Ensuring that every leaf and tree has an equal chance of being selected reduces bias and makes the sample representative of the whole population. [1 mark]
(b) Mean and Standard Deviation
Mean Value: The mean provides the average leaf length, giving an overall sense of the typical size within the population. [1 mark]
Standard Deviation: The standard deviation indicates the degree of variation from the mean. A large standard deviation means high variation, while a small standard deviation suggests that leaf sizes are more consistent. [1 mark]
Interpreting Results: By examining both the mean and standard deviation, the researcher can assess not only the average size but also how much individual leaf sizes differ from this average, helping to understand the level of diversity within the population. [1 mark]
Q: A biologist wants to investigate the effect of light position on the growth of leaves. They plan to use random sampling to collect data.
(a) Outline a procedure the biologist could follow to ensure that their sampling is random and representative. [3 marks]
(b) If the biologist finds that leaves exposed to more light tend to grow larger, what statistical tests or calculations might they perform to confirm this result? [2 marks]
Marking Points:
(a) Procedure for Random Sampling
Random Sampling Technique: The biologist could use a grid system over the area of study, randomly selecting grid points to measure leaf growth at different light positions. [1 mark]
Consistent Sampling: Ensure that measurements are taken from various points and not concentrated in one area to get a comprehensive view. [1 mark]
Avoiding Bias: Ensure that the method of sampling does not preferentially select leaves from certain areas or light conditions. [1 mark]
(b) Statistical Tests or Calculations
Mean Comparison: Calculate and compare the mean leaf sizes from different light conditions to assess differences. [1 mark]
Standard Deviation and Range: Determine the variation in leaf sizes to confirm if differences are statistically significant. [1 mark]
Q: What are the key methods to compare genetic diversity within or between species?
A: The key methods are: comparing the frequency of measurable or observable characteristics, the base sequence of DNA, the base sequence of mRNA, and the amino acid sequence of proteins.
Q: How can differences in base sequences of DNA suggest relationships between organisms?
A: By comparing the base sequences of DNA, we can identify similarities and differences which suggest evolutionary relationships, genetic relatedness, and degrees of divergence between species or individuals.
Q: What does comparing amino acid sequences reveal about genetic relationships?
A: Comparing amino acid sequences helps infer how closely related different species or individuals are, based on how similar or different the protein structures are, which reflects their genetic differences.
Q: Why has gene technology changed the methods of investigating genetic diversity?
A: Gene technology allows for direct investigation of DNA sequences, providing more precise and reliable data compared to inferring genetic differences from observable characteristics.
Q: What are the steps in a quantitative investigation of variation within a species?
A: The steps include collecting data from random samples, calculating the mean value of the collected data, and determining the standard deviation of that mean.
Q: Why is random sampling important in investigating variation within a species?
A: Random sampling ensures that the data collected is representative of the population, reducing bias and improving the accuracy of the statistical analysis.
Q: How do you design a method for random sampling?
A: Design a method that ensures each member of the population has an equal chance of being selected, such as using random number generators or systematic sampling techniques.
Q: What is the significance of calculating the mean value in data analysis?
A: The mean value provides an average representation of the data, which helps in understanding the central tendency and overall trend of the collected data.
Q: What is the role of standard deviation in data analysis?
A: Standard deviation measures the variability or spread of data values around the mean, indicating how much individual data points differ from the average.
Q: How do you interpret mean values and standard deviations?
A: Mean values give a central value of the data, while standard deviations indicate the spread. A low standard deviation means data points are close to the mean, and a high standard deviation indicates greater variability.
Q: What should students be able to do with random sampling data?
A: Students should be able to design methods for random sampling, carry out random sampling within a population, and use random samples to investigate factors like the effect of position on growth.
Q: What tools can be used to calculate the mean value of data?
A: Scientific calculators can be used to calculate the mean value of collected data.
