Unit 7 - Population and Evolution

Question 1

Hardy-Weinberg Principle

Answer 1

The allelic frequency in a population will not change from one generation to the next

Question 2

Hardy-Weinberg Equation

Answer 2

• Equations used to estimate the frequencies of specific alleles, genotypes and phenotypes in a population
• It sees if there are any changes in frequency over time

Question 3

Assumptions made by the Hardy-Weinberg Principle

Answer 3

• No mutations occur (no new alleles created)
• No migration in or out of the population
• The population is suitably large
• Mating is random (all possible genotypes can breed with all others)
• No natural selection pressures (so all alleles have an equal chance of being selected

Question 4

Hardy-Weinberg Equations

Answer 4

• p² + q² + 2pq = 1
• p + q = 1

Question 5

Variation

Answer 5

The observed differences among individuals within any given population

Question 6

Genetic Variation

Answer 6

Variation due to the genes and alleles an individual possesses

Question 7

Sources of Genetic Variation

Answer 7

• Mutations (Changes to genes and chromosomes can be inherited and passed on)
• Meiosis (Crossing over and independent segregation creates new allele combinations in gametes)
• Random Fertilisation (creates new allele combinations in zygotes)
• Random mating

Question 8

Environmental Variation

Answer 8

Variation caused by the environment in which an organism lives

Question 9

Sources of Environmental Variation

Answer 9

• Light
• Nutrient and food availability
• Temperature
• Rainfall
• Soil conditions
• pH
• Climate

Question 10

Polygenes

Answer 10

• Different genes at different loci that all contribute to a particular aspect of phenotype
• Individually they have no observable impact on phenotype
• Can act together to create observable variation

Question 11

Student’s T-Test

Answer 11

• Determines if there’s a significant difference between mean values of a variable across 2 populations
• See cognito for the equation (too hard to write out bruh)

Question 12

Pearson’s Correlation Coefficient

Answer 12

• Assesses the strength and direction of a linear relationship between two continuous variables that are normally distributed x and y
• See cognito for the equation (too hard to write out bruh)

Question 13

Selection Pressures

Answer 13

• Environmental factors that impact an organism’s survival and reproductive success
  Examples include:
• Predation
• Competition for resources
• Climate change
• Disease

Question 14

Types of Selection

Answer 14

• Directional Selection
• Stabilising Selection
• Disruptive Selections

Question 15

Directional Selection

Answer 15

• Selects for one extreme phenotype over other phenotypes
• Increases allele frequency for one extreme phenotype
• Shifts curve in the direction of the favoured extreme
• E.g. antibiotic resistance in bacteria

Question 16

Stabilising Selection

Answer 16

• Selects for the average phenotype and against extreme phenotypes
• Increases allele frequency for phenotypes closer to the mean, decreases allele frequency for extremes
• Narrows the curve and centres it
• E.g. Human birth weights

Question 17

Disruptive Selection

Answer 17

• Selects for extreme phenotypes and selects against the mean phenotype
• Occurs when an environmental factor takes two or more distinct forms
• Increases allele frequency for multiple extreme phenotypes, decreases allele frequency for the mean
• Curve shifts into multiple peaks either side of where the mean phenotype peak was
• E.g. Bird beaks becoming larger or smaller when there are two different food sources

Question 18

Adaptive Radiation

Answer 18

• When a single ancestral species rapidly diversifies into multiple new species,
• Each species is adapted to a specific ecological niche within an environment