Topic 1 Flashcards
Identify the 3 pillars of Darwin’s theory of Evolution
- Species are not immutable: species can change over time
- Species have diverged from common ancestors
- Natural selection shapes the divergence as individuals with the fittest phenotypes are better able to survive and reproduce
Define speciation
- The evolutionary process by which new species arise through reproductive isolation
- Evolutionary consequence of reproductive isolation
Define evolution
- The change in the genetic composition of a population over time
Define artificial selection
- The selective breeding process by humans
Describe the 6 agents of evolutionary change
- Mutation creates variation that may be heritable
- Genetic Drift is the random sampling of alleles across generations and is more influential in small populations
- Natural selection is a microevolutionary process that shapes the phenotypes of organisms to match their environments
- Non-random mating can alter allele frequency over generations
- Gene flow describes the spread of genetic variation across geographical area due to migration, hybridisation, or gamete dispersal
- Recombination can create novel combinations of alleles at different loci
Outline the Hardy-Weinberg theorem
- It provides the expected relationship between alleles, genotypes and phenotypes in diploid populations
- Phenotypic frequencies: p2 + 2pq + q2= 1
- Allele frequencies: p + q = 1
What are the assumptions made for HWE?
- No gene flow
- No mutation
- Infinite population size meaning no genetic drift
- Mating is random
- No selection, there is equal fitness
Understand how deviations from Hardy-Weinberg expectations can reveal microevolutionary change
If the observed frequencies do not match the HW expected frequencies, it may indicate that the assumptions made for the HW are actually occurring to alter genotypic frequencies
Distinguish between prezygotic isolation and postzygotic isolation, and list the reproductive barriers can lead to speciation
- Prezygotic isolation: when barriers to reproduction act before the union of the nuclei of 2 gametes
- Postzygotic isolation: barriers to reproduction act after the union of the nuclei of 2 gametes
- Allopatric speciation: ancestral population is divided by a physical barrier
- Sympatric speciation: ancestral population is divided without geographical barriers (eg. Different types of pollinators pollinate different characteristics of flowers)
Compare the mechanisms of inter-sexual and intra-sexual selection to explain their roles in the evolution of sexually dimorphic traits.
- Intersexual selection refers to mate choice. It is a form of non-random mating where one sex holds preferences for specific traits in mates
- Intrasexual selection refers to male-male competition. Same sex individuals compete for the access to mates.
- The sexually dimorphic traits of male mates influence the females decision on who to reproduce with based on the males strength, characteristics, and behaviour.
Describe the mechanisms driving coevolution, including the red queen hypothesis
- Coevolution is when 2 or more species affect each other’s evolution through natural selectin by exerting selective pressure leading to a cycle of adaptations and counter-adaptations
- The red queen hypothesis states that species must constantly adapt and evolve to survive while pitted against ever-evolving species
Describe bottleneck and founder effects
- Bottleneck is when a large population is temporarily reduced to few individuals such as when a population experiences mass death
- Founder effect describes a new population being founded by a few individuals that have left their environment after a bottleneck experience
