Evolution can be understood as:
Genetic change over time
Descent with modification
Genotype vs. Phenotype
Genotype: The genetic constitution of an individual.
Phenotype: The observable characteristics resulting from the genotype.
Genes vs. Alleles
Genes: Units of heredity made up of DNA that influence traits.
Alleles: Different forms of a gene.
Natural selection, genetic drift, and gene flow can cause allele frequencies in a population to change over time.
Mutations: Can lead to the formation of new alleles, essential for evolution.
Recombination: Produces different genotypes within a population, significant for evolution.
Discuss how mutations and recombination differ in their contributions to evolution.
Example: Finches’ beak size adaptations during droughts.
More birds with larger beaks survived due to food accessibility.
Example: Galls from plants; optimal gall diameter increases reproductive success.
After selection, average size of galls stabilizes around a mean.
Example: Different survival rates based on lower mandible width in birds.
Causes two or more contrasting phenotypes to be favored over the average.
Natural selection can lead to fixation where all individuals in a population have the favored allele (allele frequency = 100%).
Example: Andean geese evolved specialized hemoglobin for high-altitude advantage.
Concept: Random processes can affect allele frequencies, especially in small populations.
Impact: Affects large vs. small populations differently due to chance events determining allele passage.
Definition: Movement of alleles between populations via individuals or gametes.
Effects of Gene Flow:
Populations become more genetically similar.
New alleles can be introduced into populations.
Examine which processes/mechanisms consistently cause adaptive evolution.
Adaptations and Exaptations: Definitions and measurement methods.
Natural selection does not lead to perfect organism-environment matches due to:
Constant environmental changes
Lack of genetic variation: Without beneficial alleles, adaptive evolution cannot occur.
Evolutionary history: Natural selection operates on existing traits (phylogenetic constraints).
Ecological trade-offs: One advantageous trait may reduce another's efficacy.
Shaped by large-scale processes such as:
Speciation
Mass extinction
Adaptive radiation
Explore ecological mechanisms that underpin these long-term evolutionary patterns.