Ecology, Evolution, and Population Genetics
Evolutionary Processes
Variation, selection, and constraints
Evolution is change in heritable variation across generations. In population genetics, allele frequencies are shaped by selection, drift, mutation, migration, and recombination. Selection can be directional, stabilizing, disruptive, or balancing, but adaptation is constrained by trade-offs, pleiotropy, development, and historical contingency.
Which process most strongly increases genetic drift in small populations?
Drift is the random fluctuation of allele frequencies, which is stronger when effective population size is small.
Correct answer: Random sampling error
Define fitness in evolutionary terms.
Fitness is context-dependent and can vary with environment and frequency.
Correct answer: The expected relative reproductive success of a genotype or phenotype in a given environment.
Ecological Interactions and Community Dynamics
Interaction Types
Competition
- Both parties have reduced fitness
- Can be intra- or interspecific
Predation
- One organism benefits, one is harmed
- Shapes population cycles and defenses
Population and ecosystem processes
Population growth can be modeled with exponential and logistic equations, but real populations are limited by resource availability, stochasticity, and spatial structure. Ecosystems are shaped by trophic interactions, nutrient cycling, disturbance, succession, and feedbacks between biota and environment. Human activities alter extinction risk, biogeochemical cycles, and community resilience at global scale.
Which statement best describes the ecological niche of a species?
A niche encompasses resource use, interactions, and environmental tolerances.
Correct answer: Its role and environmental requirements within an ecosystem
Why can natural selection fail to produce an optimal trait?
Evolution often yields local rather than global optima.
Correct answer: Because of trade-offs, genetic constraints, changing environments, drift, and historical contingency.