BISC495: Patterns of Evolution Vocabulary

Systematics

study of classification and evolutionary relationships among organisms

Phylogenetic Tree

diagram showing evolutionary relationships and common ancestry

Cladistics

classification system based on common ancestry

Monophyletic Group

common ancestor with all descendants

Paraphyletic Group

common ancestor but not all descendants

Polyphlyetic Group

group lacking a recent common ancestor

Homology

similarity due to shared ancestry (ex: human arm & whale flipper)

Convergent Evolution

independent evolution of similar traits in unrelated species (ex: bird wings & insect wings)

Embryological Similarities

similar embryo development suggests common ancestry

Vestigial Structures

reduced or nonfunctional inherited traits (ex: human appendix)

Geographic Distribution (Biogeography)

species distribution patterns used as evidence of evolution

Intermediate Forms

transitional fossils linking groups

Adaptive Radiation

rapid diversification of species into different ecological niches

Reversal

return to an ancestral trait

Gene Duplication

extra copies of genes that may evolve new functions

Trade-Off

benefit in one area causes cost in another

Exaptation (Preadaption)

trait originally evolved for one function but later used for another (ex: feathers--> insulation before flight)

Sexual Selection

selection based on mating success

Selection FOR

trait directly favored

Selection OF

indirectly increases because linked to another trait

Genetic Hitchhiking

allele increases because it is linked to a beneficial mutation

Directional Selection

favors one extreme phenotype

Stabilizing Selection

favors intermediate phenotypes (reduces variation)

Disruptive Selection

favors both extremes (increases variation)

Frequency-Dependent Selection

fitness depends on how common a trait is

Evolutionary Stable Strategy (ESS)

stable strategy resistant to invasion by alternatives

Absolute Fitness (R)

R= (survival rate) x (offspring produced)

Relative Fitness (W)

fitness compared to the most fit genotype

Selection Coefficient (s)

s= 1-W, measures reduction in fitness relative to the best genotype