Chapter 17 – Speciation and Macroevolution (Vocabulary Review)

A set of vocabulary flashcards summarizing key terms and concepts from the lecture on speciation and macroevolution to aid exam preparation.

Macroevolution

Evolutionary change at or above the species level; best observed in the fossil record.

Speciation

The splitting of one species into two or more new species as allele and genotype frequencies diverge.

Morphological Species Concept

Defines species by diagnostic physical traits that distinguish one group from another.

Cryptic Species

Species that appear nearly identical morphologically but differ in genetic, behavioral, or ecological traits.

Evolutionary Species Concept

Distinguishes species by their unique evolutionary pathway inferred from structural traits, often applied to fossils.

Phylogenetic Species Concept

Identifies a species as the smallest group sharing a common ancestor on a phylogenetic tree.

Biological Species Concept

Defines species as populations that interbreed naturally and are reproductively isolated from other such groups.

Reproductive Isolating Mechanisms

Biological barriers that block gene flow between different species.

Prezygotic Isolating Mechanisms

Barriers that prevent mating or fertilization before a zygote forms.

Postzygotic Isolating Mechanisms

Barriers that prevent hybrid offspring from developing normally or reproducing.

Habitat Isolation

Prezygotic barrier in which species occupy different habitats and do not meet.

Temporal Isolation

Prezygotic barrier in which species breed at different times or seasons.

Behavioral Isolation

Prezygotic barrier in which unique courtship behaviors prevent interbreeding.

Mechanical Isolation

Prezygotic barrier caused by incompatible reproductive structures.

Gamete Isolation

Prezygotic barrier where gametes fail to fuse when they meet.

Hybrid Inviability

Postzygotic barrier in which a hybrid zygote dies or fails to develop properly.

Hybrid Sterility

Postzygotic barrier where a hybrid reaches adulthood but cannot reproduce (e.g., mule).

Allopatric Speciation

Formation of new species after geographic separation isolates populations and their gene pools.

Sympatric Speciation

Formation of new species within the same geographic area via reproductive isolation without physical barriers.

Polyploidy

Condition of having more than two complete sets of chromosomes; common in plant speciation.

Autoploidy

Polyploidy arising from chromosome duplication within a single species (2n → 4n).

Alloploidy

Polyploidy produced after hybridization between related species followed by chromosome doubling.

Adaptive Radiation

Rapid evolution of many species from a single ancestor, each adapted to a distinct ecological niche.

Convergent Evolution

Independent evolution of similar traits in unrelated lineages exposed to similar environments.

Analogous Traits

Structures with similar function but different evolutionary origins (e.g., bird vs. bat wing).

Homologous Traits

Structures similar due to shared ancestry, regardless of current function.

Gradualistic Model

Macroevolutionary view proposing slow, continuous change leading to speciation.

Punctuated Equilibrium Model

Macroevolutionary view proposing long periods of stasis interrupted by rapid speciation events.

Developmental Genes

Genes whose expression patterns control body plan, shape, and organ formation.

Pax6 Gene

Highly conserved developmental gene that initiates eye formation in all animals.

Tbx5 Gene

Gene encoding a transcription factor required for limb development.

Hox Genes

Gene family that determines the position and identity of repeated structures along the body axis.

Pitx1 Gene

Gene whose reduced expression results in diminished pelvic fins in stickleback fish.

Non-goal-oriented Evolution

Concept that evolution lacks a predetermined direction; natural selection favors traits advantageous in current environments.

Equus Evolution

Horse lineage showing trends such as size increase, toe reduction, and tooth changes, but with many branching ancestors.