Speciation - AP Biology
- Identify a type of postzygotic barrier.
- Hybrid sterility. Hybrids are viable but cannot reproduce successfully.
- Define allopolyploidy.
- Polyploidy resulting from two different species interbreeding. Hybrid polyploids from different parent species.
- What is polyploidy?
- The condition of having more than two complete sets of chromosomes. Common mechanism of instant speciation in plants.
- What is hybrid breakdown?
- Hybrids are viable and fertile but their offspring are inviable or sterile. Second-generation hybrids show reduced fitness.
- Define behavioral isolation.
- When species have different mating behaviors. Courtship differences prevent recognition and mating.
- Define habitat isolation.
- When two species live in the same area but different habitats. Microhabitat differences reduce encounter rates.
- Define allopatric speciation.
- Speciation that occurs when biological populations are geographically isolated. Geographic barriers prevent gene flow between populations.
- What is speciation?
- The formation of new and distinct species in the course of evolution. The evolutionary process creating reproductively isolated lineages.
- What is the biological species concept?
- Species are groups of interbreeding natural populations that are reproductively isolated. Defines species by reproductive compatibility and gene flow.
- What is adaptive radiation?
- The diversification of a group of organisms into forms filling different niches. Rapid evolution into multiple specialized forms.
- What is stability in hybrid zones?
- When hybrids continue to be produced. Balanced selection maintains hybrid zone over time.
- How does gene flow affect speciation?
- Gene flow can counteract speciation by homogenizing populations. Genetic exchange prevents population divergence and speciation.
- What is the morphological species concept?
- Species are defined by structural features. Based on physical characteristics and anatomy.
- Define ecological speciation.
- Speciation driven by adaptation to different ecological niches. Natural selection drives adaptation to different environments.
- What is the phylogenetic species concept?
- Species are the smallest group of individuals sharing a common ancestor. Uses evolutionary relationships to define species boundaries.
- What is genetic drift?
- Random changes in allele frequencies within a population. Stronger effects in smaller populations due to sampling.
- Define sympatric speciation.
- Speciation that occurs without physical separation of the population. Occurs through polyploidy or behavioral changes within populations.
- Define gametic isolation.
- When sperm cannot fertilize the eggs of another species. Biochemical incompatibility prevents sperm-egg fusion.
- What is prezygotic isolation?
- A mechanism that prevents fertilization from occurring. Acts before zygote formation to prevent mating or fertilization.
- What is temporal isolation?
- When two species breed at different times. Different breeding seasons prevent mating opportunities.
- What is reinforcement in speciation?
- Strengthening of reproductive barriers to reduce hybrid formation. Selection against hybrids increases reproductive isolation.
- What is postzygotic isolation?
- A mechanism that reduces the viability or reproductive capacity of hybrids. Acts after fertilization to reduce hybrid fitness.
- What is a reproductive barrier?
- Any factor that prevents interbreeding between different species. Maintains species integrity by preventing hybridization.
- What is the founder effect?
- Reduced genetic diversity when a population is descended from a small number of ancestors. Small founding populations carry limited genetic variation.
- What is mechanical isolation?
- When physical differences prevent successful mating. Structural incompatibility prevents successful copulation.
- What is fusion in hybrid zones?
- When reproductive barriers weaken and populations merge. Gene flow overcomes reproductive barriers between species.
- Identify an outcome of hybrid zones.
- Reinforcement. Selection against hybrids strengthens reproductive barriers.
- Identify a factor that can initiate speciation.
- Geographic isolation. Physical separation initiates independent evolutionary paths.
- Define peripatric speciation.
- A form of allopatric speciation where a new species forms in isolated peripheral populations. Occurs at population margins with limited gene flow.
- Define autopolyploidy.
- Polyploidy from duplication of chromosomes within a single species. Chromosome doubling within one species creates polyploids.
- What is incipient speciation?
- The initial stage of species formation where populations are diverging. Early stages before complete reproductive isolation develops.
- Identify a mechanism of sympatric speciation.
- Polyploidy. Chromosome multiplication creates instant reproductive isolation.
- Identify a type of prezygotic barrier.
- Temporal isolation. Prevents mating due to different breeding seasons or times.
- What is a hybrid zone?
- A geographic region where members of different species meet and mate. Contact zone where incomplete reproductive isolation exists.
- What is hybrid inviability?
- Hybrids fail to develop or reach maturity. Genetic incompatibilities cause developmental failures.
- What is divergence in the context of speciation?
- Accumulation of differences between groups leading to speciation. Genetic and phenotypic differences accumulate over time.
- What is a ring species?
- A connected series of neighboring populations that can interbreed, but the end populations cannot. Demonstrates how geographic variation can lead to speciation.