chapter 16 C

"What are the key characteristics of a species according to the species concepts?"

"A species is the smallest evolutionarily independent unit.Species consist of interbreeding populations that evolve independently of other populations."

"What are the advantages and disadvantages of the Morphospecies Concept?"

"Advantages: It is widely applicable and can identify both extinct and living organisms.Disadvantages: It can become arbitrary if not applied carefully, leading to confusion with cryptic species."

"What is the focus of the Phylogenetic Species Concept (PSC)?"

"The PSC focuses on identifying species based on monophyly and estimating phylogenies of closely related populations.It requires populations to have been evolutionarily independent long enough for diagnostic traits to evolve."

"What are the strengths and challenges of the Biological Species Concept (BSC)?"

"Strengths: Reproductive isolation is a meaningful criterion confirming lack of gene flow.Challenges: It may not apply well to organisms that reproduce asexually or in cases of hybridization."

"How does reproductive isolation define species in the Biological Species Concept?"

"Populations are considered separate species if they do not hybridize regularly in nature.If they do hybridize but fail to produce fertile offspring, they are also considered reproductively isolated."

"What is the significance of gene flow in the context of species formation?"

"Gene flow is crucial as it determines the evolutionary independence of populations.Species form boundaries to the spread of alleles, preventing gene flow between different species."

"What are cryptic species and how do they relate to the Morphospecies Concept?"

"Crytic species are morphologically indistinguishable but differ in traits like songs or calls.They highlight the limitations of the Morphospecies Concept when identifying species based solely on physical characteristics."

"What are the implications of applying the Phylogenetic Species Concept?"

"Applying the PSC could potentially double the number of named species.It may create confusion if traditional names and species identities are altered."

"What are the limitations of the Biological Species Concept (BSC)?"

"It can be difficult to apply in various contexts.It cannot be used on fossils and is irrelevant in asexual populations.Many different species can hybridize in nature, complicating species definitions."

"How do gene flow mechanisms differ between bacteria, archaea, and eukaryotes?"

"In bacteria and archaea, gene flow occurs without reproduction, leading to genetic recombination.Alleles can be transferred between widely diverged lineages, unlike in eukaryotes where exchange is limited to closely related organisms."

"What is the significance of Lawence and Ochman's hypothesis regarding bacterial speciation?"

"They propose that lateral gene transfer is the primary mechanism of speciation in bacteria.This suggests that bacterial species may consist of cells that have not experienced gene flow and are closely related."

"What methods did Alberto Amato and colleagues use to investigate Pseudo-nitzschia species?"

"They employed modern microscopy and molecular tools to analyze morphospecies.They utilized multiple species concepts to identify distinct lineages within previously recognized morphospecies."

"What are the advantages of using multiple species concepts in biological research?"

"It helps recognize species diversity more effectively.It organizes research on the ecological and evolutionary consequences of species differentiation."

"What morphological traits define the Pseudo-nitzschia morphospecies studied by Amato and colleagues?"

"They are characterized by needle-shaped cells.The cells overlap to form chains, which is a distinctive feature."

"How does the production of neurotoxins by Pseudo-nitzschia vary?"

"The production of dangerous neurotoxins is highly variable during algal blooms.This variability is partly due to differences among species within the Pseudo-nitzschia genus."

"What are the primary goals of conservation biologists in preserving endangered species?"

"Preservation of genetic diversity to enhance species survival.Maintaining multiple genetically distinct populations to increase resilience against environmental changes."

"What is the concept of the evolutionarily significant unit (ESU) in conservation?"

"ESUs are groups of populations that are genetically distinct and important for the long-term survival of a species.Preserving more ESUs increases the likelihood of a species' persistence in changing environments."

"What led to the reclassification of the European common skate species?"

"Two independent studies using molecular data provided evidence for the existence of two distinct species.Prior to 1926, the European skate was considered two separate species, but they were combined into one based on earlier classifications."

"What are the three stages of the classical model of speciation?"

"Isolation of populations to reduce gene flow.Divergence in traits such as mating systems or habitat use.Reproductive isolation when populations come back into contact."

"What is secondary contact in the context of speciation?"

"Secondary contact occurs when two populations that have diverged in isolation are reunited geographically.This can lead to interactions that may affect their reproductive isolation status."

"How does geographic isolation contribute to speciation?"

"Geographic isolation reduces gene flow, allowing populations to diverge due to selection and genetic drift.It serves as a barrier that triggers genetic and ecological divergence between populations."

"What are the two mechanisms of geographic isolation?"

"Dispersal across a physical barrier, leading to colonization of new habitats.Vicariance, where an existing range is split by the emergence of a new physical barrier."

"What is the allopatric model of speciation?"

"The allopatric model posits that speciation occurs when populations become geographically isolated.This isolation allows independent evolutionary processes like selection and genetic drift to act on the populations."

"What role does gene flow play in population differentiation?"

"Gene flow tends to homogenize gene frequencies, reducing differentiation between populations.Disruption of gene flow is essential for the initiation of the speciation process."

"What factors can cause isolation between populations?"

"Geographic factors that physically separate populations, such as mountains or rivers.Genetic events, like changes in chromosome number, that reduce interbreeding effectiveness."

"What are the two main hypotheses regarding geographic isolation and speciation?"

"Dispersal-and-colonization hypothesis: suggests that an organism's ability to establish new populations is influenced by its dispersal and colonization abilities.Vicariance hypothesis: posits that events splitting a species' distribution can prevent gene flow and lead to isolation."

"What predictions does the dispersal-and-colonization hypothesis make about Hawaiian drosophilids?"

"Prediction 1: Closely related species should be found on adjacent islands.Prediction 2: The sequence of branching events should correspond to the sequence of island formation."

"What are some mechanisms of vicariance that can lead to geographic isolation?"

"Slow processes like the rise of a mountain range.Rapid events such as a lava flow bisecting a population."

"How can mutations lead to reproductive isolation in populations?"

"Polyploidization can create instant reproductive isolation between parental and daughter populations.Changes in chromosome number can isolate populations genetically, especially in plants."

"What are sympatric species and why are they rare?"

"Sympatric species are those that overlap geographically.They are rare because populations with matching chromosome numbers struggle to diverge into separate species without a boundary to gene flow."

"What are some common isolating mechanisms that can lead to speciation?"

"Differences in flowering time or pollinator visitation.Single mutations causing reproductive incompatibility, such as in Japanese land snails."

"What role does ecological factors play in phenotypic divergence among species?"

"Ecological factors lead to differences in natural selection between closely related populations.Isolation must be followed by divergence for complete speciation to occur."

"What is the significance of geographic isolation in the process of speciation?"

"Geographic isolation is crucial as it divides populations, preventing gene flow.It is a necessary step for speciation, but must be accompanied by divergence."

"What are the main agents of natural selection that promote divergence between populations?"

"CompetitionPredationClimateOther ecological differences"

"How does natural selection lead to phenotypic and genetic divergence in populations?"

"Populations occupy multiple habitats with differing selection pressures.Limited gene flow can result in speciation."

"What is the significance of chromosomal inversions in evolutionary biology?"

"They result in lower rates of crossing-over among loci.Inverted chromosomes prevent matching during meiosis, affecting genetic diversity."

"What is assortative mating and how does it contribute to reproductive isolation?"

"Individuals with certain traits preferentially choose mates with similar traits.This can lead to reproductive isolation between diverging populations."

"How do environmental factors influence mating preferences in cichlid species?"

"Different depths lead to variations in LWS opsin alleles for color vision.Male coloration differences are stronger in clearer waters, affecting mate choice."

"What is the sensory drive hypothesis in relation to cichlid speciation?"

"It suggests that adaptation to different habitats influences sensory phenotypes.Divergence in sensory abilities affects mate choice based on visual traits."

"What predictions does the sensory drive hypothesis make about Pundamilia species?"

"Higher frequency of red-shifted alleles in deeper water species.Females with red-shifted alleles prefer red males as mates."

"What evidence supports the sensory drive hypothesis in cichlid fish?"

"Natural selection favors divergence in color vision based on underwater light environments.This divergence influences female mate choice and male coloration differences."

"What are the two general mechanisms that keep sympatric species separate?"

"Prezygotic isolation: prevents hybrid offspring from being formed, often due to lack of mating.Postzygotic isolation: results in hybrid offspring that are inviable, sterile, or have reduced fitness."

"What are the possible evolutionary outcomes when closely related species interbreed?"

"Reinforcement of prezygotic isolation: natural selection favors traits that reduce hybridization.Hybrid speciation: new species may arise from hybridization.Stable hybrid zones: areas where hybridization occurs consistently without leading to complete speciation."

"What is reinforcement in the context of hybridization?"

"Reinforcement occurs when hybrid offspring have low fitness, leading to natural selection favoring assortative mating.This process enhances prezygotic isolation by promoting traits that prevent fertilization between species."

"What is the significance of cryptic species in reproductive isolation?"

"Crytic species are morphologically indistinguishable but differ in traits like songs or calls.This divergence can lead to reproductive isolation despite the lack of physical differences."

"What does secondary contact refer to in evolutionary biology?"

"Secondary contact occurs when two populations that have diverged in isolation come back together geographically.This can lead to hybridization or reinforcement of reproductive barriers."

"What is the allopatric model of speciation?"

"The allopatric model suggests that speciation occurs when populations become geographically isolated.Independent selection and genetic drift act on these isolated populations, leading to divergence."

"How does the dispersal-and-colonization hypothesis explain species distribution?"

"This hypothesis posits that an organism's ability to establish new populations depends on its dispersal and colonization abilities.Successful establishment in new areas is influenced by both factors working together."

"What is assortative mating and its role in reinforcement?"

"Assortative mating occurs when individuals with certain traits preferentially choose mates with similar traits.This behavior can enhance prezygotic isolation by reducing the likelihood of hybridization."

"What are chromosomal inversions and their effect on gene flow?"

"Chromosomal inversions involve a segment of DNA being flipped, altering gene order.This can lead to lower rates of crossing-over, resulting in tighter linkage among loci and reduced gene flow."