Chapter 17: Speciation – Flashcards
Unlock all answers in this set
Unlock answersquestion
speciation
answer
the divergence of biological lineages and the emergence of reproductive isolation between lineages; requires the interruption of gene flow within a species whose members formerly exchanged genes
question
reproductive isolation
answer
a state in which two groups of organisms can no longer exchange genes; most important factor in the long term isolation of sexually reproducing lineages from one another
question
species
answer
groups of organisms that mate with one another
question
Carolus Linnaeus
answer
developed the system of binomial nomenclature
question
morphological species concept
answer
a construct that assumes a species comprises individuals that "look alike," and that individuals that do not look alike belong to a different species; Linnaeus
question
cryptic species
answer
instances in which two or more species are morphologically indistinguishable but do not interbreed; morphology of little use
question
biological species concept
answer
proposed by Ernst Mayr; species are of groups of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups; emphasizes that reproductive isolation is what allows sexual species to evolve independently of one another
question
lineage species concept
answer
species as branches on the tree of life; one species splits into two or more daughter species, which thereafter evolve as distinct lineages; embraces the idea that sexual species are maintained by reproductive isolation
question
lineage
answer
ancestor-descendant series of populations followed over time
question
Dobzhansky-Muller model
answer
is a model of the evolution of genetic incompatibility. It assumes a selective pressure against a combination of alleles in the heterozygous state, hybrids have reduced fertility or viability. The end result of this evolved incompatibility is divergence into separate species.
question
reproductive isolation
answer
develops with increasing genetic divergence
question
allopatric speciation
answer
speciation that results when a population is divided by a physical barrier; geographic speciation; members cross a barrier and establish a new, isolated population
question
sympatric speciation
answer
speciation without physical isolation; occurs with some forms of disruptive selection in which individuals with certain genotypes have a preference for distinct microhabitats where mating takes place
question
polyploidy
answer
most common means of sympatric speciation; the duplication of sets of chromosomes within individuals; can result in complete reproductive isolation in two generations
question
autopolyploidy
answer
chromosome duplication in a single species; originates when two accidentally unreduced diploid gametes combine to form a tetraploid individual; typically sterile
question
allopolyploidy
answer
the combining of chromosomes of two different species; produced when individuals of two different species interbreed; often fertile because each of the chromosomes has a nearly identical partner with which to pair during meiosis
question
reinforcement
answer
selection results in strengthening of isolating mechanisms that prevent hybridization
question
prezygotic isolating mechanisms
answer
mechanisms that prevent hybridization from occurring; mechanical isolation, temporal isolation, behavioral isolation; habitat isolation, gametic isolation
question
postzygotic isolating mechanisms
answer
mechanisms that reduce the fitness of hybrid offspring; selection against hybridization; low hybrid zygote viability; low hybrid adult viability; hybrid infertility
question
mechanical isolation
answer
differences in sizes and shapes of reproductive organs may prevent the union of gametes from different species
question
temporal isolation
answer
many organisms have distinct mating seasons
question
behavioral isolation
answer
individuals may reject, or fail to recognize, individuals of another species as potential mating partners; sometimes the mate choice of one species is mediated by the behavior of individuals of other species
question
habitat isolation
answer
when two closely related species evolve preferences for living or mating in different habitats, they may never come into contact during their respective mating period
question
gametic isolation
answer
the sperm of one species may not attach to the eggs of another species because the eggs do not release the appropriate attractive chemicals, or the sperm may be unable to penetrate the egg because the two gametes are chemically incompatible
question
low hybrid zygote viability
answer
hybrid zygotes may fail to mature normally, either dying during development or developing phenotypic abnormalities that prevent them from becoming reproductively capable adults
question
low hybrid adult viability
answer
hybrid offspring may have lower survivorship than non-hybrid offspring
question
hybrid infertility
answer
hybrids may mature into infertile adults; ex: mules
question
hybrid zone
answer
unless reproductive isolation is complete, closely related species may hybridize in areas where their ranges overlap; contain recombinant individuals resulting from many generations of hybridization
