Chapter 22 Flashcards
biological species concept
The definition of species based on the ability of populations to interbreed and produce fertile offspring
morphological species concept
The concept that all individuals of a species share measurable traits that distinguish them form individuals of other species
phylogenetic species concept
A concept that seeks to delineate species as the smallest aggregate population that can be united by shared derived characters
subspecies
a taxonomic subdivision of a species
ring species
a species with a geographical distribution that forms a ring around uninhabitable terrain
cline
a pattern of smooth variation in a characteristic along a geographical gradient
How do the morphological, biological, and phylogenetic concepts differ?
The morphological species concept defines species based on morphological differences among them. The biological species concept defines species as populations that can successfully interbreed under natural conditions. The phylogenetic species concept defines a species as a cluster of populations with a recent shared evolutionary history.
What is clinal variation?
Clinal variation is a pattern of smooth variation along a geographical gradient
reproductive isolating mechanism
a biological characteristic that prevents the gene pools of 2 species from mixing
prezygotic isolating mechanisms
A reproductive isolating mechanism that act before the production of zygote, or fertilized egg
postzygotic isolating mechanisms
a reproductive isolating mechanism that acts after zygotic formation
ecological isolation
a prezygotic reproductive isolating mechanism in which species that live in the same geographical region occupy different habitats
temporal isolation
a prezygotic reproductive isolating mechanism in which species live in the same habitat but breed at different times of day or different times of year
behavioral isolation
a prezygotic reproductive isolating mechanism in which 2 species do not mate because of differences in courtship behavior; also known as ethological isolation
mechanical isolation
a prezygotic reproductive isolating mechanism caused by differences in the structure of reproductive organs or other body parts
gametic isolation
a prezygotic reproductive isolating mechanism caused by incompatibility between the sperm of 1 species and the egg of another; may prevent fertilization
hybrid inviability
a postzygotic reproductive isolating mechanism in which a hybrid individual has a low probability of survival to reproductive age
hybrid sterility
a postzygotic reproductive isolating mechanism in which hybrid offspring cannot form functional gametes
hybrid breakdown
a postzygotic reproductive isolating mechanism in which hybrids are capable of reproducing, but their offspring have either reduced fertility or reduced viability
What is the difference between prezygotic and postzygotic isolating mechanisms?
prezygotic isolating mechanisms either prevent individuals of different species from mating or prevent sperm of one species from fertilizing the egg of another. postzygotic isolating mechanisms limit the survivorship or reporductive capability of hybrid individuals.
When a male duck of one species preformed a courtship display to a female of another species, she interpreted his behavior as aggressive rather than amorous. What type of reproductive mechanism does this scenario illustrate?
The scenario illustrates a behavioral isolating mechanism
allopatric speciation
the evolution of reproductive isolating mechanisms between 2 populations that are geographically separated
species cluster
a group of closely related species recently descended from a common ancestor
hybrid zones
a geographical area where the hybrid offspring of 2 divergent populations or species are common
reinforcement
the enhancement of reproductive isolation that had begun to develop while populations were geographically separated
parapatric speciation
speciation between populations with adjacent geographical distributions
sympatric speciation
speciation that occurs without the geographical isolation of populations
host race
a population of insects that may be reproductively isolated from other populations of the same species as a consequence of their adaptation to feed on a specific host plant species
polypoidy
the condition of having one or more extra copies of the entire haploid complement of chromosomes
What are the 2 stages required for allopatric speciation?
In the first stage of allopatric speciation, populations become geographically separated. in the second stage, they become reproductively isolated
What factor appears to promote parapatric speciation in bent grass?
Some populations of bent grass survive better on unpolluted soil, whereas others survive better on polluted soil
Why might insects form different host races be unlikely to mate with each other?
Insects from different host races spend most of their time on different host plant species. Thus, they rarely encounter each other and would be unlikely to mate under natural conditions
autopolypoidy
the genetic condition of having more than 2 sets of chromosomes from the same parent species
unreduced gametes
a gamete that contains the same number of chromosomes as a somatic cell
allopolyploidy
the genetic condition of having 2 or more complete sets of chromosomes from different parent species
how can natural selection promote reproductive isolation in allopatric populations?
natural selection cannot promote reproduction isolation in allopatric populations directly, but it can lead to genetic divergence which results in reproductive isolation
how does polyploidy promote speciation in plants
polyploidy changes the number of chromosomes sets in cells of an organism. polyploidy individuals are often reproductively isolated from their parent species because their gametes contain different number of chromosomes. when a gamete from a polyploidy individual fuses with a gamete from a nonpolyploidy individual, the resulting offspring is usually sterile because the odd number of chromosomes cannot segregate properly during meiosis
