Species Concepts and Speciation Flashcards
Speciation
process by which one species splits into two species
Microevolution
consists of changes in allele frequency in a population over time aka population genetics
Macroevolution
refers to broad patterns of evolutionary change above the species level (i.e., the origin of mammals or flowering plants, correspond to a series of speciation events)
How do new species originate from existing species?
Over time, populations of a single species connected by gene flow can diverge genetically, giving rise to a new species.
Species
basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity
What is the classification of life?
Life
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
Biological species concept
emphasizes reproductive isolation; a species is a group of population whose members have the potential to interbreed in nature, produce viable, fertile offspring, and do not produce viable, fertile offspring w/ members of other such groups
Reproductive isolation
when biological barriers impede members of two species from interbreeding and producing viable, fertile offspring; limit formation of hybrids and therefore gene flow between forming species; can act before or after fertilization of hybrids
The biological species concept relies on the disruption or impediment of which aspect of population genetics?
Mutation
Selection
Gene flow
Genetic drift
Genetic flow
Prezygotic barriers
block fertilization from occurring by impeding different species from attempting to mate, preventing the successful completion of mating, or hindering fertilization if mating is successful; Ex: habitat isolation, temporal isolation, behavioral isolation, mechanical isolation, and gametic isolation
Habitat isolation
two species that occupy different habitats within the same area may encounter each other rarely, if at all; Ex; apple maggot flies are isolated from blueberry maggot flies because they feed and lay eggs on different fruits
Temporal isolation
species that breed at different times of the day, in different seasons, or different years cannot mix their gametes; Ex: western spotted skunks mate in summer and eastern spotted skunks mate in winter or sunflower populations from the coast of Texas flower earlier than those found inland
Behavioral isolation
courtship rituals and other behaviors unique to a species are effective barriers to mating; Ex: many species, including blue-footed boobies, mate only after a unique courtship display
Pollinator isolation
species of plant that attract different types of pollinators have a barrier to reproduction; Ex; the flowering plant species Mimulus lewisii and M. cardinalis are pollinated by bees and hummingbirds respectively
Mechanical isolation
mating is attempted, but morphological differences prevent its successful completion; Ex: genital openings of snails in the genus Bradybaena do not align if their shells spiral in opposite directions
Gametic isolation
sperm of one species may not be able to fertilize eggs of another species: Ex: surface proteins on the sperm and eggs of different sea urchin species bind poorly to each other, preventing fusion and zygote formation
Many tree species are wind pollinated, meaning that they release pollen into the air. If there are many species, which of these reproductive barriers are likely to occur between tree species in the same area?
Behavioral isolation
Gametic isolation
Temporal isolation
Pollinator isolation
Both B and C
Temporal Isolation
Postzygotic barriers
prevent hybrid zygotes from developing into viable, fertile adults by reducing hybrid viability, reducing hybrid fertility, or hybrid breakdown
Reduced hybrid viability
genes of diff. parent species may interact in ways that impair hybrid’s development or survival in its environment; Ex: the hybrid offspring of diff. subspecies of salamanders of the genus Ensatina do not usually complete development
Reduced hybrid fertility
meiosis may fail to produce normal gametes, resulting in sterility, if the parent species have chromosomes of diff. number or structure; Ex: the hybrid offspring of a male donkey and a female horse, a mule, is robust, but sterile
Hybrid breakdown
first-generation hybrids are viable and fertile, but offspring in the next generation are feeble or sterile; Ex: hybrids between certain strains of cultivated rice are vigorous and fertile, but members of the next generation are small and sterile
What is a limitation of the biological species concept?
Number of species to which it can be applied to is limited; cannot be applied to extinct or asexual organisms because mating cannot be observed
Morphological species concept
distinguishes a species by its structural features; applies to sexual and asexual species and does not require information of the extent of gene flow; disadvantage: relies on subjective criteria (could be disagreements)
Ecological species concept
defines a species by its ecological niche, the sum of its interactions w/ the nonliving and living parts of the environment; applies to sexual and asexual species and emphasizes the role of disruptive selection
Summary of species concepts
Biological species concept
-Emphasizes isolation, differences, and how separate species are
Morphological species concept
-Emphasizes unity of species, how similar they are
Ecological species concept
-Emphasizes ecological aspects, such as the ecological niche the species occupies
Bacteria reproduce primarily in an asexual way. Accordingly, which species concepts is difficult to apply to bacterial species?
Biological species concept because it cannot be applied to asexual species
