Chapter 23: Origin of Species Flashcards
changes over time in allele frequency in a population over generations; evolutionary change below the species level
microevolution
the process by which one species splits into two or more species
speciation
the origin of a new group of organisms or a shift in the broad pattern of evolutionary change; evolutionary change above the species level
macroevolution
definition of a species as a population or group of a populations whose members have the potential to interbreed in nature and produce viable, fertile offspring
biological species concept
the existence of biological factors/barrier that impede members of two species from producing viable, fertile, offspring
reproductive offspring
“before the zygote”; prevents fertilization from occurring
pre-zygotic barriers
“after the zygote”; contributes to reproductive isolation after hybrid zygote is formed
Post-zygotic barriers
populations do not need to be separated by great distance. Instead, they must occupy different habitats, even within the same area.
habitat isolation
courtship displays and rituals are vital to reproduction. Such behaviors can be very specific, varying between closely related species
Behavioral isolation
Different populations may be ready to mate at different times of the year.
Temporal isolation
Sperm from one species might not be able to fertilize egg of another species
Gametic isolation
Genes of different parent species might interact in ways that impact the organisms development and survival in an environment
Reduced hybrid viability
Even if the hybrids are vigarous, they might be sterile. If the parents chromosome structure or number is abnormal, meiosis in the hybrids will fail to produce fertile offspring, genes cannot flow freely between species
Reduced hybrid fertility
The first generation hybrids are viable and fertile, but when they mate the offspring are feeble and sterile.
Hybrid breakdown
mating is physically impossible. Often this occurs because the genitalia of different species are incompatible.
Mechanical isolation
Gene flow is interrupted when a population is divided into geographically isolated populations
Allopatric speciation
The formation of new species in populations that live in the same geographic area
Sympatric speciation
An individual that has more than two chromosome sets that are all derived from the same species
Autopolyploid
A fertile individual that has more than two chromosome sets as a result of two different species interbreeding and combining their chromosomes.
Allopolyploid
Period of evolutionary change in which groups of organisms form many new species whose adaptation allow them to fill vacant ecological roles in their communities
Adaptive radiation
Earth’s evolved through slow gradual change
Gradualism
Long periods of apparent stasis, species undergo little or no morphological change, interrupted by relatively brief periods of sudden change
Punctuated equilibrium
