The process by which one species splits into two of more species
Changes over time in allege frequencies in a population
The broad pattern of evolution above the species level
According to this concept a species, is a group of population whose members have the potential to interbreed in nature and produce viable, fertile offspring- but do not produce viable, fertile offspring with other such groups
Biological species concept
The existence of biological factors that impede members of two spices from interbreeding and producing viable, fertile offspring
Offspring that result from an interspecific mating
Block fertilization from occurring
Contribute to reproductive isolation after the hybrid zone is formed
Post zygotic barriers
Two species occupy different habitats within the same area may encounter each other rarely, if ever, even though they are not isolated by obvious physical barriers
Species that breed during different times of the day, or different seasons, cannot mix their gazettes
Courtship rituals that attract mates and other behaviors unique to a species
Mating is attempted, but morphological differences prevent its successful completion
Sperm of one species Amy not be able to fertilize the eggs of another species
The genes of different parent species may interact in ways that impair the hybrids development or survival in its environment
Reduced hybrid viability
Hybrids may be sterile. If the chromosomes of the two species differ in number or structure, meiosis in the hydride may fail to produce normal gazettes.
Reduced hydride fertility
Some first generation hybrids are viable and fertile but when they mate wit one another or with either parent species offspring of the next generation are feeble or sterile.
Characterizes a species by body shape and other structural features
Morphological species concept
Views a species in terms of its ecological niche, the sum of how members of the species interact with the nonliving and living parts of their environment
Ecological species concept
Defines a species as the smallest group of individuals that share a common ancestor, forming one branch on the tree of life. Biologist trace the phylogenetic history of a speed by comparing its characteristics such as morphology or molecular sequences, with those of other organisms.
Phylogenetic species concept
gene flow is interrupted when a population is divided into geographically isolated subpopulations
Speciation occurs in populations that live in the same geographic area.
A species may originate from an accident during cell division that results in extra sets of chromosomes
An individual that has more than two sets of chromosomes that are all derived from a single species
When an infertile hybrid may be able to propagate itself asexually. In sesubsequent generations various mechanisms can change a sterile hybrid into a fertile Polyploid
Sympatric speciation can occur if gene flow is reduced by what such factors?
Polyploidy, habitat differentiation, sexual selection
A region in which members of different species meet and mate, producing at least some offspring of mixed ancestry
Reinforcing reproductive barriers
What are 3 possible ways that hybrid zones can change over time?
Reinforcement, fusion, stability
Describe these periods of apparent stasis punctuated by sudden change