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Chapter 18 Speciation What is a species? The morphological species concept expresses the following: o ___________________, in its simplest interpretation means “kind” The biological species concept relies on reproduction to define relatedness of species Ernst Mayer says, “Species : 1. Linnaeus separated species based on _________________________, i.e., their traits differed; Darwin saw that similar species are related by ________________________. 2. Ernst _____________________ (1942) developed the biological species concept: a species is a group of actually or potentially interbreeding populations that are reproductively isolated from other such groups. 3. The biological definition of a species 4. ____________________ occurs between populations of one species but not between populations of different species. 5. Biochemical genetics uses __________________________ techniques to determine relatedness of organisms; the phylogenetic species concept uses ____________________ comparisons. Speciation Is the attainment of ______________________ isolation, but __________________________ between population of the same species can be countered by gene flow. Genetic divergence: Reproductively Isolation Any heritable features of ____________________, functioning, or _______________________r that prevent _____________________________ between genetically divergent populations Prezygotic mechanisms take effect before or after fertilization 1- Behavioral Isolation: 2- Temporal Isolation: 3- Mechanical Isolation: 4- Ecological Isolation: 5- Gametic Mortality: Postzygotic Mechanisms: takes effect after fertilization Sometimes ______________________ occurs between different species, but the hybrid embryo is weak and dies. In some instances the ________________________ are vigorous but sterile Example: __________________ produced by a male donkey and female horse Allopatric Speciation Model some __________________________ arises and prevents gene flow between populations Reproductive isolating mechanisms evolved in the _________________________ populations and will result in complete_________________ when the two species can __________________________ First _______________________isolation occurs and then_______________________ isolation occurs. Geographic Isolation Isolation may be sudden as in an earthquake that results in___________________ of species Studies of enzymes from fishes on the Atlantic and Pacific sides of the Isthmus of ______________ reveal ______________________differences Allopatric Speciation of Archipelagos Archipelagos is an island chain some distance away from a ----------------------_____ The finches of the_______________________ Islands are evidently ancestors of mainland finches that invaded first a few islands and then spread to others, diverging as time progressed Sympatric Speciation ____________________may form within the home range of an existing species, in the absence of a _____________________________ In two crater lakes of East Africa exist small fish called __________________ The species in each lake are alike in their _________________________ and unlike the species in neighboring lakes and streams The lakes are small so the fish must live in _______________________________ Polyploidy: ______________________ is instantaneous for plants that are polyploid Polyploid______________________ are rare because of dosage compensation which regulates the level of gene expression in chromosomes. Parapatric Speciation Daughter species form from a ______________________ of individuals along a common border between two populations Interbreeding individuals produce hybrid offspring in this region called a __________________________ Branching and Unbranching Evolution Cladogenesis: Anagenesis: Evolutionary Trees and Rates and Change Evolutionary Trees Gradual model of speciation- Punctuation Model of speciationAdaptive Radiation A burst of ___________________________ activity that results in the formation of new species in a wide range of habitats. The presence of adaptive zones presents new ways of life by_________________, ________________________, or ____________________ access. The case of Darwin's finches illustrates the ________________________ of 13 species from one founder mainland finch. Extinctions Extinction ___________________________________ are abrupt disappearances dues to catastrophic, global events