Download Chapter 18 Speciation What is a species? The morphological

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