Formation of New Species Flashcards
Exam 1
Species
A group of organisms that can interbreed and produce viable, fertile offspring
Hybrid
A cross between two species
Gene pool
A collection of all the variants of genes in a species
Speciation
A formation of two species from one original species
When can speciation occur?
1) When groups become isolated geographically for a long period of time
2) Changes (mutations) in each group over time lead to the groups no longer being reproductively compatible
Biological Species Concept:
Members of the same biological species…
-Share the same gene pool (there is gene flow between two populations)
-Are reproductively isolated from other species (by natural biological barriers)
The Only Illustration in Darwin’s On the Origin of Species
A diagram showing speciation events leading to biological diversity. The diagram shows similarities to phylogenetic charts that are drawn today to illustrate the relationships of species.
Modern elephants evolved from the Palaeomastodon, a species that lived in Egypt 35–50 million years ago
Allopatric Speciation
Involves geographic isolation
-Dispersal
-Vicariance
-Adaptive radiation
Ex) Northern spotted owl and Mexican spotted owl look similar to one another but inhabit geographically separate locations
Sympatric Speciation
Occurs in the same geographical area; Speciation with the same physical location and conditions
-Chromosomal errors in cell division
-Reproductive isolation
Allopatric Speciation: Dispersal
When a few members of a species purposefully migrate/move to a new geographical area
Allopatric Speciation: Vicariance
When a natural situation/disaster arises to physically divide organisms; Sometimes gene flow reoccurs in an area when something that was isolating two groups is removed
Allopatric Speciation: Adaptive Radiation
From one original species, multiple others evolved, each with their own characteristics
Ex) Darwin’s finches and Honeycreeper birds
Sympatric Speciation: Errors in Chromosome Segregation
Aneuploidy - abnormality in number of chromosomes in the cell
Autopolyploidy - more than 2 sets of chromosomes from the same species; when mitosis isn’t followed by cytokinesis
Allopolyploidy - more than 2 sets of chromosomes from different species; gametes from 2 different species combine
Sympatric Speciation: Prezygotic Barriers
Prevent members of different species from mating to produce a zygote
-Temporal Isolation
-Habitat Isolation
-Behavioral Isolation
-Gametic Barriers
Sympatric Speciation: Temporal Isolation
A form of prezygotic barrier; when 2 or more species have different breeding schedules
Ex) Cicadas
Sympatric Speciation: Habitat Isolation
A form of prezygotic barrier; when members of species move; mismatches in habitat preferences
Sympatric Speciation: Behavioral Isolation
A form of prezygotic barrier;
Certain actions or lack of them impacts reproduction
Sympatric Speciation: Gametic Barriers
A form of prezygotic barrier;
incompatibility of reproductive species or games prevent fertilization; the shape of the male reproductive organ varies among male species
-Only compatible with the female of that species
-Reproductive organ incompatibility keeps the species reproductively isolated
Sympatric Speciation: Postzygotic Barriers
Keeps hybrid zygotes (one-celled embryos with parents of two different species) from developing into healthy, fertile adults; Prevents successful reproduction and leads to speciation
-Hybrid Inviability
-Hybrid Sterility
Sympatric Speciation: Hybrid Inviability
A form of postzygotic barrier; embryo produced but cannot survive development
Ex) Liger
Sympatric Speciation: Hybrid Sterility
A form of postzygotic barrier; different species produce viable offspring but offspring cannot reproduce
Ex) Mule
Other ways to define species
-Morphological species
-Ecological species
-Phylogenetic species
Morphological Species
A group of organisms that are morphologically (anatomically) similar; Individuals in different species are different in morphology
Ecological Species
Set of organisms adapted to specific resources
