Unit 2: Origin of Species Flashcards
At the genetic and proteomic level, explain why two big cats, that otherwise appear to be very different in terms of pigmentation, are from the same species.
A gene that encodes an enzyme for pigmentation could mutate so that the enzyme that is made will produce a different pigment. As a result, in a normally functioning cat, they would appear one color but in another, the mutation could cause it to appear a different one.
Speciation
The separation of two species for long enough to allow them to accumulate significant changes that allow them to become separate species.
It is the appearance of new species and a source of biodiversity.
Phylogenetic Species Concept
Species are identified by having a unique combination of traits, usually physical. DNA is primarily used today.
What are 3 disadvantages to the Phylogenetic Species Concept?
- Difficult to analyze traits that always vary
- Degree of dissimilarity can be difficult to determine
- Sometimes members of the species can look very different and members of different species can look similar
Biological Species Concept
A population/groups of population have the ability to interbreed; depends on reproductive isolation
What are some examples of prezygotic barriers?
Geographic
Habitat
Temporal (time of day)
Behavioral
Mechanical (reproductive parts)
Gametic (gametes don’t work together)
What are some examples of postzygotic barriers?
Hybrid Inviability
Hybrid Sterility
Hybrid Breakdown
Hybrid Inviability
Fertilized egg cannot progress past an early embryo
Hybrid Sterility
Interspecies offspring is viable but sterile/cannot reproduce
Hybrid Breakdown
Hybrid offspring are viable and sterile but their offspring have genetic abnormalities
What are 3 disadvantages to the Biological Species Concept?
- Difficult to determine if populations are reproductively isolated
- Some cases where two species can interbreed and won’t, or choose not to if they cannot
- Cannot be applied to asexual or extinct species
Evolutionary Species Concept
A species is derived from a single lineage that has distinction from other lineages; has its own evolutionary tendencies and historical fate
Lineage – genetic relationship between individuals and ancestors
What is a disadvantage of the Evolutionary Species Concept?
No easy way to identify a unique species, lineages are difficult to examine and quantify
Ecological Species Concept
Each species occupies an ecological niche
Ecological Niche
A set of habitat resources that a species requires, as well as its influence on the environment and other species
What is a disadvantage of the Ecological Species Concept?
Competition can occur within species
What are the two PATTERNS of speciation?
Anagenesis and Cladogenesis
Anagenesis
Species formation without branching of the evolutionary lineage
Cladogenesis
Species formation as a result of divergence from an ancestral form; branching of the evolutionary lineage
What are the two MODES of speciation?
Allopatric and Sympatric
Allopatric Speciation
Speciation that occurs when two species are geographically separated from one another
Sympatric Speciation
Speciation that occurs when there are no physical barriers preventing any members of a species from mating with one another
What is the difference between allopatric and sympatric speciation?
Allopatric speciation requires a geographical barrier, whereas sympatric does not.
What is a characteristic of allopatric speciation?
Movement of a small population to a new location
What is a characteristic of sympatric speciation?
Abrupt genetic change and exploitation of resources not used by parent population
Which of the following best describes adaptive radiation?
A) radiation that allows a new species to evolve
B) radiation that effects the reproductive fitness of a population
C) the evolution of a single species into an array of progeny (descendants) that differ greatly
D) the evolution of a single species into an array of progeny (descendants) that are very similar
C
Hybrid Zones
Zones where two populations can interbreed before reproductive isolation is complete
What could cause two populations in a hybrid zone to lose the ability to mate?
Accumulation of genetic changes
Once gene flow through a hybrid zone is diminished, the two populations are reproductively isolated
Gradualism
Change that occurs gradually over a long period of time
Punctuated Equilibrium
Isolated episodes of rapid evolutionary change between long periods of minimal evolutionary change
