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Definition
| When barriers act to prevent fertilization, such as changes in location or timing of breeding, or courtship rituals. |
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Definition
When hybrids are inviable or sterile. Such as male ligers. |
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Definition
Geographic separation of two populations of the same species. Eliminates the movement of genes. |
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Definition
| After the allopatric speciation, the geographic barrier is removed, and the two populations re-establish contact. |
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Definition
| Kinda like allopatric speciation, but two pop'ns remain connected over a narrow contact zone. |
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Definition
A connected ring of species. Example: California salamanders of genus Ensatina |
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Term
| Evolutionary processes involved in the speciation process? I |
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Definition
| 1) Natural selection: most important process, no direct selection for speciation, just a by-product |
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Term
| Evolutionary processes involved in the speciation process? II |
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Definition
| 2) Sexual selection: genes that cause sterility evolve faster than genes that cause viability. This could be a consequence of sexually antagonistic genes. Rapid and continuous evolution of these loci could be "engine of speciation" |
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Term
| Evolutionary processes involved in the speciation process? III |
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Definition
| Random Genetic Drift: In allopatric speciation, neutral mutations may accumulate in geographically separated populations, but not neutral in hybrids. |
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Term
| Which is stronger in recently separated groups, prezygotic or postzygotic isolation? |
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Definition
| Prezygotic. This suggests that prezygotic isolating mechanisms are more important in establishing reproductive barriers. |
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Definition
| When the heterogametic sex shows hybrid sterility or inviability in the early stages of heterogametic sex. |
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Term
| Dobzhansky-Muller incompatibility |
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Definition
| When hybrids experience reduced fitness due to the joining of two different derived alleles. |
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Term
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Definition
| When an extra set of chromosomes are retained from a cross between individuals of the same species |
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Term
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Definition
| When chromosome sets from two different species are merged. |
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Term
| Three outcomes of Secondary Contact |
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Definition
1) No interbreeding - speciation completed
2) Introgression - populations merge together over time
3) Partial interbreeding - hybrid zones form (but hybrids are less fit) |
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Term
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Definition
| aquisition of additional isolating mechanisms to "complete" the speciation process. |
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Term
| Typological Species Concept |
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Definition
| "group of individuals that differ from other groups by possessing constant diagnostic characters" |
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Term
| Problems with Typological Species Concept |
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Definition
1) Polymorphism within populations
2) Variation among population
3) Sibling or cryptic species |
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Term
| Biological Species Concept |
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Definition
| "Species are groups of actually or potentially interbreeding natural populations that are reproductively isolated from other groups" |
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Term
| Nondimensional species concept |
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Definition
A division of the BSC. Only applied to sympatric and synchronous species.
Ideally suited to identifying sibling species that coexist but do not interbreed. |
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Term
| Multidimensional species concept |
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Definition
A divsion of the BSC, dealing explicitly with populations that are allopatric and/or allochronic.
By this definition, if a population has the potential to interbreed, then they are classified as the same species. |
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Term
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Definition
1) Not applicable to asexual species
2) Hybridization commonly occurs in nature.
3) Difficult to establish - the word "potential" makes it hard to carry out crosses of allopatric populations. |
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Term
| Evolutionary Species Concept |
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Definition
| "A lineage evolving separately from others with its own unitary evolutionary role and tendencies." |
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Term
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Definition
1) Arbitrary - different paleontologists could disagree on how to measure "unitary evolutionary role and tendencies"
2) Descriptive, not mechanic - says nothing about the mechanisms by which species are maintained or how new species evolve. |
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Term
| Phylogenetic Species Concept |
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Definition
Defines species on basis of common phylogenetic history
"Smallest diagnosable monophyletic group of populations within which there is a parental pattern of ancestry and descent"
A monophyletic group is defined as being derived from a common ancestor and includes all descendents of that ancestor. |
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Term
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Definition
1) What characters to use?
2) What level of divergence constitutes a species?
3) How do you distinguish between gene trees and species trees?
4) Does not address mechanism. |
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Term
| Recognition Species Concept |
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Definition
"The most inclusive population of biparental organisms which share a common fertilization system"
Focuses on processes that act to preserve a common fertilization system.
Stresses positive features of species that enable the two sexes to recognize each other.
The focus is on mate-recognition systems: courtship displays, timing, habitat selection pheromones, etc. |
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Term
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Definition
1) not applicable to asexual species
2) recognition systems often go awry (hybridization) |
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Term
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Definition
"the most inclusive population of organisms having the potential for cohesion through intrinsic cohesive mechanisms.
Two classes:
1) Genetic cohesive mechanisms - gene flow and stabilizing selection
2) Ecological cohesive mechanisms - species abundance, demographic stability, fundamental niche, strength of interactions with other species... |
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Term
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Definition
| Requires thorough understanding of cohesive mechanisms at work within species. |
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Definition
| the lack of correlation between the complexity and total DNA content of an organism. |
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Term
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Definition
| The entire collection of proteins that a cell or organism produces. Contains distinctly different groups, such as enzymes, structural proteins, transport proteins, cell-signaling proteins, etc. |
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Term
| Post-translational modification |
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Definition
Permanent modifications: proteolytic processing, disulfide bond formation, addition of prosthetic groups, carbohydrates or lipids.
Reversible modifications: phosphorylation, acetylation, methylation. |
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Term
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Definition
parasitic elements whose sole purpose is to replicate themselves at the host's expense.
Class I: retrotransposons. Replication through an RNA intermediate. Also, retrosequences |
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Term
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Definition
| "the fitness advantage that some individuals have over others of the same sex solely with respect to reproduction" |
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Term
| Why does sexual selection occur? |
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Definition
Different selection pressures for males and females.
Eggs more costly to produce than sperm, therefore different limits to reproductive success of male vs. female:
Females: limited by # of eggs or pregnancies
Males: limited by # of females mated. |
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Term
| Two main consequences of sexual selection |
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Definition
1) Females should be competitive for access to females
2) Females should be choosy, since they have more to lose by making a bad decision. |
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Term
| Forms of intrasexual selection |
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Definition
Occurs in species where individual males can monopolize access to females.
1) combat - leads to sexual dimorphism in size, also evolution of weaponry
2) Sperm competition - making sure a male's sperm fertilizes eggs. Traits are selected that increase amount of ejaculate, or compounds that modify females behavior, such as influencing longevity, egg-laying rate, and re-mating rate.
3) Infanticide - Killing the children of females fathered by other males. Common in African lions.
4) Alternative male reproductive strategies - "jacking" when small salmon sneak fertilizations, giving a substantial reproductive success. |
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Term
| What are Life History characters? |
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Definition
Traits that determine the timing and details of reproduction and death, such as
1) age at first reproduction
2) total life span
3) mode and frequency of reproduction
4) fecundity
5) parental care |
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Term
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Definition
Aging is caused by the accumulation of irreparable damage to cells and tissues.
Makes two predictions:
1) lifespan should correlate negatively with metabolic rate, because damage is caused by by-products of metabolism
2) longevity should not respond to selection. |
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Term
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Definition
| Proportion of males to females |
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Term
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Definition
| sex ratio of males to females in progeny of a female |
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