Exam 2 PPTs - 2 Flashcards
how many different species are living on Earth?
- slightly over … species of animals, plants, fungi and protists have been described thus far
- conservative estimates propose that the total number of described and undescribed species is about …
- some analyses suggest that it could be as high as …
1.9 million;
9 million;
100 million
understanding what species are and how they form is central to efforts to …
preserve biodiversity
what is a species and how are they formed? species concepts: 1. ... 2. ... 3. ...
the morphospecies concept;
the phylogenetic species concept;
the biological species concept
how species are formed:
allopatric: start with original population
- initial step of speciation: ….
- evolution of reproductive isolation occurs in …
- new distinct species after …
barrier formation;
isolation;
equilibration of new ranges
how species are formed:
peripatric:
- initial step of speciation: …
- evolution of reproductive isolation: …
- new distinct species after equilibration of new ranges
new niche entered;
in isolated niche
how species are formed:
parapatric:
- initial step of speciation: …
- evolution of reproductive isolation: …
- new distinct species after equilibration of new ranges
new niche entered;
in adjacent niche
how species are formed:
sympatric:
- initial step of speciation: …
- evolution of reproductive isolation: …
- new distinct species after equilibration of new range
genetic polymorphism;
within the population
how species are formed:
classically, speciation has been hypothesized to be a three-stage process:
1. …
2. … such as mating system or habitat use
3. …
isolation;
divergence in traits;
reproductive isolation
how species are formed:
- classically, speciation has been hypothesized to be a three-stage process: isolation, divergence in traits, reproductive isolation
- speciation via this process is widespread in nature. However, in some instances, speciation can follow a different path. Stages 1 and 2 can occur … and in the … In many speciation events stage 3 …
- nevertheless, this hypothesis provides a useful framework for analyzing how speciation tasks place
at the same time;
same place;
never occurs
mechanisms of isolation:
- isolation is … between two populations
- commonly occurs as a result of … factors that cause populations to become …
reduction in gene flow;
geographic factors;
physically separated
mechanisms of isolation:
- gene flow tends to … gene frequencies and reduce the … of populations
- once gene flow is dramatically reduced or ceases, … begins and … may take place
homogenize;
differentiation;
evolutionary independence;
speciation
mechanisms of isolation:
- the allopatric model: the essence of allopatric speciation is that … creates an effective barrier to …
physical isolation;
gene flow
mechanisms of isolation:
geographic isolation through dispersal and colonization in Hawaiian Drosophila species
- the dispersal and colonization hypothesis make two predictions:
1. closely related species should be found on …
2. the sequence of … events should correspond to the sequence of …
adjacent islands;
branching events;
island formation
mechanisms of isolation:
- geographic isolation through …
vicariance;
mechanisms of divergence:
- adaptation to different …: when populations of a single species occupy multiple habitats with differing …, a frequent outcome is … and …, which can lead to …
habitats;
selection pressures;
phenotypic; genetic divergence;
speciation
mechanisms of divergence:
- selection in the seedcracking finch based on bill width and seedcracking performance - … selection
disruptive
hybridization and gene flow between species:
- what keeps two sympatric species separate?
1. … isolation: …. are never formed, usually bc … between species does not take place
prezygotic;
hybrid offspring (zygotes);
mating
hybridization and gene flow between species:
- what keeps two sympatric species separate?
2. … isolation: hybrid offspring suffer from …, … or …
postzygotic;
inviability;
sterility;
reduced fitness
hybridization and gene flow between species:
when species do interbreed, possible evolutionary outcomes include:
1. …
2. …
3. …
reinforcement of prezygotic isolation;
hybrid speciation;
stable hybrid zones
hybridization and gene flow between species:
when species do interbreed
1. reinforcement of prezygotic isolation and/or …, selection against …
genetic incompatibility;
hybrids
hybridization and gene flow between species:
when species do interbreed:
2. hybrid speciation –> selection favors hybrids in … not …
novel habitat;
occupied by parental species
hybridization and gene flow between species:
when species do interbreed:
3. hybrid zones: selection favors hybrids in …
transitional habitats
Morphospecies concept:
- the great advantage of the morphospecies concept is that it is …
- morphospecies can be identified in individuals that are … or ….
widely applicable;
extinct;
living
Morphospecies concept:
problems;
- difficult to applying groups like …, … and many … that are small and have few measurable … characters
bacteria;
archaea;
fungi;
morphological
Morphospecies concept:
problems
- fossil species that differed in … or the anatomy of … cannot be distinguished
- populations that are similar in … but were strongly divergent in … (…)
color; soft tissues; morphology; other traits; cryptic species
Morphospecies concept:
problems:
- it does not work for cryptic species, for groups that are actually … of one another but appear to be … based on …
independent of one another;
members of the same species;
morphological similarity
The phylogenetic species concept (PSC):
- … is the criterion for identifying species
- monophyletic groups are defined as lineages that contain all of the …. of a …
monophyly;
known descendants;
single common ancestor
The phylogenetic species concept (PSC):
- the rationale behind the phylogenetic species concept is that traits can distinguish populations on a phylogeny only if the populations have been … in terms of … and have …., and possibly … as well
isolated;
gene flow;
diverged genetically;
morphologically
The phylogenetic species concept (PSC):
- the appeals of this approach are that it can be applied to … - including … and …- and that it is …
any type of organism;
asexual;
fossils;
testable
The phylogenetic species concept (PSC):
- the appeals of this approach are that it can be applied to any type of organism - including asexual and fossils - and that it is testable: species are named on the basis of … in the traits used to estimate the phylogeny
statistically significant differences;
The phylogenetic species concept (PSC):
- different sources of information can lead to differing phylogenies, resulting in … under the PSC
- instituting the phylogenetic species concept could easily double the number of … and might create a great deal of confusion if traditional names and species identities are changed. proponents of the concept argue that this is not if it is a better representation of reality
conflicting species designations;
named species
The phylogenetic species concept (PSC):
- recent analyses have found that the PSC often distinguishes multiple … in populations that were formerly considered a single species
- for organisms such as …, the PSC has been immensely useful in identifying possible … that can then be further explored experimentally
cryptic species;
fungi;
species boundaries
The biological species concept (BSC):
- the criterion for identifying evolutionary independence is …
- species should be different: if populations of organisms do not … in nature, if they fail to produce … when they do …
reproductive isolation;
hybridize regularly;
fertile offspring;
hybridize
The biological species concept (BSC):
- has been widely accepted since Ernst Mayr championed it in 1942. it is used in practice by many biologists and is the legal definition employed in the endangered species act of 1973, the flagship … legislation in the US
- the great strength of the BSC is that reproductive isolation is a meaningful criterion for identifying species because it confirms …
- although this criterion is compelling in concept and useful in some situations, it is often difficult to apply
biodiversity;
lack of gene flow;
The biological species concept (BSC):
- there are several examples of species that are …
not reproductively isolated
