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Systematics Lecture2
Taxonomic Hierarchy and Species Concept
| Question | Answer |
|---|---|
| • The arrangement of organism into these ranking orders or taxonomic categories (Division, class, order, family, genus, species) in an ascending series ranging from the lowest to the highest category | Taxonomic Hierarchy |
| The least inclusive in the rank classification | Species |
| system in which taxonomic groups are assigned to different taxonomic categories, depending upon the levels of diversity of the organism | TAXONOMIC STRUCTURE |
| a category or taxonomic group of any rank within the system of classification. • used to indicate the rank of a group as well as the organisms contained within that group. | TAXON |
| the fundamental category of the taxonomic hierarchy. lowest unit of biological classification and the building blocks of classification | SPECIES |
| Latin word specere | “to look at, see”. it literally means appearance |
| It is the next principal category above species in the taxonomic hierarchy. • Those species which share certain common characters are placed together in a larger grou | GENUS |
| True or False It is more difficult to define a genus as its description must include all the closely related species grouped within a genus. | TRUE |
| in relation to plants was first used by Magnol (1689). • represents a more natural and real grouping. | FAMILY |
| True or False Less information is usually available about a family, and it is comparatively hard to recognize a family than the lower categories like genus or species. | FALSE |
| What is Macroevolution? | It is the change in the gene pool of a population from one generation to the next. |
| It is the process by which one species splits into two or more species. | Speciation |
| True or False Each time speciation occurs, the diversity of life increases. | TRUE |
| How does a new species emerge? | New species evolve from preexisting species • Speciation process: –Cladogenetic –Reticulate –Phyletic |
| new species originate from a splitting event in which each branch is a species. | Cladogenetic Speciation |
| new species results from interbreeding of two existing species. | RETICULATE SPECIATION |
| ancestral species transform s into a single descendant species. | PHYLETIC SPECIATION |
| When can we say speciation happens? | -When two populations of one species become sufficiently different so they are no longer the same species -The divergence of an ancestral species into 2 or more daughter species requires genetic change among population. |
| Speciation is successful, what now? -it is the divergence of a taxon into a number of different forms and adaptive zones. -The evolution of many diverse species from a common ancestor | ADAPTIVE RADIATION |
| the sites of multiple speciation events. | Islands that have physically diverse habitats and that are far enough apart to permit populations to evolve in isolation but close enough to allow occasional dispersions ex. Galapagos Island, Darwin's Finches |
| List the Species Concepts (3) | •Emphasizing Process (4) -Biological, Recognition, Evolutionary, Cohesion • Emphasizing product of evolution (3) -Taxonomic or morphological, Phylogenetic, Genealogical • Other species types (2) - Asexual and Cryptic Species |
| Groups of interbreeding natural populations which are reproductively isolated from other such groups (Mayr, 1963) | Biological/ Isolation Species |
| defines a species as a group of populations whose members have the potential to interbreed in nature and produce fertile offspring( offspring that themselves can reproduce). | Biological Species |
| thus, members of a ______ species are united by being reproductively compatible, at lerast potentially. | Biological Species |
| - it is often referred to as “reproductive isolating mechanisms - derived suites of characters in one or more lineages that inhibit or prevent interbreeding | Barriers to gene exchange |
| – serve to isolate the gene pools of species and – prevent interbreeding. | Reproductive barriers |
| reproductive barriers are categorized as (2) | – prezygotic – postzygotic. |
| Prevents genetic exchange (gene flow) and maintains a boundary between species | Reproductive Isolation |
| there are some pairs of clearly distinct species that do occasionally interbreed. The resulting offspring are called? | Hybrids |
| The hybrid offspring of grizzly bears (Ursus arctos) and the polar bears (Ursus maritimus) are called? | Grolar Bears |
| the branch of biology dealing with the preservation of biodiversity | Conservation biology |
| It refers to the totality of life within a given region and can be assessed or calculated in different ways | Biodiversity |
| refers to a simple count of the number of species (generally of a certaingroup, e. g., vascular plants) within a given geographical region. For example, a grassland with a total of 63 plant species has a greater species richness than a woodland with 48. | Species richness |
| takes into account not only the number of species but also how evenly they are distributed within the region. can be measured in terms of the number of individuals | Species evenness |
| is an integrative discipline and encompassesthe fields ofsystematics, ecology, geography, geology, and geochemistry. | . Conservation biology |
| Why save biodiversity? (3 reason) | - aesthetic - economic importance. - maintenance of genetic diversity |
| (which can be a species, subspecies, or distinct population segment) is one that is in danger of becoming extinct in the near future within all or a significant part of its geographical range due to one or more causal factors. | endangered taxon |
| is one thought likely to become endangered in the wild in the near future within all or part of its geographical range if the same causal factors continue to operate | Threatened Taxon |
| How does plant systematics relate to conservation biology? (4) | - taxon diagnosis. - floristic surveys, - evaluation of taxon rarity - use of phylogenetic information in evaluating conservation decisions. |
| n is one that occurs well outside the range of other members of that taxon. are often particularly important to study, as they may reveal genetically or morphologically distinctive organisms, in some cases warranting recognition as a distinct taxon. | disjunct population |
| Floristic surveys are the basis for assessing if species or infraspecies are endemic to a given region, i.e., found naturally only in a particular, often limited, geographic location and in no other place in the world. | endemic |
| Regions of high endemism are termed biodiversity _____? | “hotspots” |
| a taxon is one no longer known to exist in the wild. | extinct species |
| a taxon is one that is extinct within a particular portion of its range but present within other parts of its range. | extirpated species |
| is one that, by its absence from an ecosystem, results in the disappearance (directly or indirectly) of several other species, causing an “extinction cascade.” | keystone species |
| different species have a genetic basis for occupying different habitats (e.g., dry versus wet soils) and therefore do not normally come into contact to successfully breed | ecological or habitat isolation |
| different species breed at different times, e.g., spring versus fall or day versus night blooming flowering plants | temporal isolation |
| different species have different behaviors that inhibit interbreeding, such as (for flowering plants) different pollination mechanisms, preventing the transfer of pollen between different flower types | behavioral/ethological isolation |
| Lack of opportunities to encounter each other | Habitat Isolation |
| Different time of the year for mating activity | Seasonal Isolation |
| Breeding at different times or seasons | Temporal Isolation |
| Different courtship rituals | Behavioral Isolation |
| Physical incompatibility of reproductive parts | Mechanical Isolation |
| Molecular incompatibility of eggs and sperm or pollen and stigma | Gametic Isolation |
| Barriers to gene exchange that is occurring after a zygote forms | Post-zygotic |
| hybrids between species cannot develop properly to adulthood; interaction of parental genes impairs the hybrid’s development or survival. | hybrid inviability |
| hybrids develop to adulthood but are sterile or have reduced fertility; hybrids are vigorous but cannot produce viable offspring | Hybrid Sterility |
| hybrids are fertile but their F2 generations have reduced viability or fertility; hybrids are viable and fertile, but their offspring are feeble or sterile | Hybrid Breakdown |
| allowing mating (equivalent to pollination in seed plants), but not zygote formation | Post-mating |
| self-incompatibility mechanisms, for example, (in flowering plants) pollen landing on the stigma of another species will not germinate or will not form a functional pollen tube | mechanical or physiological isolation |
| sperm and egg come into contact, but these gametes are incompatible; thus, the sperm cannot successfully fertilize the egg | gametic isolation |
| Refer to sexually reproducing systems that are maintained by genetically-based features that promote reproduction (Paterson, 1985) Promotes Gene flow (fertility, behavior, gamete propagation and recognition) | Recognition Species |
| A single continuous lineage of ancestral descendant populations that retains its identity from other such lineages and has its own evolutionary tendencies and historical fate (Wiley, 1978) | Evolutionary Species |
| Largest or most inclusive group of individuals that maintains genetic and phenotypic cohesion (Templeton, 1989). | Cohesion Species |
| What are the Concepts Emphasizing Product of Evolution? (3) | Taxonomic or morphological species • Phylogenetic species • Genealogical species |
| Smallest group or class of individuals that are similar to one another in one or more features and different from other such groups • Species can be distinguished from each other by morphological traits • “Classical species concept” | Taxonomic or Morphological species |
| is the oldest species concept and uses differences in morphological characters to distinguish species. • In former times species were considered as inalterable units. | Morphospecies or mophological concept |
| After Charles Darwin published his book____ the morphospecies concept has been applied under the assumption that similar to identical morphological characters would reflect relatedness | On the Origin of Species by means of Natural Selection (1859) |
| Limitations of Morphological Species (2) | - High plasticity - Undetected speciation |
| Character-based, defined as the smallest group of populations or lineages that are diagnosable by a unique combination of character states in comparable individuals (Nixon & Wheeler, 1980) | Phylogenetic Species |
| “the smallest diagnosable cluster of individual organisms within which there is a parental pattern of ancestry and descent” (Cracraft 1983) | Phylogenetic Species |
| Clusters must be? in a phylogenetic tree | 1) Monophyletic (ancestor + all descendants) 2) derived through an evolutionary process of descent from an ancestral lineage 3) diagnosable through examination of derived characters |
| uses molecular markers – usually DNA sequences – to identify closely related taxa. • It is e.g. the standard species concept in bacteria, but has been tested also for eukaryotic taxa (Leliaert et al. 2009) | Phylogenetic species concept |
| the necessity of recognizing an apomorphy for the species lineage alone. | “autapomorphic species” |
| is defined as two or more lineages segments (e.g., from samples of separate populations) that can be resolved as neither monophyletic or paraphyletic (Donoghue 1988). | Metaspecies |
| similar to the “plesiospecies” of Olmstead 1995) may represent temporarily separate lineage segments that have diverged relative to one anothe | Paraphyletic species |
| All members of the group are more closely related to one another than to any organisms outside the group (Baum & Shaw, 1995) | Genealogical species |
| Other Species Types (2) | - Asexual species - Cryptic species |
| Reproducing without sex, yet are recognizable morphological or genetic units • Ex. Apomictic populations that develop seed without fertilization, wherein the embryo is a clone of the original parent | Asexual Species |
| Not morphologically distinguishable from another species • Genetically different from other populations | Cryptic Species |
| defines a species by its ecological niche, focuses on unique adaptations to particular roles in a biological community, ex. two species may have similar appearance but can be distinguishable based on what they eat and the depth of water they are found | ecological species concept |
| Mechanisms of Speciation (2) | Allopatric and Sympatric speciation |
| geographic isolation leads to speciation, the initial block to gene flow may come from a geographic barrier that isolates a population. | Allopatric Speciation |
| takes place without geographic isolation • occurs when a new species arises within the same geographic area as its parent species. | Sympatric Speciation |
| Biogeographical Relationships between pairs of species (3) | -Allopatry - Sympatry - Sympatry |
| 2 related species are separated by distribution/ living in different countries or regions | Allopatry |
| occurrence of 2 related species in one general area, living in the same country. | Sympatry |
| partial overlapping of 2 allopatric areas | Parapatry |
| True or False Many plant species have originated from sympatric speciation that occurs when accidents during cell division result in extra sets of chromosomes. | TRUE |
| New species formed in sympatric speciation are called ____, in that their cells have more than two complete sets of chromosomes. | polyploid |
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