SYSTEMATICS

• Typological Species Concept


  Defines species as a group whose members share certain characteristics that distinguish them from other species. Also called the morpho-species concept. Species can be segregated from another species by physical features and can be recognized by their physical features. Also referred as the essentialist species concept. Members of species can be recognized by their essential characters.
• Biological Species Concept

  Groups of actually or potentially interbreeding natural populations, which are reproductively isolated from other such groups. Involves interbreeding among populations of the same species and reproductive isolation between populations of different species.
• Evolutionary Species Concept

  A single lineage of ancestor-descendant populations which maintains its identity from other such lineages, and which has its own evolutionary tendencies and historical fate.
• Species

  The population of organisms whose members can interbreed and produce viable, fertile offspring but do not interbreed with other groups. Maintained by gene flow and reproductive isolation.
• Gene Flow

  The movement of genes from one generation to the next or from one region to another region.
• Reproductive Isolation

  Mechanisms that prevent members of different species from producing offspring.
• Speciation

  The evolutionary process by which new species arise, involving the splitting of a single evolutionary lineage into two or more genetically independent lineages.
• Geographic Isolation


  The geographic feature that keep the different portions of the species from exchanging genes like distance, a canyon, a river, or a mountain.
• Range


  The geographic area over which a species can be found.
• Reproductive Isolating Mechanisms (RIMs)

  • Pre-zygotic barriers
  • Post-zygotic barriers
• Pre-zygotic barriers

  Prevent members of different species from mating to produce a zygote, a single-celled embryo.
• Behavioral Isolation

  • Inborn behavior patterns that prevent breeding between species. E.g. two species might have different courtship behaviors or mate preferences and thus find each other "unattractive".
• Habitat Isolation


  • Two species might prefer different habitats and thus be unlikely to encounter one another. Even when living in the same common locality, species occupy diverse habitats due to different biological or genetic tendencies thereby limiting gene flow.
• Temporal Isolation

  • Two species might reproduce at different times of the day or year and thus be unlikely to meet up when seeking mates.
• Mechanical Isolation


  • Two species might have bodies or reproductive structures that simply don't fit together. There is a physical or biological structure that prevents mating.
• Post-zygotic Barriers

  Blocks reproduction after fertilization and zygote formation. Keep hybrid zygotes from developing into healthy, fertile adults.
• Hybrid Inviability

  • A hybrid individual develops but either dies before birth or if born alive, cannot survive maturity.
• Hybrid Breakdown

  • Successful mating with viable, fertile offspring, but when the offspring try to have offspring, things go wrong. The second generation can be either inviable, infertile, or show reduced fitness.
• Hybrid Sterility

  • Even if the hybrid offspring is otherwise perfectly healthy, either one or both sexes is sterile and doesn't have functional gametes.
• Allopatric Speciation

  Occurs when a population is geographically isolated from another population of the same species, preventing gene flow between populations and leading to genetic divergence over time.
• Sympatric Speciation

  Occurs when new species evolve from a single ancestral species occupying the same geographical area, usually involving the development of reproductive isolation mechanisms within the same habitats.
• Classification

  The systematic grouping or organisms based on structural or functional similarities of evolutionary history.
• Hierarchical Classification

  Arrangement of various organisms into successive levels of the biological classification either in a decreasing or an increasing order from kingdom to species and vice versa.
• Taxonomic Characters

  • Morphological Characters
  • Physiological Characters
  • Behavioral Characters
  • Ecological Characters
• Morphological Characters

  • General external Morphology, Special structures, Internal morphology (anatomy)
• Physiological Characters

  • Metabolic Factors, Body secretions
• Behavioral Characters

  • Courtship and other isolating mechanism, Other behavioral patterns
• Ecological Characters

  • Habitat
• Taxonomic characters refers to any attribute or feature by which a member of taxon differs.
• Character State


  Two or more forms of characters
• Taxonomic characters have diagnostic aspects as indicator of differences, function as indicator of relationships, help in classification of organisms.
• Characteristics of taxonomic characters: apply to all members of the taxon, qualitative and absolute, observable without special equipment, dissection or histological preparation, fairly constant, fairly indestructible.