What sort of Biological Entity is it? “SPECIES” What sort of Biological Entity is it?

What is a “Species”? Biological Species Concept: 1 or more populations of individuals that can interbreed and produce fertile offspring, and are reproductively isolated form other such groups. Members of a species have a shared gene pool. Different populations can mate and produce fertile offspring.

What is a “Species”? But…what about asexual organisms? Morphological Species Concept: Groups of organisms that share certain morphological or biochemical traits. This is rather subjective. Phylogenetic Species Concept: Groups of organisms (or lineages) that share recent common ancestry.

Speciation How do species arise? Microevolution Pre-existing organisms (ancestors). Divergent Evolution Adaptation to specific environmental cues. (This contrasts Convergent Evolution) Similar adaptations in organisms from very different lineages.

Speciation Biological Species Concept: Reproductive Isolation 1 or more populations of individuals that can interbreed and produce fertile offspring, and are reproductively isolated form other such groups. Reproductive Isolation Prevents Gene Flow. If no gene flow, then populations can develop into more and more different sub-populations…perhaps eventually forming species.

Reproductive Isolating Mechanisms Pre-Zygotic Isolating Mechanisms Post-Zygotic Isolating Mechanisms

Pre-Zygotic Isolating Mechanisms Prevent Reproduction Attempts Habitat Isolation Isolated in space/habitat. Temporal Isolation Mating occurs at different times Behavioral Isolation Differences in mating displays, calls, chemicals… Mechanical Isolation Incompatibility of reproductive organs … (“the key doesn’t fit the lock”)

Post-Zygotic Isolating Mechanisms Copulation occurs, but offspring are kept from developing & breeding. Gamete Isolation – sperm & egg don’t fuse. Zygote Mortality – Zygote dies, unable to function. Hybrid Inviability – Hybrid is produced, but does not survive to adulthood. Hybrid Sterility – Hybrid is produced, but is unable to produce viable gametes.

Speciation Formation of new species via reproductive isolation. Allopatric Speciation 2 populations become reproductively- isolated while separated from each other (geographic barrier).

Speciation Sympatric Speciation 2 populations become reproductively-isolated while occupying the same geographic area.

How Fast? Gradualist Model Punctuated Equilibrium Model

Systematics Science of organizing the diversity of life. Taxonomy – Identification & Naming Phylogeny – Analyzing evolutionary relationships among groups. Classification – Placing organisms into an organized categorization scheme.

Taxonomy Identification & Naming Taxon: a group of organisms (Taxa) “Species” – the most fundamental group. Group of interbreeding populations that are reproductively isolated from other such groups (and evolving independently of other such groups).

Taxonomy New species each given a “Scientific Name” Carolus Linnaeus Binomial Nomenclature 2-word Latin name. Pinus strobus Dictyostelium discoideum Bubo virginianus “Common Names” also… Can be misleading

Taxonomy Pinus strobus 1st word = Genus 2nd word = specific epithet A generalized name 2nd word = specific epithet A descriptive name Always in italics or underlined. Genus is capitalized, epithet is lower case. Specific epithet never used alone!

Phylogeny Grouping new species/taxa with closely-related taxa from an evolutionary perspective. Phylogenetic Trees:

Phylogeny Outgroups:

Classification Categorizing organisms into a hierarchy of names (hopefully) according to their relatedness. Historically – based on convenience. Starting at Species (the most exclusive group), organisms are grouped into more and more broad & inclusive Taxa. “Species” is the only level that really exists as an true single entity.

Classification Kingdom Phylum/Division Class Order Family Species Genus Species Animalia Chordata Mammalia Primates Hominidae Homo Homo sapiens

Classification Tyto Homo alba sapiens Homo Tyto Hominidae Tytonidae Animalia Chordata Mammalia Aves Primates Strigiformes Hominidae Tytonidae Homo Tyto Tyto alba Homo sapiens

Systematics Tree of Life: http://tolweb.org/tree/phylogeny.html