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

2. 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.

3. 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.

4. 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.

5. 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.

6. Reproductive Isolating Mechanisms
Pre-Zygotic Isolating Mechanisms
Post-Zygotic Isolating Mechanisms

7. 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”)

8. 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.

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

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

11. How Fast?
Gradualist Model
Punctuated Equilibrium Model

12. 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.

13. 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).

14. 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

15. 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!

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

17. Phylogeny
Outgroups:

18. 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.

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

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

21. Systematics
Tree of Life: