1. Origin of Species
Chapter 14

2. What you need to know! The biological concept of species.
The difference between microevolution and macroevolution.
Prezygotic and postzygotic barriers that maintain reproductive isolation in natural populations.
How allopatric and sympatric speciation are similar and different.
How punctuated equilibrium and gradualism describe two different tempos of speciation.

3. Macroevolution
Our focus thus far has been on microevolution: how single populations transform over time
Microevolution is not sufficient to explain the diversity of life on our planet
It can only account for how an individual species adapt to various environmental changes
Macroevolution focuses on the evolution of all species from a common ancestor
Speciation (how new species emerge from previously existing ones ) is the mechanism of macroevolution

4. What is a Species?
The Biological Species Concept: A population (or group of populations) who can mate and produce fertile offspring with one another but not with a different group
Other concepts: morphological species, ecological species, phylogenetic species
Taxonomy names the various species on our planet:
Canus lupus
Homo sapien
Felis catus
For new species to arise (speciation) a single species must become reproductively isolated

5. Reproductive Isolation
Prezygotic (before zygote) – prevent mating and/or hinder fertilization)
Temporal isolation: reproduce at different times of day or year
Habitat isolation: same area but not the same habitat
Behavioral isolation: different mating practices
Mechanical Isolation: structural differences in reproductive organs prevent mating
Gametic isolation: sperm cannot fuse with egg

6. Reproductive Isolation
Postzygotic (after zygote) – fertilized eggs don’t develop into fertile adults:
Hybrid inviability: hybrids fail to develop or to reach sexual maturity
Hybrid sterility: offspring cannot reproduce (mule) due to ineffective gametes
Hybrid breakdown: offspring that grow and reproduce (F1) but their offspring (F2) are weak or sterile

7. Speciation Allopatric Speciation
Interbreeding becomes impossible due to geographic isolation (rivers, canyons, mountains)
New species evolve on the fringes of large ancestral populations
Sympatric Speciation
Sudden mutation within a population leads to new species
Polyploidy plants mutate by altering chromosome number in a non-disjunction error

8. Adaptive Radiation Colonization of a new habitat Example:
New habitats usually vary from the original habitat
Example:
Original Species A migrates to an unpopulated island chain
A is geographically isolated from the original population and speciates into B
B migrates to unpopulated islands
B is geographically isolated from the original population and speciates into C
& 6. C migrates to other islands
C is geographically isolated and speciates into D
D migrates to other islands
D is geographically isolated and speciates into E

9. Models of Speciation
Gradualism: species descend from common ancestors and gradually diverge
Punctuated equilibrium: period of apparent stasis followed by rapid adaptive radiation

10. Evolutionary Trends
Exaptation: structure that evolved in one context and later adapted for another function
Evo-devo: study of development and the relationship with evolution
Paedomorphosis: the retention in the adult of features that were juvenile
Trends do not necessarily indicate goal driven evolution

11. Phylogeny & Systematics
Chapter 15

12. What you need to know!
The taxonomic categories and how they indicate relatedness.
How systematics is used to develop phylogenetic trees.
The three domains of life including their similarities and their differences.

13. Phylogeny
Phylogeny – evolutionary history of a species or group of species
Sources of evidence:
Fossil Record
Systematics – classifying organisms and evolutionary relatedness
Morphological homology
Molecular homology

14. Systematics Morphological Homology Molecular Homology
similarities due to shared ancestry (homologous structures)
determined by how two organisms appear
Analogous structures can be misleading (convergent evolution NOT relatedness)
Molecular Homology
Similarities in the DNA base sequences
Most accurate
20 billion + base pairs sequenced so far (1,000’s of species) – BLAST Lab

15. Taxonomy Carolus Linnaeus (1701-1778)
Mostly morphological (grouping, separating organism due to body plans)
Latin based binomial nomenclature:
Each species is ID’d by genus (capital letter) and species (lower case)
Canis familiaris, Canis lupus, Felix domestica, Homo Sapien

16. All organisms classified in a hierarchy
Taxon Memory Wolf
Domain (broad) Did Eukarya
Kingdom King Animalia
Phylum Philip Chordata
Class Come Mammalia
Order Over Carnivora
Family From Canidae
Genus Germany Canis
Species (specific) Singing Lupus

17. Phylogenetic Trees

18. Cladistics
Organizing organisms into clades according to their phylogenetic (evolutionary) relationship
Using comparative morphology (taxonomy), and DNA analysis
Ancestral species placed on the bottom, with new features leading to novel descendants
Ingroups are the focus organisms, outgroups are close relatives

19. Cladogram

20. Molecular Systematics
Comparing nucleic acids and DNA for relatedness (most accurate)
Examples:
DNA Comparisons
Molecular Clocks: rate of genetic change
Nuclear DNA slower than mitochondrial DNA
Genome Evolution: Compare organisms entire genetic code (humans vs. chimps 99%)

21. Domains – Universal Tree of Life