Chapter 24: The Origin of species -Macroevolution = the origin of new taxonomic groups - Speciation = origin of new species - Anagenesis vs. Cladogenesis

I. What is a Species?

1. Species Concepts A. Ecological Species Concept – defines a species based on its niche B. Pluralistic Species Concept – factors that make species vary C. Morphological Species Concept – unique structural features D. Genealogical Species Concept – unique genetic history / one tip on the branching tree of life E. Biological Species Concept – potential to interbreed and produce viable, fertile offspring / hinges on reproductive isolation or barriers

2. Isolation Barriers Reproductive Barrier – any factor that impedes 2 species from producing fertile, viable offspring A. Prezygotic – hinder fertilization of ova - habitat iso – live in different habitats - behavioral iso – signals and behaviors - temporal iso – different times of day or year - mechanical iso – anatomical incompatibility - gametic iso – gametes don’t fuse

2. Isolation Barriers B. Postzygotic Barriers – prevents hybrid zygote from developing - Reduced Hybrid Viability – aborted embryo - Reduced Hybrid Fertility – sterile offspring / meiosis failure - Hybrid Breakdown – viable F1, F1s produce sterile or feeble offspring

II. How is a Species Made?

1. Allopatric Speciation Speciation takes place in populations with geographically separate ranges Mountain range, land bridge, land production Increases when a population is small and isolated Can be observed in ring species where bottom organisms can’t breed

1. Allopatric Speciation A. Adaptive Radiation – many diversely adapted species from a common ancestor B. Both pre and post zygotic barriers may evolve from allopatric speciation

Sweet Video

2. Sympatric Speciation Speciation takes place in geographically overlapping populations Result from chromosomal change, non- random mating A. Polyploid Speciation in Plants - extra sets of chromosomes - autopolyploid – more then 2 sets - allopolyploid – 2 species make a polyploid hybrid

Autopolyploid

Allopolyploidy

2. Sympatric Speciation B. Animals and Sympatric Speciation - Genetic factors cause dependence on resources not used by parents - Preferences for mates color or looks (non-random mating) / cause behavioral isolation

3. Speed of Speciation A. Gradualism – small changes over time B. Punctuated Equilibrium – rapid change and then no change

III. Speciation to Macroevolution

1. Evolution Novelties Come From Older Structures A. Eye Spots ---- Eyes B. Exaptations – structures that evolve in one context but become co-opted for another function / ex. Hollow bones

2. Evo-Devo Looking at evolution biology and development of organisms together Genes that control development play a major role in macroevolution A. Allometric Growth – growth rates at different times during development / change the growth rates a little (genes) and it can really change the adult / Type of heterochrony B. Heterochrony – evolutionary change in the rate or timing of developmental events / salamander feet - paedomorphosis – reproductive development accelerates compared to somatic development / adults retaining juvenile ancestral traits C. Homeotic Genes – determine basic features where things develop / Hox gene changes leg buds Kinda Sweet Video

Allometric Growth

Heterochrony

Hox Gene

3. Trends Trends ≠ goal or end point Bush growing in all directions not just one Species selection – idea that the species that endure the longest and generate the greatest number of new species determine the direction of evolutionary trends / people argue that it is gradual changes that cause the trends not numbers of individuals