The Origen of Species Ch 24

Macroevolution Evolution above the species level that produces novelties like vertebrae or feathers and contributes to speciation Speciation- the process by which new species arise Species: capable of reproducing and making fertile offspring

Reproductive Isolation Prevents different species from making fertile offspring. May be “prezygotic” or “postzygotic”

Prezygotic barriers 1. Habitat isolation 2. Behavioral Isolation 3. Temporal(time) isolation 4. Mechanical isolation 5. Gametic isolation

Postzygotic barriers 1. Reduced hybrid viability- zygote doesn’t develop 2. Reduced hybrid fertility- offspring is sterile 3. Hybrid breakdown- fertile hybrids mate but their offspring are weak/sterile

Allopatric Speciation “Different country” speciation due to geographic separation Mountains forming, rivers separating, continental drift,etc

Sympatric Speciation “Same country” speciation- Some barrier prevents mating (Temporal, behavioral…) Common in plants that easily become polyploid instead of diploid --may result from Habitat differentiation and sexual selection

Adaptive radiation (divergent evolution) -many species arise from a common ancestor which moved into a new area or niche

Rates of Speciation Gradualism- gradual accumulation of adaptations Punctuated equilibrium- stable periods with occasional bursts of rapid changes in the fossil record

Evolution of Genes that Control Development “Evo-devo” is the branch of study where evolution and developmental biology meet. -Slight changes can make major differences in morphology difference between species.

Homeotic Genes Master control genes that determine the location and organization of body parts Hox genes determine positional information in animal embryos that prompt cells to develop structures in a particular place Changes can create drastic morphological effects