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- Reproductive isolating mechanism's
- 1) ecological RIM's
- 2) Temporal RIM's - breeding at diff times
- 3) Behavioral RIM's - potential mates, meet but do not mate. (visual, auditory, chemical (moth pheromone)
Hybridization and polyploidy
- interbreed between 2 species
- Hybrids are generally sterile
- From species A and species B
- genome of hybrid: "AB" (1 set from 1 parent, 1 set from 2nd parent)
Chromosomes cant pair in meiosis:
- possible solutions: reproduce veg.
- -become polyploid - more than 2 sets of chromosomes
- (50% of plants are polyploid)
Where do polyploids come from?
- From hybrids: AB hybrid
- -errors in mitosis or meiosis
- AABB tetraploid - meiosis fine
- (wheat, tobacco, crops)
How do we study macro evolution?
- 1) fossils
- 2) dating - radiometric
- 3) morphology
- 4) biochemical evidience/data
- organs are homologous (similar in form because of common ancestory)
- ex: anatomy of bones in arms (bats, humans)
- ex: organs are analogous - similar in form because of similar functioon (insects and bird wings)
- ex: a.a. sequences
- ex: DNA nucl. seq.
- -If 2 like species have closer seq. they are closer related.
- Cheat grass 0
- Sunflower 9 0
- sage brush 8 1 0
- How many diff. in a.a. in a part protein?
- Time increases left to right
Pace of evolution:
- Punctuated equilibria
- What causes big change:
- a) appearance of polyploid
- b) developmental change early in dev.
- c) change in regulatory genes
- d) genetic drift
- dissapearance of a taxonomic group
- -physical factors (volacones, ice age)
- -biotic factors (constantly occuring)
- sometimes mass extinctions
- 65 million years ago- most recent (theory asteroid)
prezygotic vs postzygotic:
- pre - prevent formation of zygote
- post - after formation of zygote
- prevention gamete
hybrid inviability or infertility