Download The Origen of Species

yes no Was this document useful for you?
   Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Document related concepts
no text concepts found
The Origen of Species
Ch 24
• Evolution above the species level that
produces novelties like vertebrae or feathers
and contributes to speciation
– Speciation- the process by which new species
– Species: capable of reproducing
and making fertile offspring
Reproductive Isolation
• Prevents different species from making fertile
• 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
• 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
Sympatric Speciation
• “Same country” speciationSome barrier prevents mating
(Temporal, behavioral…)
– Common in plants that easily
become polyploid instead of
--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
• Punctuated equilibrium- stable periods with
occasional bursts of rapid changes in the fossil
Evolution of Genes that Control
• “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