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Chapter 24: Origin of Specie - Coggle Diagram
Chapter 24: Origin of Specie
Biological Species Concept
Species=group of populations that can be interbreed and produce a viable fertile offspring
Limitation
s: cannot apply to fossils or asexual organisms
Morphological species concept
: based on physical traits
Ecological species concept
is smallest group sharing a concept
Phylogenetic species concep
t is smallest group sharing a common ancestor
Reproductive Isolation
: key to speciation
Prezygotic Barriers:
before fertilization
Habitat Isolation
: different habitat
Temporal Isolation
: different breeding :season/times
Behavioral Isolation
: unique courtship rituals
Mechanical isolation
(incompatible reproductive structures)
Gametic isolation
(sperm cannot fertilize egg)
Postzygotic Barriers
(after fertilization)
Reduced hybrid viability (
offspring don’t develop properly)
Reduced hybrid fertility
(offspring sterile, e.g., mule)
Hybrid **
breakdown** (offspring of hybrids are weak/sterile)
Modes of Speciation
Allopatric Speciation: geo/reproductive isolation
Examples: island species, river barriers mountain ranges
Evidence: adaptive mediations on archipelagos (Darwin's finches)
Sympatric Speciation:
occurs in the same geographic area
Polyploidy
Habitat Differentiation
Sexual selection
Patterns in fossils
Punctuated equilibrium:
species appear suddenly, persist unchanged, then disappear
Gradualism
: species diverge slowly over time.
Hybrid Zones
Reinforcement: hybrids are less fit - reproductive barriers strengthen.
Fusion: hybrids are equally fit → species merge back.
Stability: hybrids continue to be produced.
Time Course of Speciation
can be rapid: few generations
can be slow: millions of years
Average: 6.5 million years