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(What is a Species?, Barriers to Reproduction, Geography of Speciation,…
What is a Species?
Other Ways to Define Species
Morphological Concept
Defines species by body shape
Good for all organisms but is an opinion
Ecological Concept
Defines species by role in environment
Focuses on disruptive selection
Phylogenetic Concept
Smallest group on a family tree
Uses DNA comparisons
Biological Species Concept
Main Definition
Group of populations that breed in nature
Create healthy babies that can have babies
Separated from other groups
Gene flow holds the species together
Problems with this Concept
Does not work for fossils or bacteria
Gene flow happens between species
Example is the Grolar bear
Barriers to Reproduction
Prezygotic Barriers (Before Fertilization)
Blocks Mating
Habitat Isolation (Different places)
Temporal Isolation (Different times)
Behavioral Isolation (Unique rituals)
Blocks Fertilization
Mechanical Isolation (Parts do not fit)
Gametic Isolation (Sperm cannot join egg)
Postzygotic Barriers (After Fertilization)
Reduced Hybrid Viability
Baby is weak or does not develop
Example is Ensatina salamander
Reduced Hybrid Fertility
Baby is sterile
Example is the Mule
Hybrid Breakdown
Grandchildren are weak or sterile
Example is rice strains
Geography of Speciation
Allopatric Speciation (Different Country)
How it Happens
Physical barrier stops gene flow
Barrier depends on movement
Process
Groups change by mutation and selection
Example is Mosquitofish body shape
Evidence
More barriers mean more species
Example is shrimp in Panama
Sympatric Speciation (Same Country)
Polyploidy (Cell Division Accident)
Autopolyploid (Same species)
Allopolyploid (Different species like oats)
Sexual Selection
Choosing mates by color
Example is Cichlid fish
Habitat Differentiation
Using a new resource
Example is maggot fly on apples
Hybrids and Time
Hybrid Zones
Definition
Region where species meet and mate
Happens when barriers are incomplete
Three Outcomes
Reinforcement (Barriers get stronger)
Fusion (Species merge into one)
Stability (Hybrids continue)
Speed of Speciation
Patterns in Fossils
Punctuated Equilibrium (Fast change then stop)
Gradualism (Slow steady change)
Genetics
Single gene change (Snail shell)
Few genes change (Flower color)