Origin of Species Flashcards
Speciation
the process by which one species splits into 2+ species
_____ is at the focal point of evolutionary theory.
Speciation
Macroevolution
broad patterns of evolutionary change above the species level over long time spans/formations of new groups
Biological Species Concept dictates that:
a species is a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring
The Biological Species Concept places an emphasis on _____ _____.
Reproductive Isolation
Reproductive Isolation
impedes two different species from producing viable, fertile offspring
Prezygotic Barriers
Block fertilization from occurring
Postzygotic Barriers
Reduce survival among hybrid embryos
Types of Prezygotic Barriers
- Habitat Isolation
- Temporal Isolation
- Behavioural Isolation
- Mechanical Isolation
- Gametic Isolation
Types of Postzygotic Barriers
- Reduced Hybrid Viability
- Reduced Hybrid Fertility
- Hybrid Breakdown
Allopatric Speciation
gene flow is interrupted/reduced when a population is divided into geographically isolated sub-populations
Sympatric Speciation
Speciation takes place in geographically overlapping populations
Allopatric means:
other country
What two factors can drive sympatric speciation?
- Habitat Differentiation
- Sexual Selection
Polyploidy
Presence of extra sets of chromosomes due to accidents during cell division, resulting from barriers to gene flow
Autopolyploid
An individual with 2+ chromosome sets derived from one species
Allopolyploid
A species with 2+ chromosomes, derived from a different species
Hybrid Zone
A region in which members of different species mate and produce hybrids
What are the three possible outcomes when closely related species meet in a hybrid zone?
- Reinforcement
- Fusion
- Stability
Reinforcement
Strengthening of reproductive barriers that occurs when hybrids are less fit than parent species
Fusion
Weakening of reproductive barriers that occurs if hybrids are as fit as parents; parent and hybrid species will fuse into one if gene flow is great enough
Stability
The continued formation of hybrid individuals that occurs when hybrids have increased fitness relative to the parent species
In the reinforcement of reproductive barriers, ______ species will be preferred to _____ species.
Allopatric; Sympatric
The fusion of the parent and hybrid species, if ____ ____ is great enough.
gene flow
Habitat Isolation
Differences in where species live, preventing them from encountering one another
Temporal Isolation
Difference in species-specific mating cycles, causing mating to be unlikely
Behavioural Isolation
Distinct differences in courtship behaviours/traditions that aren’t noticed/recognized by females of different species
Mechanical Isolation
Physical differences in genitalia preventing successful mating
Gametic Isolation
When sperm and egg of different species cannot fuse to form a zygote
Reduced Hybrid Viability
Resulting hybrid embryos often do not survive or will have major morphological anomalies that cause them to die off.
Reduced Hybrid Fertility
Hybrid offspring will often be sterile/infertile
Hybrid Breakdown
occurs when first generation of hybrid offspring are viable and fertile, but when they mate, their offspring are inviable/infertile
