Ch.24 - Origin of Species Flashcards
What are the four species concepts?
Biological
Morphological
Ecological
Phylogenetic
Describe the biological species concept
A species is a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring.
- Individuals of on species DO NOT produce viable, fertile offspring w members of other species.
__________ refers to the biological factors that prevent members of two diff species fr producing fertile offspring.
Reproductive isolation refers to the biological factors that prevent members of two diff species fr producing fertile offspring.
________ are offspring that result fr interspecific matings.
Hybrids are offspring that result fr interspecific matings.
Differentiate pre- and post-zygotic barriers.
Pre-zygotic barriers prevent mating (e.g. habitat, temporal or behavioral isolation/mate recog) and/or prevent fertilization (mechanical or gametic isolation).
Post-zygotic barriers result in inviability, infertility, or breakdown of the hybrid.
What is habitat isolation?
Habitat isolation is a pre-zygotic barrier in wh two species rarely encounter ea/o bc they live in sep habitats, even though there is no geo barrier.
What is temporal isolation?
Temporal isolation is a pre-zygotic barrier in wh two species breed at diff times (of day/seasons/years).
What is behavioral isolation?
Behavioral isolatin is a pre-zygotic barrier in wh courtship rituals and other behaviors do not overlap b/w two species.
What is hybrid breakdown?
Hybrid breakdown is a post-zygotic barrier in wh some first-gen hybrids are fertile, but when they mate w another hybrid or w either parent species → offspring of 2+ gen are feeble or sterile.
What are some limits of the biological species concept?
Doesn’t work for fossils or asexually reprod orgs.
Not helpful when there is gene flow b/w two groups but they are ecologically or morphologically distinct.
Overemphasizes gene flow and downplays role of NS.
What is allopatric speciation?
Pop divided by a geo barrier → gene flow interrupted → ea subpop’s gene pool is subject to unique mutation, drift, and NS → reproductive isolation, i.e. interbreeding prevented, even if contact restored.
- “allos” – other, “patra” – homeland
- Outcome deps on mobility of species
- Caution: geo separation IS NOT a biological barrier.
THINK: german guy saying “Allo!” fr an island.
What is sympatric speciation?
Speciation that occurs in pops that live in same geo area → ↓ gene flow. I.e. a reprod barrier isolates a subpop.
- Less common than allopatric speciation
- Caused by polyploidy, habitat differentation, and sexual selection.
Think: sym = same.
T/F: polyploidy is much more common in plants than animals.
TRUE
Polyploidy is much more common in plants than animals.
One cause of sympatric speciation in wh extra sets of chromos arise due to accidents during cell division.
Estimated that ~80% of plant species resulted fr polyploid speciation.
What is habitat differentiation?
Habitat differentiation is a cause of sympatric speciation in wh subpops use specific habitats or resources NOT avail to all members of pop.
How does sexual selection result in sympatric speciation?
Individuals w certain inherited traits are more likely to obtain mates → choosiness of one sex in selecting a mate can result in initial (sympatric) sep of pops.
T/F: The definition of species based on the biological species concept does not apply to organisms that reproduce asexually
TRUE
The definition of species based on the biological species concept DOES NOT apply to organisms that reproduce asexually
T/F: Vicariance events are more common on islands than in mainland island such as looking at the Galapagos island
TRUE
Vicariance events are more common on islands than in mainland island such as looking at the Galapagos island
E.g. ice age produced many diff species mainly bc of vicariance events → glaciers physically separated pops fr ea/o.
T/F: Polyploidy can result in sympatric speciation
TRUE
Polyploidy can result in sympatric speciation
T/F: Allopatric speciation is common bc gene flow prevents genetic divergence in sympatric speciation.
TRUE
Allopatric speciation is common bc gene flow prevents genetic divergence in sympatric speciation.
Many groups of organisms form _______ in which members of diff species meet and mate, producing at least some offspring of mixed ancestry.
Many groups of organisms form hybrid zones in which members of diff species meet and mate, producing at least some offspring of mixed ancestry.
- Over time, hybrid zones may remain stable, barriers reinforced (↓ reprod), or barriers break down (↑ reprod).
T/F: speciation must be driven by many genes
FALSE
speciation can be driven by few OR many genes
T/F: The last ice age produced many different species mainly because populations dispersed and colonized new habitats.
FALSE
The last ice age produced many diff species mainly bc of vicariance events; the glaciers physically separated pops fr ea/o.
Which of the following statements about reinforcement is true?
- Increases # of intermediate phenotypes.
- Also called dispersive selection.
- A type of natural selection.
- Decreases morphological diff b/w two incipient species.
Which of the following statements about reinforcement is true?
- Increases # of intermediate phenotypes.
- Also called dispersive selection.
- A type of natural selection.
- Decreases morphological diff b/w two incipient species.
Reinforcement—aka disruptive selection—favors extreme phenotypes over intermediate phenotypes.
Allopatric speciation can begin w a _______ event, in wh a geo barrier such as water isolates a population, or a ________ event, in wh a subset of a population migrates to a diff habitat.
Allopatric speciation can begin w a vicariance event, in wh a geo barrier such as water isolates a population, or a dispersal event, in wh a subset of a population migrates to a diff habitat.
