Chapter 24 Flashcards
How do prezygotic barriers block fertilization from occurring?
- stop different species from trying to mate
- prevent successful mating
- disrupt fertilization if mating works
Consists of changes in allele frequency in a population over time
Microevolution
Refers to broad patterns of evolutionary change above the species level
Macroevolution
States that a species is a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring.
Biological species concept
What does the biological species concept say?
A species is a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring. They do not breed successfully with members of other populations.
The existence of biological factors, or barriers, that impede two species from producing viable, fertile offspring
Reproductive isolation
The offspring of crosses between different species
Hybrids
When two species do not encounter each other at all (or very rarely) because they live in different habitats. They are not isolated by physical barriers,but they still do not encounter each other often because they live in different habitats
Habitat isolation
When species that breed at different times, seasons, or years cannot mix their gametes.
Temporal isolation
When behaviors that are unique to a species, such as courtship rituals, are effective barriers to mating.
Behavioral isolation
When morphological differences can prevent successful completion of mating
Mechanical isolation
When the sperm of one species may not be able to fertilize eggs of another species
Gametic isolation
List 3 post-zygotic barriers
1) reduced hybrid viability
2) reduced hybrid fertility
3) hybrid breakdown
What are the 5 types of isolation?
1) Habitat
2) Temporal
3) Behavioral
4) Mechanical
5) Gametic
What are the two types of speciation?
Allopatric and sympatric
Gene flow is interrupted or reduced when a population is divided into geographically isolated subpopulations. Give an example.
Allopatric speciation; Example: the flightless cormorant (bird) from the Galapagos probably originated from a flying species on the mainland.
What are the 3 factors that can cause sympatric speciation to occur by reducing gene flow?
1) polyploidy
2) sexual selection
3) habitat differentiation
Is polyploidy (presence of extra sets of chromosomes) more common in plants or animals?
Plants
A species with multiple sets of chromosomes derived from different species
Allopolyploid
An individual with more than two chromosome sets, derived from a single species
Autopolyploid
A region in which members of different species mate and produce hybrids
Hybrid zone
The origin of new species
Speciation
Broad patterns of changes in species
Macroevolution
Speciation that happens in populations that geographically overlap
Sympatric speciation
Extra sets of chromosomes because of accidents during cell division
Polyploidy
List the 3 possible outcomes when species meet in a hybrid zone
Reinforcement
Fusion
Stability
T or F: Sometimes speciation requires change in one or many genes
True
Changes in allele frequency in a population over time
Microevolution
How is a hybrid created?
When different species breed
What are two forms of reproductive isolation barriers?
Prezygotic and postzygotic
What are some examples of prezygotic barriers?
Habitat isolation, temporal isolation, behavioral isolation, mechanical isolation, gametic isolation
What are some examples of postzygotic barriers?
Reduced hybrid viability, reduced hybrid fertility, hybrid breakdown
Gene flow is interrupted or reduced when a population is divided into geographically isolated sub-populations
Allopatric speciation
Speciation that takes place in geographically overlapping populations
Sympatric speciation
Periods of apparent status punctuated by sudden change
Punctuated equilibria
T or F: Regions with many geographic barriers typically have more species than regions with fewer barriers
True
Give two examples of viable offspring that surpass prezygotic barriers
1) Mule
2) Donkey
What do biologists compare when grouping organisms?
Morphology, physiology, and DNA sequence
The making of a new species
Speciation
What occurs when hybrids survive but are sterile?
Reduced hybrid fertility
Where reinforcement occurs, should reproductive barriers be stronger for sympatric or allopatric species?
Sympatric
Views a species in terms of its ecological niche
Ecological species concept
The existence of biological factors (barriers) that impede two species from producing viable, fertile offspring
Reproductive isolation
