Studied by 14 people
What is at the focal point of evolutionary theory?
speciation
What must evolutionary theory explain?
How new species originate and how populations evolve
Microevolution
Consists of changes in allele frequency in a population over time
Macroevolution
Refers to broad patterns of evolutionary change above the species level
What can be used to define a species?
Biological Species concept
Morphological species concept
Ecological species
Phylogenetic species concept
Reproductive Isolation
The existence of biological factors (barriers) that impede two species from producing viable, fertile offspring
Hybrids
The offspring of crosses between different species
How can reproductive isolation be classified?
By whether factors act before or after fertilization
What the are prezygotic barriers?
Habitat Isolation
Temporal Isolation
Behavioral Isolation
Mechanical Isolation
Gametic Isolation
What are the postzygotic barriers?
Reduced Hybrid Viability
Reduced Hybrid Fertility
Hybrid Breakdown
What is Hybrid Breakdown?
Two related species can hybridize, and their F1 offspring are fertile.
But successive generations (F2 and beyond) suffer lower viability or fecundity.
Thus, they cannot become an established population.
What is an example of hybrid breakdown?
Rice cultivars
Cultivars have been artificially selected and some are related enough to hybridize
F1 = fertile and viable
F2 = stunted and sterile
What is Hybrid Sterility
Example in explanation
Tigers and Lions are sister taxa, but seperate for millions of years
Their hybrid offspring are viable and robust, but sterile.
Chromosomes are not homologous, so they don’t migrate during meiosis normally
What is Hybrid Inviability
Example in explanation
Tigers and Lions are sister taxa
Their hybrid offspring are viable and robust, but sterile
A mating between a lion and leopard will produce sterile hybrids
A mating between a tiger and leopard will produce inviable hybrids
Zygotes divide, but embryo miscarries or is stillborn
What types or organisms can’t the biological species concept be applied to?
Why?
Fossils or asexual organisms (including all prokaryotes)
The biological species concept emphasizes absence of gene flow
Can gene flow occur between distinct species?
Yes; grizzly bears and polar bears can mate to produce “grolar bears”
What concepts emphasize unity within a species rather than separateness of different species?
Morphological Species Concept
Ecological Species Concept
Phylogenetic Species Concept
What does the morphological species concept define?
What does it apply to?
Defines a species by structural features
It applies to sexual and asexual species but relies on subjective criteria
What are the different bacteria shapes?
Spheres (cocci), Rods (bacilli), Spirals
What does the ecological species concept view?
What does it apply to?
It views a species in terms of its ecological niche
It applies to sexual and asexual species and emphasizes the role of disruptive selection
What does the phylogenic species concept define?
What does it apply to?
It defines a species as the smallest group of individuals on a phylogenetic tree
It applies to sexual and asexual species, but it can be difficult to determine the degree of difference required for separate species (DNA Evidence)
Based on DNA similarities
What are the ways in which speciation can occur?
Allopatric Speciation
Sympatric Speciation
What is allopatric speciation?
A population forms a new species while geographically isolated from its parent population.
What is sympatric speciation?
A subset of a population forms a new species without geographic separation.
Evidence of allopatric speciation?
15 pairs of sibling species of snapping shrimp (Alpheus) are separated by the Isthmus of Panama
These species originated 9 to 13 million years ago, when the Isthmus of Panama formed and separated the Atlantic and Pacific waters
Barriers to reproduction are ________; separation itself is not a _________ _________
Barriers to reproduction are intrinsic; separation itself is not a biological barrier
Where does speciation take place in sympatric speciation?
Geographically overlapping populations
What is behavior isolation?
Courtship rituals and other behaviors unique to a species are effective barriers
What is polyploidy?
Where is it common?
How does it occur?
The presence of extra sets of chromosomes due to accidents during cell division
Polyploidy is much more common in plants than in animals
Polyploidy conditions occur through meiosis errors
What is an autopolyploid?
An individual with more than two chromosome sets, derived from one species
Common polyploid plants
State the type
Seedless Watermelon = triploid
Banana = triploid
Blackberries = tetraploid
Peanuts = tetraploid
Sweet Potato = hexaploid
Wheat = hexaploid
Strawberry = octopoid
What is an allopolyploid?
A species with multiple sets of chromosomes derived from different species
What is the basic idea of the biological species concept?
That a group of organisms that can successfully interbreed and produce fertile offspring
What’s the difference between microevolution and macroevolution?
Macroevolution is broader, such as the evolution of lungs, or tetrapods.
Where can you determine that the species is different?
They may look alike, but there is some issue that prevents them from interbreeding.
What is habitat isolation?
Where organisms may be in the same environment, but in slightly different habitats so they never interact
In the water and on land
What is temporal isolation?
Different mating periods, such as the season, time of day, etc.
What is behavioral isolation?
Different courtship rituals
Dancing, singing
What is mechanical isolation?
Reproductive organs don’t line up
Such as when snail shells are in the opposite ways
What is gametic isolation?
They can mate, butter gametes aren't chemically compatible
The sperm and egg don’t merge, which means no zygote is made
Is geographic isolation the same as habitat isolation?
Nope
Are the species concepts perfect?
No, not all the time
What is reproductive isolation simply?
The absence of gene flow (intermitting, immigration, emigration)
What is the difference between allopatric and sympatric speciation?
Allopatric speciation is when a geological barrier prevents a population from interacting, so they are not able to reproduce with each other
The reproductive barriers cause speciation
Sympatric speciation is when a population’s organisms evolve into unique species by different evolutionary pathways in the same environment until they are reproductively isolated from each other
What type of organisms are usually polyploids?
Plants, not animals bc they are too complex
How to polyploidy conditions occur?
Errors in meiosis
Non normal meiosis
Explain an autopolyploid production
Both parents species are of the same species, and due to meiosis errors, their gametes have a full set of chromosomes. This then leads to an offspring with double the amount of chromosomes.
Failure to reduce chromosome # during meiosis
Explain an allopolyploid production
Two matings
One species(A) has a proper gamete and makes a zygote with a different species(B) whose gamete has had meiosis errors resulting in a gamete with a full chromosomal set. This hybrid then mates with an organism from species A. Species A again gives the proper gamete, and the hybrid has a meiosis error with a full chromosomed gamete. Together, they will make what the first mating should have properly had
Hybridize between two species, and not reduce chromosome #
What type of speciation are allopolyploids and autopolyploids?
Sympatric Speciation
What type of speciation is habitat differentiation (habitat isolation)
Why?
Sympatric because they are still in the same geographical area, just occupying slightly different habitats and niches
What can sexual selection be connected to?
What’s an example of this connection?
Behavioral isolation
A fish species’s slight was affected, changing how they saw the colors of other fish
This impacted the attraction between the fish species, eventually causing speciation
What can sexual selection drive?
Sympatric speciation
What is the punctuated equilibria?
A model that contrast with the model of gradual change
A long period of no change followed by rapid changes or vice-versa
What would be considered a short time vs. a long time in an evolutionary standpoint
Thousands of years vs. Millions of years
What did punctuated equilibria ‘solve‘?
Examples of species from the fossil record that appear suddenly, persist essentially unchanged for some time, and then apparently disappear
What macroevolution in relation to speciation?
The cumulative effect of many speciation and extinction events
Note 
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