SPECIATION DEFINITIONS
Organisms are classified as the same species if they appear identical by anatomical criteria.
Morphological Speciation
The red deer, and elk are genetically compatible, and would (and do) interbreed when put together in a zoo condition, however, they are unable to do so naturally due to being located on different continents.
Allopatry
The basis of all genetic variation in organisms.
Mutations
Refers to an aspect of the environment, genetics, behavior, physiology, or ecology of a species that reduces or impedes gene flow from individuals of other species. These can be geographic or reproductive.
Isolating Barrier
Slide 11 - SI SESSION 12/6/2023
HARE VS. RABBIT
They are two different species!
Hares are larger, faster, and have longer ears + legs.
Rabbits are smaller, fluffier, and overall "cuter".
They even have different diets and social patterns.
The idea that species are the smallest possible groups whose members are descended from a common ancestor and who all possess defining or derived characteristics that distinguish them from other such groups.
Phylogenetic Speciation
Over time, a difference in elevation between water pools has caused a genetic divergence of two frogs species, who are unable to mate with each other due to inaccessibility.
Allopatry
Forces a diverged population to adapt to its new environment - become less similar to its original population.
Natural Selection
Provide me with an example of a pre-mating reproductive barrier!
Acceptable responses:
Behavioral isolation - differences in behavior that prevent members of different species from mating.
Ecological isolation - isolating barriers that are consequences of the ecology of different species (habitat, temporal, pollinator).
Mechanical isolation - Reproductive structures do not fit together mechanically, making it difficult for fertilization to occur.
SLIDE 12 - SI SESSION 12/6/2023
These are two different species! The one on the left is the American alligator, and the one on the right is the crocodile.
The evolution of reproductive barriers between populations by adaptation to different environments or ecological niches.
Ecological Speciation
Two birds, while genetically compatible and found in the same general location, typically do not interbreed due to the differences in song preference between species.
Sympatry
This evolutionary force is essential to speciation by decreasing genetic variation within a population but increasing genetic variation among populations.
Genetic Drift
Provide me with an example of a post-mating barrier!
Copulatory behavioral isolation - Behavior of an individual during copulation is insufficient to allow normal fertilization.
Gametic Isolation - Transferred gametes unable to fertilize eggs.
Slide 13 - SI SESSION 12/6/2023
WEASEL VS. STOAT
They are different species! Stoats are bigger and have long tails with fuzzy black tips - and weasels have a shorter tail that are the same color as their body. Stoats turn white in the winter - and they have different patterns of movement.
The idea that species are groups of actually (or potentially) interbreeding natural populations that are reproductively isolated from other such groups.
Biological Speciation
Two coral systems are able to release and spread their gametes over a large distance, mingling with distantly located reef systems. However, due to differences in release times and gametic incompatibility, they do not interbreed.
Sympatry
This evolutionary force disrupts speciation, by decreasing genetic variation among populations.
Gene Flow
Provide me with a postzygotic barrier!
Intrinsic barriers - Reflects a developmental problem in hybrids that is relatively independent of the environment. (Hybrid inviability, hybrid sterility - physiological & behavioral).
Extrinsic - Isolation depends on the environment (ecological inviability - cannot find and appropriate ecological niche & Behavioral sterility - cannot obtain mates).
SLIDE 14 - SI SESSION 12/6/2023
The one on the left is a Dorper sheep, and the one on the right is a Merino sheep! These two - while looking different, are two breeds of the same species!