Macroevolution in action!
Formation of a new species… what
is a “Species”?
 Many definitions of species exist
 Morphological – based on finding physical/structural
similarities


Advantages: applies to both sexual/asexual organisms
Disadvantage: subjective
 Ecological – based on the niche of an organism (its role in
ecosystem)
 Phylogenetic – based on an animal’s ancestry/genetic
history

Compare physical characteristics/molecular similarities
 Paleontological – focus on morphologically-discrete species
known only from the fossil record
Biologic Species concept
 Defined as:
 Population/group of populations that can successfully
interbreed, producing viable, fertile offspring
 Speciation often requires major genetic changes
 Hinges on reproductive isolation – something that
keeps two groups that would normally interbreed from
doing so
Allopatric vs. Sympatric Speciation
 Allopatric - “away from one’s fatherland”
 Physical barrier divides 1 population into two
 Mountains, channels, islands, rivers, lava flows, etc.
 Leads to a divergence of the gene pool through
mutations, selection, etc.
 If enough time passes, will likely be unable to mate if
reintroduced
Sympatric Speciation
 Species evolves while alongside its fellow organisms.
 How?



Polyploidy
Habitat differentiation
Sexual selection
 Reminder: zygote = fertilized egg
Reproductive Isolation
 Leads to speciation…
 …By preventing gene flow among populations
 Prezygotic Isolation – prevents fertilization
 Mechanical
 Habitat
 Behavioral

Mating songs
 Temporal
 Gametic
 Polyploidy (plants)
Mechanical
Habitat
Behavioral
Temporal
Gametic
 Post-Zygotic Isolation
 Fertilization has occurred, but the hybrid isn’t viable,
can’t reproduce

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Reduced hybrid inviability – development/survival of hybrids
is impaired
Reduced hybrid fertility – hybrids fail to produce functional
gametes
Hybrid breakdown – offspring of hybrids are feeble/infertile
Cool stuff!
(Male partner listed first)
Camel + Llama =
Cama
Tiger + lion =
Tiglon!
Lion + tiger =
Liger
Zebra + horse =
Zebroid
Donkey + horse =
Mule
Horse + Donkey =
Hinney
False Killer Whale + Dolphin
Wolphin
Leopard + Lion =
Leopon
Grizzly + Polar Bear
Grolar/ Pizzly
Goat + Sheep =
Geep
Cattle + Bison=
Beefalo
Human + Chimpanzee =
Humanzee?