What is Cultural Diversity?. How would you define cultural diversity?
How Diversity Evolves
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Transcript of How Diversity Evolves
How Diversity Evolves
Macroevolution
The evolution of large scale diversity
Evolutionary novelties Wings, feathers,
brain sizes
Speciation: origin of new species
What is a species?
The morphological species concept: if it looks like a duck, and quacks like a duck…
What is a species?
The morphological species concept:
Mature leaves of arrowhead plants (Sagittaria sagittifolia)
What is a species?
The biological species concept: groups of interbreeding natural populations that are reproductively isolated from other such groups.
What problems might exist with this definition?
What is Speciation?
For speciation to occur, populations must attain reproductive isolation.
Genetic Divergence: when populations become reproductively isolated.
Reproductive Isolating Mechanisms
Any heritable features that prevent interbreeding between populationsIsolating mechanisms can be physical (body form), physiological (body function), or behavioralIsolating mechanisms can be prezygotic or postzygotic.
Note: a zygote is a fertilized egg.
Reproductive Barriers
Prezygotic Isolation
Temporal (reproduce at different times)
Prezygotic Isolation
Behavioral (courting behaviors are different)
Bird courtship behavior include visual, acoustic and tactile rituals that identify members of the same species.
Prezygotic Isolation
Mechanical (differences in reproductive organs)
Plants and their pollinators
Prezygotic Isolation
Habitat (same area but different habitats)
Microhabitats of Manzanita in Nevada
Prezygotic Isolation
Gametic Mortality (egg & sperm incompatibility)
Correct chemical signal needed for successful fertilization
Postzygotic Isolation
If fertilization does occur the embryo is often weak and dies.
In others, hybrids are vigorous but sterile.
Mules are produced by a male donkey and female horse.
Mechanisms of Speciation
Allopatric speciation: geographically isolated by a physical barrier.
Sympatric speciation: species form within home range of an existing species.
Allopatric Speciation
“allo” = different; “patric” = lands
Antelope squirrels and the Grand Canyon
Evidence for Allopatric Speciation
Allopatric Speciation
Archipelagos island chain and adaptive radiation low competition and
predation abundant habitats
and resources
Sympatric Speciation
“sym” = together
Cichlids of Lake Barombi Mbo Many species by
feeding modes (open water, bottom feeders, shoal feeders)
Sympatric Speciation
Polyploidy
How does this happen? Improper separation
during meiosis & mitosis
50% of all flowering plants are polyploidy
Animal problems
The Evolution of Wheat
Evolutionary Trees and Rates of Change
Trees summarize information about the relationship among species over time.
Two types of models:Gradual model: branches at slight angles
to show slow changes over timePunctuation model: horizontal branches
show abrupt speciation followed by stable conditions
Evolutionary Trees and Rates of Change
Macroevolution and “Evo-Devo”
Genetic changes in developmental biology
Homeotic genes Control timing, rate, and
spatial patterns in embryos
Subtle changes can have profound effects
Paedomorphosis Axolotl
“Evo-Devo” Research
Macroevolution and Earth’s History
Macroevolution and Historical Events
Evolution Today?