Chapter 14- Origin of Species
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Adaptive radiation
Allopatric speciation
Behavioral isolation
Biological species concept
Ecological species concept
Gametic isolation
Genealogical species concept
Gradualist model
Habitat isolation
Hybrid breakdown
Hybrid inviability
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Hybrid sterility
Mechanical isolation
Morphological species concept
Polyploidy cells
Punctuated equilibrium
Reproductive barrier
Speciation
Sympatric speciation
Taxonomy
Temporal isolation
Something to remember:
• Most of the time evolution is gradual,
sometimes though it can be observed over
several generations
Speciation
• Evolution of a new species
– Biological species conceptpopulation or group of
populations whose members can
interbreed and produce fertile
offspring
• Ring species- forms a ring
around geographic feature
(may cause speciation)
Speciation con’t
– Morphological species concept- classify species by measureable
phenotypic traits
– Genealogical species concept- defines species by a set of
organisms with unique genetic history
– Ecological species concept- idendifies by ecological niche (role
in env)
Reproductive barriers
• Keep species separate
• Can cause speciation
– Ex: mosquitoes in London Underground
Prezygotic reproductive barriers
• Prevents mating
• Temporal isolation- mating/flowering occurs at
different times/seasons
• Habitat isolation- populations live in different
habitats and don’t meet
• Behavioral isolation- no attraction between sexes
• Mechanical isolation- genitalia structure/flowers
differs, prevents copulation
• Gametic isolation- gametes die before uniting
Postzygotic reproductive barriers
• Prevents development of fertile adults
• Hybrid inviability- zygotes fail to develop or reach
sexual maturity
• Hybrid sterility- don’t produce functional gametes
• Hybrid breakdown- offspring of hybrids are weak or
infertile
Geographic isolation
• Causes speciation
• Allopatric speciation
• Ex: lakes dry up into smaller lakes, fish can’t move from
one to another
• Ring species sometime end up as new species
• Occurs when gene pool changes to create a
reproductive barrier
• More likely to happen in small, isolated pop’s
Geographic isolation con’t
• Galapagos finches
• Adaptive radiation- evolution of many
species from a common ancestor due to
new environments
Sympatric speciation
• Reproductive isolation develops and new species arise
without geographic separation
– Widespread in plants
• Accident in meiosis produces cells with extra chromosome
sets
• Polyploid cells- cells that has more than 2 sets of
chromosomes
• 2n gametes can self-fertilize and produce a 4n plant
• Production of a 4n cell is an instant speciation event,
because it now can’t reproduce with parent species
– Ex: strawberries
• 2n gamete fused with 1n gamete produces 3n which is sterile
b/c odd chromosomes can’t form homologous pairs
Sympatric speciation con’t
– Chemicals can be used to
induce these errors to
hybridize plants
• Ex: yield of wheat with
resistance of rye
– Polyploid crops: oats, potatoes,
bananas, peanuts, barley,
plums, apples, sugarcane,
coffee, wheat, cotton,
strawberries
– 25-50% of plant species are
polyploid
Tempo of speciation
Tempo of Speciation con’t
• Gradualist- populations evolve gradually
as they become adapted to new
environments
– Very few fossil sequences show the steady
accumulation of small changes
• Punctuated equilibrium- long periods of
little change with abrupt episodes of
speciation
• * although evolution is jumpy when viewed
as a whole its relatively steady