Speciation Notes

Speciation

• Speciation - a process of producing two individual species from one

• Species - members of the population that interbreed to produce fertile offspring

Three Causes of Speciationa. Geographic isolation

b. Reproductive isolation• Organisms may

appear to be alike and be different species. These meadowlarks look almost identical, yet do not interbreed with each other—thus, they are separate species.• Organisms may look

different and yet be the same species. These two ants are sisters—two ants of the species Pheidole barbata, fulfilling different roles in the same colony.

c. Change in chromosome number• Polyploid species result from nondisjunction

(chromosomes fail to separate properly) during meiosis or mitosis.

Prezygotic and Postzygotic barriers

• Prezygotic Barriers: 1)Temporal isolation (2 species reproduce at different times

of day, year or season.

2) Habitat Isolation

3) Behavioral Isolation (different courtship behaviors)

• Postzygotic Barriers:Hybrid inviability and sterility (ie. Mules)

So, how long does it take for a new

species to evolve?

Rates in Speciation

a. Polyploid speciation only takes one generation

b. Gradualism- the idea that species evolve at a slow, steady rate, with small, adaptive changes gradually accumulating over time.

c. Punctuated Equilibrium - argues that speciation occurs quickly, in rapid bursts, with long periods of genetic equilibrium in between.

• Caused by changes in the environment, which rapidly change a population’s gene pool

• i.e. Raise in temperatures, introduction of competitive species, reproductive isolation

Types of evolution

• Gradualism

• Punctuated Equilibirum

Do patterns of evolution always look

the same?

Why might they be different? What causes the evolution of

new species?

Patterns of Evolutiona. Divergent Evolution-

when species that were once similar diverge (become more and more different)

b. Adaptive Radiation- When one species evolves into an array of different species to fit environmental habitats

c. Convergent Evolution - when species that were unrelated evolve similar characteristics

• Occurs when unrelated species occupy similar environmental habitats in different areas of the world. Similar environmental pressures and similar natural selection pressures allows different species to look alike.

Where did the first living thing come from?

• Stanley Miller (Exobiology)

– Student at the University of Chicago (now professor at UCSD)

– Designed experiment showing formation of organic compounds (amino acids)

– http://www.ucsd.tv/miller-urey/

– Check out the Stanley Miller interview here

What is Exobiology?

• http://www.chem.duke.edu/~jds/cruise_chem/Exobiology/index.html