macroevolution: evolution of a new species. levels of evolutionary study microevolution: examines...
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Macroevolution: Evolution of a New Species
Levels of Evolutionary Study• Microevolution: examines changes to the
genes (alleles) within populations– Population Genetics: studies the changes in
the numbers & types of alleles in a population• Examines evolution within a species.• Small changes that do not lead to new species, but
can lead to new variations.
• Macroevolution: examines the evolutionary changes that create new species– Speciation: the formation of new species
over time
•Species: a group of organisms that can interbreed and produce fertile offspring
•Speciation: the evolution of new speices (by genetic change or change in form)– Occurs when members of a
similar populations can no longer interbreed!
Macroevolution
Methods of Speciation
• Geographic Isolation • Reproductive Isolation
– Genetic Isolation– Behavioral Isolation
• Chromosomal– Polyploidy– Hybridization
Methods of Speciation• Geographic Isolation: physical barriers
divide a population and prevent interbreeding
Beetles in Grassland Become Green
Beetles in Woody Habitat
Become Brown
Methods of Speciation• Reproductive Isolation--occurs when formerly
interbreeding organisms can no longer mate & produce fertile offspring– Genetic: genetic differences are too great to breed
successfully– Behavioral: mating behaviors or mating seasons
don’t allow for mating• Chromosome Numbers
– Polyploidy: any species with extra sets of chromosomes. Common in plants.• Can interbreed or self-fertilize, forming separate
species– Hybridization: when two closely related species
attempt to mate• Usually results in sterile offspring • Ex: donkey + horse = mule
Speed of Speciation
• Gradualism– Idea that species originate thru a slow,
gradual change of adaptations over long periods of time
• Punctuated Equilibrium– Idea that species can remain stable for long
periods of time until environmental changes cause many new species to appear • Speciation occurs in less than 10,000 years!
Patterns of Macroevolution
• Divergent Evolution• Convergent Evolution• Coevolution
• Species diverge or become increasingly distinct from one ancestral species
• Ex: Darwin’s finches
• Also called adaptive radiation
Divergent Evolution
Convergent Evolution• Process by which unrelated species
become similar as they adapt to similar environments
Ostrich
Africa
Emu
Australia
Rhea
South America
Coevlution
• When species who live in close contact evolve adaptations to one another’s existence.
Extinction!• When all the members of a species die
off or fail to reproduce– Estimated that 99% of all species that ever
lived have become extinct– Most extinctions are the
result of environmental change, can cause well adapted species to becomepoorly adapted!
– If the environment changes faster than a species can adapt, extinction can result!