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!