Patterns In Evolution

Two Major Patterns Observed

Macroevolution

• Macroevolution: evolution of groups larger than an individual species. Takes a long period of time

Macro= looking at bigger sections of evolution

The 6 Patterns that influence how macroevolution occurs are…1-Mass Extinctions -2-Adaptive Radiation3-Convergent or Divergent Evolution4-Co-evolution5-Punctuated Equilibrium6-Gradualism

Mass Extinction

• Loss of complete huge number of species and ecological systems

• Causes could be: – large asteroid during the Cretaceous period l

throwing huge amonts of dust and vapor altering global climate affects organisms…like dinosaurs

– Volcanic eruptions, continental shifts, changing sea levels, other major environmental changes

Adaptive Radiation

• A single species or a small group of species evolved into several different forms and live in different ways– Darwin’s Finches

Convergent Evolution

• Unrelated organisms come to resemble each other

• This effect is due to different organisms undergoing adaptive radiation in different places BUT in ecologically similar environments

• Face similar environmental demands

• Examples: streamlined bodies and flippers of water organism ( shark, dolphin, seals, penguins)

Convergent Evolution

Divergent Evolution

• Because of different environments organisms begin to look more and more different over generations

• Ex) Dog and Wolf

Coevolution

• Two species evolve in response to each other due to ecological interactions– Flowers and insects(Madagascar orchid and hawk

moth)– Plants and plant eating insects: plants have

developed poisons to prevents plant eating insects from feeding on them. Natural selection in insect eating plant favored variants that could alter, inactivate, or eliminate the poisons both organisms change in response to each other

Coevolution

Macroevolution is also influenced by… RATE

• Rate= how quickly the evolution occurs Quick= Punctuated Equilibrium

Gradual= Gradualism

Punctuated Equilibrium

• Pattern of long, stable periods interrupted by brief periods of rapid changes. Punctuated on the right

When does this type of evolution occur?

• Small populations become isolated from the main part of the population .Population changes quicker because genetic changes can spread more quickly among fewer organism

• Small group of organisms migrate to a new environment GALAPAGOS FINCHES

Gradualism

slow change in a population over a long periodof time

Microevolution

• Quick change in gene frequency within a population.

• Quicker then macroevolution. • observed over short periods of timeExamples: Antibiotic resistance, Pesticide resistance

Microevolution

Antibiotic resistance

Bacteria can evolve quicker when they are resistant to the antibiotic. This is because of genetic shuffling due to their quick reproduction rateswhich means more chances for mutation (changes) less likely to be killed by antibiotics if they have changed their genes SO SMART!!

http://www.pbs.org/wgbh/evolution/library/11/2/quicktime/e_s_6.html

Microevolution example• Imagine that you go to the mountaintop this year, sample these beetles,

and determine that 80% of the genes in the population are for green coloration and 20% of them are for brown coloration. You go back the next year, repeat the procedure, and find a new ratio: 60% green genes to 40% brown genes.

• You have detected a micro evolutionary pattern: a change in gene frequency. A change in gene frequency over time means that the population has evolved.

What caused the microevolution?

• Mutations in genes• Migration of organism• Genetic Drift of alleles• Natural Selection of the environment for a

given trait