Transcript Patterns In Evolution

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 Radiation
3-Convergent or Divergent Evolution
4-Co-evolution
5-Punctuated Equilibrium
6-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 period
of time
Microevolution
• Quick change in gene frequency within a
population.
• Quicker then macroevolution.
• observed over short periods of
time
Examples: 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 rateswhich 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