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Biology 4th Block Room 128
Mr. R. Bair Biology Teacher
Mrs. MV Smith Resource Teacher
Name the five forces that cause microevolution
Date: April 25 & 28, 2008
Drill
Test /quiz tomorrow
Microevolution: change in the frequency of alleles
1) Natural Selection/survival of the fit enough
2) Mutation- 1 allele becoming another due to a mutation
3) Genetic Drift-chance event
4) Genetic Flow-migration of organisms
5) Non-random mating
a.
b.
c.
d.
Naturalist on ship
Went to Galapagos Islands, Darwin where most important obsrvations took place
i.
observed finches.
Every island had its own type of finch
Ideas of Adaptive Radiation (Finch/Bird)
These finches, better known as 'Darwin's Finches' illustrated adaptive radiation. This is where species all deriving from a
common ancestor have over time successfully adapted to their environment via natural selection.
Previously, the finches occupied the South American mainland, but somehow managed to occupy the Galapagos
islands, over 600 miles away. They occupied an ecological niche with little competition.
As the population began to flourish in these advantageous conditions, intraspecific competition became a factor, and
resources on the islands were squeezed and could not sustain the population of the finches for long.
Biology 4th Block Room 128
Mr. R. Bair Biology Teacher
Mrs. MV Smith Resource Teacher
Due to the mechanisms of natural selection, and changes in the gene pool, the finches became more adapted to the
environment, illustrated by the diagram below.
As competition grew, the finches managed to find new ecological niches, that would present less competition and allow
them, and their genome to be continued.
As indicated by the diagram above, the finches adapted to take advantage of the various food sources available on the
island, which were being used by other species. Over the long term, the original finch species may have disappeared,
but by diversifying, would stand a better chance of survival.
All in all, the finches had adapted to their environment via natural selection, which in turn, has allowed the species to
survive in the longer term, the prime directive of any species
http://www.biology-online.org/2/15_adaptive_radiation.htm
Environment drives the change
e. Darwin back to England
f. Malthus=population grow faster than food supply
i. Competition for food
ii. Organisms that compete the best survive
 Darwin gets home and read a book by Thomas Malthus
This idea leads to Darwin to his ideas of Natural Selection
g. Darwin used the term natural selection to describe his theory of evolution. Natural selection is the way organisms
that are best suited to an enviroment survive. These offspring can pass their helpful traits to their offspring.
h. Darwin came up with the idea of Natural Selection
i. Natural Selection= those best suited to an enviroment will have a better chance of passing down their genes.
(know this)
His book “On the Origin of the Species”
Different types of finches on different islands. That they adapted to their enviroment.
Best suited to their enviroment are better to survive and pass down to their
genes
Darwin's theory of evolutionary selection holds that variation within species occurs randomly and that the survival or extinction of
each organism is determined by that organism's ability to adapt to its environment. He set these theories forth in his book called,
"On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life" (1859) or
"The Origin of Species" for short. After publication of Origin of Species, Darwin continued to write on botany, geology, and
zoology until his death in 1882. He is buried in Westminster Abbey.
Darwin's work had a tremendous impact on religious thought. Many people strongly opposed the idea of evolution because it
conflicted with their religious convictions. Darwin avoided talking about the theological and sociological aspects of his work, but
other writers used his theories to support their own theories about society. Darwin was a reserved, thorough, hard working scholar
who concerned himself with the feelings and emotions not only of his family, but friends and peers as
well.http://www2.lucidcafe.com/lucidcafe/library/96feb/darwin.html
j.
Adaption – a characteric passed down that will allow offspring to deal better with their enviroment.
Characterics passed down that will be benfificial to the enviroment
Survival is not random, but depends the heritable characteristics of individuals.
Individuals who inherit characteristics that make them good enough to survive are likely to leave more offspring.
Biology 4th Block Room 128
Mr. R. Bair Biology Teacher
Mrs. MV Smith Resource Teacher
Microevolution

Change in the frequency of alleles in a population over generations (short time period)
List 2 forms o evidence for evolution?
1. Comparative anatomy
2. Comparative embryology
3. All living things have DNA
4. Cells
5. Fossil Evidence
6. DNA Code
Ancestor- the people that came before you!
What cause of evolution is responsible for the moths being darker in the city and lighter inn the county.
Small change in the frequency of alleles I a population over generations
Kettelwell’s Moths
Industrial Revolution
 Darkened Trees
 City moths observed to be lighter
 Country moths observed to be lighter
Selection Pressure Kettlewell’s moths
 Industrial Revolution
• Darkened Trees
• City moths observed to be darker
• Country moths observed to be lighter
 Selection Pressure
• Trees Darker in the city by Soot
Biology 4th Block Room 128
Mr. R. Bair Biology Teacher
Mrs. MV Smith Resource Teacher
Forces Which Cause Microevolution
 Natural Selection
 Those best suited to the environment will survive
 Survival of the fit enough

Trees darkened in the city soot
1. This process supplies the new genetic material for
evolution
2. Long term time scale events which crate an destroy
species
3. Short term events which change frequency of
alleles/genotypes and traits/phenotypes
4. Movement of genes into or out of a population
5. chance occurs which change the frequency of alleles
c. Mutation
B. Macroevolution
A. Microevolution
E. Gene Migration
D. Genetic Drift
Biology 4th Block Room 128
Mr. R. Bair Biology Teacher
Mrs. MV Smith Resource Teacher
Forces Which Cause Microevolution





Natural Selection
Mutation
Gene Flow (Migration)
Genetic Drift chance (freak accident)
Non-Random Mating
Natural Selection
Genetic Drift
Mutation
Gene Flow (Migration)
Non-random mating-mate is selected (different cultures)
The Dynamics of Speciation - Gradualism or Punctuated Equilibrium?
A current debate is whether new species arise gradually at a constant rate or in bursts of speciation that may
coincide with environmental change.
Evidence for Evolution
Fossils (Vestigial Trait- trait that is useless to the organism but is left over from evolution
Comparative Anatomy
Comparative Embryology
Comparative Genomics (DNA)
Biology 4th Block Room 128
Mr. R. Bair Biology Teacher
Mrs. MV Smith Resource Teacher
Biology 4th Block Room 128
Mr. R. Bair Biology Teacher
Mrs. MV Smith Resource Teacher
Inference 3: The unequal ability of individuals to survive and reproduce leads to a gradual change in a population, with
favorable characteristics accumulating over generations.
These three inferences are a statement of Darwin’s Theory of Evolution.
Divergent evolution-two organisms becoming less alike through evolutionary changes
Convergent evolution-two organisms becoming more alike through evolutionary changes
Vestigial Trait=trait which is left over from evolution-serves no purpose
Snakes-vestigial leg bones
Human-Vestigial organ-appendix
Convergent evolution
Convergent evolution is the emergence of biological structures or species that exhibit similar function and appearance
but that evolved through widely divergent evolutionary pathways. The similarities that are shared in the case of
convergent evolution are not the result of evolution from a common ancestor sharing those similarities. Instead, the
similarities are typically explained as the result of common adaptive solutions to similar environmental pressures.
http://www.iscid.org/encyclopedia/Convergent_Evolution