Download Insect Evolution

10/1/2011
Insect Evolution
Part I: Macroevolution
Part II: Microevolution (now)
Diversity of Form and Function
DDT
DDT
What is DDT?
Prior to 1972 when its use was banned, DDT was a commonly used pesticide. Although it is no longer used or produced in the United States, we continue to find DDT in our environment. Other parts of the world continue to use DDT in agricultural practices and in disease‐control programs. Therefore, atmospheric deposition is the current source of new DDT contamination in our Great Lakes. DDT, and its break‐down products DDE and DDD, are persistent, bioacculumative, and toxic (PBT) pollutants
What harmful effects can DDT have on us?
• Probable human carcinogen • Damages the liver • Temporarily damages the nervous system • Reduces reproductive success • Can cause liver cancer • Damages reproductive system Source: EPA
DDT
Source: EPA
Pesticide Resistance
Why Are We Concerned About DDT?
• Even though DDT has been banned since 1972, it can take more than 15 years to break down in our environment. Fish consumption advisories are in effect for DDT in many waterways including the Great Lakes ecosystem.
Source: EPA
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Pesticide Resistance
in bed bugs
Pesticide Resistance
how does it happen?
http://www.npr.org/2011/01/19/133057071/be
d‐bug‐genome‐reveals‐pesticide‐resistance
Review
Definitions
• Gene – the functional unit of heredity
• Allele – One of several forms of the same gene, differing by mutation of the DNA sequence.
• Locus (plural “loci”) – A site on a chromosome occupied by a specific gene
• Genotype – The set of genes possessed by an individual organism. Can also be used to refer to its genetic composition at a specific locus or set of loci singled out for discussion.
• Phenotype – The morphological, physiological, biochemical, behavioral, and other properties of an organism manifested throughout its life.
Gene
Protein
Physical Appearance
Genotype
e.g. AABb versus AaBb
Phenotype
Another way to think about phenotype is as any
observable characteristic of an organism
e.g., height, hair color,
high cholesterol, preferences
Genotype + Environment = Phenotype
Terms to know
Adaptations – the many evolved properties of organisms that enable them to survive and reproduce
Evolution!
• Evolution, more precisely, is changes in population‐
level allele frequencies (genetic changes) through time. • Evolution is a process that occurs at the level of populations, not at the level of individuals.
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Populations change over time
What did Darwin propose?
What about his ideas was new?
** the allele frequencies
present in a population today
are not the same
as those that were present in
that population five hundred
thousand years ago or even
last week.
Natural Selection
Natural Selection
•A proposed mechanism for evolution
•Occurs when some organisms in a population leave more offspring than others
•A proposed mechanism for evolution
•Occurs when some organisms in a population leave more offspring than others
•To result in evolution, variation, reproduction, and inheritance must be present
Natural selection
Natural selection
A process by which heritable traits conferring survival and reproductive advantage to individuals tend to be passed on the succeeding generations and become more frequent in a population while traits less favorable are eliminated
A process by which heritable traits conferring survival and reproductive advantage to individuals tend to be passed on the succeeding generations and become more frequent in a population while traits less favorable are eliminated
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Natural selection
Natural selection
A process by which heritable traits conferring survival and reproductive advantage to individuals tend to be passed on the succeeding generations and become more frequent in a population while traits less favorable are eliminated
A process by which heritable traits conferring survival and reproductive advantage to individuals tend to be passed on the succeeding generations and become more frequent in a population while traits less favorable are eliminated
Natural selection
A process by which heritable traits conferring survival and reproductive advantage to individuals tend to be passed on the succeeding generations and become more frequent in a population while traits less favorable are eliminated
Natural Selection
Natural Selection
Variation – natural populations often have a lot of phenotypic variation!
These are all
Males of the
Same species!
Variation – natural populations often have a lot of phenotypic variation!
But, can some of this variation be inherited?
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“Fitness”
Fitness – the number of offspring produced that survive to reproductive age
Artificial selection – Selection by humans. The criterion for “fitness” is a trait humans choose.
Artificial selection
• Selective breeding carried out by humans to
produce a desired change in phenotype.
Artificial selection
Teosinte (left) and
its modern
descendent, corn,
a product of
artificial selection
A variety of vegetables of the
Brassica oleracea species
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Artificial selection
What can cause Evolution?
•
•
•
•
•
Genetic Drift
Genetic drift and selection are the two most important causes of allele substitution in populations
Genetic Drift
Definition: Random change in allele frequencies or genotypes in a population
Most common in small populations or in founder events.
Genetic Drift
Gene Flow (immigration)
Mutation
Natural Selection
Sexual Selection
Genetic drift
Occurs because populations are finite in size.
Genetic Drift
Founder effects
Founder effects – The principle that the founders of a new population
carry only a fraction of the total genetic variation in the source
population
Some alleles are lost at random.
e.g. An island population
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Genetic Drift
Genetic Drift
Founder effects
Founder effects
Founder effects – The principle that the founders of a new population
carry only a fraction of the total genetic variation in the source
population
Some alleles are lost at random.
e.g. Another continent
Genetic drift in natural populations
case study: the argentine ant
In rare cases the reduction of genetic variation may actually benefit a population
Genetic drift in natural populations
case study: the argentine ant
On NPR: http://www.npr.org/templates/story/story.php?storyId=1141932 and http://www.npr.org/templates/story/story.php?storyId=6084197
Genetic drift in natural populations
case study: the argentine ant
Genetic drift in natural populations
case study: the argentine ant
The Argentine ant passed through a genetic bottleneck during its introduction to California. Overall, the number of alleles in the • A boat brought argentine ants to the USA • This founder event created a founder effect –
low genetic diversity in the new population (evolution through genetic drift)
• Because the ants all “smell” similar now, they aren’t aggressive to other colonies
• Thus, they cooperate instead of destroying each other.
introduced range is half that found in the native range.
PNAS | May 23, 2000 | vol. 97 | no. 11 | 5948-5953
Reduced genetic variation and the success of an invasive species
Neil D. Tsutsui, Andrew V. Suarez, David A. Holway, and Ted J. Case
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Sexual Selection
References on Evolution
Occurs when mating is non‐random Evolution 101 (review of the basics):
http://evolution.berkeley.edu/
http://www.pbs.org/wgbh/evolution/
References on Evolution
Advanced Textbooks: Futuyma, D.J. 2005. Evolution. Sinauer Associates: Sunderland, MA.
Freeman and Herron 2007. Evolutionary analysis. Prentice Hall: NJ.
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