Transcript Natural Selection in Action

How effective is Natural Selection?
Micro-evolution
small evolutionary changes within species
Macro-evolution
large evolutionary changes that result in
classification as a new species
Agricultural Pests
Alternating Crops
Farmers alternate corn & soy; corn-borers have
evolved to remain dormant one season….or more
Agricultural Pests
Winnowing & Sieving
Weed seeds have evolved sizes & shapes of the
predominant crop
Weeding
Weed leaf shape & color has evolved to match the
crop where it grows
Rice
Vetch
(weed)
Lentil
Barnyard Grass
(weed)
Agricultural Pests
Pesticides
Insects rapidly evolve tolerance, via many
mechanisms…..
1960 - 100 species tolerant
1970 - 313 species tolerant
1980 - 829 species tolerant
Tolerance to Heavy Metals
Agrostis grass
• Small strip mines abandoned for
fifty years
• Iron, copper, zinc, lead: greater
than 2000 ppm
– (normal is less than 10 ppm)
• Each mine with its own mix of
metals
• Only 3 plants per 1000 could
tolerate these conditions
Tolerance to Heavy Metals
Agrostis grass
• Mine plants’ offspring tolerant of metals particularly those of the mine of origin
• Mine plants also grow well in unpolluted soil
• However, mine plants are displaced when
competing against non-mine plants in unpolluted
soil
• Mine plants have evolved earlier flowering times
- effectively avoid crossing with non-mine plants!
Protective Coloration
The Pepper moth
• All populations originally whitish
• In polluted areas, black moths increases from 1%
to 95% in 50 years
Protective Coloration
The Pepper moth
Kettlewell’s experiment
• Release marked white and black moths
• Capture moths after a period of time
• Is the proportion of recaptures different
between the two forms?