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Biology 3300- Adaptation

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BIOL 3300
Theresa Burg

Biologth3300 Feb.24 , 2014 Adaptation- Chapter 10 Only natural selection can produce adaptation - Mutation and migration can introduce new alleles Adaptation  trait (s) that increase individual fitness Oxpeckers believed to reduce numbers of ticks on cattle Spend 85% of the time grooming cattle, probing in the ear - Exclusion experiments o Control group: birds o Experimental group: birds excluded  How are the birds excluded? • A man literally chased the birds around to keep them away from the cattle  How many individuals were looked at? o 1 month: two groups o 2 month: switch treatments o 3 month: randomly reassigned cattle o At the beginning and end of each month measurements were made:  Amount of earwax  Were birds drinking blood  The number of ticks o We predict the number of ticks would increase when the birds were excluded  We can see in 2 instances (trials 1&3) that cattle did have a larger number of ticks when the birds were excluded  There was 1 case where less ticks were found with birds excluded  None of the cases are significantly different from one another  Small sample sizes  Based on this data it does not appear that the birds have an impact on the number of ticks present o We predict more ear wax when no birds.  Does appear to have a correlation between the amount of earwax and the presence/absence of birds  All significant cases - Concluded that Oxpeckers eat earwax (and blood – not shown), but cattle are not the native hosts for Oxpeckers - When studying adaptations o Differences among populations/species are not always adaptive, may be mutation and drift o Not every trait is a result of an adaptation o Adaptations are compromises (ex: horns in big horn sheep- larger horns can help in fighting but become very heavy) 3 Approaches to Studying Adaptation - Experimental o Threat display by tephritid fly appears similar to the jumping spider  Have similar color, similar levels of striping, moved wings/arms  Possibility for mimicry  Hypotheses: 1) Null: flies do not mimic jumping spider 2) Flies mimic spider to deter non-spider predators 3) Flies mimic spider to deter predation by spiders • A is untreated  both variables present • B own wings cut and reglued (control used to see if regluing has an effect) • C has no pattern on the wings • D attached tephritid fly wings to housefly • E untreated  both variables absent  Predictions: 1) (no mimicry) all predators will attack fly 2) (mimicry deters other predators) A&B (banded wings on tephritid fly) will deter other predators only 3) (mimicry deters spiders) A&B will deter spiders only  Control worked so we can look at what the data tells us (A&B are NOT different)  25% of the time there was an attack on fly C  Conclude that both the pattern and wing waving are important in deterring jumping spiders  We can reject hypothesis 1  there is some mimicry  We can reject hypothesis 2  We fail to reject hypothesis 3 - Observational
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