Ward_Lect33A_Echinodermata_ppt

Ward_Lect33A_Echinodermata_ppt - BIS2C Winter 2009 (Ward)...

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BIS2C Winter 2009 (Ward) Lecture 33. Echinodermata Today’s lecture (9 March) Arthropoda (Hexapoda): concluded introduction to Deuterostomes Echinodermata major features of echinoderms echinoderm diversity Wednesday Chordates
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Why are holometabolous insects so diverse compared to other hexapods? 1. Complete metamorphosis permits specialization of stages for feeding (larva) and reproduction and dispersal (adult). 2. An extended life cycle (four life stages) means greater longevity and hence greater fitness. 3. The hemimetabolous insects are more vulnerable to predation in the adult stage. 4. All of the above.
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Why are holometabolous insects so diverse compared to other hexapods? 1. Complete metamorphosis permits specialization of stages for feeding (larva) and reproduction and dispersal (adult). 2. An extended life cycle (four life stages) means greater longevity and hence greater fitness. 3. The hemimetabolous insects are more vulnerable to predation in the adult stage. 4. All of the above.
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Nymphs constrained to resemble adult morphology to some degree. Encumbered with appendages, wing pads, etc.
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Larva free to develop very different (specialized) morphology for feeding, unencumbered by adult appendages. Adults specialize on dispersal and reproduction.
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Other trends in insect evolution Coevolution with flowering plants Insect orders (major clades) arose in Permian (260 mya) or earlier Angiosperms originated about 150 mya Thus, coevolution with flowering plants had an effect on diversification within insect orders, not on the origin of major clades
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Other trends in insect evolution Coevolution with flowering plants Recall the method of multiple sister-group comparisons for testing effects of different factors on rates of diversification . For example, latex- and resin-bearing plants have more species, on average, than sister taxa without these features. Similarly, clades of phytophagous (plant-feeding) insects have been compared to sister taxa that are not plant feeders. Guess which ones show higher net diversification?
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Other trends in insect evolution Coevolution with flowering plants On average, plant-feeding insects are more species-rich than sister taxa that do not feed on plants (predators or scavengers).
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On average, plant-feeding insects are more species-rich than sister taxa that do not feed on plants (predators or scavengers). What are likely explanations for this pattern? 1. Predators and scavengers have lower extinction rates. 2. Clades of plant-feeding species tend to be older than their non-plant-feeding sister groups. 3. Plant-feeding insects have fewer natural enemies.
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Ward_Lect33A_Echinodermata_ppt - BIS2C Winter 2009 (Ward)...

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