HO-Lecture2-09F

HO-Lecture2-09F - Take-home Questions 1-Explain how the...

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1 Take-home Questions 1-Explain how the size of insects contributes to increasing their diversity. 2-Explain how interactions among insects and other insects and organisms contributes to insect diversity 3-Criticize Gaston’s (1990) and Stork’s (1997) approach to estimating the global number of insect species. Variety and numbers: How many and why so many insect species -insects are by far the most diverse group of organisms on earth -but, exact number of species is unknown, and estimates vary widely due to many reasons How many species of insects? -estimates variable, up to 80M species; 5M- 10M most likely -number of described spp. ~1M; fluctuates due to synonymy / homonymy problems to -regardless of actual number, clearly insects: -are most diverse group of organisms -constitute ~half of global species diversity (more if only consider terrestrial species) Insect species relative to other taxa -insects comprise -~50% of all described spp. of living organisms -~75% of all animal species -e.g., more species of beetles than: (i) species of flowering plants (ii) all other non-arthropod animal species
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2 Why are there so many insects? -several factors conducive to tremendous diversity of insects: -small size : finer-grained environment (e.g. leaf feeders, root feeders, sap suckers, miners, etc., on a single bush) -highly organized, complex neuro- motor system : superior to other invertebrates, comparable to vertebrates; better responses to changing environments Why are there so many insects? -rapid developmental cycles : allows rapid evolution to cope with variable environments -coevolution through interactions with other coevolution through interactions with other organisms : diversification via bottom-up (plant defenses) and top-down (predator, parasitoids, pathogens) forces, and competition Why are there so many insects? -wings : limited largely to insects, greatly facilitate dispersal -metamorphosis : reduces competition for resources between adults and immatures, allows separation of major functions between them, i.e. feeding and reproduction How many insect species are there in the world? -current consensus: ~750-950K described spp. , i.e. with scientific names -however, synonymy problems: e.g., recent review of 2 common butterfly families showed up to 80% of accepted species names were redundant synonyms -unknown how much synonymy created yearly by taxonomists How many insect species are there in the world? - estimates quite variable : up to 80M spp.; between 5M-10M most plausible - current consensus: ~8M spp. exist worldwide , concentrated largely in the tropics - but , substantial debate over accuracy of estimates of insect diversity; none over magnitude of diversity
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3 Early estimates -1883, British entomologist Wray: ~20K insect species in the world
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This note was uploaded on 05/14/2010 for the course ENTO 313 taught by Professor Bernal during the Spring '10 term at Texas A&M.

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HO-Lecture2-09F - Take-home Questions 1-Explain how the...

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