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8 Cards in this Set
- Front
- Back
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Groups of Arthropods |
Hexapoda 1.02m Chelicerata 112,000 Myriapoda 12.000 Crustacea 67,000 |
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When did they first appear? |
They are the earliest identifiable fossil land animals. Structural differences between the lateral appendages of annelid polychaetes and early arthropods suggest they arose 500a. There are fossils from 517Ma some Ediacran from 555Ma |
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What supports tracheta? What supports tetraconata? |
Hexapods and Myriapods may be in a group called tracheata due to their tracheoles. However, others argue that they are witith Tetroconata. Hexapods and crustaceans are supported by molecular data, ommatidial structure, presence of neuroplasts and similar axongenesis of pioneer neurons (Richter, 2002) Through analysis of Nuclear ribosomal genes, nuclear protein coding, Mitogenomics and Hox gene its determined that the correct grouping is tetraconata. |
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What does tetraconata mean? |
They have 4 cone cells and 8 retinular cells |
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What are neuropil areas? Why is the brain useful for phyologeny? |
A neuropil is any area of the nervous system that is composed mainly of unmyelinated neurons, dendrites and glial cells, so it is very synaptically dense. Brain organisation shows great stability in time. For example, scorpions that have been geographically isolated for 225myrs have near identical brain organisation. This is because mutations of the higher brain rarely lead to advantage. E.g. a fruit fly with a midline fusion mutation cant negotiate curves. Opposing this, Hemiptera have walking versions and rowing versions which reveal an acquired modification of the central complex. |
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1. What forms mandibulata? What is an opposing theory to mandiulata? |
Hexapoda, crustacea and Myriapoda. Myriochelata, where crustaceans and hexapods are together, and chelicerate and myriapoda are together. |
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1. What evidence supports mandibulata? |
· Dachshund expression in the mandible is at the tip in all but the chelicerate, where it is at the base. · The cap-n-collar expression is separated into labral and mandibular domains in mandibulata |
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Myriochelata evidence |
only nervous system |
