arthropod introduction 2

Question 1

reasons for arthropod success

Answer 1

• body size
• cuticle
• flexible bauplan:
  
  • tagmosis and regional specialization
  • modification of appendages

Question 2

bauplan

Answer 2

the generalized structural body plan that characterizes a group of organisms and especially a major taxon (such as a phylum)

Question 3

tagmosis

Answer 3

evolutionary process that creates tagmata by fusing and modifying segments

Question 4

tagmata

Answer 4

a specialized grouping of multiple segments or metameres into a coherently functional morphological unit

Question 5

arthropod speciation rates

Answer 5

large organisms tend to be good dispersers lowers likelihood of allopatric speciation

very small organisms also tend to be good disperses lowers likelihood of allopatric speciation

Question 6

arthropod cuticle

Answer 6

provides skeletal support
- especially important in colonization of land (water 1000 x denser than air)

relatively impermeable to water

• maintaining homeostasis, esp avoiding desiccation on land (epicuticular waxes)
• rate of water loss as low as 0.01% of that in soft bodied organisms such as the land snail

proved uniquely flexible
- segments and their appendages are modified in a variety of ways both with and within individual arthropod types

Question 7

tagmosis and appendage modification

Answer 7

arthropod bauplan has undergone various forms of regional specialization
- tagmosis

most arthropods have bodies composed of functionally specialized regions ( e.g head, thorax, abdomen )
- tagmata

Question 8

centipede ( chilopoda )

Answer 8

two tagmata :
head - fusion of 5 segments
trunk - varying no. of segments

Question 9

locust (hexapoda : insecta )

Answer 9

three tagmata :
head - fusion of 5 segments
thorax - 3 segments, bears walking limbs
abdomen - primitively 11 segments, although usually fewer - most segments have lost appendages

Question 10

lobster (crustacea)

Answer 10

three tagmata :
head - fusion of 5 segments
thorax/pereon - 8 segments - partly fused head - bears walking limbs
abdomen/pleon - 6 segments - appendages often modified as gills or for swimming