arthropods : hexapoda

Question 1

hexapoda

Answer 1

insects and their allies
• 3 pairs of walking limbs
• 3 tagmata - head, thorax, abdomen

950,0000 described extant species
- average 7000 new described species annually

Question 2

hexapoda : primarily terrestrial

Answer 2

devonian origin : 390 MYA

dominated terrestrial ecosystems ever since

Question 3

hexapoda : orders

Answer 3

classified into 30 living orders including :

• ordonta : dragonflies and damselflies
• hemiptera : true bugs
• coleoptera : beetles
• hymenoptera : ants, bees, wasps
• diptera : true flies
• lepidoptera : butterflies and moths

( coleoptera, hymenoptera, diptera, lepidoptera contain most species )

Question 4

mantophasmatodea

Answer 4

heel walkers

new insect order - first recognized in 2002

Question 5

hexapoda : abundance

Answer 5

200 million insects for every human alive

tropical forresrs insects make up 40% of animal biomass

single army ant colony - 22 million workers

Question 6

hexapoda : success factors

Answer 6

( apply to all arthropods )

• body size
• cuticle
• flexible bauplan

(specific to insects )

• evolution of flight
• metamorphosis

Question 7

hexapoda : flight

Answer 7

wingless insects only 1% of extant species

key to success in terrestrial and FW systems

Question 8

insect metamorphosis : ametabolous

Answer 8

( no real metamorphosis )

Question 8

insect metamorphosis : ametabolous

Answer 8

( no real metamorphosis )

juveniles are like small adults

Question 9

insect metamorphosis : hemimetabolous

Answer 9

( incomplete metamorphosis )

Question 10

insect metamorphosis : hemimetabolous

Answer 10

( incomplete metamorphosis )

juveniles resemble adults but lack fully developed wings and sexual structures

Question 11

insect metamorphosis : holometabolous

Answer 11

( complete metamorphosis )

holometabolous development allows adults and young to exploit different niche space

avoid damage to developing wings

holometabolous insect orders dominate

Question 12

insect limitations

Answer 12

size :

• weight up to 100g ( largest beetles )
• wingspan up to 28 cm ( lepidoptera )
• carboniferous ‘dragon flies’ - wingspan > 75cm
• size is limited by insect respiratory systems
• oxygen supplied to tissues directly via diffusion in trachea
• diffusion distances increases with body size