BIOL 111 Lecture Notes - Ecdysis, Endoskeleton, Honey Bee

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Arthropods I
Ecdysozoans:
Arthropods:
- Coelomates
- Most dominant group of animals (most diverse)
- Appoximately 1000000 spiecies
arthropods diversity dominated by beetles
- Burgess shale: Cambrian explosion Anomalocaris: heard shelled
species, development of eyes, mouth part, predatory appendages,
armour, approx 1m in length
Diversity example:
Sytiscus: predaceous diving beetles, adults collect air under wings and use this to
breathe underwater
Honey bee: among most complex social life (eg. worker bees dance to communicate
location of new food course)
Arthropod: Joined foot
- Largest eukaryotic phylum
- Very abundant (1x108 alive at once)
- Includes: insects, crustaceans, arachnids
- Reduced segmentation: body regions head, (cefalo)thorax, abdomen
- Jointed appendages: specialized
Ex. Trilobite: one of first arthropods out there
- Rigid exoskeleton: ecdysozoan = molting
non living (can by penetrated by living tissue, like nerves),
secreted by epidermis
covers all external surface, digestive tract, tracheae
composed of layers
chitin/protein +CaCO3 (in crustaceans)
Exoskeleton advantages:
- Physical support
- Place for muscle attachment
- Physical protection: from abrasion, predation, parasite entry,
desiccation
- Location of pigments: camouflage, warning, color, mating, poison
- Jointed appendages & exoskeleton allow faster locomotion
- Change morphology between larval and adult stages
Exoskeleton disadvantages:
- Inflexible and heavy (if thick and protective)
Not as strong: limits size of organisms
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