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Lecture 14

Lecture 14 - Arthropoda.docx

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Biology (Sci)
BIOL 111
Suzanne Gray

October 20 , 2011 Arthropods I Which of the following statements about mollusks is true? Many have trochophore layer Which of the following mollusks groups have a closed circulatory system? Cuttlefish Protostome group: Ecdysozoans  Arthropods are found in this group (coelomates)  Most diverse eukaryotic group  Within arthropods, beetles make up 35% The diversity of Arthropods: Dytiscus: predaceous diving beetle, adults collect air under wings and use this to breathe underwater ▯▯▯▯▯▯ ▯▯▯▯ ▯▯▯▯▯▯▯▯ ▯▯▯▯▯ ▯▯▯▯▯▯▯▯▯▯ ▯▯▯▯▯ ▯▯▯▯▯▯ ▯ Honey bee (Apis): has among most complex social life (i.e. worker bees dance to communicate location of new source)  Angle of waggle relative to sun communicates position of food source  Duration of waggle communicates distance of food source  Work was awkward a Nobel prize  However, new data show that up to 93% of the time other bees ignore the dance  Early experiments were conducted with artificial feeders and few food sources  Other cues such as odor are likely important Example: The Bombardier Beetle  Anti-predation function: steaming by shooting out a chemical at boiling temperature (firing apparatus) October 20 , 2011 Arthropods I Arthropods:  “Jointed foot”  Largest eukaryotic phylum  Very abundant (10 individuals alive at any one time)  Example: insects, crustaceans, arachnids  Reduced segmentation; body regions condensed into specialized function organs  Jointed appendages; divided up a segmented body plan into specialized functions  Rigid Exoskeleton forces ecdysozoans to go through a molting phase o Non-living o Secreted by epidermis o Covers all external surfaces, digestive tract and tracheae o Composed of layers o Chitin, proteins and CaCO (in crustaceans) 3 Advantages of a rigid Exoskeleton:  Physical support  Place for muscle attachment  Physical protection o From abrasion, predation, parasite entry, desiccation  Location of pigments (camouflage, warning, coloration, mating  Jointed appendages and exoskeleton allow faster locomotion  Opportunity to change morphology between larval and adult stages Disadvantages of a rigid exoskeleton  Inflexible and heavy (thick and protective)  Continuous growth in size is not possible o Must be periodically shed (molted)  Requires energy to form and shed  Prevents use of cilia as effectors  Respiration through skin not possible o Spiracles (pores) and tracheae (tubes) Discontinuous Growth " ▯▯ ▯▯▯▯ ▯▯▯#▯ ▯$ ▯  Mass grows continuously, but size changes in stepwise fashion - %▯ ▯▯$ ▯▯▯▯▯▯▯& ▯▯▯ ▯▯▯▯ ▯▯ ▯$▯ ▯▯▯▯ ▯▯▯▯ ▯ ▯▯▯▯▯ ' ▯▯▯( ▯▯ 5 ▯▯▯▯▯▯ ▯▯*▯▯▯▯ ▯▯ Clams have exoskeletons – do they experience periodic molting events like anthropods? No, they are not ecdysozoans th October 20 , 2011 Arthropods I Skeletons: 1. Hydrostatic skeleton a. Cnidarians b. Worms c. Shell-less mollusks 2. Exoskeleton a. Shelled mollusks b. Arthropods 3. Endoskeleton a. Echinoderms b. Vertebrates % ▯▯▯▯▯-, ▯▯▯ , ▯ ▯▯ Musculo-Skeletal Systems in Arthropods: A) Skeletal muscles: need a resistor to act against (i.e. a skeleton) B) Are often found in antagonistic pairs  Act in opposite directions  Muscles can only pull, not push  Example: biceps/triceps ▯▯ ▯▯!▯▯▯▯ ▯ ▯▯!▯▯▯▯▯ B o▯▯▯ ▯▯ o▯ ▯▯▯ i▯▯▯▯▯▯▯▯▯a$ed? *▯J▯▯▯▯▯ ▯▯ ▯ ▯▯▯▯▯▯▯▯▯ ▯▯ ▯! ▯▯▯▯▯▯ ▯▯ Neurons and Chemical Synapses A neuron at rest is characterized by: 1.Higher concentrations of K+ outside of the neuron 2.Higher concentrations of Na+ outside of the neuron 3.H
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