BIOL 22000 Lecture Notes - Lecture 12: Polysaccharide, Reuptake, Muscle Fatigue
26 Jun 2018
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Lecture 12
Skeletons -Functions
oFunctions
Support
Support against gravity (land animal)
Maintain form and shape (aquatic animals)
Protection (skull)
Movement
Something firm for muscles to work against
Three Types of Skeletons
oHydrostatic Skeleton
oExoskeletons
oEndoskeletons
Hydrostatic Skeleton
oFluid held under pressure in ta closed compartment (inside body)
oVolume cannot change, you cannot compress it
oWell suited for aquatic animals
oProvides support for crawling and burrowing in terrestrial animals
oDisadvantages
Provides little protection
Cannot support body of the ground
Water is heavy so the organism is heavy too
oAnimals with hydrostatic skeletons move by contraction of muscles against a
relatively non-compressible internal fluid
Like squeezing a water-filled balloon
oExample – Earthworm
Made up of repeating segments
Segments are divided by partitions (septa)
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Filled with coelomic fluid
Bristles on ventral surface (setae)
Muscles
Longitudinal – shorten and expand segment
Circular – compress and elongate segment
Even if the shape of the compartment is different, the volume is still the
same (mentioned above) (volume of fluid doesn’t change)
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Exoskeletons
oHard encasement on the surface of an anima
oMollusks (clams)
Hard shell of calcium carbonate
As animal grows, shell is enlarged by adding to outer edges
Keeps the same shell through out its life
oArthropods (lobster)
Jointed exoskeletons (cuticle) consisting of:
Chitin (polysaccharide similar to cellulose)
Fibrils of chitin are embedded in protein matrix
Additional hardening by adding organic compounds and calcium
salts
Exoskeleton is periodically shed (molted) and replaced as animal grows
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find more resources at oneclass.com
Document Summary
Three types of skeletons: hydrostatic skeleton, exoskeletons, endoskeletons. Hydrostatic skeleton: fluid held under pressure in ta closed compartment (inside body, volume cannot change, you cannot compress it, well suited for aquatic animals, provides support for crawling and burrowing in terrestrial animals, disadvantages. Water is heavy so the organism is heavy too: animals with hydrostatic skeletons move by contraction of muscles against a relatively non-compressible internal fluid. Like squeezing a water-filled balloon: example earthworm. Even if the shape of the compartment is different, the volume is still the same (mentioned above) (volume of fluid doesn"t change) Exoskeletons: hard encasement on the surface of an anima, mollusks (clams) As animal grows, shell is enlarged by adding to outer edges. Keeps the same shell through out its life: arthropods (lobster) Fibrils of chitin are embedded in protein matrix. Additional hardening by adding organic compounds and calcium salts.
