Biomechanics Flashcards
How can unicellular organisms move?
by changing shape using elements in the cytoskeleton, such as pseudopodia, cilia or flagella
How do amoebas ‘crawl’?
using pseudopodia
What is a turbellarian and how does it move?
A platyhelminth that uses propulsive forces from cilia to move
How do gastropods move?
Propulsive forces generated by movement of cilia
What is a choanocyte?
Flagellated cell that lines the internal chambers of a sponge
What are 3 similarities between the sliding filaments of skeletal muscle and the sliding microtubules of cilia?
Both are powered by ATP, both use an ATPase (muscles use myosin and cilia use dynein), both are regulated by calcium ions
How do muscles work in hard-bodied invertebrates (without a skeleton)?
the muscles are directly attached to a rigid exoskeleton.
How are the limbs of decapods coordinated?
by contractions in the preceding segment
Name 4 groups of organisms that swim using cilia and/or flagella
protozoa, macroalgal gamete, larvae, and some meifauna
Which organisms move using wave-like undulations?
many worms
Which organisms move using fluid propulsion?
medusoid coelenterates (jellyfish), cephalopods, pectinid bivalves
Which organisms use flattened appendages (controlled by muscular contractions) to move?
some decapod crustaceans, fish, cetaceans and pinnepeds
Name 8 ways metazoans may move across a substratum
ameoboid action, ciliary creeping, peristatic waves, looping, walking, running, jumping, burrowing
Name 2 metazoans that use ciliary creeping/gliding to move
platyhelminths and molluscs
Name 2 metazoans that use peristaltic waves to move across substrata
annelids, echiurans (spoons worms), sipunculans (unsegmented marine worms) and molluscs
Name 2 metazoans that use looping to move across substrata
hirudinea (leeches) and rotifers (platyhelminth)
Name 2 metazoans that walk across substratum
polychaetes and echinoderms
Name 2 metazoans that run across substratum
arthropods
Name 2 metazoans that jump across substratum
some crustaceans and gastropods
Name 4 metazoans that burrow into substratum
nemerteans, annelids, sipunculans, echiurans
What is a hydroskeleton
a fluid-filled body compartment in soft-bodied invertebrates
How may a crustacean be considered a multitasker?
crustaceans use rythmic movements of its thoracic appendages for both walking and gaseous exchange
How may female brine shrimp be considered multitaskers?
the beating of their phyllopods is used for swimming, gaseous exchange and supplies water to the ovisac
Give an example of convergent evolution in locomotion
undulatory (sinusoidal) swimming is seen in certain nematode worms as well as marine polychaete worms
Name 3 forces which animals must overcome to move through water
friction, drag and gravity
What is the scaling effect?
how the relative importance of counteracting forces differs between animals of different sizes
What are the 2 main forms of drag?
viscous drag and pressure drag
What does Reynolds’ Number quantify?
the drag effects on the fluid flow over an animal moving through water
What is the equation for Reynolds’ Number (in words)?
Reynolds’ Number = incident velocity x (foil length x (desity/viscosity) )
What are the units of Reynolds’ Number?
it is unitless
What is laminar flow and which animals generate it?
Fluid flow in parallel layers, generated by the movement of animals with a low reynolds number through water.
What is the most prominent force to overcome in animals with a low (less than 10) Reynolds’ Number?
viscous drag
What is pressure drag and where is it seen?
drag produced by low pressure generated from turbulent flows of high Reynold’s number animals moving through water.
What is the advantage of having a fusiform shape (wide in middle and tails off either end)?
It’s streamline, which reduces pressure drag.
How does the relative importance of drag change as an organism gets bigger?
drag is less of a problem in bigger organisms
What is Gray’s Paradox?
1936 observation by Sir James Gray that the apparent power output of fast-swimming fish and cetaceans was insufficient for them to swim at the speed they do
What did Kramer propose in 1960?
That the compliance (elasticity) of dolphin skin delays the generation of turbulence, thus reducing pressure drag.
What is the most important source of drag in fast-swimming fish (e.g. sharks) and how is it reduced?
Frictional drag - reduced if the boundary layer maintains a turbulent flow, which is absorbed by denticles in skin.
What are the 3 groups of organisms which move through sediment?
hard-bodied “diggers”, soft-bodied “burrowers”, and specialised “drillers”
How does the Nephtys polychate move through sediment?
uses pharynx to apply pressure to thixotrophic sand, causing it to liquify and the worm to rapidly burrow
How do barnacles attach so firmly to sediment?
The shape and ribbing of the base plate increases the adhesion of of a protein glue (that is coded for by the same gene that contributed to mammalian clotting agents - Factor XIII)
