Biomechanics

Question 1

How can unicellular organisms move?

Answer 1

by changing shape using elements in the cytoskeleton, such as pseudopodia, cilia or flagella

Question 2

How do amoebas ‘crawl’?

Answer 2

using pseudopodia

Question 3

What is a turbellarian and how does it move?

Answer 3

A platyhelminth that uses propulsive forces from cilia to move

Question 4

How do gastropods move?

Answer 4

Propulsive forces generated by movement of cilia

Question 5

What is a choanocyte?

Answer 5

Flagellated cell that lines the internal chambers of a sponge

Question 6

What are 3 similarities between the sliding filaments of skeletal muscle and the sliding microtubules of cilia?

Answer 6

Both are powered by ATP, both use an ATPase (muscles use myosin and cilia use dynein), both are regulated by calcium ions

Question 7

How do muscles work in hard-bodied invertebrates (without a skeleton)?

Answer 7

the muscles are directly attached to a rigid exoskeleton.

Question 8

How are the limbs of decapods coordinated?

Answer 8

by contractions in the preceding segment

Question 9

Name 4 groups of organisms that swim using cilia and/or flagella

Answer 9

protozoa, macroalgal gamete, larvae, and some meifauna

Question 10

Which organisms move using wave-like undulations?

Answer 10

many worms

Question 11

Which organisms move using fluid propulsion?

Answer 11

medusoid coelenterates (jellyfish), cephalopods, pectinid bivalves

Question 12

Which organisms use flattened appendages (controlled by muscular contractions) to move?

Answer 12

some decapod crustaceans, fish, cetaceans and pinnepeds

Question 13

Name 8 ways metazoans may move across a substratum

Answer 13

ameoboid action, ciliary creeping, peristatic waves, looping, walking, running, jumping, burrowing

Question 14

Name 2 metazoans that use ciliary creeping/gliding to move

Answer 14

platyhelminths and molluscs

Question 15

Name 2 metazoans that use peristaltic waves to move across substrata

Answer 15

annelids, echiurans (spoons worms), sipunculans (unsegmented marine worms) and molluscs

Question 16

Name 2 metazoans that use looping to move across substrata

Answer 16

hirudinea (leeches) and rotifers (platyhelminth)

Question 17

Name 2 metazoans that walk across substratum

Answer 17

polychaetes and echinoderms

Question 18

Name 2 metazoans that run across substratum

Answer 18

arthropods

Question 19

Name 2 metazoans that jump across substratum

Answer 19

some crustaceans and gastropods

Question 20

Name 4 metazoans that burrow into substratum

Answer 20

nemerteans, annelids, sipunculans, echiurans

Question 21

What is a hydroskeleton

Answer 21

a fluid-filled body compartment in soft-bodied invertebrates

Question 22

How may a crustacean be considered a multitasker?

Answer 22

crustaceans use rythmic movements of its thoracic appendages for both walking and gaseous exchange

Question 23

How may female brine shrimp be considered multitaskers?

Answer 23

the beating of their phyllopods is used for swimming, gaseous exchange and supplies water to the ovisac

Question 24

Give an example of convergent evolution in locomotion

Answer 24

undulatory (sinusoidal) swimming is seen in certain nematode worms as well as marine polychaete worms

Question 25

Name 3 forces which animals must overcome to move through water

Answer 25

friction, drag and gravity

Question 26

What is the scaling effect?

Answer 26

how the relative importance of counteracting forces differs between animals of different sizes

Question 27

What are the 2 main forms of drag?

Answer 27

viscous drag and pressure drag

Question 28

What does Reynolds’ Number quantify?

Answer 28

the drag effects on the fluid flow over an animal moving through water

Question 29

What is the equation for Reynolds’ Number (in words)?

Answer 29

Reynolds’ Number = incident velocity x (foil length x (desity/viscosity) )

Question 30

What are the units of Reynolds’ Number?

Answer 30

it is unitless

Question 31

What is laminar flow and which animals generate it?

Answer 31

Fluid flow in parallel layers, generated by the movement of animals with a low reynolds number through water.

Question 32

What is the most prominent force to overcome in animals with a low (less than 10) Reynolds’ Number?

Answer 32

viscous drag

Question 33

What is pressure drag and where is it seen?

Answer 33

drag produced by low pressure generated from turbulent flows of high Reynold’s number animals moving through water.

Question 34

What is the advantage of having a fusiform shape (wide in middle and tails off either end)?

Answer 34

It’s streamline, which reduces pressure drag.

Question 35

How does the relative importance of drag change as an organism gets bigger?

Answer 35

drag is less of a problem in bigger organisms

Question 36

What is Gray’s Paradox?

Answer 36

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

Question 37

What did Kramer propose in 1960?

Answer 37

That the compliance (elasticity) of dolphin skin delays the generation of turbulence, thus reducing pressure drag.

Question 38

What is the most important source of drag in fast-swimming fish (e.g. sharks) and how is it reduced?

Answer 38

Frictional drag - reduced if the boundary layer maintains a turbulent flow, which is absorbed by denticles in skin.

Question 39

What are the 3 groups of organisms which move through sediment?

Answer 39

hard-bodied “diggers”, soft-bodied “burrowers”, and specialised “drillers”

Question 40

How does the Nephtys polychate move through sediment?

Answer 40

uses pharynx to apply pressure to thixotrophic sand, causing it to liquify and the worm to rapidly burrow

Question 41

How do barnacles attach so firmly to sediment?

Answer 41

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)