Support and Locomotion

Question 1

Define skeleton

Answer 1

The structure in the body that provides support

Question 2

What are the types of skeleton?

Answer 2

Endoskeleton, exoskeleton, hydrostatic skeleton and cytoskeleton

Question 3

What is an exoskeleton?

Answer 3

A rigid eternal skeleton derived from the ectoderm, mainly found in invertebrates

Question 4

What is an endoskeleton?

Answer 4

An internal skeleton made of mineralised tissue, usually derived from the mesoderm

Question 5

What is a hydrostatic skeleton?

Answer 5

A fliud-filled cavity (e.g. coelom) surrounded by muscle

Question 6

Some properties of a skeleton

Answer 6

• Provides support
• Maintain body shape
• Attachment site for muscles
• Transmit forces of muscle contraction
• Protects the body (exoskeletons)

Question 7

What is a coelom?

Answer 7

A fluid-filled cavity that develops within the mesoderm and is enclosed in a thin lining (the peritoneum)

Question 8

Examples of acoelomates

Answer 8

Flatworms and nemerteans

Question 9

Acoelomate body plan

Answer 9

1. Ectoderm
2. Endoderm (gut)
3. Mesoderm (mesenchyme)

Question 10

Support in acoelomates

Answer 10

• Elasticity of body wall
• Body musculature
• Hydrostatic qualities of mesenchyme

Question 11

Some examples of blastocoelomates (pseudocoelomates)

Answer 11

Rotifers and roundworms

Question 12

Blastocoelomate body plan

Answer 12

1. Ectoderm
2. Mesoderm (muscle)
3. Blastocoelom (pseudocoelom)
4. Endoderm (gut)

Question 13

Support in blastocoelomates

Answer 13

• Hydrostatic skeleton (blastocoelom)
• Body musculature
• Outer cuticle

Question 14

Some examples of coelomates

Answer 14

Annelid worms and vertebrates

Question 15

Coelomate body plan

Answer 15

1. Ectoderm
2. Endoderm
3. Mesoderm
4. Coelom

Question 16

Support in coelomates

Answer 16

• Hydrostatic skeleton (coelom)
• Body musculature

Question 17

What are the two muscle movements involved in annelid worm movement?

Answer 17

Longitudinal muscles relax and circular muscles contract: makes this part of the body onger and thinner

Longitudinal muscles contract and circular muscles relax: makes this part of the body shorter and thicker

Question 18

How do annelid worms move?

Answer 18

They alternately contract longitudinal and circular muscles in each segment. This displaces internal fluid and allows for movement.

Question 19

Some examples of cnidarians

Answer 19

Hydra and jelly fish

Question 20

Support in cnidarians

Answer 20

• Water-filled coelenteron (gut sac) constrained by body wall musculature
• Mesenchyme stiffened with fibers
• Some include bits of shell or sediment into column wall (polypoid forms)
• Hard skeletal structures (axial skeletal structures, calcareous sclerites)

Question 21

Some examples of arthropods

Answer 21

Crustaceans, spiders, scorpions and insects

Question 22

Support in arthropods

Answer 22

Exoskeleton

Question 23

What are arthroidal or articular membranes in arthropods?

Answer 23

The thin cuticle between body and limb segments

Question 24

What are exites and endites in arthropods?

Answer 24

Additional structures on limbs either laterally (exites) or medially (endites)

Question 25

What is the difference between the biramous limbs of crustaceans and the uniramous limbs of some other arthropods?

Answer 25

Biramous limbs have large exites and uniramous do not

Question 26

What is molting in arthropods?

Answer 26

The shedding of the exoskeleton

Question 27

Some examples of mollucs

Answer 27

gastropods (snails), squids and octopi

Question 28

Support in molluscs

Answer 28

Exoskeleton as shells or pen in the squid

Question 29

Some examples of echinoderms

Answer 29

Star fish, sea urchins and sea cucumbers

Question 30

Support in echinoderms