Support and Locomotion Flashcards
Week 1
Define skeleton
The structure in the body that provides support
What are the types of skeleton?
Endoskeleton, exoskeleton, hydrostatic skeleton and cytoskeleton
What is an exoskeleton?
A rigid eternal skeleton derived from the ectoderm, mainly found in invertebrates
What is an endoskeleton?
An internal skeleton made of mineralised tissue, usually derived from the mesoderm
What is a hydrostatic skeleton?
A fliud-filled cavity (e.g. coelom) surrounded by muscle
Some properties of a skeleton
- Provides support
- Maintain body shape
- Attachment site for muscles
- Transmit forces of muscle contraction
- Protects the body (exoskeletons)
What is a coelom?
A fluid-filled cavity that develops within the mesoderm and is enclosed in a thin lining (the peritoneum)
Examples of acoelomates
Flatworms and nemerteans
Acoelomate body plan
- Ectoderm
- Endoderm (gut)
- Mesoderm (mesenchyme)
Support in acoelomates
- Elasticity of body wall
- Body musculature
- Hydrostatic qualities of mesenchyme
Some examples of blastocoelomates (pseudocoelomates)
Rotifers and roundworms
Blastocoelomate body plan
- Ectoderm
- Mesoderm (muscle)
- Blastocoelom (pseudocoelom)
- Endoderm (gut)
Support in blastocoelomates
- Hydrostatic skeleton (blastocoelom)
- Body musculature
- Outer cuticle
Some examples of coelomates
Annelid worms and vertebrates
Coelomate body plan
- Ectoderm
- Endoderm
- Mesoderm
- Coelom
Support in coelomates
- Hydrostatic skeleton (coelom)
- Body musculature
What are the two muscle movements involved in annelid worm movement?
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
How do annelid worms move?
They alternately contract longitudinal and circular muscles in each segment. This displaces internal fluid and allows for movement.
Some examples of cnidarians
Hydra and jelly fish
Support in cnidarians
- 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)
Some examples of arthropods
Crustaceans, spiders, scorpions and insects
Support in arthropods
Exoskeleton
What are arthroidal or articular membranes in arthropods?
The thin cuticle between body and limb segments
What are exites and endites in arthropods?
Additional structures on limbs either laterally (exites) or medially (endites)
What is the difference between the biramous limbs of crustaceans and the uniramous limbs of some other arthropods?
Biramous limbs have large exites and uniramous do not
What is molting in arthropods?
The shedding of the exoskeleton
Some examples of mollucs
gastropods (snails), squids and octopi
Support in molluscs
Exoskeleton as shells or pen in the squid
Some examples of echinoderms
Star fish, sea urchins and sea cucumbers
Support in echinoderms
