Lec 20

Hydrostatic skeleton

A skeleton based on liquid found in soft-bodied invertebrates, where circular and longitudinal muscles contract against extracellular liquid.

Exoskeleton

A hard outer structure found in arthropods, made of chitin, where muscles attach.

Chitin

A protein and carbohydrate that composes the hardened outer surface of exoskeletons.

Trapdoor spider

An example of an animal with an exoskeleton that uses it for protection and mobility.

Weevil

Another arthropod with an exoskeleton.

Trap Jaw Ant

Uses jaws for escape jumps.

Exoskeleton Drawback

Cannot grow; requires shedding.

Endoskeleton

A skeleton located inside the body, typically bony and derived from cartilage, allowing for growth with the organism.

Cartilaginous Template

Structure from which endoskeleton develops.

Osteoblasts

Cells that lay down new matrix and build new bone.

Osteoclasts

Cells responsible for dissolving bone.

Matrix

A gelatinous substance containing calcium phosphate, which hardens to form bone.

Axial skeleton

The part of the skeleton that includes the skull, vertebral column, sternum, and ribs.

Appendicular skeleton

The part of the skeleton that includes the pectoral girdle, pelvic girdle, arms, legs, hands, and feet.

Endochondral bone

Bone formed from a cartilaginous template that develops under specific conditions and allows for growth.

Bmp4

Bone Morphogenetic Protein that influences bone development and is correlated with beak size in Darwin's finches.

Darwin's finches

A group of finch species known for their rapid diversification in beak sizes, attributed to skeletal development and Bmp4 signaling.

Dynamic organs

Bones are considered dynamic organs because they continuously remodel through the action of osteoblasts and osteoclasts.

Predation risk of exoskeletons

Exoskeletons must be shed for growth, which increases the organism's risk of predation during this vulnerable time.

Cartilaginous bone formation

The process by which initial cartilage is replaced and developed into bones, often starting with the formation of blood vessels.