1. Apply Concepts How do muscles enable movement

CH 28 ANIMAL SYSTEMS II 28.2 Movement and Support

 To move all animals must: 1. Generate physical force 2. Apply that force against air, water, or land in order to push or pull themselves around.

 Animals have three main kinds of skeletal systems:  Hydrostatic skeletons  Exoskeletons  Endoskeletons.

Hydrostatic Skeletons  Consists of fluids held in a gastrovascular cavity  Alters the body’s shape drastically by working with contractile cells in its body wall  Cnidarians and annelids.

 Hydra closes its mouth and the cells encircling its body wall constrict  Elongates and its tentacles extend  Mouth opens, allowing water to flow out, and longitudinal cells in its body wall contract, shortening the body.

Exoskeletons  External skeleton usually made of chitin or calcium carbonate  Many arthropods and most mollusks  Jointed exoskeletons allow to swim, fly, burrow, walk, crawl, and leap  May be water tight  Offer protection from predators.

 Molting  Breaking out of their exoskeleton and grow a new one to allow for growth  Relatively heavy especially in large arthropods.

Endoskeletons  Structural support system within the body.

 Vertebrates have an endoskeleton made of cartilage or a combination of cartilage and bone  Sharks and some other fishes have skeletons made entirely of cartilage  Girdles  Support limbs and allow for movement.

 Cannot protect an animal the way that an exoskeleton can  Internal skeleton can grow as an animal grows, so the animal does not need to molt  Lighter weight than exoskeleton.

Joints  Places where parts of a skeleton are held together that allows them to move with respect to one another.

 Ligament  Connects bones together at joints  Strong connective tissues.

Muscles and Movement  Specialized tissues that produce physical force by contracting when stimulated  Muscles relax when they aren’t stimulated  Generate force in only ONE direction.

 Muscles are arranged in pairs or groups that pull parts of the skeleton in opposite directions.

 Tendon  Attaches muscle to bones around the joints  Tough connective tissue.

 Exoskeleton  Muscles are attached to the inside of the exoskeleton  Endoskeleton  Muscles are attached around the outside of bones.

Vertebrate Muscular and Skeletal Systems  The shapes and relative positions of bones, muscles, and joints are linked very closely to the functions they perform  Many very different arrangements  Many very different kinds of movement.