Animals have to move to find food and sexual partners. To proliferate their species and to avoid predators and adjust to varying environmental conditions, animals exhibit different ways of moving. Ants communicate and cooperate with other ants by using chemicals (pheromones) that can alert others to danger or lead them to a promising food source. Ants (leafcutter ants) can lift and carry objects many times their own weight. Just for instance the tiny leafcutter ant (pictured below figure 2a) can lift and carry in its jaws something 50 times its own body weight of about 500mg. Some lizard like desert monitor (figure 2b) have skin that is perfectly adapted to live in desert environment. They run fast reaching up to 35 km per hour to find food and evade predators. Earthworms have a unique movement when they are in the process of reproducing. Even do earthworms are hermaphrodites meaning they both have eggs and sperm within their bodies, they cannot self fertilize and need to mate with another individual as shown in figure 2c.
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Figure 2. Shows (a) tiny leafcutter ants (b) running lizard on scortching sand (c) earthworms mating
Animal Locomotion
Animals around us are able to move themselves in more than one way for a variety of different purposes such as finding food or finding sexual partners. These animals mostly rely on locomotion, which refers to the movement or the ability to move from a certain place to another. The most common means of animal locomotion are the following: walking (cow and pig), running (dog and ostrich), swimming (fish, shrimps), flying (only enjoyed by select groups of animals such as insects, birds, and one mammal, the bat), crawling (alligators and beetles), hopping (with rabbits and frogs), and gliding (flying fish and paradise tree snake).
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Figure 3. Shows a Paradise Tree Snake one of the most colorful snakes in South East Asia. This snake can take flight from tree to tree by flattening it’s body out and taking a leap of faith!
Three types of skeleton
A skeletal system is necessary to some organisms to support the body to stand upright, protect its internal organs, and allow for the movements of an organism. There are three different skeleton designs that fulfill these functions and these are the: hydrostatic skeleton, exoskeleton, and endoskeleton.
• Hydrostatic Skeleton
A hydrostatic skeleton occurs in a body compartment in which a volume of fluid is held under pressure. This is common in aquatic and burrowing animals. An example with this type of skeletal system is a hydra, sea anemones, earthworms, Cnidarian and other invertebrates with a semi-enclosed body cavity made of a few layers of cells. There is no solid “bone” but the animal under aquatic pressure can stay upright and move. Earthworms have smooth muscles and fluid-filled body compartments.
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Figure 4. Hydrostatic skeleton in invertebrates
• Exoskeleton
Rigid, armor-like coverings characterize an exoskeleton. Muscles are attached inside. Joints are thin and flexible. The best examples are found in arthropods (insects, crustaceans). When insects grow, they shed off their old “armor” and grow a new one. Cite other examples such as those in clams and snails.
• Endoskeleton
An endoskeleton consists of rigid but flexible support made of bones, cartilage surrounded by masses of muscles. In sponges, cells are supported on spicules. The endoskeleton of echinoderms is made from calcium plates underneath the skin.
Axial Skeleton vs. Appendicular Skeleton:
I. Axial skeleton – skull and backbone (spiral cord); rib cage
II. Appendicular skeleton – bones of the appendages (arms, legs, fins) and bones linking the appendages to the axial skeleton – the pectoral and pelvic girdles
5. Draw on the board the differences among striated or skeletal muscle, smooth muscle and cardiac muscle. Illustrate the parts of a striated muscle as seen in an electron photomicrograph. Locate the following parts: dark band; light band; A-band; Iband; Z line; sarcomere; myosin; actin filaments; troponin; tropomyosin
6. Explain the sliding filament theory of muscular contraction.
7. The thin myofilaments, actin, stay at the center and the thick myofilaments, myosin, slide past one another. Every muscle that contracts is therefore a “pull” not a push. You can demonstrate this by interlocking your fingers and sliding them past one another.