Section 28.1 Summary – pages  The exoskeleton is a hard, thick, outer covering made of protein and chitin (KI tun). Arthropod exoskeletons provide protection

Section 28.1 Summary – pages  In other species, the exoskeleton is made of separate plates held together by hinges.  In some species, the exoskeleton is a continuous covering over most of the body. Arthropod exoskeletons provide protection

Section 28.1 Summary – pages  In many aquatic species, the exoskeletons are reinforced with calcium carbonate.  The exoskeleton protects and supports internal tissues and provides places for attachment of muscles. Arthropod exoskeletons provide protection

Section 28.1 Summary – pages  First, they are relatively heavy structures. The larger an arthropod is, the thicker and heavier its exoskeleton must be to support its larger muscles.  Exoskeletons have their disadvantages. Why arthropods must molt

Section 28.1 Summary – pages Why arthropods must molt  A second and more important disadvantage is that exoskeletons cannot grow, so they must be shed periodically. Shedding the old exoskeleton is called molting.

Section 28.1 Summary – pages  When the new exoskeleton is ready, the animal contracts muscles and takes in air or water.  This causes the animal’s body to swell until the old exoskeleton splits open, usually along the back. Why arthropods must molt

Section 28.1 Summary – pages  Thus, the new exoskeleton hardens in a larger size, allowing some room for the animal to continue to grow.  Before the new exoskeleton hardens, the animal puffs up as a result of increased blood circulation to all parts of its body. Why arthropods must molt

Section 28.1 Summary – pages  When the new exoskeleton is soft, arthropods cannot protect themselves from danger because they move by bracing muscles against the rigid exoskeleton.  Most arthropods molt four to seven times in their lives before they become adults. Why arthropods must molt

Section 28.1 Summary – pages Segmentation in arthropods  In most groups of arthropods, segments have become fused into three body sections—head, thorax, and abdomen.

Section 28.1 Summary – pages  In other groups, even these segments may be fused. Segmentation in arthropods  Some arthropods have a head and a fused thorax and abdomen.

Section 31.1 Summary – pages How reptiles use their sense organs  Reptiles have a variety of sense organs that help them detect danger or potential prey.  The heads of some snakes have heat-sensitive organs or pits that enable them to detect tiny variations in air temperature brought about by the presence of warm-blooded animals.

Section 31.1 Summary – pages How reptiles use their sense organs  Snakes and lizards are equipped with a keen sense of smell.  Have you ever seen a snake flick out its tongue? The tongue is picking up molecules in the air.

Section 31.1 Summary – pages How reptiles use their sense organs  The snake draws its tongue back into its mouth and moves it past or inserts it into a pitlike structure called Jacobson’s organ, where special cells identify them. Jacobson’s organ Tongue

Swim bladder Section 30.1 Summary – pages Bony fishes evolved swim bladders  A fish with a swim bladder can control its depth by regulating the amount of gas in the bladder.

Section 30.1 Summary – pages  Some fishes remove gases from the swim bladder by expelling them through a special duct that attaches the swim bladder to the esophagus. Bony fishes evolved swim bladders  In fishes that do not have this duct their swim bladders empty when gases diffuse back into the blood.

Section 30.1 Summary – pages A Bony Fish Lateral line system Swim bladder Scales Gills Fins Kidney Urinary bladder Reproductive organ Stomach Intestine Liver Heart

Section 31.2 Summary – pages Birds have feathers  A feather is a lightweight, modified protein scale that provides insulation and enables flight.

Section 31.2 Summary – pages Birds have feathers  Preening, keeps the feathers in good condition for flight.  During preening, a bird also uses its bill or beak to rub oil from a gland near the tail onto the feathers.  This is especially important for water birds as a way to waterproof the feathers.

Section 31.2 Summary – pages Birds have feathers  The shedding of old feathers and the growth of new ones is called molting.  Most birds molt in late summer. However, most do not lose their feathers all at once and are able to fly while they are molting.

Section 31.2 Summary – pages Birds have wings  A second adaptation for flight in birds is the modification of the front limbs into wings.

Section 31.2 Summary – pages Birds have wings  Powerful flight muscles are attached to a large breastbone called the sternum and to the upper bone of each wing.  The sternum supports the enormous thrust and power produced by the muscles as they move to generate the lift needed for flight.

Section 31.2 Summary – pages Flight  For birds, the ability to fly is the result of complex selective pressures that led to the evolution of many adaptations. Wings Hollow bones Beaks Legs Digestion Air Sacs

Section 32.1 Summary – pages Mammals can learn  Mammals can accomplish complex behaviors, such as learning and remembering what they have learned.

Section 32.1 Summary – pages Mammals can learn  Primates, including humans, are perhaps the most intelligent animals.

Section 32.1 Summary – pages Mammals can learn  Chimpanzees, for example, can use tools, work machines, and use sign language to communicate with humans.

Section 32.1 Summary – pages Motor area Sensory area Language area Vision area General interpretation area Cerebrum Speech area Taste area Intellect, learning, and personality Hearing area Brain stem Cerebellum Balance area Mammals can learn