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In quadrupeds, walking is a type of movement in which each foot hits the ground in rotating order, front left, back right, front right, and back left, with three feet on the ground at one time.


The airfoil is the shape of the wing when looked at as a cross-section. If you cut off the tip of an airplane's wing and then stared straight at the cut surface, that shape is the airfoil.

Afferent Pathway

A neuronal signaling pathway which starts in the body and arrives at the brain

Air Sacs

Cavities inside birds which collect air during their multi-step breathing process.

Alveolus (plural Alveoli)

Tiny sand-grain-sized air sacs in which oxygen is exchanged for carbon dioxide.

Angle Of Attack

The angle of attack is the angle of the wing that determines the amount of lift or drag. If you stick your arms out to your sides and rotate them so both your thumbs point up and then down you are changing the angle of attack.


Strong three layered vessels carrying blood from the ventricles away from the heart are called arteries. Since the pressure is higher, they are stronger than the veins.

Atrium (plural Atria)


Bipeds are animals that utilize two-limbed locomotion (birds, humans, etc).

Body-caudal Movement

Body-caudal movement is the primary form of movement in most fish. Swishing the tail back and forth cancels the lateral forces out, and the animal is pushed forward.


Bounding is a type of movement in which front (or back) legs touch the ground simultaneously.


The smallest of branches from the bronchi that form a tree of tubes.

Bronchus (singular Bronchi)

A tube leading from the trachea toward the lung. There are typically two, one going towards each lung.

Buccal Pumping

The process of throat muscles pushing the floor of the mouth up and forcing air out of the mouth and into the lungs. This is seen in amphibians.


The ability to stay afloat, and it is all a matter of density. In fluids like water, objects with higher densities (like rocks) sink while those with lower densities (such as inner tubes) float.


Cantering is a three beat type of quadruped movement in which one limb strikes the ground followed a simultaneous strike by the two diagonal limbs, and then the final limb. For example: front left, then front right and back left together, and then back right. This name finds its origins in Canterbury, United Kingdom and is short for Canterbury pace, a reference to the leisurely speed medieval pilgrims took to the city.


The capillaries are the smallest vessels and the site of gas exchange in the body.

Caudal Fin

Basically, it's the tail fin.

Carbonic Acid

A weak acid formed by dissolved carbon dioxide.

Cellular Respiration

The process by which cells take in oxygen and use glucose to produce carbon dioxide, water, and usable energy (ATP)

Circulatory System

Body system containing a heart and either the blood or hemolymph which it pumps throughout the animal carrying nutrients, oxygen and waste. Closed systems also contain blood vessels.

Closed Circulatory System

Circulatory system in which blood is enclosed in a network of vessels rather than flowing freely throughout the body.


Heat transfer between two objects that are touching


Heat transfer between objects and the liquid or air that surrounds them.

Counter-current Exchange Pathway

An arrangement of arteries in relation to the gills so that blood is flowing in the opposite direction of the water during gas exchange. This orientation ensures that the maximum gas exchange can take place since the blood is always passing water that is fully oxygenated.

Counter-current Heat Exchanger

A special arrangement of the blood vessels so that heat is conserved within the body. Blood vessels going towards sites of heat loss (such as gills or ends of limbs) run alongside the blood vessels returning from that site so that heat transfers between them and remains within the body core and is not lost to the environment.


A substance that prevents things from freezing


A dome-shaped structure located just beneath the lungs that causes inhalation or exhalation by flattening during inhalation and relaxing during exhalation.


Movement where molecules or particles will move from an area where they are very concentrated into an area where they are less concentrated. Think of it as spreading out to use the whole space.


Density is a measure of an object's mass in comparison to its volume (density= mass/volume). Density can increase either by increased mass or by decreased volume. Picture a jar of raisins and a jar of peanut butter. If both jars are the same size, the peanut butter would have a higher mass and consequently a higher density. To increase the density of the raisins you would have to either increase the mass of the raisins (squash more and more raisins into the original jar) or decrease the volume (take the same amount of raisins from the original jar and squash them into a smaller jar).

Dynamic Lift

The upward lifting movement caused by moving forward while holding the pectoral fins or wings at a particular angle.


Animals which receive heat primarily from external sources (reptiles, amphibians, and fish).

Efferent Pathway

A neuronal signaling pathway which exits the brain and goes to the body.


Animals which create their own heat (mammals and birds).


A tiny flap that regulates air going into the windpipe. It closes when you swallow to prevent food from being inhaled. The next time someone accuses you of eating too fast and inhaling your food you can tell them, "Thank you, but my epiglottis works just fine."


A sustained period of lowered metabolism to decrease body temperature during the warmer months.


Flapping involves pushing the wings downward and backward to generate lift and forward motion, while also folding the wings on the upstroke to decrease the counterproductive forces. This is the most energy demanding way to fly, and lazy birds prefer a nice glide.


The method of walking, bearing, or carriage that an animal has is called its gait.


The site of gas exchange in many aquatic organisms. As water flows through the gills' tiny folds, oxygen is collected and carbon dioxide is released.


Gliding is movement through air, unaided by flapping. It is created by dynamic lift.


The hemolymph containing body cavity of an animal with an open circulatory system.


Hemocyanin is the oxygen-binding molecule in hemolymph similar to hemoglobin in the blood. It turns blue when oxygenated.


Iron-rich protein in red blood cells that binds oxygen and carbon dioxide, allowing them to be carried around the body in the blood.


A combination of blood and interstitial fluids within a hemocoel that bathe the organs and provide nutrients. This is almost the equivalent of a literal bloodbath.


Animals which usually keep a constant body temperature, but have specific periods where their temperature is different, such as during hibernation. Ground squirrels are heterotherms.


A sustained period of lowered body temperature during the colder months.


The process of regulating and maintaining the body's internal environment.


Animals who maintain a constant internal body temperature across a wide range of environmental conditions. Humans are homeotherms.

Hydrostatic Skeleton

A hydrostatic skeleton is a fluid-filled cavity surrounded by muscles. Muscle constriction changes the animals shape, causing movement. Think jellyfish.


The state of having a higher solute concentration than the surrounding environment.


A portion of the brain that processes signals from the body and then sends out other signals to trigger a behavioral response. For example, it receives temperature sensor readings from blood vessels and then tells the body if it needs to generate more heat or release heat.


The state of having a lower solute concentration than the surrounding environment.


The chief organ in mammalian respiration which is actively ventilated via a suction-pump mechanism of inhalation and exhalation

Median-paired Fin Movement

The pectoral fins are used to steer the fish and quickly change directions in median-paired fin movement. This is primarily used by tiny fish.

Neutral Buoyancy

Neutral buoyancy is when an object has the exact same density as the fluid it is located in. Neutrally buoyant objects neither float nor sink.

Open Circulatory System

Circulatory system which lacks blood vessels. The nutrient-carrying hemolymph is pumped throughout the open body cavity and directly contacts the cells.


Organisms which are unable to regulate the water levels inside of their bodies and are at the mercy of osmosis at all times.


The movement of water between two places from an area of low solute concentration to an area of high solute concentration.


Organisms which need to keep a constant solute concentration in side their bodies.

Ostia (singular Ostium)

Small openings or orifices. Insects have ostia along the tube-like structure running along their back which is used to move hemolymph throughout the body.


Animals that are oviparous produce eggs that hatch outside the body. This allows birds to fly without carrying heavy babies. This also allows for the existence of omelets.


Pacing occurs when the left front foot and left back foot touch the ground simultaneously and vice versa.

Patagia (plural Of Patagium)

Patagia are specialized gliding membranes. Each thin patagium is two layers of skin with connective tissue, muscles, and nerves in between.

Pectoral Fins

Pectoral fins are paired fins located behind the gills of the fish. They may be used to create dynamic lift. If Arnold Schwarzenegger was a fish he would have really buff pectoral fins.


Animals whose temperature changes according to the environmental temperature. Snakes are poikilotherms.


Pronking is a type of quadruped movement in which all four limbs hit the ground at the same time. This is typical of antelope and cartoon animals.

Pulmonary Circulation

The part of the circulatory pathway where the blood goes from the heart to the lungs and back to the heart again. A single circulation pathway does not have this special trip to the lungs.


Quadrupeds are animals that utilize four-limbed locomotion. Man's best friend (whether you're an equestrian, a dog-trainer, or a hippopotamus lover) is a quadruped.


The type of heat caused by the absorption of electromagnetic waves (AKA sunlight).


The process by which organisms exchange oxygen and carbon dioxide.

Rotary Gallop

A rotary gallop occurs when the animals' front feet hit at almost the same time and the back feet hit almost at the same time. Whichever side (right or left) hits first for the front pair of feet hits second for the back feet.

Sardine Run

Millions of Sardines migrate and predators follow closely behind.


Schooling occurs when fish move as a synchronized and unidirectional unit, like a flash-mob. All schooling fish are also shoaling.


Sessile animals are stuck. Sessility is the characteristic of being attached to a surface and unable to move from it. Sessile animals must rely on currents to carry nutrients to them.


Shoaling is when fish swim close together for social reasons. Shoaling fish are not necessarily schooling.


Substances which are dissolved in a solution. In this chapter we discuss salts and other compounds dissolved in water and blood.

Swim Bladder

The swim bladder is an organ located underneath the dorsal fin which consists of one or two air sacs that inflate or deflate to change the buoyancy of the animal. Submarines use ballast tanks to do the same thing.

Synoatrial Node

A bundle of cells in the heart that sends an action potential electrical signal to cause a contraction of the heart. This is commonly called the pacemaker (and if it fails an artificial pacemaker takes over its job)

Systemic Circulation

The part of the double circulation pathway where the blood travels through the rest of the body after it goes to the lungs. System, systemic. You got it!


The windpipe, a tube connecting the mouth to the bronchi.


The network of tubes found in insects which supplies oxygen directly to the tissues.

Tidal Volume

The amount of air breathed in or out during a respiratory cycle

Tranverse Gallop

Transverse Gallop is when the animals' front feet hit at almost the same time and the back feet hit almost at the same time. Whichever side (right or left) hits first for the front pair of feet also hits first for the back pair of feet.


Trotting is a type of movement in which diagonally paired legs (such as front right and rear left) touch the ground simultaneously


Thinner-walled large vessels that carry blood back to the atria of the heart are called veins. The larger diameter decreases the resistance to help the blood get back to the heart with the lower pressure behind it.


The process of actively moving air to the site of gas exchange such as taking a breath.


The ventricle is where blood exits the heart. This has to be the strongest part of the heart because it needs to provide the force to get the blood where it needs to go and back to the heart again.



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