All sites of gas exchange, a gas undergoes net diffusion from where its partial pressure is higher to where its lower

Gills are out folding of the body surface specialized for gas exchange in water

Effectiveness of gills is increased by ventilation and counter-current exchange between blood and water

Gas exchange in insects relies on a tracheal system, a branched network of tubes that brings oxygen directly to cells

In mammals, air inhaled through the nose passes through the pharynx into the trachea, bronchi, bronchioles, and deadend alveoli, where gas exchange occurs.

Amphibians ventilates its lungs by positive pressure breathing, which forces air down the trachea.

Birds use a system of air sacs as bellows to keep air flowing through the lungs in one direction only, prevents the mixing of incoming and outgoing air.

Mammals ventilate their lungs by negative pressure breathing , which pulls air into the lungs when the rib muscles and diaphragm contract. Incoming and outgoing air mix decreasing the efficiency of ventilation.

Sensors detect the level of Ph of cerebrovascular fluid and a control center in the brain adjust the breathing rate and depth to match metabolic standards.

Additional input to the control center is provided by sensors in the aorta and carotid arteries that monitor blood levels of oxen as well as carbon dioxide

Cells balance water gain and loss through osmoregulation

a process based on the controlled movement of solutes between internal fluids and the external environment and on the movement of water.

osmoconformers are isoosmotic with their marine environments, do not use osmosis

Osmoregulators control water up take and loss in a hypoosmotic environment

water conserving organs help terrestrial animals avoid desiccation.

Transport epithelial contains specialized epithelial tissue cells that control solute movements required for waste disposal and osmoregulation

Protein and nucleic acid metabolism generates ammonia. most aquatic animals excrete ammonia

Most excretions systems carry out filtration, reabsorption, secretion, and excretion. Invertebrates system include the protonephrida of flatworms, the metanephrida of earthworms, and the malpighian tubules of insects.

Excretory tubules consist of nephrons and collecting ducts

Excretaory tubules and blood vessels pack the mammalian kidney

Blood force pressure forces fluid from blood in the glomerulus into the lemen of bowman's capsule

The ureter conveys urine from the renal pelvis to the urinary bladder

Within the nephron, selective secretion and the re-absorption in the proximal tubule alter filter volume and composition

The descending limb of the loop of henle is preamble to water but not salt.

The distant tubule and collecting duct regulate potassium and salt levels in body level

Fresh water live in water less concentrated than body fluids. Fish gains water through body absorption causing a loss of salt

Marine body fish- Lives in water more concentrated than body , fish lose water and gain salt