2Gas ExchangeGas exchange is a physical method that organisms have for obtaining oxygen from their surroundings and removing excess carbondioxide.Respiratory surface is the surface through which gas exchange takes place.
3Characteristics of Respiratory Surface It must be thin walled for diffusionIt must be moist (CO2 and O2 must be in solution)It must be in contact with a source of oxygen that exist in the surrounding mediumIn multicellular organisms, it must be in contact with the transport system.(to carry dissolved materials to and from the cells of the organism)
4Characteristics of Respiratory Surface Gas exchange through respiratory surfaces takes place by diffusion.The larger the surface area of respiratory surface, the greater the amount of gas exchange can occur in a given time.
5In protists and small In large organisms multicellular organisms (animals)exchange of gasestakes place directlybetween cells andenvironmentMost of the body cells are farther from the outside environment, also they have protective outer layer, therefore they need specialized organs or systems that include respiratory surface
6Gas Exchange in Protists They have no specialized respiratory systems.Respiratory surface is cell membrane.Gas exchange occurs through body surface by diffusion.
12Gas Exchange in Large, Multicellular Organisms Animals in Water*dissolved O2 is less than 1% in water.*the O2 that is part of H2O is not available for gas exchange.*O2 diffusion is slow in water.* to obtain enough O2 they must constantly move large amount of water over their respiratory surface.Animals on Land*O2 makes up 21% of the air.*O2 diffusion is faster.*They must keep their respiratory surface moist*Most air – breathing animals have respiratory system that extend inside the organism to lower the amount of water lost by evoporation.
13Respiratory PigmentsRespiratory pigments are colored substances in blood that carry O2 and CO2 between the respiratory surface and the body cells.Hemoglobin RedHemocyanin BlueChlorocruorins GreenHemoerythrins Red
15Gas Exchange in Earthworm The skin is the respiratory surface. Skin is thin and secretes mucus that keeps it moist.The O2 passes through the moist skin into the capillaries and the blood carries O2 to the cells by hemoglobin and picks up CO2 from the cells to the capillaries. CO2 then diffuse through the skin into the air.
18Gas Exchange in Grasshopper In grasshopper gas exchange doesn’t depend on circulatory system.Blood does not carry O2 and CO2.The respiratory gases are transported through a series of branching air tubes that are called tracheal tubes.
19Gas Exchange in Grasshopper Air enters and leaves the body of grasshopper by small openings called spiracles. From each spirical tracheal tubes branch into the body.The fluid filled ends of these tubes acts as respiratory surface. O2 diffuses from tubes to cells and CO2 diffuses from cells into the tubes.
20Gas Exchange in Spiders Spiders have book lungs which consist of a series of thin parallel plates of tissue .The plates of tissue recieve O2 from the outside environment through a spiracle.
22Gas Exchange in FishMany animals living in water like fish, oysters, clam and lobsters use gills for respiration.Gills are thin layers of tissue that are richly supplied with blood vessels.As water passes over them, dissolved O2 diffuses from the water across the gill tissue and into the blood. CO2 from the blood diffuses out of the gills into the water.