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Presentation on theme: "GAS EXCHANGE."— Presentation transcript:


2 Gas Exchange Gas 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.

3 Characteristics of Respiratory Surface
It must be thin walled for diffusion It 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 medium In multicellular organisms, it must be in contact with the transport system.(to carry dissolved materials to and from the cells of the organism)

4 Characteristics 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.

5 In protists and small In large organisms
multicellular organisms (animals) exchange of gases takes place directly between cells and environment Most 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

6 Gas Exchange in Protists
They have no specialized respiratory systems. Respiratory surface is cell membrane. Gas exchange occurs through body surface by diffusion.

7 O2 CO2

8 Gas Exchange in Hydra Respiratory surface is cell membrane.
By diffusion both cell layers can exchange dissolved oxygen and carbon dioxide with their surroundings.

9 Gas Exchange in Hydra O2 CO2 CO2 O2

10 Gas Exchange in Planaria
Planarian has no respiratory system. O2 and CO2 diffuse into and out of individual cells Respiratory surface is cell membrane.


12 Gas 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.

13 Respiratory Pigments Respiratory pigments are colored substances in blood that carry O2 and CO2 between the respiratory surface and the body cells. Hemoglobin Red Hemocyanin Blue Chlorocruorins Green Hemoerythrins Red

14 Gas Exchange in Earthworm

15 Gas 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.

16 Gas Exchange in Grasshopper

17 Gas Exchange in Grasshopper

18 Gas 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.

19 Gas 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.

20 Gas 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.

21 Gas Exchange in Fish

22 Gas Exchange in Fish Many 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.

23 Respiratory Systems in Vertebartes

24 Respiratory Systems in Vertebartes

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