GAS EXCHANGE

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.

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)

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.

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

Gas Exchange in Protists

• They have no specialized respiratory systems. • Respiratory surface is cell membrane. • Gas exchange occurs through body surface by

diffusion.

O2

CO2

Gas Exchange in Hydra

• Respiratory surface is cell membrane.

• By diffusion both cell layers can exchange dissolved oxygen and carbon dioxide with their surroundings.

Gas Exchange in Hydra

CO2

O2

CO2O2

Gas Exchange in Planaria

• Planarian has no respiratory system.

• O2 and CO2 diffuse into and out of individual cells

•Respiratory surface is cell membrane.

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.

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

Gas Exchange in EarthwormO2 CO2

• 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.

Gas Exchange in Earthworm

Gas Exchange in Grasshopper

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.

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.

Gas Exchange in Grasshopper

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.

Gas Exchange in Fish

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.

Respiratory Systems in Vertebartes

Respiratory Systems in Vertebartes