G AS EXCHANGE IN A NIMALS Biology ATAR Unit 2 Chapter

Tracheal system Spiracles Lungs Air sacs Alveoli Gills Diffusion Concentration gradient Counter-current system All multicellular organisms need systems for gas exchange The type of system an organism has is dependent its size and on the environment it lives in All systems have common characteristics that increase the efficiency of gas exchange KeywordsMaking connections

G AS E XCHANGE Gas exchange in animals is by diffusion The 2 main gases exchanged is O 2 into the body and CO 2 out of the body A high concentration of CO 2 is more dangerous to organisms than a low concentration of O 2 Oxyge n Carbon dioxide

G AS EXCHANGE SURFACES Characteristics of effective exchange surfaces: 1. Large surface area to volume ratio 2. Thin & permeable 3. Moist – enables the dissolution of O 2 for diffusion into the blood stream 4. High concentration gradient is maintained across the membranes

T YPES OF GAS EXCHANGE SYSTEMS SystemAnimalExample Moist skinAdult amphibians Cnidarians Frogs Jellyfish Tracheal system Insects Arachnids Grasshopper Redback spider LungsMammals Reptiles Humans Lizards Lungs with air sacs BirdsChickens GillsFish Crustacean Juvenile amphibians Goldfish Crabs Tadpoles

M OIST SKIN CNIDARIANS Cnidarians are aquatic animals Gases continually diffuse across the membranes AMPHIBIANS (FROGS) Tadpoles have external gills Frogs rely on their lungs and their moist skin for gas exchange

T RACHEAL SYSTEMS Insects have holes (spiracles) which lead into tubes (tracheas) The O 2 diffuses through these from the outside air and CO 2 leaves by diffusion in the opposite direction

G ILLS The amount of dissolved O 2 in water is a lot less than it is in air Therefore, gills have a greater surface area as compared to the lungs of a similarly sized mammal Gills are highly convoluted structures with a very high surface area. Blood flows in the opposite direction to the water ( counter-current ) increasing the efficiency of gas exchange Gills rely on water flowing over them to ensure maximum O2 uptake Gills are the most efficient gas exchange system out of all 3 types of systems

L UNGS WITH AIR SACS Birds have lungs with air sacs They are inflated and deflated by the muscles of the rib cage The air sacs force air through very fine tubes where the gas exchange takes place

L UNGS Mammals and reptiles have lungs. The air travels: 1. In through the nostrils 2. Down the trachea 3. Into the alveoli of the lungs Gas exchange takes place in the alveoli Alveoli dramatically increase the surface area of the lungs