1. UNIT 2 The nutrition function Natural Science 2. Secondary Education RESPIRATION IN DIFFERENT ANIMALS

2. UNIT 2 What is diffusion? Diffusion is the transfer of gases between the external environment and the circulating liquid, through tissues that are thin enough to allow these gases to pass. When the circulating liquid reaches the respiratory organs, it is carbon dioxide-rich and oxygen-poor. When air reaches the respiratory organs, on the other hand, it is oxygen-rich and carbon dioxide-poor. This is when diffusion occurs: oxygen will move from the area of high concentration to the area of low concentration (from the air to the circulating liquid), and carbon dioxide will do the same (it will move from the circulating liquid to the air). Diffusion in living things Air with O 2 Air with CO 2 Blood with O 2 Blood with CO 2 O2O2 CO 2 Exchange tissue Natural Science 2. Secondary Education

3. UNIT 2 What is diffusion? Diffusion can occur: Diffusion in living things Through the body surface. This occurs in sponges, polyps, worms and some amphibians. Through gills: This occurs in molluscs, crustaceans, fish and some amphibians. Through tracheae: In insects. Through lungs: In amphibians, reptiles, birds and mammals. Natural Science 2. Secondary Education

4. UNIT 2 RESPIRATION IN WATER THROUGH THE BODY SURFACE THROUGH GILLS Click on each box to find out more How some animals take oxygen from the water is carried out Natural Science 2. Secondary Education

5. UNIT 2 This is seen in animals that live underwater or in very wet environments, like the soil. Sponges, cnidarians (polyps and jellyfish), worms and some amphibians absorb air in this way. Respiration through the body surface The animal absorb O 2 through its surface The animal eliminates CO 2 through its surface O2O2 O2O2 CO 2 Respiration through the body surface in an annelid. Go back to the Start menu Wet environment Body surface How some animals take oxygen from the water Natural Science 2. Secondary Education

6. UNIT 2 Gills are very thin sheets or filaments full of capillaries. When water passes through the gills, carbon dioxide from the circulating liquid inside the organism is exchanged for oxygen from the water. Gills are the respiratory organs of aquatic molluscs, crustaceans, fish and some amphibians. Respiration through gills Blood with O 2 Blood with CO 2 Water Water with O 2 Water with CO 2 Respiration through gills in a fish. O2O2 CO 2 How some animals take oxygen from the water Go back to the Start menu Natural Science 2. Secondary Education

7. UNIT 2 RESPIRATION IN AIR THROUGH TRACHEAE THROUGH LUNGS Click on each box to find out more How some animals take oxygen from the air is carried out Natural Science 2. Secondary Education

8. UNIT 2 This type of respiration occurs in almost all insects. Tracheae are very thin tubes that branch out to provide the animal’s tissues with oxygen. They lead out of the body through pores called spiracles. Respiration through tracheae CO 2 O2O2 Spiracle Trachea The insect’s tissues Exoskeleton Respiration through tracheae in an insect. How some animals take oxygen from the air Go back to the Start menu Natural Science 2. Secondary Education

9. UNIT 2 This type of respiration occurs in amphibians, reptiles, birds and mammals. Lungs are made up of millions of tiny tubes or cavities called alveoli, which are full of capillaries. This is where oxygen passes into the blood. Lungs are connected to the external environment by the rest of the respiratory tract (airways). Respiration through lungs Blood with O 2 Blood with CO 2 O2O2 CO 2 Respiration through lungs in a mammal. Lungs Airways How some animals take oxygen from the air Go back to the Start menu Natural Science 2. Secondary Education