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GAS EXCHANGE IN ANIMALS We will be studying the diversity of adaptations for this process in four animal groups: Mammals Fish BirdsInsects.

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Presentation on theme: "GAS EXCHANGE IN ANIMALS We will be studying the diversity of adaptations for this process in four animal groups: Mammals Fish BirdsInsects."— Presentation transcript:

1 GAS EXCHANGE IN ANIMALS We will be studying the diversity of adaptations for this process in four animal groups: Mammals Fish BirdsInsects

2 AN OVERVIEW Cellular respiration requires O 2 and produces CO 2 : C 6 H 12 O 6 +6O 2 6CO 2 +6H 2 O Gas exchange provides a means of supplying an organism with O 2 and removing the CO 2 glucose+oxygen carbon dioxide+water

3 Organism level Cellular level Respiration ATP Gas exchange medium (air or water) Fuel molecules from food CO 2 Gas exchange surface O2O2 CO 2 Circulatory system

4 THE SOURCE OF OXYGEN Air about 21% oxygen thinner at higher altitudes easy to ventilate Water amount of oxygen varies but is always much less than air even lower in warmer water harder to ventilate

5 GAS EXCHANGE SURFACES Gases move by diffusion. Diffusion Diffusion is greater when: the surface area is large the distance travelled is small the concentration gradient is high Gas exchange also requires a moist surface O 2 and CO 2 must be dissolved in water to diffuse across a membrane

6 GAS EXCHANGE SURFACES Therefore, an efficient gas exchange surface will… have a large surface area provide a small distance for gases to diffuse across be moist …and will be organised or operate in a way that maintains a favourable concentration gradient for the diffusion of both gases. A circulatory system may operate in tandem with the gas exchange system to maintain the concentration gradient

7 Depends on: the size of the organism where it lives – water or land the metabolic demands of the organism – high, moderate or low STRUCTURE OF THE GAS EXCHANGE SURFACE

8 TYPES OF GAS EXCHANGE SURFACE

9 WATER AS A GAS EXCHANGE MEDIUM No problem in keeping the cell membranes of the gas exchange surface moist BUT O 2 concentrations in water are low, especially in warmer and/or saltier water SO the gas exchange system must be very efficient to get enough oxygen for respiration

10 GETTING OXYGEN FROM WATER: FISH GILLS Gills covered by an operculum (flap) Fish ventilates gills by alternately opening and closing mouth and operculum water flows into mouth over the gills out under the operculum Water difficult to ventilate gills near surface of body

11 GETTING OXYGEN FROM WATER: FISH GILLS Each gill made of four bony gill arches. Gill arches lined with hundreds of gill filaments that are very thin and flat.

12 GETTING OXYGEN FROM WATER: FISH GILLS Gill filaments are have folds called lamellae that contain a network of capillaries. Blood flows through the blood capillaries in the opposite direction to the flow of water.

13 ENHANCING THE EFFICIENCY OF FISH GILLS Gills have a very large surface area: four arches with flat filaments with lamellae folds Gills are thin-walled and in close contact with water: short distance for diffusion Gills have a very high blood supply to bring CO 2 and carry away O 2 dark red colour Gills are moist: fish live in water!

14 ENHANCING THE EFFICIENCY OF FISH GILLS Fresh water flows over gills in one direction. COUNTER-CURRENT FLOW: water and blood in the gills flow in opposite directions maintains a favourable concentration gradient for diffusion of both gases Concurrent flow animation Countercurrent flow animation

15 CONCURRENT FLOW

16 COUNTER-CURRENT FLOW

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18 GETTING OXYGEN FROM AIR: MAMMALS, BIRDS & INSECTS As a gas exchange medium, air has many advantages over water: Air has a much higher oxygen concentration than water Diffusion occurs more quickly so less ventilation of the surface is needed Less energy is needed to move air through the respiratory system than water

19 BUT as the gas exchange surface must be moist, in terrestrial animals water is continuously lost from the gas exchange surface by evaporation SO the gas exchange surface is folded into the body to reduce water loss. GETTING OXYGEN FROM AIR: MAMMALS, BIRDS & INSECTS

20 WARM-BLOODED ANIMALS Warmth speeds up bodys reactions enables faster movement etc BUT increases evaporation of water from lungs AND increases demand for energy to stay warm SO higher demand for gas exchange to provide O 2 for and remove CO 2 from respiration

21 MAMMAL LUNGS: VENTILATION Two lungs ventilated by movement of diaphragm and ribs

22 MAMMAL LUNGS: STRUCTURE Air enters via trachea (windpipe) Trachea branches into two bronchi (one bronchus to each lung) Bronchi branch into bronchioles System of tubes (held open by rings of cartilage) allow air to flow in and out of lungs

23 MAMMAL LUNGS: STRUCTURE Rubber cast of human lungs

24 MAMMAL LUNGS: STRUCTURE Healthy lungs Smokers lungs

25 MAMMAL LUNGS: STRUCTURE Many alveoli at the end of the bronchioles walls made of flat cells; only one cell thick each alveolus lined with moisture surrounded by capillary network carrying blood

26 GAS EXCHANGE IN MAMMALS Inhaled air: 21% O 2 and 0.04% CO 2 Blood arriving: low in O 2 and high in CO 2 O 2 in lung air dissolves in moist lining diffuses into blood CO 2 in blood diffuses into moist lining diffuses into lung air Exhaled air: 17% O 2 and 4% CO 2 Blood leaving: high in O 2 andlow in CO 2

27 GAS EXCHANGE IN MAMMALS Gas exchange animation

28 GAS EXCHANGE IN MAMMALS

29 Large surface area many tiny alveoli area as big as a tennis court in humans! Short distance for diffusion alveoli and capillary walls only one cell thick cells are flattened so very thin capillaries pressed against alveoli Moist wet lining of alveolus system internal to reduce water loss by evaporation ENHANCING THE EFFICIENCY OF MAMMAL LUNGS

30 Maintaining a concentration gradient air (with depleted O 2 and excess CO 2 ) is exhaled replaced with fresh inhaled air blood (having lost CO 2 and been enriched with O 2 ) returns to heart to get pumped around body replaced with blood collected from body ENHANCING THE EFFICIENCY OF MAMMAL LUNGS

31 BIRD LUNGS Birds have a high demand for oxygen: warm-blooded so metabolism is high flight requires a lot of energy Additional challenge: air at higher altitude is thinner lower in O 2 …yet some species have been seen flying over Mt Everest! Birds have a very efficient gas exchange system to cope with low O 2 supply & high O 2 demand

32 BIRD LUNGS Birds have lungs and air sacs: air sacs are not sites of gas exchange air sacs enable a one-way flow of air through lungs

33 BIRD LUNGS: VENTILATION Passage of air through lungs: in trachea rear air sacs rear bronchi parabronchi in lungs out trachea front air sacs front bronchi

34 BIRD LUNGS Main air tubes through lungs are the parabronchi. Tiny air capillaries loop away from and back to parabronchi one way flow of air Blood capillaries run alongside air capillaries BUT blood flows in opposite direction to air flow COUNTER-CURRENT EXCHANGE of gases

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36 ENHANCING THE EFFICIENCY OF BIRD LUNGS Large surface area many tiny air capillaries Short distance for diffusion air and blood capillary walls made of flattened, thin cells air & blood capillaries alongside each other Moist lining of air capillaries is wet system is internal to conserve moisture

37 ENHANCING THE EFFICIENCY OF BIRD LUNGS Maintaining a concentration gradient Air flows in one direction through lungs regardless of whether the bird is inhaling or exhaling One way passage in both parabronchi and air capillaries; other way in blood capillaries COUNTER-CURRENT EXCHANGE

38 INSECT TRACHEAL SYSTEM Completely different system! Air tubules (trachea & tracheoles) throughout the body which open to the environment via spiracles

39 INSECT TRACHEAL SYSTEM Trachea kept open by circular bands of chitin Branch to form tracheoles that reach every cell Ends of the tracheoles are moist Oxygen delivered directly to respiring cells – insect blood does not carry oxygen

40 Oxygen delivered directly to respiring cells Can pump body to move air around in tracheal system BUT Size of animal limited by relatively slow diffusion rate ENHANCING THE EFFICIENCY OF INSECT TRACHEAE

41 DIVERSITY fish gills mammal lungs bird lungs insect tracheae


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