Unit 3; Requirements for life; Adaptations for gas exchange
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- Created on: 17-11-16 18:56
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- Adaptations for Gas Exchange
- Problems with size increase
- diffusion needs:
- short diffusion path
- large SA:V
- permeability
- mechanism to make conc gradient
- Unicellular: diffusion is all through membrane
- Multicellular: larger animal = smaller SA:V, so diffusion isn't enough
- diffusion needs:
- Gas Ex in vertebrates
- Amphibians
- permeable, moist skin w capillary network, active species have lungs
- Reptiles
- complex internal lung structure to increase SA
- Birds
- no diaphragm but efficient ventilating ribs & flight msucles
- Amphibians
- Gas Ex in fish
- occurs over gills which have:
- 1 way water flow pushed by vent mechanis
- many folds for large SA
- large SA so water movement prevent gill collapse
- Cartilaginous fish have poor efficiency
- must swim to ventilate
- have parallel flow so blood can only ever have 50% O2 concentration
- only occurs on part of gill
- Bony FIsh
- operculum over gills & internal bones
- Ventilation; Inhalation
- 1. mouth open
- 2. operculum close
- 3. mouth floor lowers
- increase vol & derease pressure in mouth
- 4. water flows in as external pressure is higher
- opposite for exhalation
- Structure
- 4 gill pairs
- bone gill arch
- thin projections on arch are filaments
- gas ex occurs over gill lamella
- Counter-Current flow
- blood & water flow opposite directions
- allow blood O2 to reach 80%
- occurs over entire gill lamella
- occurs over gills which have:
- Human Breathing System
- Structure
- lungs in airtight space (thorax) enclosed by ribs
- membranes line thorax & lungs to reduce friction
- diaphragm is sheet of muscle below thorax
- intercostal muscles between ribs
- thorax is flexible with cartilage rings, goes into 2 bronchi, to bronchioles , to alveoli
- Ventilation; Inhalation
- 1. external intercostal muscles contract
- 2. ribs pull up & out
- 3. diaphragm flattens so thorax volume increases
- 4. reduced lung pressure forces air in
- opposite for exhalation
- gas exchange in alveoli is efficient as:
- large SA:V
- walls are one cell thick
- lining of moisture which traps air
- extensive capillary network which carries gas away
- Structure
- Gas Exchange in Insects
- exoskeletons are rigid with thin waxy layer reducing water loss
- small SA:V so gas exchange has to occur through spiracles along body
- spiracles lead to chitin lined trachea which branch to tracheoles
- hairs prevent water loss & solids entering
- movements of abdomen ventilate trachae
- gas exchange occurs between tracheole ends & muscle fibres
- Gas Exchange in Plants
- Oxygen enters stems and roots through diffusion
- Gas exchange in leaves through stomata, down concentration gradient
- once in leaf, gases diffuse through inter-cellular spaces into cells
- stomata are small pores on leaf surface
- 2 guard cells make stomata & have uneven thickness walls
- During the day guard cells are turgid & open, at night they are flaccid and closed
- chloroplasts produce ATP provide energy for K+ to active transport to guard cell
- stored starch is converted to malate which, with K+, reduces water potential so water enters, guard cells stretch & stoma opens
- Problems with size increase
- gas exchange in alveoli is efficient as:
- large SA:V
- walls are one cell thick
- lining of moisture which traps air
- extensive capillary network which carries gas away
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