Gas Exchange Adaptations Flashcards
- What are the conditions for gas exchange surfaces?
- Large Surface Area: Volume
- Short diffusion pathway (thin)
- High concentration gradient (eg good supply)
- Moist for gases to dissolve
- Permeable to gases
- What is the total oxygen requirement of an organism proportional to?
The oxygen needed is proportional to volume
- What is the rate of oxygen absorption proportional to in an organism?
Rate of oxygen absorption is proportional to its surface area.
- What happens to the surface area to volume ratio of an organism as size increases?
As size increases, the surface area to volume ratio decreases.
- In small and unicellular organisms where does gas exchange take place?
Across the external surface membrane
- What is the gas exchange surface of an Amoeba?
Surface cell membrane
- Describe the surface area to volume ratio of an Amoeba.
Very large surface area to volume ratio
- Describe the diffusion path of an Amoeba?
Short diffusion pathway across a thin permeable cell membrane. The cytoplasm is constantly moving which maintains the concentration gradient for diffusion.
- What is the gas exchange surface of a flatworm?
Body Surface
- How does the flattened shape of a flatworm aid gas exchange?
Reduces the diffusion distance between the surface and the cells.
Every internal cell is close to the external environment.
Increases surface area so that all cells can access oxygen.
- What is the gas exchange surface of an earthworm?
Body Surface
(Moist covered in mucus for dissolving gases)
- Explain how the shape of the earthworm aids gas exchange.
The earthworm has a cylindrical body, giving rise to a high surface area to volume ratio.
- Other than shape explain one other feature of earthworms that aids oxygen absorption.
The circulatory system maintains a concentration gradient at body surface but also provides oxygen to cells at the centre.
- Amphibia have aquatic tadpoles what is the gas exchange surface of a tadpole?
Gills (don’t ventilate like fish though, gradient maintained by movement through water) and Body surface
- Adult amphibians have two gas exchange surfaces. What are they?
Body Surface
Simple Lungs/respiratory system
- What is the gas exchange surface in a fish?
Gills
- What is the function of gill rakers?
To trap any debris or material that may block the gills
- How does the gas exchange surface of a fish fulfil the general requirements of a gas exchange surface?
- Many Gill Filaments with many gill lamellae => Large surface area to volume ratio
- Lamellae have an extensive capillary network => Maintains a concentration gradient
- Thin surface layer of cells increases rate of diffusion
- How do fish maintain a concentration gradient of oxygen across their gill surface?
- Lamellae have an extensive capillary network => Maintains an oxygen concentration gradient => Increases rate of diffusion
-BONY FISH: Blood flow is counter-current to water movement, so the gradient exists across the entire surface.
- Describe the movements that result in water entering the bony fish.
1) Mouth opens, Operculum closes
2) Buccal Cavity Floor drops => Increase Buccal cavity volume => Decreases Pressure
3) Water drawn into the mouth from a higher pressure outside to a lower pressure inside
- Describe the movements that result in water passing over the gills and exiting the fish.
1)Mouth closes, Operculum opens
2) Buccal cavity floor is raised => Decreases volume => Increases pressure
3) Water is forced out of the operculum over the gills due to the increase in pressure inside the operculum to the lower-pressure environment.
- What is meant by “counter-current flow” and “parallel flow”.
Counter-current flow is used by Bony Fishes.
- Blood flows in the opposite direction to water.
Parallel Flow is used by Cartilaginous fishes
- Blood flows in the same direction as water
- Explain why counter-current flow is more efficient at absorbing oxygen into the blood.
Counter-current is more efficient because the blood always has a lower oxygen concentration than water when they meet. This means the concentration gradient is maintained across the entire length of the gills. A higher proportion of oxygen is extracted from the water than in parallel, which hits an equilibrium at 50% saturation.
- Sketch graphs to illustrate counter-current and parallel flow label the lines and add arrows to show the direction of movement of the blood and water.
% Saturation of O2 in Blood (y) - Distance along gill length (x) graph
Counter-current
A line from top left to bottom right of the graph is water flow & a parallel line above this from bottom right to top left represents blood flow.
Parallel flow
A line from top left (Water flow) and a line from bottom right (Blood). Curve (DECREASING RATE) and levels off meeting at 50% somewhere in the middle of the gill length.
- Predict the gas exchange features of an active fast swimming fish.
- Large Gill surface area: Many Gill filaments and lamellae
- Counter-current Flow system (Maximising oxygen gradient across entire gill length) OR Ram ventilation (swim fast with their mouths open)
- High blood flow rate: Strong circulatory system to quickly transport oxygenated blood to tissues.
- Thin Gill epithelium: shorter diffusion distance
- Draw and label a diagram of the human lungs and associated structures.
Larynx and epiglottis
Trachea with C-shaped rings of cartilage
2 Bronchi
Bronchioles branch out
Alveoli
Rib cage + Intercostal muscles
Outer Pleural membrane
Pleural Cavity
Inner Pleural Membrane
Diaphragm below lungs
- Explain the significance of the cartilage being C-shaped in the trachea.
The C-shape allows a bolus of food to pass through the oesophagus
Cartilage prevents the trachea from collapsing when air pressure falls.
- What is the gas exchange surface in humans?
Alveoli
- Give an advantage to a terrestrial organism of internal lungs.
Reduces water loss and the gas exchange surface from drying out
- How do the features of the gas exchange surface in humans fulfil the general features of gas exchange surfaces?
- Large surface area: Many cloud-like alveoli with folds to increase surface area
- Maintained concentration gradient: Rich Blood Supply
- Short diffusion pathway: Thin walls (one cell thick)
- Moist lining
- Permeable to gases
- What is the role of surfactant?
Reducing the surface tension of water prevents the alveoli from collapsing and sticking together due to the H-bonds of water. Difficult to reinflate.
- How is a concentration gradient maintained at the gas exchange surface?
Rich blood supply in capillaries, constant blood flow maintains the concentration gradient. Lower in blood than in air.
- What happens when the intercostal muscles contract?
When the intercostal muscles contract the ribcage exapnds up and outwards.
Pulls the outpleural membrane and the inner pleural membrane out.
Increases thoracic cavity volume and alveoli to expand. Alveolar pressure decreases to below atmospheric so air is drawn in.
- What happens when the diaphragm contracts?
The diaphragm flattens so volume increases and pressure decreases.
- Describe the role of the pleural membranes in negative pressure breathing.
The membranes pull the lungs which expand the alveoli so that they have negative pressure to draw air in
- Why do insects have an impermeable cuticle?
Waxy cuticle reduces water loss
- What is the function of the spiracles in insects?
To allow air in and out
- What is the advantage to an insect of being able to open and close the spiracles?
During inactivity, they can close their spiracles to reduce water loss
- They have air sacs to function as temporary stores in hot conditions when spiracles close.
- What is the gas exchange surface in an insect?
Tracheole ends
- Describe the ventilation movements of an insect.
During low activity:
- The gases dissolve at the fluid-filled ends of the tracheoles and diffuse directly into muscle cells.
During the activity:
- They ventilate via mass flow.
Whole body contractions ventilate the tracheal system, so air is pumped into the thorax and mostly out of the abdomen. Speeds up air flow through spiracles, maintaining a concentration gradient.
- Anaerobic respiration in cells also causes lactic acid production. This reduces the water potential in the muscle cells, water diffuses in from the tracheoles by osmosis. Reducing fluid levels in the tracheoles exposes a greater surface area and creates a shorter diffusion distance.
- Draw and label a diagram of a TS of a typical leaf.
Waxy cuticle
Upper epidermis
Palisade mesophyll
Spongey Mesophyll + Air spaces
Lower epidermis + Stomata + Guard cells
Waxy cuticle
- Why is the upper epidermis transparent?
To allow light to pass through to the chloroplasts in the palisade layer
- Which is the main photosynthetic tissue of a leaf?
Palisade Mesophyll
- How does water enter a leaf?
Xylem
- Which tissue removes photosynthetic products from a leaf?
Phloem transports products to the rest of the plant
Stomata opening allow gases to diffuse out
- What is the function of an open stomata?
Allow gas exchange to occur
- What is the significance of the air spaces in spongy mesophyll?
Air spaces allow gases to quickly diffuse from the stomata to palisade cells in the gaseous state and vice versa.
Air spaces create a larger surface area of mesophyll cells for gas to diffuse.
- What is the advantage to a plant of closing stomata at night?
Reduce water loss by transpiration
- Draw a pair of guard cells showing the relative thickness of the cell wall.
The inner wall is much thicker than the outer wall.
So when it becomes turgid it curves with the outer wall stretching more
- Describe the mechanism of stomatal opening.
Potassium-Malonate Theory
Opening stomata to allow gases to palisade mesophyll:
1) As photosynthesis occurs, the guard cells produce more ATP.
2) The ATP actively transports potassium ions into the cell, which convert starch molecules into malonate ions.
3) The malonate ions reduce the water potential inside the guard cell.
4) Water diffuses into the cell by osmosis down the concentration gradient.
5) Causes the guard cells to expand and become turgid
6) The Outer Wall stretches whilst the inner wall does so less => Guard cell curves and creates a pore between the two.
Closing to minimise water loss:
(The reverse happens at night)
- Give a BRIEF (no more than 5 bullet points) account of how stomatal density can be investigated.
- Paint a thin layer of the lower epidermis of a leaf with clear nail varnish
- Peel off when dried using forceps and place under a microscope on a slide
- Using the 10x zoom, find a field area and then focus with the x40 objective lens to count the number of stomata in view at 3 fields of view and calculate a mean.
- To calculate the stomata field view area: Field view area at x40 = diameter in mm and pi r^2. Where 1epu = 0.025mm at x40
- Mean number of stomata per mm^2 = mean no. stomata per field view/ area of the field view in mm^2
