Unit 3 Surface Area:Volume & Gas Exchange Flashcards
How does the size of an organism relate to its surface area: volume ratio.
The larger the organism size the ratio of surface area: volume ratio decreases
Describe why a smaller organism might have a higher metabolic rate.
PPQ
- The smaller the organism the larger the SA: V ratio
- So more heat is lost in relation to body size than in larger organisms which have a smaller SA:V ratio
- Therefore there is a faster rate of respiration which releases heat
Describe why smaller organisms don’t need any special adaptations.
- They have a larger SA: V ratio so there is a big surface for the exchange of substances
- So can simply exchange substances like OXYGEN & CARBON DIOXIDE across their surface by diffusion
Describe why the shape of an organism can affect heat exchange.
- Animals which are more compact have a smaller SA: V ratio minimising heat loss compared to those which are less compact have higher SA:V ratio e.g big ears
Describe why larger organisms need special exchange surfaces.
- Larger organisms have a smaller SA: V ratio = means they overcome a long diffusion pathway
- Larger organisms usually have a higher metabolic rate= Demands efficient transport of waste out of cells
Name 3 features of an efficient gas exchange surface.
- Larger surface area
- Thin/Short diffusion distance
- Steep concentration gradient
Define breathing and ventilation & respiration
Breathing = movement of air in (inspiration) and out (expiration) of the lungs
Ventilation = special word for breathing
Respiration = chemical reaction to release energy in form of ATP
Describe the adaptations of the alveolar epithelium.
- Alveoli epithelium are one cell thick = which creates a short diffusion pathway
- A large number of alveoli = large surface area for faster rate of gas exchange
- Surrounded by a network of capillaries = Maintains concentration gradient for oxygen and carbondioxide
Describe how gases move into the blood of the human body.
Nasal cavity ➜ Trachea➜ Bronchi(2) ➜ Bronchioles➜Alveoli➜Alveolus➜Across alveolar epithelium➜Capillary endothelium➜Blood
Describe the mechanism of breathing
INSPIRATION
External intercostal muscles!
= Contract to pull ribs up & out
Internal intercostal muscles
= Relax
Diaphram!
= Contracts to move down & flattens
Air pressure in the lungs
= Pressure decrease in thoracic cavity below atmospheric pressure
Lung volume!
= Increases
Movement of air
= Air moves into lungs down a pressure gradient
REQUIRES ATP = ACTIVE PROCESS
Describe the mechanism of breathing
EXPIRATION
External intercostal muscles!
= Relax
Internal intercostal muscles
= Contract to pull ribs down & in
Diaphram!
= Contracts to move up & dome
Air pressure in the lungs
= Pressure increase in thoracic cavity above atmospheric pressure
Lung volume!
= Decreases
Movement of air
= Air moves out of lungs up a pressure gradient
DOES NOT REQUIRE ATP = PASSIVE PROCESS
Give the equation for pulmonary ventilation
Pulmonary Ventilation = Tidal volume × Ventilation rate
dm3min-1 dm3 min-1
Describe the adaptations of the insect’s tracheal system.
Tracheoles have thin walls
= Creates a short diffusion pathway to cells
Highly branched/ Lots of tracheoles
= Creates a large surface area for gas exchange
Body can be moved by muscles to move air
= maintains concentration gradient for oxygen & co2
Fluid at end of tracheoles that move out into tissues during exercise
= Faster diffusion through air to gas exchange surface
Describe the main features in an insect’s gas exchange system.
Spiracles, valve-like openings (O2 & CO2 leave)➜
➜Attached to the Tracheae, a network of internal tubes - supported by rings to prevent collapse➜
➜Tracheoles (smaller tubes) - extend throughout tissues to deliver oxygen to respiring cells
Describe the process of gas exchange in insects
- Gases move in and out of tracheae through spiracles
- Diffusion gradient generated as cells respiring allows for oxygen to diffuse into body cells while CO2 diffuses out
- Contraction of abdominal muscles of tracheae allows for mass movement of air in and out
Describe how insects are adapted to reduce water loss
- Insects have a waterproof exoskeleton
- Insects have a small surface area to volume ratio where water can evaporate from
- Spiracles can open or close to reduce water loss
Give the equation for Fick’s Law.
Diffusion ∝surface area × difference in concentration/
length of diffusion path
Describe the adaptations of a Fish’s gas exchange system.
Countercurrent flow- Water & blood continuously flow in opposite directions= maintains concentration gradient of oxygen across entire length of lamellae (Equilibrium never reached)
GIll has many gill filaments - covered in lamellae = Creates a large surface area for gas exchange
Capillary network in lamellae & very thin gill lamellae =
Creates a short diffusion distance for gases
Describe why fish cant use their bodies as an exchange surface
- Have a waterproof outer membrane
- & Small surface area to volume ratio
Explain the process of gas exchange in a Fish
- Fish opens its mouth to enable water to rush over gills
- Passes over lamellae (O2 diffuses into bloodstream/waste CO2 diffuses out into water)
- Flows out through the back of gills
Describe the adaptations of a Leaf for gas exchange.
Thin & Flat = Short diffusion pathway for gas exchange
Mesophyll cells = have a large surface area for rapid diffusion
Many minute pores on underside of leaf allow = Allow gases to easily enter
Describe gas exchange in Dixotyledonous plants
- Oxygen diffuses out of the stomata
- and carbon dioxide diffuses into stomata for photosynthesis so more growth
Describe how plants are adapted to reduce water loss and xerophyatic adaptations
MORE STOMATA MAY MEAN MORE WATER LOSS SO LESS PHOTOSYNTHESIS AND LESS GROWTH
- Stomata close at night when photosynthesis is not occurring
XEROPHYTIC ADAPTATIONS - Curled leaf & layers of hair trap moisture increase local humidity
- Thicker, waxy cuticle to reduce evaporation
